Scraping Progress Advice/Pointers for the Newb

bmarsh · Oct 6, 2017

Posting again in the right section.

Can I get some advice/pointers on what you consider the progress of this scraping? How do you assess the point count at this stage? I know I have a little ways to go to pick up spotting in a few areas. At what point should I transition from rough scraping to semi-finish finish scraping? I did 2 semi-finish passes before I took the photos just to see. I'm restoring a Monarch 12CK lathe (personal hobby use) it is 1000% better in the current condition than it was. Input appreciated as this is my first scraping project.

Peter. · Oct 6, 2017

As I said in the general thread it's a good start but you need to get blue on these areas before you start going for points. You're still at the roughing stage until you get the surface down to bring the ends to bear.

Alex McGilton · Oct 6, 2017

I can see that by the long silver streak in the close up that your cuts are going nearly the full diagonal,it's fine for roughing should all traces be later covered by the finishing passes. For finishing passes it is best to have more confined and distributed scrape marks of constant depth. Shorten the stroke, and make sure to have gaps to the left and right of each scrape. To reduce glare and improve viability you can add a background coulor to the piece before rubbing it to the blueing, others use red-lead or canoed die in yellow or red for background, while I have found that cadmium red oil paint from the art store works well when spread thin and pink. I'm curious to see someone else try it.

Look through the archives on this forum, most if not all beginner questions have been answered.

dcsipo · Oct 6, 2017

bmarsh said:
Posting again in the right section.

Can I get some advice/pointers on what you consider the progress of this scraping? How do you assess the point count at this stage? I know I have a little ways to go to pick up spotting in a few areas. At what point should I transition from rough scraping to semi-finish finish scraping? I did 2 semi-finish passes before I took the photos just to see. I'm restoring a Monarch 12CK lathe (personal hobby use) it is 1000% better in the current condition than it was. Input appreciated as this is my first scraping project.

View attachment 209462 View attachment 209463

I do not know for sure, but from the pictures it looks like your blade radius is to large, or you just have a very low attack angle. Make sure it is a 90 mm radius blade. Shorten your strokes to 1/2" to 5/8". Change the attack angle, your scrape marks should be 1/8" to 3/16" wide and about the same distance apart. Hard to tell if you are rounding off the edges, but your marks do not go all the way out to the edge, you either rounding over, or the edges have more wear. You want to get it to about 20 PPI before you switch to a 60 mm radius blade where you change to about a 1/4" stroke and concentrate hitting the highs only. Having strokes that goes almost the full width of the part creates less randomness in your checker-boarding. With that pattern you tend to repeat the scraping marks in the same place. Also, i would say at this point stone harder you have very few peaks and the valleys are too wide between them. Finishing a lathe cross slide does not require much more than 20 PPI, except when you plan to use it as the master for the mating part.

dee
;-D

machtool · Oct 7, 2017

Peter. said:
As I said in the general thread it's a good start but you need to get blue on these areas before you start going for points. You're still at the roughing stage until you get the surface down to bring the ends to bear.

Good point about the ends being worn or washed out. That's when a feeler gauge of 0.001" or 0.002" comes into play.If you can still shovel a 2 thou shim in under the ends, you still have a way to go, by bringing the middle down. Probably another 4 - 6 passes. If a one thou feeler is starting to bite, or is only going in 1/2 an inch or so, you can start to shorten up the stroke and tighten the radius.

Regards Phil.

bmarsh · Oct 7, 2017

Thanks for the input. You confirmed where I thought I’m at in the process. I think I may change my attack angle and verify my blade radius and see if I can decrease the width of my scrape marks a bit. I will post again when I think I’m done

AlexO · Oct 7, 2017

Peter. said:
As I said in the general thread it's a good start but you need to get blue on these areas before you start going for points. You're still at the roughing stage until you get the surface down to bring the ends to bear.

View attachment 209478

In my opinion ( worth very little ! ) you're DONE. Now's the time to get a good idea how everything goes together and what needs to be tweaked and where. You're running some risk of having to do everything again.

Peter. · Oct 7, 2017

bmarsh said:
Thanks for the input. You confirmed where I thought I’m at in the process. I think I may change my attack angle and verify my blade radius and see if I can decrease the width of my scrape marks a bit. I will post again when I think I’m done

Your basic scraping is pretty good so I wouldn't go getting too fussy about making too many adjustments. As you move forward you'll find your technique developing quite quickly going by what you've done already. Make sure your scraper is uber-sharp. What are you using to sharpen it right now?

bmarsh · Oct 7, 2017

Peter. said:
Your basic scraping is pretty good so I wouldn't go getting too fussy about making too many adjustments. As you move forward you'll find your technique developing quite quickly going by what you've done already. Make sure your scraper is uber-sharp. What are you using to sharpen it right now?

I’m currently honing the scraper blade with a diamond hand stone until I can get a diamond wheel for my bench grinder. I would love to have one of those accufinish machines but that’s just not an option right now.

Peter. · Oct 7, 2017

I put a 6" diamond wheel on my bench grinder with an ally backing plate. It worked passably well but you had to be careful not to scorch the disk because of the high speed. Now I have re-purposed a slow speed chisel blade grinder to turn the discs at 350rpm and it's much better.

If you have a lathe get a 6" or 8" disc and double-sided-tape it to the faceplate, or remove the jaws from your chuck.

dcsipo · Oct 7, 2017

Peter. said:
I put a 6" diamond wheel on my bench grinder with an ally backing plate. It worked passably well but you had to be careful not to scorch the disk because of the high speed. Now I have re-purposed a slow speed chisel blade grinder to turn the discs at 350rpm and it's much better.

If you have a lathe get a 6" or 8" disc and double-sided-tape it to the faceplate, or remove the jaws from your chuck.

Put an 85[SUP]o[/SUP] wood block on your cross slide, cover everything with a towel, run the lathe 100 to 150 rpm. use windex for lubrication. Get one of those 1200 or 2000 grit lapidary disks. Try to sharpen each side evenly. if you get an 8000 grit diamond hand lap take a few swipes for the finishing blade. For roughing, it really does not matter wether you hand lap. Get a 400 or 600 grit lapidary disk for shaping the blades. They are 10 or 15 bucks on amazon. Amazon.com: 6" lapidary disk

dee
;-D

Peter. · Oct 7, 2017

3pcs 6" Inch Grit 8# 15# 2# Diamond Coated Disc Flat Lap Wheel Lapping | eBay

dcsipo · Oct 7, 2017

Peter. said:
3pcs 6" Inch Grit 8# 15# 2# Diamond Coated Disc Flat Lap Wheel Lapping | eBay

damn...that is a deal.

dee
;-D

MattiJ · Oct 8, 2017

dcsipo said:
damn...that is a deal.

dee
;-D

Thats what I am also using but in 240-600-3000 Grit.
3pcs 6inch Grit 24/6/3 Diamond Coated Wheel Cutting Lapping Disc Flat Lap | eBay
I use them mostly on normal 3000 rpm bench grinder and only problem is that they cut carbide too fast..something you don't hear too often if you are used to sharpening carbide tooling on silicon carbide wheel.

I take the finishing pass on 3000 grit with extremely light touch/pressure, partly because the high rpm's

Peter. · Oct 8, 2017

I bought one of these, fitted an ally backing plate and it works great for those discs - the rpm is perfect and it's even already the right size shaft for the diamond disc's centre hole. So far it's been propped upright in the bench but I'm soon to make a proper stand for it with adjustable tilt. Will take 6" and 8" discs.

MattiJ · Oct 8, 2017

And if someone wants shiny this stuff actually works despite the price:

8pcs 5gram Diamond Polishing Lapping Paste Compound Syring Set .5 - 1Micron | eBay

After 3000 grit disk it takes only couple of seconds to polish the edge with 3 or 1 micron paste.
Less is more with the fine diamond paste, use too much and the insert is just sliding on top of the greasy layer.
Tiny amount something like 1/5 of match head is enough to cover 1-2" wide track on ~5" disk

Richard King · Oct 15, 2017

Sharpening Carbide Blades

Everyones suggestion is fine. But If you mail the blades Steve Watkins over in Navasota TX. He has an ACCU-Finish 2. Also Steve can plane those deep scratches out and help you as he has become an excellent machine rebuilder. He has a thread on here now. Just scroll down the list. Rich

Hopefuldave · Oct 16, 2017

Peter. said:
I bought one of these, fitted an ally backing plate and it works great for those discs - the rpm is perfect and it's even already the right size shaft for the diamond disc's centre hole. So far it's been propped upright in the bench but I'm soon to make a proper stand for it with adjustable tilt. Will take 6" and 8" discs.

Ahh! I knew I rescued two of those from the skip for a reason! Although the ones I have have a swinging arm driven from the spindle, I suspect for optical polishing?

Do you run water/liquid onto the diamond disc when polishing?

Dave H. (the other one)

Monarchist · Oct 16, 2017

Hopefuldave said:
Ahh! I knew I rescued two of those from the skip for a reason! Although the ones I have have a swinging arm driven from the spindle, I suspect for optical polishing?

Can't see your fotos very well

but .. could be.

Time was there were similar polishers at work near conduit ends in ditches all over Hong Kong, (and not-only..) some with MULTIPLE arms polishing ends of several fibre-optic cables at a time. "Dry" - AFAIK, anyway.

I haven't kept up, but ISTR newer connector technology no longer needs as much of that, so there may have been a whole generation of such devices and their discs surplused-off.

Richard King · Oct 16, 2017

I have seen lappers made from old tread mill and sewing machine motors mounted inside welded frames, one young guy who was short of funds made one from wood box. When I taught a class in Sweden we mounted a 600 grit Glendo wheel in a lathe set on 260 rpm and made a angle mount bolted on the compound. For years I used a Baldor grinder with a 300 grit diamond wheel that ran at high RPM, but had to use mineral spirits or coolant to keep the blade cool. One great advantage to a 300 rpm lapper, the blade stays cool. Every time I have seen someone who hand lapped a diamond lap, they were shocked how much better a powered lap worked. Rich

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