I need some advice

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Marc Phillips

Member
Joined
Jun 1, 2004
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Location
Columbus, GA, USA.
Heya all

I am turning a couple of antler pens ... ordered pens. I turn between centers with Johnny's bushings as I do all my pens.

For a reason I am unaware of, the pen blank keeps getting turned off center... there is a noticeable wobble on the head stock end but the tailstock end is spinning true, on both the upper and lower blanks.

I don't know what is causing this unless the antler is warping as I turn it.

I don't know how "fresh" the antler is .... it was given to me to make these pens.

Thanks for any tips you can give me.
 
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Marc, you said there was noticeable wobble in the headstock end, do you mean the spindle is wobbling, or the bushing is not fitting up to the dead center and is wobbling, or just the blank is running out of round? Johnny's bushing shouldn't be a problem, I would suspect maybe the dead center is worn a bit, or maybe it's not seating well in the spindle, OR the worst of all possibilities your bearings are kaputski. :eek:Could even be some CA on the dead center, I apply the CA and sand with the barrel between the dead center and the live center I got tired of scraping the gunk off the dead center, I finally got smart and started making Delrin bushings for CA and sanding.
 
My bad for not being clear...

The blank starts out rough of course... as I spin it round, all is fine. Then as it gets closer to being the finished shape I started getting a chatter with the skew... but not on the tailstock end of the blank, just the headstock end. I looked and the blank was out of round.

I took off a tiny bit more to get it round again and it did it again... I am not able to explain this at all.

I will go check and clean the headstock and check the bushings and all of that... and thanks all for the suggestions.

Let me know if the above makes any sense....
 
As a temporary measure until you can identify the root problem, rough turn, turn to final size on the tailstock end, stop the lathe and flip the blank end-for-end, and turn to final size the remaining end now positioned at the tailstock side.... given that you are using between centers bushings, this is a lot quicker to do than if you were using a mandrel, and allow you to get your order completed.
 
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wolftat said:
How far is your tool rest from the blank when you are turning it?
Click to expand...

It is too far... but I don't have a way to get it closer. I am turning on a Jet 1642 and can't get in closer.

I had JohnnyCNC make me an extended dead center, but that introduced it's own wobble due to the Colet chuck. I have a small round tool rest but it doesn't get me any closer.

You think that is it? ... I can try the extended dead center again... maybe just chuck in into the Nova with the pin jaws or something....
 
lwalden said:
As a temporary measure until you can identify the root problem, rough turn, turn to final size on the tailstock end, stop the lathe and flip the blank end-for-end, and turn to final size the remaining end now positioned at the tailstock side.... given that you are using between centers bushings, this is a lot quicker to do than if you were using a mandrel, and allow you to get your order completed.
Click to expand...

Thanks.... good idea, and will at least get the order out while I try and figure out what the problem is. I honestly started to think it was the antler, since this has never happened with wood or acrylic.
 
Johnny makes a really nice tool rest just for turning between centers. And It's very reasonaly priced.
 
EBorraga said:
Johnny makes a really nice tool rest just for turning between centers. And It's very reasonaly priced.
Click to expand...

It's not the right-left length of the tool rest, it is the way the Jet 16 is designed for larger turnings... you can't push the banjo in any further, and there is still a large gap between the blank and the rest.

I have a Robust tool rest that leans in towards the blank but is wide enough right-left that I can't move it in any further.

Rock and a hard place.

I need a 3 1/2" Robust, but it doesn't exist.
 
I'm using a tool rest that was made by JohnnyCNC and it took away a lot of the chatter I was getting. He is an easy guy to talk to so you may want to contact him about making a custom one for your machine. I do mostly TBC and his short rest is a great size for it.
 
Marc Phillips said:
It's not the right-left length of the tool rest, it is the way the Jet 16 is designed for larger turnings... you can't push the banjo in any further, and there is still a large gap between the blank and the rest.

I have a Robust tool rest that leans in towards the blank but is wide enough right-left that I can't move it in any further.

Rock and a hard place.

I need a 3 1/2" Robust, but it doesn't exist.
Click to expand...

I have the JET1442 and think I know what you need... I have the set sold by Lee Valley with the various round bars, but the post is vertical... it would be more better if we had about a 15 or 20 degree slant/tilt from the top of the banjo hole towards the center line between the headstock and tail stock... with the banjo in all the way over the ways, there is still about an inch or inch and half distance between the pen blank and the tool rest. Plus my post is too long... the tool rest sits a little higher than I would like... not sure if I can cut of 1 inch stainless steel or not.
 
TellicoTurning said:
I have the JET1442 and think I know what you need... I have the set sold by Lee Valley with the various round bars, but the post is vertical... it would be more better if we had about a 15 or 20 degree slant/tilt from the top of the banjo hole towards the center line between the headstock and tail stock... with the banjo in all the way over the ways, there is still about an inch or inch and half distance between the pen blank and the tool rest. Plus my post is too long... the tool rest sits a little higher than I would like... not sure if I can cut of 1 inch stainless steel or not.
Click to expand...

I have one of those modular SS post rest systems... still doesn't reach. I am glad to have someone else looking for a solution with me :)

Right now I am thinking that I just need to cut the corners off my Robust tool rest, since it is the only tool rest I have found that leans in towards the work.
 
Does it do the same thing with a piece of wood instead of the antler? Antler can be softer in the center than the exterior..could be your cutting the soft stuff but not the hard stuff. If it works ok for wood but not antler maybe you can try a freshly sharpened negative rake scraper as you get closer to size..just a thought
 
I agree that you are probably running up against the fact that antler is not consistent in density. The outer shell of compact bone is much harder than the inner core of lammelar or marrow bearing bone. So when you turn a piece of antler and turn into the soft part, your tool tends to bounce or push backwards when it meets the leading edge of the harder section.

The best solution to this is to Turn at maximum speed with a large heavy (and of course, very sharp) tool and to shift your stance and grip so that your forward hand (usually left) is on top of the tool, with all four fingers wrapped around the tool and the heel or palm applying downward pressure against the toolrest. It also helps to position your back hand so that either the fingers or the wrist (depending on how you hold it) can be braces against the hipbone to help minimize in and out movements of the tool. BUT NEVER put the end of the tool against your hip!!!!!! always brace against the hand holding the handle, but with the handle itself projecting past the hip. This might not be quite as critical when turning a pen, but habits learned are usually habits kept, and a good sized bowl blank at medium high speed could very easily catch a tool with enough force to fracture a bone or other unpleasantness if the end of the tool is braced directly against it.
 
It sounds like you having difficulty due to the difference in density of the material. When I turn antler I use thin CA to solidify the soft center and it seems to make it turn more evenly along the entire length of antler.
 
splinter99 said:
Does it do the same thing with a piece of wood instead of the antler? Antler can be softer in the center than the exterior..could be your cutting the soft stuff but not the hard stuff. If it works ok for wood but not antler maybe you can try a freshly sharpened negative rake scraper as you get closer to size..just a thought
Click to expand...

Well.... sure didn't think of that!

Thanks... I will try that...
 
When I do inlays of acrylic in wood I sometimes get chatter because of the difference in hardness. Someone on the forums suggested a wide skew, like over an inch. Also, not that it's germaine to this post, but I saw a video of a guy drilling antler on a lathe and instead of chucking the antler in the headstock he chucked up the drill bit and then held the antler in his hand so he could drill through the pithy part of the antler. I've only made a few antler pens and that's what I did.
 
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