Working on my DIY Tool Post Grinder-Ugh

Janderso

Janderso

Jeff Anderson
H-M Platinum Supporter
Joined
Mar 26, 2018
Messages
8,672
I thought three was a charm.
I have thrown four hunks of metal in the scrap bin. Under sized the resistance fit for the inner race.
It's been a journey and I'm learning a bunch.
I found run out in my MT6 to MT4 dead center adapter for my lathe spindle. So I cut my own in a three jaw. Solved one problem.
Then I found too much runout in my live center, switched to another. Got that worked out.
Set up the tail stock to stop turning a .002" taper over 6". Now I'm within 0002"
Now I just need to learn how to not over shoot my spec of .5907".
I sneak up on it with a sharp HSS tool bit. Cut the last .003" and blow it by .001" ish.
Maybe 5 is a charm. Fortunately I have a 10' piece of 1" 1018.

Grrrr.
Hey, if you aren't making mistakes you aren't learning right!!
 
Maybe switch to a friendlier material? 12L14, 1215 or 1144?
 
Last edited:
Janderso said:
I found too much runout in my live center, switched to another. Got that worked out.
Click to expand...

If you need absolute concentricity, it's hard to beat a dead center in the tailstock.

It's a little fiddly figuring out just how tight is tight. If you're warming up the workpiece, and it's got any length to it, you've gotta remember to back it out and run it back in now and then so it doesn't over tighten. But the wobble on 'em is absolutely zero.....

Janderso said:
I sneak up on it with a sharp HSS tool bit. Cut the last .003" and blow it by .001" ish.
Click to expand...

3 on radius or diameter? if it's three on diameter, that's one and a half on the tool bit, and while good sharp HSS tools will take a fraction of that, especially in mild steel, it's hard to get predictable results. Set your dimension 0.030 over the final, take three passes with the "sharp" tool at 0.010 (five thousandths cut) as a minimum, so it LANDS on the number. Sneaking up seldom never ends well.

Or after you're done learnin' and need a part- once you realize you're off track and gonna be close, leave it a whisker high, a file (good lathe file), or emery tape can bail you out. Making some presumptions about your finish, the first thousandth comes off FAST, and it really slows down after that. Care and measuring and adapting your technique with emery tape to not put a "belly" in the journal, or taper the end down... if it's a few tenths to a few thousandths, Even if you wanted to, you don't have enough meat left to take it out of round before you get it down to dimension.
Take one of the scraps, which has YOUR finish on it, pick a dimension just below (wherever it's at), and play with it. Or heck, pick a dimension and see EXACTLY how small of a cut you can take three times in a row to get the same diameter reduction three times in a row, while landing on a target.

When you say "resistance fit", you're talking about a "two squished thumbs will push it home" press fit? If you're after that, check the bearing tolerances.... And if you're after that, your final part might appreciate a more "polished' finish. Straight off of the lathe, you'll be sitting "lightly" on high spots that are gonna go loose in short order. "Cheating with files and emery will get you more contact surface for a transitional fit to stay that way over time.
 
Jake M said:
If you need absolute concentricity, it's hard to beat a dead center in the tailstock.

It's a little fiddly figuring out just how tight is tight. If you're warming up the workpiece, and it's got any length to it, you've gotta remember to back it out and run it back in now and then so it doesn't over tighten. But the wobble on 'em is absolutely zero.....



3 on radius or diameter? if it's three on diameter, that's one and a half on the tool bit, and while good sharp HSS tools will take a fraction of that, especially in mild steel, it's hard to get predictable results. Set your dimension 0.030 over the final, take three passes with the "sharp" tool at 0.010 (five thousandths cut) as a minimum, so it LANDS on the number. Sneaking up seldom never ends well.

Or after you're done learnin' and need a part- once you realize you're off track and gonna be close, leave it a whisker high, a file (good lathe file), or emery tape can bail you out. Making some presumptions about your finish, the first thousandth comes off FAST, and it really slows down after that. Care and measuring and adapting your technique with emery tape to not put a "belly" in the journal, or taper the end down... if it's a few tenths to a few thousandths, Even if you wanted to, you don't have enough meat left to take it out of round before you get it down to dimension.
Take one of the scraps, which has YOUR finish on it, pick a dimension just below (wherever it's at), and play with it. Or heck, pick a dimension and see EXACTLY how small of a cut you can take three times in a row to get the same diameter reduction three times in a row, while landing on a target.

When you say "resistance fit", you're talking about a "two squished thumbs will push it home" press fit? If you're after that, check the bearing tolerances.... And if you're after that, your final part might appreciate a more "polished' finish. Straight off of the lathe, you'll be sitting "lightly" on high spots that are gonna go loose in short order. "Cheating with files and emery will get you more contact surface for a transitional fit to stay that way over time.
Click to expand...
Very good advice
Especially the .010" approach.
I actually decided to cut it large by .002 but somehow even screwed that up. The lathe file was my plan :)
I'm not mad just disappointed in myself.
 
Janderso said:
Very good advice
Especially the .010" approach.
I actually decided to cut it large by .002 but somehow even screwed that up. The lathe file was my plan :)
I'm not mad just disappointed in myself.
Click to expand...
And use the emery paper/cloth with a backer (like a paint stirring stick) to keep it flat.
 
You know, if you had a tool post grinder, getting that last.001 would be trivial... Just sayin'! Hang in there, Jeff.
 
Your more persnickety than me. I would just run a center punch around the i.d. and smack the bearing in. Mike
 
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