I have a 1947 South Bend 9C horizontal bench lathe with 48" bed that I am having an issue with regarding the headstock alignment.
I am the second owner of the lathe and purchased it from a golf course where it was used to clean up shafts for the mowers so not used a lot.
Most of the bed flaking is still present and there are no dings in the bed and no significant bed wear.
I have the lathe mounted on a 2" laminated bench that is bolted to a concrete floor and to the wall so a very rigid setup.
I have leveled the lathe using a precision level that is .0002/10in so is is level at the headstock and tailstock ends within 1 division on the level.
When I do a 2 collar test I am getting about .004 taper over 8 inches so a lot more than I should be getting. It was larger at the headstock end.
I was able to get the taper out by purposely twisting the bed but did not like leaving it like that as I knew there had to be something else going on.
I needed to put about 0.05" of shims on one side of the tailstock foot to get the taper out over the 8 inches.
So I re-leveled the bed and the then checked the headstock alignment. I used a backplate with a bolt in it that I cut a flat on the head.
I put a test indicator on the carriage and set the indicator to 0 with the bolt closest to the operator. I then rotated the spindle 180 degrees so that the bolt was furthest away from the operator and saw that it was off by a little over .003" so this really surprised me as I did not expect this. This was over about a 6" circumference.
But this confirmed that the headstock was skewed towards the operator and was causing a taper in the 2 collar test by pointing the bar towards the operator at the tailstock end.
So I pulled the headstock off to see if there was anything under it which there was not, and then cleaned all the mating surfaces and put it back in place.
I repeated the test with the backplate and again it was still off by .003".
Since there is no way to adjust the headstock, and I did not want to just start grinding on the headstock I put a 0.004" brass shim under the back edge of the headstock at the inside of the V facing the operator thereby twisting the headstock counterclockwise as viewed from above. I tightened everything back down and checked to make sure the bed was still aligned and then repeated test with the backplate and it was not off by about .0005" from front to back so a lot better.
I then did another 2 collar test and it was better but not perfect so I shimmed the bed at the tailstock end but only needed about .015" of shims to get the rest of the taper out so a big improvement. When I did the 2 collar test after shimming, I was able to get to less than .0005" over 8 inches so very acceptable. I then repeated the 2 color test after aligning the tailstock to the headstock and again I was able to less than .0005" over 8 inches.
Now the lathe is cutting as expected but I still have the shim under the headstock.
My questions are these:
Has enyone else ran into an issue like this and if so how did you fix it?
Is it OK to shim the headstock to get the twist out?
Any ideas on how it got to be this far off?
I should state that I do not know if there was a crash on the machine at some time in the past that may have warped the headstock of even if it was replaced.
Any thoughts or suggestions would be welcome.
Thanks, Dan
I am the second owner of the lathe and purchased it from a golf course where it was used to clean up shafts for the mowers so not used a lot.
Most of the bed flaking is still present and there are no dings in the bed and no significant bed wear.
I have the lathe mounted on a 2" laminated bench that is bolted to a concrete floor and to the wall so a very rigid setup.
I have leveled the lathe using a precision level that is .0002/10in so is is level at the headstock and tailstock ends within 1 division on the level.
When I do a 2 collar test I am getting about .004 taper over 8 inches so a lot more than I should be getting. It was larger at the headstock end.
I was able to get the taper out by purposely twisting the bed but did not like leaving it like that as I knew there had to be something else going on.
I needed to put about 0.05" of shims on one side of the tailstock foot to get the taper out over the 8 inches.
So I re-leveled the bed and the then checked the headstock alignment. I used a backplate with a bolt in it that I cut a flat on the head.
I put a test indicator on the carriage and set the indicator to 0 with the bolt closest to the operator. I then rotated the spindle 180 degrees so that the bolt was furthest away from the operator and saw that it was off by a little over .003" so this really surprised me as I did not expect this. This was over about a 6" circumference.
But this confirmed that the headstock was skewed towards the operator and was causing a taper in the 2 collar test by pointing the bar towards the operator at the tailstock end.
So I pulled the headstock off to see if there was anything under it which there was not, and then cleaned all the mating surfaces and put it back in place.
I repeated the test with the backplate and again it was still off by .003".
Since there is no way to adjust the headstock, and I did not want to just start grinding on the headstock I put a 0.004" brass shim under the back edge of the headstock at the inside of the V facing the operator thereby twisting the headstock counterclockwise as viewed from above. I tightened everything back down and checked to make sure the bed was still aligned and then repeated test with the backplate and it was not off by about .0005" from front to back so a lot better.
I then did another 2 collar test and it was better but not perfect so I shimmed the bed at the tailstock end but only needed about .015" of shims to get the rest of the taper out so a big improvement. When I did the 2 collar test after shimming, I was able to get to less than .0005" over 8 inches so very acceptable. I then repeated the 2 color test after aligning the tailstock to the headstock and again I was able to less than .0005" over 8 inches.
Now the lathe is cutting as expected but I still have the shim under the headstock.
My questions are these:
Has enyone else ran into an issue like this and if so how did you fix it?
Is it OK to shim the headstock to get the twist out?
Any ideas on how it got to be this far off?
I should state that I do not know if there was a crash on the machine at some time in the past that may have warped the headstock of even if it was replaced.
Any thoughts or suggestions would be welcome.
Thanks, Dan