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8th July 2021, 11:50 AM #16
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8th July 2021 11:50 AM # ADSGoogle Adsense Advertisement
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8th July 2021, 11:57 AM #17
AFAIK, there are three types of misalignment for tail stocks:
- Simple misalignment, when every time you slide the stock away and back, the misalignment is the same every time.
eg. Xmm too high & Ymm to the left, etc., etc.
Often this can be remedied by re-aligning with either adjusters or shims. - Slop in the ways. Normally any vertical misalignment will remain constant, but it may vary in the left/right (or back/forth if you prefer) direction.
eg. Xmm too high, but varies between Xmm too far left and Xmm too far right.
This typically needs the gap between the ways to be re-machined parallel and the tailstock re-adjusted/modified to suit. It's also a PITA, and is WHY we often recommend the kiss test when looking for lathes to buy. You do not want this lathe. - A poorly made live tail spur. This is obvious, as all you need to do is bring the points up to kiss and then rotate the live spur. The point will orbit around the drive spur point in a circle of fixed radius.
Easily fixed... replace the spur if it bothers you that much. Just don't mistake this for a tailstock issue, as you can spend a lot of money trying to 'fix' a non-existing problem.
As I alluded to in my earlier post, I suspected the latter in my case. As a matter of curiosity, I checked it yesterday and yup. It's the culprit.
It is of the type where it's a stamped cone pressed onto a bearing... and apparently it's a bit 'cam shaped.'
'Twas about 1mm out of true on the lathe, but I could bring it back to true by removing the cap from the bearing, rotating it about 45° and pressing it back on. Admittedly it took a few tries to get it positioned correctly.
I anticipate that it will rotate out of position again in the future, but as I also said earlier, that doesn't worry me. This particular spur is one I only use on long spindles because of it's short length. Using it, I can fit spindle blanks up to 3cm longer than I can with my good double-bearing spur on my existing bed w/out the need to eff around with an extension bed. (Been doing a lot of copy turning of balusters. Booooooooring!)
- Andy Mc
- Simple misalignment, when every time you slide the stock away and back, the misalignment is the same every time.
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16th July 2021, 06:20 AM #18GOLD MEMBER
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I'm not going to follow up with exactly what everyone else has said except 1 point. If something is not square, it will all come out in the wash, if no changes to the machinery is made in between cuts. Here is a rolling pin, made with (post cut discovery) a saw blade that cut slight off 90deg. after glue up, and each subsequent rotation from the same start point, the celtic knot is absolutely perfect in joint size and alignment (due to exact replacement of removed material) and the lathe slightly off in alignment 0.5mm. not noticable over the 900mm length.
Rolling pin.jpg
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16th July 2021, 06:22 AM #19GOLD MEMBER
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16th July 2021, 08:37 AM #20
Yes, that is correct to a point. However the nature and scale of the error/s is in your favour.
The error in verticality of the saw cut, will not have any appreciable effect (once turned) because in reality all of the inserts are square to each other, IF as you correctly point out - "no changes to the machinery is made in between cuts" & OR the blank is not flipped end for end for any of the cuts.
The error in lathe center alignment is 0.5 mm in say 450 mm or about 1 : 900. Not really going to be noticeable on a 30 to 45 mm cylinder to anyone but the most fastidious craftsman.
Now those same errors on a 12 to 15 mm diameter cylinder 35 to 60 mm long (a pen blank) will be quite apparent to most viewers. The shorter and thinner the work piece the more apparent the error.
For an experienced craftsman on architectural turnings a 0.5 mm center alignment error wouldn't even raise an eyebrow, but for thin spindles, i.e. finials etc, its a real problem that has to be accommodated.Mobyturns
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16th July 2021, 10:30 AM #21
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17th July 2021, 02:04 AM #22GOLD MEMBER
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