Bringing the Art of Scraping into the 21st Century?

I?m not going to mention the techniques of bluing up a part as imho these will never change. Or even mention that bluing is an art in its self. This thread will only cover the uses of a hand scraper or not as the case maybe. My method will probably make my old grandfather turn in his grave (he was a scraping hand up until he retired) and the purists cringe into their boots.
A brief explanation about how my alternative method came about.
Trying to keep this as brief as possible; I recently bought a Chinese bench top mill. All in this tread and includes some brief posts on my scraping method (start at page 4 about scraping). http://www.factorydaily.com/forums/showthread.php?t=40213 (XJ20 what do you think please?)
As only to be expected with a Chinese mill it was in need of some serious scraping. So off I set scraping the ways of my machine with my old hand scraper (old file modified) and the usual other tools. It wasn?t until I got to scraping the ways of my column that I stopped to think ?there has to be an easier way?. Added to the fact that I had a lot of bearing area to scrape was the fact that there is a 0.09mm (0.00354?) of bow in the column. So I sat and pondered ?do I take this somewhere and have it skimmed on a surface grinder or just dig in and do it by hand?. Well the thought of taking it and the price got to me (tight Yorkshire man that I am) so how was I going to remove all that metal without loosing a week of my life. I then thought about the fact I had been using a Dremel type tool to remove some burrs on the castings so I put on a round belt sander type thing (see picture) and proceeded thrashing off metal off either end of my column after a quick blue so I could see where I was removing it. I realised very quickly I was removing metal far quicker and easier than I would have been with my scraper. So I stopped and wondered could this make my scraper obsolete? I went to the bench and picked up my X-Y saddle (already hand scraped) and blued it up on my surface plate. Very nervously to start I removed some of the blue (did a re scrape of the surface) and to cut this story short it worked a treat. Where before I had my surfaces within +/-0.005mm (0.0001968?) of each other I now cannot measure the error as my DTI pointer barely moves while all set up on my surface plate.
The hand scraper is not quite obsolete yet as the sanding bobbin is to large to get right under the dovetails but I have a plan. I remembered seeing some one with a narrow file sander (see here http://www.axminster.co.uk/product.a...file=1&jump=60 ) and know this will work as a scraper if the front drum is small enough to fit right under the dovetail. If I were doing a lot of this scraping (absolutely no plans to) I would look into modifying (if needed) the nose of the file sander but for a one off job I will probably just stick to my hand scraper to get where the sanding bobbin can not get.
This may all sound like crazy talk to the purists and all I will say is that with the right technique and a little practise IMHO I can do an equivalent job as the above average hand scraper as fast (if not faster), as accurate (if not more accurate) and far easier on the back so don?t knock it until you have tried it.
Before anybody decides to take a sander to their ways I would highly recommend a practice on an unimportant part of their casting as it is not as easy as it sounds. It requires a light touch (which varies as the job gets close to finished) and the tool at just the right angle or you will very quickly remove to much metal and spoil your bearing.
Ok guys get the out I got my asbestos suit on and what can?t speak can?t lie (that would be my X-Y axes saddle).
I?ll post some pictures of my saddle blued up if anyone is interested when I get a minuet?
John
EDIT: Please see post #41 Page 4 before reading the rest of this thread. :END EDIT

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I had to scrape a set of set precise ballnuts into a set of mounts here at work a few years ago and I used a sanding disc instead of a scraper - primarily due to convenience and time.
In my opinion it is the same priniciple - manually removing small amounts of material to achieve the desired results.
No flames from me....
Scott

If anyone is interested in knowing more about scraping see this thread http://www.factorydaily.com/forums/showthread.php?t=11874 (Way lapping, Scraping, Gib adjustment and Lock screws)
John

John,
it sounds good to me. Infact I'll use that procedure when I do my rail risers.
Steve

John, thank you for this post and your description of scraping your mill's ways. Having never done scraping, it has always seemed an almost mystical endeavor. You make it sound much more down-to-earth.
By the way, what's that wooden thing attached to your scraper? Is it something you add during the conversion from a file?
Best regards,
Randy

like Scotts says, same principal. The other way is file. no one seems to say much about the humble file anymore but they have a tremendous ability to remove material! for roughing, press on the back of the file where you want to remove material - this can provide a lot control
Scraping is a valuable bench skill - anything that isn't flat will be distorted when clamped. So a casting or some precision items should have a reference datum formed by filling & scraping - this is where it comes in as a valuable bench-work skill
The ultimate move into the 20th century is a power scraper. Biax is the on to get, probably come up on ebay, bloody expensive new (are they still made?)
the one thing i can see is that hand scraping tends to have a self regulated depth of cut - when you are finishing with lighter strokes you don't accidentally take out a thou and a half....that might be a weakness of the dremel that deserves some experiment at least
imo its not an art or a guild or anything to be purist about. its a technique that through efforts like yours, more and more will realize is very useful around the shop (for a lot more than machine ways) and that is is not beyond them to get good results from...so i applaud your efforts

Thanks to all that have replied to this thread it is appreciated especially from the experienced members.
I did think that this could have slipped down and off the page never to be seen again without reply. It is only now after my first efforts on my mill that I can really appreciate what my grandfather was trying to tell me nearly 28 yrs ago now. I really wish I had pushed him for more guidance when I had the chance, but such is life. I may at times seem over enthusiastic but now I have seen what can be archived it makes my mind boggle (I can?t get over the flatness of an AA (00) grade surface plate its mind blowing to me, is that sad? lol).
I?ve added some tips I have picked up so far form using my method in case anybody wants to give it a try.
First thing I did was to put the bobbin on the rotary tool without a sanding belt fitted. I switched on the tool and carefully rubbed the bobbin on a piece of sand paper to curve the rubber at the edge (front edge that will contact the metal) so that it would not gouge the metal. Not sure if this made any difference because of the stiffness of the belts.
For roughing I use new belts at what is speed 2 (it has 9 speeds keep it slow) on my tool, as they ware down but before they are completely shot I turn them around to use the other end. Then when both ends are getting quite blunt and clogged I remove it, put it to one side and replace with a new one. If they clog while still good I use the rubber belt cleaning block seen in the picture in the first post to refresh them.
At what I?ll call the middle stage I slow the tool down to its lowest setting and lighten my pressure on the belt. This gives you more control of the amount of material you are removing and helps prevent you taking too much at a time. I?ll keep using the belt, refreshing as necessary until they barely removing any metal and change for a new one at that stage only.
For the finishing stage I reuse all the worn belts, refreshing as I go. Now a very light touch is all that is needed. Never use new belts at this stage it will ruin all your hard work.
Keep the angle of the belt quite low but not so all the width of the belt is used, just the front edge.
To do wider surfaces it will require a narrow rotary tool like pictured, other wise the body will hit the material forcing you to increase the angle of the belt and would give poor results.
Hopefully that will be enough to tell you the basics the rest will only come with practise and experience. I have quickly gained a technique that works very well imo and am happy to work on my mill with confidence. I?m sure that others could do as I did which was to take the plunge and go very carefully to start but I would strongly advise starting on a scrap piece or a part of a casting that will not be used in the final bearings.
I am going to finish my mill using this method and am also going to retouch all the surfaces I scraped with my scraper. I have been considering doing a detailed description with picture of the whole job start to finish but am unsure if there would be enough interest to go to what would be a lot of trouble. If this might interest you please post and let me know. I think it would also be good if the big brains of the zone could asses my methods and point out any problems or just give advice to improve the over all process. I have gained a lot from this site and its generous members it would be nice to give something of value back. Or maybe I should write a book titled ?Bringing the Art of Scraping into the 21st Century? and make some money? Nah I don?t think so lol.

John

John, thank you for this post and your description of scraping your mill's ways. Having never done scraping, it has always seemed an almost mystical endeavor. You make it sound much more down-to-earth.
By the way, what's that wooden thing attached to your scraper? Is it something you add during the conversion from a file?
Best regards,
Randy

Hi Randy,
No problem I just hope it helps others
Not quite sure what you are asking; the only wooden thing is the handle of the file.
John

Mcgyver,
I have read some of the posts (more than once) on the thread I linked to for more information about scraping. You generously supplied a lot of the information so I would like to say a personal thank you to you for that. It was that thread that encouraged me to have a go at the task and the fact I have the camelback straight edge my grandfather gave me.

the one thing i can see is that hand scraping tends to have a self regulated depth of cut - when you are finishing with lighter strokes you don't accidentally take out a thou and a half....that might be a weakness of the dremel that deserves some experiment at least

With this comment in mind and the fact I appreciate your input.
While reading through the thread I came across this statement.

A scraped surface is accurate to a few tenths. (0.0001?) or so.

Just to be sure of what this statement means; is it describing the maximum difference between the highest points and the lowest points on a surface?
To your knowledge is this statement correct?
If not what figure would you use in the statement?
Would that be the best possible accuracy achievable using a hand scraper period?
The best accuracy that could be expected within a reasonable amount of time?
I maybe pushing my luck but would you briefly explain the benefits of scraped bearing on a milling machine. Comparing it to a bearing finished on a surface grinder with a few scrapes using a power scraper (no bluing involved)?
What would be the recommended difference between the high and low points on a milling machines ways (thinking about the oil reservoir effect)?
It may or may not be a big deal (depending on your answers to the figure in question) but I have achieved a higher accuracy on one of the ways of my X-Y saddle using the dremel. I know I could do better but would be unable to measure my results with the DTI I have. I won?t get excited about this until you or another suitable skilled member gives their opinions/answers to my question.
One last point; I?m not looking for bragging rights I am genuinely interested in the skill of scraping and its benefits. I would also be very interested to know if my method is at least equal to if not better than using a hand scraper.
John

I recall being told by an old hand that when finish scraping (ie light, small cuts) the depth of cut typically is in the neighborhood of a tenth, so that may be where it comes from
John thanks for the kind words - but i want to emphasize that old expression "the different between a layperson and expert is 5%". I happily share what i know but you'll get us both into trouble if you take it as being some deep expertise or authority on the matter. I'm no where near qualified to be the scraping expert....in fact by the time you finish the mill i think you're going to get to wear that hat around here .
To your surface grinder vs scraping question, don't know if there is a big advantage once the job is done. Some even push back on the value of the oil reservoir benefit. still, its one big honking surface grinder to take the main castings of a mill - if you're not talking production, grinding might be precluded just because the equipment isn't available. I guess the other aspect is the nature of scraping mating parts. A is done to a reference and B is done A. for example, to surface grind dovetails that's going to take some careful work to keep the angles perfect so they mate. when scraping, we don't care, the exact angle doesn't matter, so long as the parts are the same. sort of like making model T's requires standardization and production but for onesy machine reconditioning the hand fit nature of scraping might be more efficient.

I recall being told by an old hand that when finish scraping (ie light, small cuts) the depth of cut typically is in the neighborhood of a tenth, so that may be where it comes from
John thanks for the kind words - but i want to emphasize that old expression "the different between a layperson and expert is 5%". I happily share what i know but you'll get us both into trouble if you take it as being some deep expertise or authority on the matter. I'm no where near qualified to be the scraping expert....in fact by the time you finish the mill i think you're going to get to wear that hat around here .
To your surface grinder vs scraping question, don't know if there is a big advantage once the job is done. Some even push back on the value of the oil reservoir benefit. still, its one big honking surface grinder to take the main castings of a mill - if you're not talking production, grinding might be precluded just because the equipment isn't available. I guess the other aspect is the nature of scraping mating parts. A is done to a reference and B is done A. for example, to surface grind dovetails that's going to take some careful work to keep the angles perfect so they mate. when scraping, we don't care, the exact angle doesn't matter, so long as the parts are the same. sort of like making model T's requires standardization and production but for onesy machine reconditioning the hand fit nature of scraping might be more efficient.

I will probably have to buy the book that was mentioned in the other thread. It?s a shame to think out of 50,000 odd members none are skilled in scraping. For the sake of old mills/lathes needing re scraping and diy improvers with these Chinese mills it is a skill that should not be lost and more widely used imho. I?ve spent some time digging around on the net for information but it is thin on the ground to say the least.
Thanks any way for helping me getting started.
As for being an expert, is there any point? One thing for sure even with my very limited knowledge my cheap Chinese mill will be a far better machine for my efforts.
Regards,
John
If anyone reading this has the book (they will know which book I am talking about) it would be excellent if they can chip in here with some information.
EDIT :You threw me a bit there with your edit
One thing I would like to say about the scraped vs grinded surface. I have tested the effects of ?sticktion? between the two and a scraped surface is far superior in eliminating/reducing this effect. END EDIT

I can't believe that guy who didn't know what a file handle was!!!
Does this mean that he has been using files without handles forever?
LOL what is the world coming too?

Also I have a question.
How do you flag the surfaces with a dremmel?

Also I have a question.
How do you flag the surfaces with a dremmel?

Flag?
I may know what you?re talking about but by another name.
John

Hi Randy,Not quite sure what you are asking; the only wooden thing is the handle of the file.

That was a small joke. Apparently far too small. I rarely use handles on my files, usually holding at the rear of the file body itself.
Best regards,
Randy

Flag?

Hmm, ...... maybe Flake?
Bob

If we are talking about ?flaking? or ?spot marks? this can easily be achieved with a flicking action of the dremel. I?ve had a go and achieved good results; with more practice I would think you would not be able to tell the difference between a scraped "spot mark" and a dremel produced one.
John

That was a small joke. Apparently far too small. I rarely use handles on my files, usually holding at the rear of the file body itself.
Best regards,
Randy

that, and more so the response, was pretty funny. i don't know how you can stand using files without handles though, and do hope you don't open up a forearm one day!
John, just notice the file scrapper - now i know why you abandon the scraper for dremel - that would be killer using a scraper that short......or did it start out as a 14 bastard and that's how much you had to sharpen it try forging one out of a full size file, its a lot easier.

i don't know how you can stand using files without handles though, and do hope you don't open up a forearm one day!

The first stitches I ever received were actually to my left forearm. I was fishmouthing the end of a piece of tubing for a recumbent tricycle I was building, using a half-round file (with a handle!) and the file slipped off the tube, my weight carried my arm forward against the very sharp beveled end of the tubing and I neatly filleted my arm. I could fold back the flap of skin at least an inch. I'm looking at the scar right now...
I find I get much better control in holding the file by the body. Like in draw filing, but I hold files pretty that much now for all filing. Of course, needle files have integral handles, and I use my thumb and first two fingers to control them.
I suppose I am a fairly odd one also in that I mount my hacksaw blades with the teeth facing the handle so I cut on the pull stroke...
Best regards,
Randy

Yeah, at first I thought it might be a designer housing for the electric motor inside it?
But you say that the power just comes from a tendon/muscle/bone type of motor?
How "Fred" (as in Flintsone) is that?
Pres

How "Fred" (as in Flintsone) is that?

If files were meant to be used with handles, they'd come with handles!
Best regards,
Randy

John, just notice the file scrapper - now i know why you abandon the scraper for dremel - that would be killer using a scraper that short......or did it start out as a 14 bastard and that's how much you had to sharpen it try forging one out of a full size file, its a lot easier.

The scraper you see in the picture started out life with 7? (I read somewhere that 6? was ideal) of blade. You just need to ask Warren aka itsme about these mills as they need a large amount of material removed. I made and am using a new one about 12? long now.
John

I have been considering doing a detailed description with picture of the whole job start to finish but am unsure if there would be enough interest to go to what would be a lot of trouble. If this might interest you please post and let me know.

I think that is a great idea!
Steve

question #1 What is flaging?
In the old days when you finished the fitting part of the job, a good millright would "flag" the surfaces. The reason for this was to retain oil on the surface.
It's done by putting the edge of the scraper down on the surface then banging the handle with one hand while turning the scraper with the other hand. The mark left on the surface (if you do it right) looks like a flag blowing in the wind.
question #2
Why do you use file handles?
The first reason is the end of the file is not made for your hand it's made for a file handle. If you use a file on a lathe without a handle you could get hurt real bad if the file kicks back on you. And second I was taught that the oils from your hands made the swarf stick to the file and made it not cut as well as a clean DRY file. Most people think that a file is an abrasive tool, it's not. It's a lot of small cutters in a row and it works better if the swarf falls off.
If you clean your file and flush it with solvent then dry it. the file will cut much better then a oily dirty file.

If you use a file on a lathe without a handle you could get hurt

yup, saw this happen a few times. Each time it was caused by the object thrown by my German high school machine shop teacher when he caught someone filing in the lathe
JROM, I agree with you, those newer to the craft (not a trade for me) would do well to learn how to use files. About as important as being able to tap a hole imo

... would do well to learn how to use files. About as important as being able to tap a hole imo

Or better - properly de-burring their parts!
Scott

If you use a file on a lathe without a handle you could get hurt real bad

That is the one situation where I always use a file handle (the only thing I file in the lathe is breaking the edge of a piece I've turned.) And though I'm right-handed, I use the left-hand filing technique so if the file does catch and is flung, I'm not in its path.
Best regards,
Randy

And I thought we were discussing ?hand scraping? here?

question #1 What is flaging?
In the old days when you finished the fitting part of the job, a good millright would "flag" the surfaces. The reason for this was to retain oil on the surface.
It's done by putting the edge of the scraper down on the surface then banging the handle with one hand while turning the scraper with the other hand. The mark left on the surface (if you do it right) looks like a flag blowing in the wind.

So if I told you that ?flaging? as you put it or ?flaking? as my grandfather put it (a ?hand? for over 40 years) is done for show and is actually detrimental to a bearing way, you would already know that?
John

I like my version better. I've seen alot of high end machines over the years with "flaged" ways and I don't think they went to all that trouble for show.
Also when you use abrasives on soft metal some of the rocks always get embeded in the metal........not to good for a bearing surface. Except for surface grinders grinding hard material.

I like my version better. I've seen alot of high end machines over the years with "flaged" ways and I don't think they went to all that trouble for show.

I?ve just been Googling and found this. http://www.desktopcnc.com/swarf/frosting.htm Seems to confirm what my grandfather told me.

Also when you use abrasives on soft metal some of the rocks always get embeded in the metal........not to good for a bearing surface. Except for surface grinders grinding hard material.

So how do they stop grains from a grind wheel from embedding into ways finished on a surface grinder "cast iron" which are not a ?hard? metal?
John

And I thought we were discussing ?hand scraping? here?

My apologies, John, for diverting your thread.

So if I told you that ?flaging? as you put it or ?flaking? as my grandfather put it (a ?hand? for over 40 years) is done for show and is actually detrimental to a bearing way, you would already know that?

Please explain further, John. From what I have read on scraping, the flaking creates mini lubricant pockets to avoid the moving part wringing onto the stationary part of the bearing. Is that wrong, or is there something in the flaking process that disturbs the surrounding surface?
EDIT: You must have posted the immediately preceeding entry while I was composing this one. I withdraw the question.
Best regards,
Randy

....would do well to learn how to use files. About as important as being able to tap a hole imo

Oh come on: tapping holes is nowhere near as boring as filing . Somehow as an apprentice I successfully avoided ever having to do the filing thing to make a square peg and hole that would not allow a 0.001" feeler gauage in the gap. And I still hate filing or scraping.
EDIT: I guess I have to apologise for diverting your thread. And also commit the sin of saying I think your Grandpapa was wrong; at least based on what I was taught. The nice mottled flaking is done in a nice symmetric pattern for visual effect but the underlying purpose is to provide lubricant reservoirs.

My apologies, John, for diverting your thread.

No need for an apology I was jesting.
John

EDIT: I guess I have to apologise for diverting your thread. And also commit the sin of saying I think your Grandpapa was wrong; at least based on what I was taught. The nice mottled flaking is done in a nice symmetric pattern for visual effect but the underlying purpose is to provide lubricant reservoirs.

I think it would be wise for me just to leave this thread to you guys .
John

Well John, I tried your method today. Works excellent.
Very very fast once you get the hang of it. Very light touch as you say. There is no muscle work whatsoever using a grinder.
I held the dremel with a very very light feel. I pretty much just held at it's center point in my hand so it would remain level. Then just lightly touched down to the hi spots with no hand pressure at all once the parts were getting close.
It is quite different than hand scraping that is for sure and I can see where somebody with a shaky hand could get into trouble fast. But I found it very easy after an hour or so of practicing.
These are not bearing surfaces so they just needed to be nice and flat.
I'll post 4 pics and explain them.
Pic1 is the top of the headstock riser block that the head stock mates to, which I had made flat to the surface plate.

Pic2 is a before shot of the headstock that sits atop the headstock riser- So the head stock would be made flat using the head stock riser block top surface as the reference.

Pic 3 is the head stock surface after using the dremel for about an hour referencing it to the headstock riser surface.
Pic4 was a final test and it is very interesting to note. This is the surface of the head stock AFTER being made flat to it's reference surface the head stock riser. I placed the head stock on the surface plate this time and note the pattern is now reversed. The high spots are exactly where the areas were never touched with the dremel.
Very very effective method using a dremel IMHO if you can handle the very light touch that is needed to make it work.
IMAGE(http://i109.photobucket.com/albums/n48/S_J_H/cnc%20bench%20lathe/cnclathe020.jpg)
IMAGE(http://i109.photobucket.com/albums/n48/S_J_H/cnc%20bench%20lathe/cnclathe021.jpg)
IMAGE(http://i109.photobucket.com/albums/n48/S_J_H/cnc%20bench%20lathe/cnclathe023.jpg)
IMAGE(http://i109.photobucket.com/albums/n48/S_J_H/cnc%20bench%20lathe/cnclathe022.jpg)
Steve

Also when you use abrasives on soft metal some of the rocks always get embeded in the metal........not to good for a bearing surface. Except for surface grinders grinding hard material.

Just a quick note on this comment; because I am willing to learn and question what I believe to know I took a microscope to my way surfaces. Not the most high tech gear but good enough IMVHO to check JROM?s point. At fifty times magnification there was no sign of embedded grit from the abrasive belts. I put this down to the fact that they are very well adhered and the very low cutting force. Because of the high contrast between the two materials it would have been easy to see unless they are so microscopic and I really needed a probing electron micro scope which I have sent away for an overhaul so was unavailable

Well John, I tried your method today. Works excellent.
Very very fast once you get the hang of it. Very light touch as you say. There is no muscle work whatsoever using a grinder.
I held the dremel with a very very light feel. I pretty much just held at it's center point in my hand so it would remain level. Then just lightly touched down to the hi spots with no hand pressure at all once the parts were getting close.
It is quite different than hand scraping that is for sure and I can see where somebody with a shaky hand could get into trouble fast. But I found it very easy after an hour or so of practicing.

Hi Steve,
Please to here it went well. Thanks for posting.
Did you use an abrasive belt on a rubber bobbin or a grind wheel?
I use the former and do know there are at least two different grit grades (could be more?). If you are using the same and are finding that you are needed too light a pressure to control the removal rate you could use an already partly used belt or give it a quick spin on something like concrete to blunt it a bit. Obviously by the sounds of things this is not a problem for you but would help anyone else who is a bit heavy handed.
John

John, I used those tiny little abrasive bands on the rubber bobbin. I also removed the small outboard steel washer on the rubber bobbin and this gives a little smoother action.120 grit works pretty good for fast removal.
I did my rail risers today on the lathe bed. All I can say is this method will very quickly get you a nice flat surface. One thing though, sure is messy!

Fellow citizens, the thread is "Bringing the art of scraping into the 21st century", and no way will I comment on the use of an angle grinder or other abrasive method to ensure accurate fits in machinery.
The next thing someone will advocate using a sheet of wet & dry paper on a paving stone to lap a machine part flat.
Dear John, go back to bed, read a good book, but don't propose bodge methods as a synonym for skilled work practice for the 21st cent.
Anybody who grinds cast iron is asking for trouble.
Cast Iron in it's natural state is machined and scraped, but when it's flame hardened it can only be ground.
One last thing on bluing a surface plate, if the blue transfers to the part being tested and shows up as blue it's TOO thick and just smears everywhere, it should be applied sparingly and when transferred should show up as a GREY marking on the part.
The final test for an accurate surface is 25 dots of contact per sq inch.
Ian.

Ian,
You probably can't control the rotary tool with as much precision as a skilled hand scraper and it is certainly limited in use for surface type( dovetails would be very difficult to use it on) but for a hobby level work you can still beat the heck out of the machined finish done with one of our hobby mills. I'll estimate flatness to well under .0003" no problem and done very quickly. You can dust off a very small amount of material with the right touch.
In my case I am only flattening clamping surfaces not a bearing surface.
The surface is very good now.
I'll have to get a .0001 indicator and test out just how much control I can get in material removal with the rotary tool.
In my pics I deliberately used a heavy coat of hi spot blue just for the pics. In reality my flats show only small speckles that are very difficult to see.
Steve

handlewanker,
I could sit here and type quite a few word is response to your post but I will not. I certainly will not insult you with a comment like ?Dear John, go back to bed, read a good book, but don't propose bodge methods as a synonym for skilled work practice for the 21st cent?. At the end of the day I can not respect the opinion of a person who is not at least willing to entertain the fact that there could just be another way of doing things. I could say ?give it a try and see for your self? but I know for a fact you would not. All I will say is ?what can?t speak can not lie? and ask you is the world flat or round?
Regards,
John
At this point I could go into detail describing the accuracy I have archived with my method (burn him, burn him lol) but will just say ?try it for yourself, get a piece of scrap and give it a try then judge for yourself?. It will require practice and some experience to achieve good results but that has to be expected. Or if you read through this thread and decide it?s not worth trying and cannot possibly achieve good results because other members say so then move on and good day to you.
This will very likely be my last post in this thread unless some one has a genuine question or an opinion that they are at least willing to discuss in a civil manner. I have nothing to prove here all I was trying to do was help others. The fact that one member gave it a try and was happy with his results has made all my posts in this thread worth it.
John

Because I have never been one to go quietly and I have mentioned on more than one occasion ?what can?t speak can?t lie? I thought I would put some money where my mouth is and add some pictures of my saddle. Not quite perfect but I am still perfecting the technique.
All the work on this has been done with a rotary tool.
For the sake of the pictures I added more Prussian blue pure dry pigment and thinners so I could get a very thin coat on the inspection grade surface plate. The saddle was slid approximately 6mm (1/4?) vertically and horizontally with no down pressure and the pictures were taken in day light with no flash. There is a little glare from the sun which was quite low at 6.00 p.m.
When I have perfected the technique I will post updates if needed but the 9000 rpm of my rotary tool is to fast and about 1000-2000 rpm is better. The bobbin is approximately 15mm in diameter and I have switched from the standard wood sanding belts to wet and dry belts ranging between 250- 600 grit used dry.
John
EDIT: I have added a picture of the saddle before scraping.

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I'll have to get a .0001 indicator and test out just how much control I can get in material removal with the rotary tool.

Steve,
The 0.0001? would not be enough try 0.00005? or less.
John

Hallo John, as the title of the thread is referring to SCRAPING, which I might remind you is a precise surfacing process, I will agree that you CAN produce a surface to your own satisfaction by any method you choose, but I still consider grinding it bodge work where machinery refitting is concerned, especially on sliding surfaces.
Sorry if it ruffles your feathers, but that is my opinion.
I will further add that I HAVE had the occasion to use a 100mm angle grinder on my lathe to prepare a flat surface so that I could mount a steel plate carrying the flat pulley drive mechanism behind the headstock.
The lathe originally had an overhead belt drive from line shafting, but got bombed during the war, and laid in the corner of a factory covered in rubble for a number of years.
I used the angle grinder because the surface had a thick scale from the casting process, and it was required to get down to bare metal so that the mounting plate for the belt drive mechanism could be fitted on a flat surface.
In no way would I consider it a parallel to the scraping process, but served to produce a flat surface for static mounting.
At the same time the surface was tested by chalking it and mating the mounting plate,(previously flattened), in the same way you would use a surface plate.
The final test was a dab of blue on the plate to make sure that there was enough surface area in contact to give a stable bolting face.
The end justifies the means.
If you're happy with your method, use it, but don't describe it as bringing the ART of scraping into the 21st cent, it's just another way to get to where you want to go.
I'm sure there will be many people that will use the method, so enough said, on with the motly.
By the way, are you a member of the flat earth society? Just asking as you did mention it.LOL.
Ian.

Hallo John, as the title of the thread is referring to SCRAPING, which I might remind you is a precise surfacing process, I will agree that you CAN produce a surface to your own satisfaction by any method you choose, but I still consider grinding it bodge work where machinery refitting is concerned, especially on sliding surfaces.
Sorry if it ruffles your feathers, but that is my opinion.
.

It is not your opinion that ruffled my feathers as you put it but the wording of your reply. Leaving all the niceties a side if we can? I am willing to listen to other peoples opinions we all have the right to that I presume?
Please educate me to why in your opinion the method I describe here is a bodge method. Is there a problem using ?wet and dry? paper on cast iron bearing surfaces keeping in mind that the cutting forces are extremely light?
If another method can produce a surface at least as good as a scraped surface can that be classed as a bodged method?

For some unknown reason that I don?t know handlewanker has left without reply. Maybe he will return later and answer my question if not for my education then for the benefit of anyone else reading this thread.
I am not arrogant enough to say there are no issue using the method I have described and am very willing to be educated as that is the main reason for me joining this website. So if anybody more educated than me would like to step in and give some answers to the above questions PLEASE do. I would not want anyone to use this method if there is a problem. I started this thread with no other aim but to help others as I have been helped.
One thing I have learned from this thread is that trying to help others is a thankless task and should be avoided in the future.
At the end of the day it is the reader?s choice to ether use the information or not but it has been given in good faith.
I will admit that while writing the first post to this thread I did consider adding a question mark at the end of the title but being human which I am, forgot.
At this point I would very much appreciate a moderator deleting this thread if that is at all possible.
John
EDIT: I?ve just learnt that you can edit the title to a thread

One thing I have learned from this thread is that trying to help others is a thankless task and should be avoided in the future.

I read through this before I started to reply, and actualy did see a few thank you's thrown in. I'm sure plenty of others have gotten some useful info from this as well. We try to never delete threads here unless they get completely out of hand. 1500 views and one person doesn't likethe terminology you used. Ignore it and move on.

Sorry,I know little on scraping.Would not Moglice bring the art of scraping into the 21st century?I have read Molgice does not require scraping.I don't think so,as 100% contact would not allow for lubricant.Should Moglice be scraped or spotted?
Larry

For some unknown reason that I don?t know handlewanker has left without reply. Maybe he will return later and answer my question if not for my education then for the benefit of anyone else reading this thread.
I am not arrogant enough to say there are no issue using the method I have described and am very willing to be educated as that is the main reason for me joining this website. So if anybody more educated than me would like to step in and give some answers to the above questions PLEASE do. I would not want anyone to use this method if there is a problem. I started this thread with no other aim but to help others as I have been helped.
One thing I have learned from this thread is that trying to help others is a thankless task and should be avoided in the future.
At the end of the day it is the reader?s choice to ether use the information or not but it has been given in good faith.
I will admit that while writing the first post to this thread I did consider adding a question mark at the end of the title but being human which I am, forgot.
At this point I would very much appreciate a moderator deleting this thread if that is at all possible.
John
EDIT: I?ve just learnt that you can edit the title to a thread

John;
Here you have another bunch of THANKS!. I haven't posted before on this thread, but I was following it. Please, don't delete it.
Regards,
Kreutz.

Hi John, sigh, once again I will state, not out of wanting to be awkward but just to produce the end product as is required, that if you use ANY ABRASIVE method you will by the nature of the abrasive material make a ploughed field, (multiple vee grooves) of the surface and this will leave you with millions of sharp pointed crumbly peaks that under the sliding of one piece of metal on another just shear off and so you end up with a rapidly lower, although miniscule, area of non support.
Abrasives will produce grooves and sharp jagged peaks, whereas scraping will result in a series of undulating hills, more condusive to oil film retention and load bearing.
Ian.

Read this whole thread with great interest. I have a well worn bridgeport that I would like someday to tackle. I have no experience at all and have read everything I can find on the subject of scraping and other possible methods. The table has the usual sag that no doubt will require a lot of material removal to correct.
Now for the probably dumb question. Wouldn't the sharp peaks, grooves etc. described above show up when the part is blued up against the surface plate? The pictures of the "dremel" method surfaces appear to be lacking any such sharp edges or grooves, just a nice oval spot pattern.
Also, I read that the scraping method also leaves sharp burrs at the end of a stroke thus the need to lightly stone the finished hand scraped surface.
What am I overlooking?

Read this whole thread with great interest. I have a well worn bridgeport that I would like someday to tackle.

Hi,
A bit late replying to this as I didn't get an email reminder.
I would say if you have an old Bridge port the iron will be of good quality so I would stick to conventional methods.
If you want to give my method a go for removing iron faster you could always finish off with a scraper.
Good look,
John

but seriously i guess i was just looking for a way to do this without the appropriate(read expensive to me)master surfaces and squares.

I am no expert but I have been reading the tome, Conelly's Machine Tool Repair and Applications of Hand Scrapping as well as some other metrology stuff.
You can have your master surfaces for the price of three dimensionally stable (preferably) pieces of metal plus labor (each). You can start with nothing precise and make your surface plates, straight edges, squares, v-blocks, dovetail gauges, and parallels with no external reference. The will have random uncalibrated dimensions but with enough pieces and time they will be flat, square, and parallel.
The trick is, you need to scrape the three pieces relative to each other. With two pieces, you could wind up with each mirroring the convexities and concavities of the other. But three surfaces cannot spot true to each other unless they are all truly flat (within tolerance). And you want three, anyway, because otherwise, how do you know that your precision master surface is STILL a precision master surface. You use one as your working master and periodically verify it against the other two.
You use each one in turn as the temporary master and spot the others to it, scrape the other two, then for the next pass you choose a different one for the temporary master.
1: Spot B and C against A
2: Spot A and C against B
3: Spot A and B against C
4: Spot B and C against A
5: spot A and C against B
6: spot A and B against C
...
You also swap the pieces end for end.
If your hunks of metal aren't very stable, you have to repeat this process frequently.
Likewise, I believe if you have a flat surface plate, three blocks can be tested on the flat surface plate for being right angles. I.E. Spot B and C against A on the reference plate for both flatness and angle (which will show up as not flat). Of course, you could get 90 degrees in one axis but not the other but there are ways to compensate for this, too. Like using more than two adjacent surfaces on each block and rotating them. If you didn't first prepare flat surfaces to use at this stage, you could probably use 5 blocks (90+90+90+90=360), 4 at a time. As more surfaces are involved, the various rotations involved could get complicated. Using the same N+1 technique, you could probably also make 45 and 60 degree references.
The trick is getting the dimensionally stable pieces of metal so you don't need to keep adjusting them. They need to be of a shape such that they don't bend under their own weight and they need to be aged or stress relieved. Even rotating them between the oven and the freezer for a few cycles can reportedly help age them. Cast iron is more stable than hot rolled steel which is more stable than cold rolled. Aluminum is a bit soft and expands a lot with temperture. Engineered shapes such as angles, I beams, square/rectangular tubes, trusses, and castings have better strength to weight ratios when it comes to holding their shape against gravity.
Using the sanding technique or careful use of a power scraper, you can even start with pieces that are way out of alignment to start. Though if you remove drastic amounts of metal, this changes the internal stresses.

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