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You are correct sir, based on the information I have gleaned from watching the lapping repair-recertification videos anyway.
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Scraping my Shars 4" Milling Vise
- Thread starter macardoso
- Start date
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- Mar 26, 2018
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.003" is a lot to scrape!
We measured the typical depth of scrape to be .0002 to .0003" per scraping session, that's tedious as hell. Too bad you don't have access to a surface grinder.
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Yeah, i'm really roughing hard for such a small surface and the incremental drop in the surface is quite slow. But it is also pretty neat - in my mind - that I can work a surface into precision (hopefully) without access to some of the more precision machining equipment.
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I got another good hour of scraping in yesterday and was pretty spot on with my guess of 1 hour to correct the damage done by the stone.
I now have a nice and flat surface with decent bearing contact. I have a few hollows, but I expect them to fill in as I start high pointing. I am getting about 20-30 points per inch all over with 5 points per inch in the bare sections. All of my contact points are tiny so I only think I have 5% bearing or so. Doesn't quite look like the pictures I see of finished scaping yet.
In the image below I've marked all my high points with sharpie. This both makes it possible to share a picture of the work here as well as helps me when I go to actually scrape this in.
You can see some bare spots in the top left corner, along the very right edge, and a higher distribution at the edges of the bed rails compared to the middle.
What I learned on day 3:
1) A lot of damage can be done to a surface very quickly, and it is very slow to repair
2) A very light rubbing of blue followed by a dry rubbing on the surface plate creates a bunch of blue circles with a burnished (almost black looking) dot in the middle. In the later stages of scraping this makes it easier to see your high points
3) The wide radius of the stock Sandvik blade wasn't too bad to rough with, but I feel I am having accuracy issues with aiming for high points. I have started to develop a tighter radius on the blade but that is a lot of work when shaping completely by hand.
4) I can see my work better with a single overhead light rather than all the lights on in the basement. Makes it easier to get a contrast between the surface and the high points.
I think I will high point for an hour and see where I get to. Would like to see a slightly more even distribution before I call it finished.
Then I get to go back and work on getting the bottom parallel to the bed.
I now have a nice and flat surface with decent bearing contact. I have a few hollows, but I expect them to fill in as I start high pointing. I am getting about 20-30 points per inch all over with 5 points per inch in the bare sections. All of my contact points are tiny so I only think I have 5% bearing or so. Doesn't quite look like the pictures I see of finished scaping yet.
In the image below I've marked all my high points with sharpie. This both makes it possible to share a picture of the work here as well as helps me when I go to actually scrape this in.
You can see some bare spots in the top left corner, along the very right edge, and a higher distribution at the edges of the bed rails compared to the middle.
What I learned on day 3:
1) A lot of damage can be done to a surface very quickly, and it is very slow to repair
2) A very light rubbing of blue followed by a dry rubbing on the surface plate creates a bunch of blue circles with a burnished (almost black looking) dot in the middle. In the later stages of scraping this makes it easier to see your high points
3) The wide radius of the stock Sandvik blade wasn't too bad to rough with, but I feel I am having accuracy issues with aiming for high points. I have started to develop a tighter radius on the blade but that is a lot of work when shaping completely by hand.
4) I can see my work better with a single overhead light rather than all the lights on in the basement. Makes it easier to get a contrast between the surface and the high points.
I think I will high point for an hour and see where I get to. Would like to see a slightly more even distribution before I call it finished.
Then I get to go back and work on getting the bottom parallel to the bed.
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- Mar 26, 2018
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Sitting on hold with a call at work and got another highpointing cycle in (note the tally count on the casting web).
Used Richard King's suggestions from another thread to add contrast (red canode) before bluing. After bluing I rubbed the part on the clean side of the surface plate. Pretty easy to see the high points now.
And with high points marked by sharpie for easy visual
Still have some bare areas (especially under the fixed jaw) but I am getting much better contact. High pointing is slow. I was originally going to do 10 cycles, but it might be more like 5 and see where I get to.
Used Richard King's suggestions from another thread to add contrast (red canode) before bluing. After bluing I rubbed the part on the clean side of the surface plate. Pretty easy to see the high points now.
And with high points marked by sharpie for easy visual
Still have some bare areas (especially under the fixed jaw) but I am getting much better contact. High pointing is slow. I was originally going to do 10 cycles, but it might be more like 5 and see where I get to.
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- Mar 26, 2018
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Highpointing cycle #3
Getting a lot more tiny high points. I can tell there are some areas bearing more heavily, especially the inside edge of the fixed jaw (right of keyway, left side of image), top right of image, bottom left of image, and in general the edges of the rails over the inside.
Getting closer. Think I might make pass #5 only hit the high points in these heavier bearing areas. Will see. Hinging on the surface plate is showing really nice flatness.
Getting a lot more tiny high points. I can tell there are some areas bearing more heavily, especially the inside edge of the fixed jaw (right of keyway, left side of image), top right of image, bottom left of image, and in general the edges of the rails over the inside.
Getting closer. Think I might make pass #5 only hit the high points in these heavier bearing areas. Will see. Hinging on the surface plate is showing really nice flatness.
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- Mar 26, 2018
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Here is after highpointing cycle #4.
I am experimenting with only highpointing the areas where there was lots of bearing to try to even it out. I was taking the very lightest cuts on the surface - probably less than a tenth.
And here is after the blue-up. Notice the middle areas, which were bearing less before and now bearing more heavily. This meant that only the very lightest cut completely changed the bearing pattern, kind of wild. I'm going to selectively scrape only these regions this time, then probably 2 passes over the whole surface and call it quits.
What I learned on day 4:
1) Whatever your distribution of high points is after the roughing phase will continue through highpointing. The highpointing increases the bearing contact all over, but the relative distribution remains the same. So I would say keep roughing until you have an even distribution of high points all over.
2) The hinge test is very sensitive at determining flatness once the surface is moderately well finished. My one partial high pointing pass noticeably changed the hinge test results.
I am experimenting with only highpointing the areas where there was lots of bearing to try to even it out. I was taking the very lightest cuts on the surface - probably less than a tenth.
And here is after the blue-up. Notice the middle areas, which were bearing less before and now bearing more heavily. This meant that only the very lightest cut completely changed the bearing pattern, kind of wild. I'm going to selectively scrape only these regions this time, then probably 2 passes over the whole surface and call it quits.
What I learned on day 4:
1) Whatever your distribution of high points is after the roughing phase will continue through highpointing. The highpointing increases the bearing contact all over, but the relative distribution remains the same. So I would say keep roughing until you have an even distribution of high points all over.
2) The hinge test is very sensitive at determining flatness once the surface is moderately well finished. My one partial high pointing pass noticeably changed the hinge test results.
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- Mar 26, 2018
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The bedways of the vise are done. Did a quick check of the moving jaw to see how it fits up and yeah... gonna be scraping that too.
The moving jaw is very rough on the surface and all the contact is in the middle of the bed rails. I feel like one or two slides of the jaw and my beautifully scraped surface will be all scored up.
I'll scrape this in. Might need to add a groove to the corner so I can get the blade in there. I won't go for as pretty of a surface. Maybe 10 ppi instead of the 30-40 I got on the bed. Then I still need to finish the geometry on the bottom (half done) and get it parallel to the bed. This is a lot of work!
The moving jaw is very rough on the surface and all the contact is in the middle of the bed rails. I feel like one or two slides of the jaw and my beautifully scraped surface will be all scored up.
I'll scrape this in. Might need to add a groove to the corner so I can get the blade in there. I won't go for as pretty of a surface. Maybe 10 ppi instead of the 30-40 I got on the bed. Then I still need to finish the geometry on the bottom (half done) and get it parallel to the bed. This is a lot of work!
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- Apr 23, 2018
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- 6,509
It's just a little vise, he thought, it'll be quick and easy!