[Oldmanandhistoy]

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.

[Oldmanandhistoy]

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

[handlewanker]

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.

[Oldmanandhistoy]

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?

[Oldmanandhistoy]

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

[ger21]

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.

[lgalla]

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

[kreutz]

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.

[Geof]

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.....

Give yourself another 26 years and then maybe you will be the cantankerous old codger even if you are in the wrong hemisphere.

And I am not going to apologise for being off-topic, sometimes a bit of levity is needed.

[handlewanker]

Once more to the breach dear friend, once more, so, John, I finally went to bed, it was after 4.00AM our time, having turned into a pumpkin.
I'm sorry if I left you panting for a reply, but I know that in the true spirit of forgetfullness, I will try to clarify what I'm so dead against that perturbs you.

Firstly, when you have an existing slide, male or female, dovetail or square section, you must first make the male half true to the original surface configurations, I.E. a lathe bed should be level and straight by any means you can devise, whether it be with an angle grinder, planer, or surface grinder, and a mill base casting must have the various slide ways, be it a turret mill with dovetails in the bed or a horizontal with vertical vees, made true before the saddle can be applied to it.

The surface is now carefully and evenly scraped all over to remove the gouge marks left by the previous methods, and this includes surface grinding.
If you examine the surface under a 50 X magnifier you will see that it is like a ploughed field, granted very evenly ploughed but nevertheless having peaks of crumbly material that will by no stretch of the imagination support another surface of like finish.

The result, if you think a surface ground finish is good enough, is that the peaks will rapidly wear down and the resulting residue becomes gritty grinding paste that further gouges the surface and accelerates wear.

All of this wear down, or as some daft idiot once told me, "it's the bedding down you have to have", occurs where the slides work on one another, and in the case of the lathe bed the bed ways, will rapidly become untrue just where you use it the most, at the chuck end.

The scraper has a flat scraping motion, cutting on a fairly broad front, even though the front is a curved shape, and one of the reasons you should not raise the handle end above 30 degrees to get the scraper to cut is because you will just dig furrows instead of levelling the surface.
The curved front is important otherwise you'd dig in the corners of the scraper and make it impossible to attack small areas or high spots, don't believe me, try it for yourself.

The raising of the handle to get it to cut, indicates that it's high time to resharpen the scraper, otherwise you just rub a hard skin on cast iron, especially as it's a material that work hardens beautifully.

When using the scraper you should work at 45 degrees to the forward movement, alternatively changing direction, and criss crossing your path, so that you don't dig yourself into a hole.

The surface should have a series of overlapping basket weave like patterns as you proceed, and by this manner you will bring even the most worn surface dead true, as good as a professional would get.

I cite you a case history in brief.
The lathe I aquired, a Colchester Bantam circa 1920/30, had, and I kid thee not, .013" of wear on the raised vees from the chuck to halfway along the bed.

A candidate for a regrind by some expensive engineering works no doubt, for there is no way that even the great Jehovah himself would contemplate scraping that much material off of the other unworn end, let alone one of his relapsed sinners.

So I hand planed the three raised vees and two flats with a hand planer device, which is another story, so I won't bore you, and finished off the "ploughed field effect" by a scrape all over.
Needless to say the saddle, when first laid on the bed,had daylight under it, and you could see light under it viewed end to end, but by carefull attention to keeping the crosslide ways square to the longtitudinal axis a good fit was attained, and now as a testimony for the work involved I can bore a hole 50mm diam and 100mm deep without being tapered.

I've seen some people put up with .002" taper on a 6" length by filing the outside diams of work pieces, but when you've got a taperd bore it's enough to drive you to drink.

So John, I dinna like the hand grinding of a slide way, but if it suits your taste and you're happy with the end product, go for it, but don't promote the assumption that it is the next logical step forward or an evolutionary step in "the art of scraping", for by so doing I would be deeply affronted.

I would however add that it would be an admirable alternative for producing surfaces that don't move but need to be flat or otherwise, and I frequently use an angle grinder on steel structures when bolting faces are required.
Ian.

[handlewanker]

'Lo John, I see you mentioned that you were having trouble with a too fast hand grinder.
I take it that's one of the electric die grinder types with all the sanding and grinding thingies you get in a kit?

If it's a mains 240 volt plug in type, you can use a dimmer switch, which will handle about 350watt, to control the speed, but if it's a rechargeable one with built in batteries you're stuck with it.

I would have thought that a higher speed would have been beneficial otherwise you just rub the surface and load the stones up.
You mentioned that 1000 to 2000 rpm would be OK, so why not get a flexible shaft (on Ebay) and run it off of a 1/8th hp motor, they do about 1425 rpm or 2800 rpm usually.

My 13mm electric drill does 2400 rpm top wack, and has a variable speed trigger.
Ian.

[Oldmanandhistoy]

'Lo John, I see you mentioned that you were having trouble with a too fast hand grinder.
I take it that's one of the electric die grinder types with all the sanding and grinding thingies you get in a kit?.

http://www.cnczone.com/forums/showthread.php?t=43426

And I do appreciate the information regarding scraping btw.

[Oldmanandhistoy]

And I am not going to apologise for being off-topic, sometimes a bit of levity is needed.

No need for an apology I was jesting.

John

#33

[Oldmanandhistoy]

John;

Here you have another bunch of THANKS!

Thank you

John

[wjfiles]

I have been following this thread but maybe I missed something.
30 or 40 years ago I seem to recall that the quality of scraping was measured by the number of points to the square inch and not by a perfectly flat surface. Different surfaces depended on load factors and application, required a different number of points,A tradesman I worked with took a lot of pride in the different effects created by scraping he produced.
WJF

[Oldmanandhistoy]

I have been following this thread but maybe I missed something.
30 or 40 years ago I seem to recall that the quality of scraping was measured by the number of points to the square inch and not by a perfectly flat surface. Different surfaces depended on load factors and application, required a different number of points,A tradesman I worked with took a lot of pride in the different effects created by scraping he produced.
WJF

Hi WJF,

Welcome aboard and thank you for adding the information, I as I am sure many others would be grateful if you could add any detail to the point you made; for the sake of education.

I’m not looking for bragging rights I am genuinely interested in the skill of scraping and its benefits.

Post #9 page 1.

On the subject of points contact I have added a pictures taken in the same circumstances as my last posted pictures post #41 page 4. I have also included a close up picture of the surface with out blue. I have only had about 10 hrs total practice but see no problem using the method as described in the same post as the aforementioned pictures producing a surface with 25, 50 or 100 points contact. http://www.cnczone.com/forums/showpo...0&postcount=41

As handlewanker has already said he see no problem using the method for none sliding surfaces BUT the method used for sliding surfaces would be a “bodge” method in his opinion. What I would like to determine as a FACT would be if it is indeed a “bodge” method for sliding surfaces? I would be grateful and happy to concede that my method is indeed detrimental to a sliding surface if this is indeed a fact. I’m using it on my own mill

I don’t know how useful the added pictures will be but they maybe enough to show why it is a “bodge” method?

EDIT:Just for the sake of onlookers the difference between the blue points and the surrounding surface is less than 0.00005” (0.00127 mm).

John

[Geof]

.... no problem using the method for none sliding surfaces BUT the method used for sliding surfaces would be a “bodge” method in his opinion. What I would like to determine as a FACT would be if it is indeed a “bodge” method for sliding surfaces?...John

I do not see why it should be considered a bodge method or why it is not suitable for sliding surfaces. Analyse what is going on with scraping and what type of surface is being generated.

Using a scraper generates a scalloped surface from the curved cutting edge of the scraper. Using a rotating abrasive tool will generate a scalloped surface from the periphery of the tool.

Flat is measured only on the high spots, the peaks between adjacent scallops, and as wjfiles points out the number of peaks, spots of blue, per square inch is an index of the quality of scraping. For a highly loaded sliding surface a high peak density is needed for a static mounting surface a low density will suffice.

Provided the same spot density has been obtained by either method I do not see how they would perform differently in the same application. If someone wants to argue differently I would like to see their reasoning not just a blanket 'it is the wrong technique'.

[Oldmanandhistoy]

If someone wants to argue differently I would like to see their reasoning not just a blanket 'it is the wrong technique'.

That is ALL I am asking for.

Geof,

Thank you for your post it is VERY much appreciated if only to stop me thinking I am talking complete ****e. I am also still happy to be corrected for my ignorance if indeed I need to be?

John

[Oldmanandhistoy]

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

Hi Larry,

I’ll be the first to admit I know virtually nothing about Moglice but it is something on my list to investigate in the near future. Hopefully some one in the know will answer your question and it will get me started in the subject.

John

EDIT:See here fourth paragraph form the end.http://www.moglice.com/newsite/frame...ightframe.html

[Oldmanandhistoy]

Analyse what is going on with scraping and what type of surface is being generated.

Using a scraper generates a scalloped surface from the curved cutting edge of the scraper. Using a rotating abrasive tool will generate a scalloped surface from the periphery of the tool.

Just a note on this point; when removing a blue spot with the tool I use I don’t drop it on to the blue and then lift off. I do a kind of flicking action vertically over the surface so the worked point will be close to flat.

I don’t think the shape is what is important to the suitability of my method for sliding surfaces. I think it is more down to what effect using “wet and dry” paper has on the surface.

The surface is now carefully and evenly scraped all over to remove the gouge marks left by the previous methods, and this includes surface grinding.
If you examine the surface under a 50 X magnifier you will see that it is like a ploughed field, granted very evenly ploughed but nevertheless having peaks of crumbly material that will by no stretch of the imagination support another surface of like finish.

This statement interests me and so the question is does using “wet and dry” paper leave an unsuitable surface as described here where a surface finished with a hand scraper does not?



John