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Lathe Turning out of Round

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Forum topic by J. Crate Larkin posted 443 days ago 1062 views 0 times favorited 6 replies Add to Favorites Watch
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J. Crate Larkin

19 posts in 559 days


443 days ago

Topic tags/keywords: question lathe turning

I posted a while ago about my Jet JWL 1220 with bed extension turning spindles out of round, even when the centers were only a few inches apart. I am utterly perplexed by this problem, because there seems to be no reason for it to happen. I have just ruined another beautiful tiger maple spindle, so I thought I would post this question, not being as well versed in the mechanics of turning on this type of lathe as some of my fellow WWs. The question is: my other two lathes (both cheap, homemade models) have dead centers in their tailstocks and turn perfectly. Is it possible that it could be the live center in the Jet’s tailstock that is the culprit? (Sorry, but at this point I’m just grasping at straws here.) Thanks in advance for any insight you may be able to provide.

-- J. Crate, Maryland


6 replies so far

View David Kirtley's profile

David Kirtley

1276 posts in 1625 days


#1 posted 443 days ago

I would check the alignment of the headstock and tailstock. If the center were the problem, it would be noticeably wonky.

First things I would have suggested if you had not said other lathes were not having the same issues:

Check that you are not over tightening the tailstock. It will flex the workpiece. Also make sure that the center spurs and the live center are deep enough and you are not pressing too hard. Can also be a problem of the tools being too dull (or not ground properly or presented to the wood at a good angle) and too much force is bending the workpiece.

Steps I would take were it mine:

If it is bolted down, you might be twisting the bed. Check it for straightness and level.

Take headstock loose and check for any burs or foreign objects under it. Same for tailstock. This is the most likely source of misalignment.

How you can test the alignment:

Buy a piece of hollow linear rail shaft (mcmaster carr sells and much cheaper than test bar and accurate enough for a wood lathe) and use it for a test bar and run up and down the machined edge of the bed with a dial gauge to see if it is parallel to the bed. It can fit between centers. You can get a dead center for your headstock as well. You do not do this with the piece rotating. A test bar can be made but a bit beyond what you can do without chucks and adequate through spindle clearance on a lathe without a fixed height tool holder that can travel the length of the bed.

Once you figure out what is going on, you can shim the headstock parallel. Tedious but not hard.

-- Woodworking shouldn't cost a fortune: http://lowbudgetwoodworker.blogspot.com/

View MNgary's profile

MNgary

235 posts in 1044 days


#2 posted 443 days ago

If either the live center in your tailstock or the center in your headstock is not perfectly true that could be the problem.

-- I dream of the world where a duck can cross the road and no one asks why.

View Rick M.'s profile

Rick M.

3873 posts in 1007 days


#3 posted 443 days ago

Mine does that if the tailstock loosens and slips backward. Look at the hole where the live center has been and see if it looks wallowed out. You might try drilling a shallow 5/16 or 3/8 hole in the wood blank so the live center can get in there nice and snug with plenty of bearing surface.

-- |Statistics show that 100% of people bitten by a snake were close to it.|

View Wildwood's profile

Wildwood

989 posts in 762 days


#4 posted 443 days ago

From looking at your picture, wonder tools are sharp enough? Looks like you are forcing dull tools to cut. If alignment already pretty close try sharpening your tools more often. Let tool do the cutting, don’t force them.

Before checking alignment clean head/tailstock Morse taper. I use shotgun bore brush & shop vac.

I use a dead center in headstock and live center in tailstock to check alignment. Wish had two dead centers for alignment checks.

Tailstock has to be locked down, during this check. You can actually see tailstock move into alignment as you lock it down on some lathes.

If lathe bolted to bench insure all bolt have even torque before checking alignment.

Yes, OEM live centers not always the best. You can always buy a live center and use that in tailstock. That is least expensive op, over buying a new live center.

On your lathe could always loosen headstock hex bolts and try to bring it into alignment with tailstock if have a left or right alignment or add shims for height issue. Not big fan of shims on tailstock but they work too.

-- Bill

View REO's profile

REO

597 posts in 701 days


#5 posted 442 days ago

the head stock and tail stock being out of line will not cause an out of round turning. nor when turning with chisels will it cause a tapered turning! when the centers are not tight enough to prevent the center from traveling in the soft grain and causing an oblong slot that the center slides in as it spins or the tail stock bearing center is wearing out the soft grain grabs and the hard grain gets bounced over. These can cause an out of round turning especially when scraping instead of shear cutting. check the end where the tail stock has been supporting it . Is the hole round or oval?

View Grandpa's profile

Grandpa

3078 posts in 1302 days


#6 posted 442 days ago

I believe the machine will turn perfectly round stock. When one of the centers move then the out of round turning occurs. If the tail stock for instance can slip to the side or the center is worn and moves or it slips in the wood then it is off the center line. Then the out of round begins.

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