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| Taper question |
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| AdeV:
My lathe is turning a taper... :( The piece is ~7.5" diameter, and has had a few thou turned off it, as you can see. The length being measured is around 1.5". It is tapered 0.003" (thinner near the headstock)... I tried cutting using both the cross-slide - which I thought may be slightly off-line, hence the taper - but the final cut was taken using the carriage on power feed - cutting away from the headstock - which had the same result (so, as it transpires, it looks like I got my cross-slide straightened up nicely :D) What's out of line to cause that? The spindle? I'm not sure it can be anything else, unless I'm doing something stupid somewhere? The taper attachment is not in use... Also, although I'm using a 4-jaw chuck, the disc was dialled in to within a few tenths, maybe 1/2 thou once I'd cinched all the jaws down hard. |
| CrewCab:
If it's an error in the turning then headstock bearings seem the first thing to investigate, however, have you measured the work piece at both ends with a mike or vernier, just wondered if it could be a bed error assuming the gauge is mounted on the carriage? ................ :scratch: then again I could be woofing up the incorrect tall leafy thing :wack: CC |
| ieezitin:
Adve. Your in the sweet spot for bed ware there being close to the chuck, your saddle does a lot of movement at that point! One thing to check. Your chuck is it seated firmly on the nose? Are there any burrs and or crud on the threads?. Stick a clock on it and see if there is movement and or check the threads. If you have a test bar slam in a dead center and rig up to tailstock and dial in and or make cuts if necessary if its a consumable bar, this will tell you once you have truth if you cut again and there is a variance then the bearings may be failing. Are you using excessive oil in the spindle bearings? So many variables that you need to knock down one by one. it’s a PITA in your situation but a process of elimination from here out. Hope this helps. Anthony. |
| Darren:
Somebody please feel free to correct me if I'm wrong, but even if the headstock was slightly out of alignment it would still cut straight. Not straight with the reas of the bar in the chuck but the cut area wouldn't be tapered. Same goes for not being true in the four jaw chuck. |
| ieezitin:
Darren. Hope this drawing works. I have tried to answer your question as I read it. Please feel free to ask or tell me if I have your question wrong. Adev. Your chuck jaws could be going a scew over that length too. You may not have a problem other than the jaws in the chuck. All the best . Anthony. |
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