OD grinder tilt table pivot wprn to 2 thou clearance....how to repair

The stud bearing surface shows a little wear maybe some slight galting and measures 1.3749 , the hole is a good 2 tho

over....

My first thought was to lap the pivot hole out round and make a new hardened oversize stud. The depth to

diameter is about half though.

I dont know If i could get a straight hole ....

makes me think I really should go for a jig grinder .

I suppose I could put the tilt table up on the bridgeport and use a boring head to just clean up the hole ....

The big stud pivot is internal threaded

3/8-16 down the center for which I take to be only a lock.


Any ideas how a more experienced person would repair this?

Thanks
Dave

Generally I don't repair it but just use 2 dial indicators on the table, one at both end for making adjustments, adjusting to the difference on both indicators.
If the table will be servo swiveled to grind different features in one cycle during running I make a bronze bushing to run on or better yet replace with a needle roller bearing setup boring the hole oversize and making a new hardened pivot pin.
Bob

If it is a running fit (intended to move or rotate) then how much clearance would you choose. Perhaps it is wore less than you think. The out of round of the male and female portion might be a better indicator of wear.

If the male is centered (has centers)I would have it spray built up and grind.. but if it is .001 under new size i would not touch it...depending on the ability of the machine likely would not touch it for .003

If the male is not a centered part then likely you could not get .0015 to the original part center..so you would need to make a new part..Fixing it likely I would do just that... just make a new part with having centers. so you with that might get only .0005 better.

Yes if really needing you could spray the ID.. set it up on a jig grinder for the ID and make a new male part with centers.

lalatheman said:

The stud bearing surface shows a little wear maybe some slight galting and measures 1.3749 , the hole is a good 2 tho over....

Click to expand...

Might I ask, why do you care ? In general, I throw a test part up, touch it end-to-end, measure it, adjust the taper, grind, measure, adjust, until the taper is gone. Done. Now grind away happily. What do you gain by having the pivot be a super-accurate fit ?

SeaMoss said:

Might I ask, why do you care ? In general, I throw a test part up, touch it end-to-end, measure it, adjust the taper, grind, measure, adjust, until the taper is gone. Done. Now grind away happily. What do you gain by having the pivot be a super-accurate fit ?

Click to expand...

Well, that's one way to do it. If you have a good pivot that the table rotates about truly, you can calculate(or just learn from prior experience on that machine) how much each .001" of movement at the end of the table affects taper/inch. Then it's just a matter of touching off in two places, calculating the difference, offsetting the table a know amount with an indicator, and you're taper free.
As CarbideBob pointed out, you can do much the same if the pivot is not good by using two indicators to show actual rotation and eliminate the error due to slop in the pivot. It's just a little more of a PITA. If I was doing multiple set ups per day in that machine, I'd probably want to fix it too, if I had the time.

Derek Smalls said:

If you have a good pivot that the table rotates about truly, you can calculate(or just learn from prior experience on that machine) how much each .001" of movement at the end of the table affects taper/inch. Then it's just a matter of touching off in two places, calculating the difference, offsetting the table a know amount with an indicator, and you're taper free.

Click to expand...

Except he said the hole was a big-ass .002" over .... I'm sorry, I don't see two thou as making doodly-squat of diffference in this case. If it was fifty or something, yeah, but two thou on a one and three-eights bore ? On a grinder where you have to mess with the taper anyhow ? bfd.

I think he's stroking it

SeaMoss said:

Except he said the hole was a big-ass .002" over .... I'm sorry, I don't see two thou as making doodly-squat of diffference in this case. If it was fifty or something, yeah, but two thou on a one and three-eights bore ? On a grinder where you have to mess with the taper anyhow ? bfd.

I think he's stroking it

Click to expand...

True, except when making very fine adjustments. It's a grinder, so you're typically looking to get things pretty straight, that means adjusting the table to better than .001". When the pivot is sloppy, it's like trying to indicate a vise on a mill without one end clamped, you can do it, but what a pita.