Slight wobble? - Woodworking Talk - Woodworkers Forum
 
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post #1 of 10 Old 01-29-2011, 04:39 PM Thread Starter
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Slight wobble?

I haven't turned many bowls, but I have noticed that the ones I have done always have two spots opposite each other that are a little rougher than the rest. At first I just attributed this flaw to my lack of experience.

Today I noticed that the headstock and tailstock are out of alignment by about 1/16". Although I was getting a very slight vibration as I roughed out the bowl sides, I thought everything would even out after I put it in the chuck. It didn't. You can see in the pic how the tool is cutting smoothly but there are rough spots opposite each other once more (well, I guess you can't see the one on the other side).

I'm using a JET 1442VS that I bought over the summer and a PSI Barracuda chuck that I bought about the same time. The chuck jaws are a little loose when open, but seem good and tight when I crank it down on the workpiece.

Is my problem more likely the headstock or the chuck? The noob factor? Something else? I was going to call JET today but it seems they won't answer the phone until Monday. You guys will probably be better help, anyway.

Rob
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post #2 of 10 Old 01-29-2011, 05:10 PM
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Can you improve alignment by loosening and retighten the headstock? If not need to adjust leveling bolts at bottom of legs.
I removed shelf and concrete blocks and shelf, lift lathe with car jack and adjusted leveling bolts until head/tailstock aligned on my Jet 1642. Took half hour of fussing with it.
Do not think headstock or chuck run out is a problem for rough spots 180 out. . I could be wrong about that! Some folks might recommend changing bevel angle on your bowl gouge, not sure that is your problem. Think sharper tool, lighter touch and perhaps higher/lower lathe speed might solve your problem.
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post #3 of 10 Old 01-29-2011, 07:34 PM
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The 1442 has a rotating headstock so it may just simply be out of alignment with true 0. That's the first thing I'd check.

Take the chuck off and put in a spur drive (with the point) and align it with your tailstock live center. Then if you still have run-out with the chuck I would suspect your chuck insert/adapter.
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post #4 of 10 Old 01-29-2011, 07:41 PM
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The alignment problem is unrelated to the rough spots on the wood in the picture. The two rough spots are due to the wood grain direction, the fixes are: sharp tools, tool technique and sanding. Some woods are just difficult and require more sanding but most can be cut cleanly with practice.

The alignment issue will be a problem only when the wood is fixed at the headstock (faceplate or chuck) and you are using the tailstock. Then you may have uneven wall thickness, chatter and general aggravation.
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post #5 of 10 Old 01-30-2011, 01:08 AM
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The rough spots are due to grain orientation like the last response stated. Sharper tools, lighter cuts and more correct bevel angle should eliminate most of this. Certain woods are more prone to this than others. Dry wood versus green will also contribute. When all else fails, sand it into submission
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post #6 of 10 Old 01-30-2011, 08:12 AM
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I thought your lathe came with same legs as Jet 1642 model. You can also loosen and retighten bolts/screws use to mount lathe to bench. The ways on both these lathes can bow uneven tightening can throw head/tailstock out of alignment. With legs have to mess with leveling bolts.

OEM centers (prong/revolving) not always the best quality make sure you lock down tailstock when checking alignment.

You might find this tool helpful: http://www.packardwoodworks.com/Merchant2/merchant.mvc?Screen=CTGY&Category_Code=lathes-acc-mrstool

Also dirty Morse tapers head/tailstock might not allow centers to seat properly. A taper mate can solve that problem. A cheaper alternative is shotgun bore brush and cleaning rod. I use both.

http://www.packardwoodworks.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=packard&Catego ry_Code=lathes-acc-tapacc-tapmt

Amazing how great minds work everyone picked up on sharper tools, lighter touch, lathe speed. Guy mentioning 80 grit turning tool to address unruly wood grain hit the nail on the head.
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post #7 of 10 Old 01-30-2011, 08:29 AM Thread Starter
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Quote:
Originally Posted by Neal Addy View Post
The 1442 has a rotating headstock so it may just simply be out of alignment with true 0. That's the first thing I'd check.
That's a good point. I didn't think of that. I'll definitely check it.

As for sharpening, my skills/knowledge are certainly lacking. I may work on that for a week or two before I even turn the lathe back on. I'll also try a different bevel.

If it ends up being a matter that sandpaper can easily correct, then I'm not too worried about it. I have noticed that I can see light through the walls of a few bowls except in two spots opposite each other, though, so I'm thinking something is keeping me from cutting evenly (should have mentioned that before).

You guys have given me plenty of ideas to work with. I appreciate it. I'll be out today, but I'll let you know when and if I figure something out. Please let me know if anything else comes to mind.

Thanks,
Rob
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post #8 of 10 Old 01-30-2011, 01:28 PM
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Rob that could be simple wood movement also.

Tim
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post #9 of 10 Old 02-06-2011, 11:26 AM Thread Starter
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This weekend I made some changes based on the feedback you all gave me and it has made a difference.

First, I easily adjusted the headstock so that it lined up with the tailstock and felt pretty stupid about not doing that in the first place.

I researched sharpening more, changed the bevel on the tool, and I think I've improved my technique a little there. The gouge is definitely sharper, anyway. That has allowed me to make much lighter cuts and still make progress.

Though these things made a noticeable improvement, I found that Slatron was right on - I am getting some wood movement as well.

Great advice everyone. I was pretty frustrated before but I'm beginning to feel better about it.

Thanks,
Rob
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post #10 of 10 Old 02-07-2011, 10:37 AM
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There is an excellent woodturning club in Cincinnati. You will be able to find lots of good advice and maybe some hands on teaching that will go a long way toward improving your turning.
What you were seeing in the photo is not wood movement I don't believe. It's mostly just not cutting clean. Sharpening helps, reducing the angle of the cutting edge can help. Spray some water on and try another pass. It can help. Try not pushing the tool so hard. When you force a cut it raises the fibers and pulls the out leaving a look like that. Lighten up and slow down how fast you are feeding the tool.
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