Shaper Scraping Help

[Richard King 2]

Now that I have my students teaching as I expect them to do, I am going to watch. Jon & Jeff, please talk about the checkerboard pattern and PPI and POP from the pic of the blued ram please explain how it should be blued all the way to the edge and where the 3 points under plate are placed and using a feller gage to be sure blue goes to the edge, I also suspect the ram bottom is side to side convex as in John Saunders parallel..

Pete I know you are learning here and I hope before you try to show members or if your doing You Tube, be sure you know what your doing before trying to teach others what your doing. Hobby The Vacaville class Jon coordinated.

 

[Pete301]

Now that I have my students teaching as I expect them to do, I am going to watch. Jon & Jeff, please talk about the checkerboard pattern and PPI and POP from the pic of the blued ram please explain how it should be blued all the way to the edge and where the 3 points under plate are placed and using a feller gage to be sure blue goes to the edge, I also suspect the ram bottom is side to side convex as in John Saunders parallel..

Pete I know you are learning here and I hope before you try to show members or if your doing You Tube, be sure you know what your doing before trying to teach others what your doing. Hobby The Vacaville class Jon coordinated.

Thanks again Richard for all your help. I’ll take your teaching concern to heart and avoid ever doing that. Of course at this point,if I tried to teach scraping it would be the worlds’ shortest video!
Pete

 

[Pete301]

Pete, we don't really care if the slot is flat and parallel with anything, just the ways. There should be some information here or on youtube about 'hinging' the part, it should swivel on each end about 30% in from the ends. If it does, it's flat. And if it's flat, they are on the same plane.

Stefan Gottswinter talks about hinging in the beginning of this video;

I'll be interested to see how you test the angled surface of the dovetail (male) to see if they are consistent to the flat ways.
Thanks for the video. A lot to absorb.
I'm impressed with your effort. That will be a cool machine with a cool story when you are done.

Thanks for the video. A lot to absorb there.
I put 3 pads on the surface plate and below is a photo of the current ram coverage. Also a photo of the setup I used to measure the ram angled ways to check if they were parallel.
I’m confused about putting the ram on 3 points. Do I do that while both scraping and measuring? Or just measuring. It would seem likely that the ram would move around on me while I try to scrape it on the 3 points?

 

[eeler1]

Clever fixture for measuring the dovetail, Pete. Blue up those surfaces too, so you get a sense of the plane and not just the single line.

I'll be offline for a few days. I don't have the experience to teach, but have a grasp of the basics. I hope Richard keeps chiming in here, especially on measurement of the geometric surfaces.

The 3 points usually involves two at one end and one at the other. Here's a reference;

https://demonstrations.wolfram.com/StaticEquilibriumForAPlateWithSupportAtThreePoints/

Set those points about 30% in from the ends and you get minimal sag of the piece. Hard to do with an odd shape like you have. Hence Keith Ruckers cradle with two points touching on each side of the casting at one end, and creating the single point under the bottom at the other.

That picture of the scraped bar that Richard posted is a pretty good representation of what you want the ways to look like. You don't want 100% blue. About 40-60% blue is the goal, kinda splotchy and evenly distributed. The bare (low) spots will hold oil so it gets spread around as the ram cycles.

You get that pattern by alternating the direction of your scraping, 45* across the ways, then switching to the other 45* and scraping again. Testing for hinge and flat and blue coverage after each or each couple of passes. Looks like you have been doing a crosshatch, but perhaps a bit more aggressive would give a more definite pattern.

As RIchard mentioned, it's important to not roll the edges (which is easy to do) by lifting off the part as you scrape to the edge. And test with the part on the surface plate, using a feeler gage to see if you have gaps around the edge. You are going to scrape to the lowest point on the ways, might as well know where that is early on.

Only other suggestion I can offer right now is to watch some youtube videos by people who have a background in the process. We mentioned Stefan Gottswinter and Keith Rucker. There are others too. Stick with conventional methods and you won't get too far off into the weeds.

 

[Richard King 2]

Just want you all to know Stefan and Keith and 30,000 other folks around the world are part of my student family. They are teaching what i taught them

 

[Pete301]

Clever fixture for measuring the dovetail, Pete. Blue up those surfaces too, so you get a sense of the plane and not just the single line.

I'll be offline for a few days. I don't have the experience to teach, but have a grasp of the basics. I hope Richard keeps chiming in here, especially on measurement of the geometric surfaces.

The 3 points usually involves two at one end and one at the other. Here's a reference;

https://demonstrations.wolfram.com/StaticEquilibriumForAPlateWithSupportAtThreePoints/

Set those points about 30% in from the ends and you get minimal sag of the piece. Hard to do with an odd shape like you have. Hence Keith Ruckers cradle with two points touching on each side of the casting at one end, and creating the single point under the bottom at the other.

That picture of the scraped bar that Richard posted is a pretty good representation of what you want the ways to look like. You don't want 100% blue. About 40-60% blue is the goal, kinda splotchy and evenly distributed. The bare (low) spots will hold oil so it gets spread around as the ram cycles.

You get that pattern by alternating the direction of your scraping, 45* across the ways, then switching to the other 45* and scraping again. Testing for hinge and flat and blue coverage after each or each couple of passes. Looks like you have been doing a crosshatch, but perhaps a bit more aggressive would give a more definite pattern.

As RIchard mentioned, it's important to not roll the edges (which is easy to do) by lifting off the part as you scrape to the edge. And test with the part on the surface plate, using a feeler gage to see if you have gaps around the edge. You are going to scrape to the lowest point on the ways, might as well know where that is early on.

Only other suggestion I can offer right now is to watch some youtube videos by people who have a background in the process. We mentioned Stefan Gottswinter and Keith Rucker. There are others too. Stick with conventional methods and you won't get too far off into the weeds.

Thanks for the advise and 3 point reference info. I’m making progress