Scraping help/advice appreciated

I am wanting to learn how to scrape for flatness/alignment and eventually how to scrape for points and for the ways of a lathe/mill.

I understand conceptually how it works but
Wanted to ask before I put anytime / money into making equipment.

Any pointers or help would be greatly appreciated.

Also does anyone know the condition of the large surface plate in the metal shop?

You need a straight edge to be able to scrap in any ways. Additionally your mini-lathe is probably not worth the trouble to scrap in since it does not have the mass. The way you would do it is grind in the ways in the bed then scrape the carriage & compound to match the re-ground ways.

In your case the fruit is not worth the squeeze. Point is, if you move your machine and not get it exactly level again, the point is moot. By level, I mean with a precision level such as the Starrett 98-6.

I am aware of the limitations of my 7x14 import mini lathe,

for me scraping it in would be about the journey as well as the destination,
and to learn on something that is relatively inexpensive and very easy to find parts for.

I plan on buying nicer machines in the future and would much rather make any beginner mistakes on a “cheep” mini lathe.

@TBJK Do you know the state/grade of the large surface plate?

No, we do not know the grade. Did you have a straight edge? Preferably a camelback straight edge?

I don’t have a proper camelback straightedge.
I do have a small cast iron blank,
I thought scraping in a small straight edge would be a good place to start.
but the resulting straightedge would probably only be big enough for the cross slide.

A am looking to get a hold of a larger straight-edge casting though.

Looks like he is only selling the 9 inch camelback castings at the moment.

You might run into problems with it. Is the casting stressed relieved? You might have problems getting it flat since it’s not a camelback. They are certainly more temperamental about temperature changes. There are several places you can get a fresh new camelback, if that’s what you might be after. Otherwise eBay will have the smaller sizes you might want. This guy pours them fotodoc on eBay

This guy in England makes them as well.

Windyhill foundry was doing the straight edges for Keith. So he is another source.

Thanks for the sources, I’m not ready to buy a casting yet though.

I don’t know if the cast iron I have is stress relieved, but I have used it before and it machines nicely I also did not notice any distortion.

Do you know if we have any scraping tools at DMS,
Or would I need to buy/build them myself?

also, is it ok to use Prussian Blue Fitting Compound such as this on the surface plate?

Thats going to be probably a little too thick, you will need to thin it some. How do you plan on holding your cast while you scrape it? You will likely need to make a fixture to keep it from moving on you. It will help if you use 2 contrasting colors, you will also need rollers to roll it out for each color.

Here you can see we used red & yellow.

I believe one of these magazines has an article about scraping

I’ll let you know when I drop off the magazines at the machine shop.

probably a vice with paper towels or a super glue “arbor”, or maybe a wood fixture.

Do you know if anyone has a larger straight edge I could borrow when I get around to scrapping the ways?

Or anyone that may be willing to provide in-person instruction for scraping?

Thanks, that would be great.

I probably won’t be able to make it to DMS this coming week though.