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Lathe changing center while turning

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Forum topic by PlankPenguin posted 09-16-2019 02:07 AM 465 views 0 times favorited 8 replies Add to Favorites Watch
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PlankPenguin

3 posts in 36 days


09-16-2019 02:07 AM

Topic tags/keywords: question lathe turning

So i’ve recently had a problem with my new lathe.
While i was working on a Piece of about 20cm length, i noticed, after truing my spindle, that when i was working in the middle of it, the livecenter side off the spindle wasn’t running true anymore.
When working near the live center, the middle wasn’t true anymore.

This started getting really annoying, when i started working on a pool cue.

What could cause this?
Is it my tools not being sharp enough, or is my lathe no good?

Thanks for the Help


8 replies so far

View MrUnix's profile

MrUnix

7482 posts in 2712 days


#1 posted 09-16-2019 02:20 AM

For long thin spindles, like a pool cue, you really need a steady rest or other means to support the work piece and keep it from deflecting. Kind of hard to determine from your description, but it sounds like that may be problem.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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PlankPenguin

3 posts in 36 days


#2 posted 09-16-2019 07:05 AM

I have a shop built steadyrest (seen in the attatched pic) but even with the steadyrest this problem occurs…
But i thought if that even hapens with spindles that are about 6” long, that i would not need a steadyrest for those.

Cheers Penugin!
https://s3.amazonaws.com/vs-lumberjocks.com/pxwxipw.jpg!

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Wildwood

2743 posts in 2647 days


#3 posted 09-16-2019 09:27 AM

Do you get the same result with spindle blank mounted on the lathe turning by hand?

Think 20 CM little more than 7” or just 6”’s long would not think need a steady but could be wrong. You don’t say what type of drive center using or chuck but think don’t have a good hold of spindle blank.

If using a four prong drive center that is not properly seated could be the problem especially if ends of the spindle blank not perfectly square. Whether using a four prong or step center have to provide a hole made with an awl on each end so center point either of these centers and also live center can hold the blank. Normally not a problem for live center if that end not perfectly square as long as have a hole for live center.

OEM four prong centers (come with the lathe) notoriously bad!

That’s why prefer a two prong center, over four or step centers ends don’t have to be square. Mark centers provide hole each end seat my two prong center seat into blank with mallet mount in lathe bring up tailstock and tighten. Would use same procedure for four prong center.

If using a 4-jaw chuck don’t seat the end of the blank up against the back of the chuck, make sure have marked and used an awl for live center. I just use jaws of chuck and bring up the tailstock with blank seated in hole provided for live center before tighten jaws.

I would use more than one steady for blank pictured!

Good luck with it.

-- Bill

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Wildwood

2743 posts in 2647 days


#4 posted 09-16-2019 12:25 PM

If you can wiggle the headstock spindle with your hand could need bearings or have a bent headstock spindle!

-- Bill

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PlankPenguin

3 posts in 36 days


#5 posted 09-16-2019 04:25 PM

i just tried the lathe again and I think it really is my four prong drive center.
But since i only have a faceplate, and that isn’t really good for spindles, i’ll have to try to get my spindle more attatched to my drive center.
The problem seems to be, that i’m able to make my piece turn more true and less true, depending on the rotation of the wood in regards to the drive.
And when i use my tools to much it just seems to shift ever so slightly causing the problem…

View Nubsnstubs's profile

Nubsnstubs

1619 posts in 2243 days


#6 posted 09-16-2019 06:07 PM

Penguin, try this. Mount a piece onto your lathe about an inch or two longer than the finished length. Turn the end at the tail stock to just under 3/4” OD. Remove it from the lathe, remove your spur center and insert the 3/4” end into the lathe spindle. Use the dimple made by the spur to center the work piece at the tail stock. Tighten and start turning. If it’s steady and not wobbling around, then it’s your spur. If it still wobbles as you are cutting, it could have too much pressure between centers causing flex. Relax the tension at the tail stock being careful here as too much can cause the piece to take flight. It’s worth a try.

when i was working in the middle of it, the livecenter side off the spindle wasn’t running true anymore. If that’s true, the dimple at the live center should be a lot larger than what you started with. When you get the off center action again, stop and check for any looseness at the live center. Also, check to make sure the quill is locked. If not, it could have sloppy tolerance that could cause wobble. If not locked, it could possibly unscrew causing that off center situation you mentioned. ................ Jerry (in Tucson)

-- Jerry (in Tucson) www.woodturnerstools.com

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Wildwood

2743 posts in 2647 days


#7 posted 09-16-2019 08:33 PM

Does your lathe have a Morse taper (MT1 or MT2) or solid threaded spindle? Also what size headstock spindle and TPI do you have? Like said before OEM four spur drive leave a lot to be desired and perhaps an after market spur center might work better whether lathe has Morse taper or solid threaded spindle.

Any out of round spindle blank can wobble little bit until trued with a roughing gouge. Also seems your not getting the spur drive seated into the blank.

-- Bill

View kaerlighedsbamsen's profile

kaerlighedsbamsen

1309 posts in 2226 days


#8 posted 09-16-2019 08:50 PM

If it is the live center side that is making trouble it is probably not the drive side that is the problem. Sounds more like a loose bearing or bent tip of the live centre

-- "Do or Do not. There is no try." - Yoda

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