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Forum topic by fladdy posted 11-03-2014 11:33 PM 2437 views 0 times favorited 16 replies Add to Favorites Watch
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fladdy

93 posts in 2481 days


11-03-2014 11:33 PM

Topic tags/keywords: pen turning lathe

Over the past fall, I’ve tried my hand at turning pens. I tried again today, but had a few problems and was wondering if anyone has had any similar issues. My biggest issue is when I go to put the gouge to the wood, the wood stops spinning. So I would stop the lathe, tighten everything down and get the same result. I bought a few different nuts and the same thing would happen. I have sharpen the tools so I don’t think that’s the issue.

I’m using a lathe from Harbor Freight with an adaptor and a screw in mandrel from Penn State Industries. Today I had to tighten the nuts so tight that the brass tube crimped and caused the wood blank to break off into chunks.

I don’t think that I should have to tighten the mandrel so tight that it crimps the brass tubes, but am I doing something else wrong? Any tips or thoughts is always appreciated.
Thanks.

-- Fladdy


16 replies so far

View Bill7255's profile

Bill7255

354 posts in 1752 days


#1 posted 11-03-2014 11:50 PM

Something is definitely wrong. I think you need to post a picture of your setup. You said you tightened the “nuts” indicating there is more than one. The pen mandrels I have have a thumb screw. Depending on the pen I sometimes need a spacer to avoid running out of threads. Post a picture.

-- Bill R

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Madwood

68 posts in 2519 days


#2 posted 11-03-2014 11:57 PM

I’ve turned a few dozen pens using the same setup and never had a problem like what you describe. The only thing I can come up with is maybe you’re using the incorrect bushings for the kit? Each style kit has dedicated bushings which are generally not interchangible with others. Other than that…I got nuthin’.
John

-- In the shop making chaos out of order

View fladdy's profile

fladdy

93 posts in 2481 days


#3 posted 11-04-2014 12:21 AM

Well, I can’t post a picture as the mandrel is no longer straight. ;)

Bill: The thumb screw would never stay tight by itself so I got a few nuts to fit on the mandrel. I first tried it with one nut and it would loosen up. So I put a second nut as well to help hold things tight. I have been using extra bushings to avoid running out of thread as well

Madwood: I’m using 7mm bushings to make some slimline pens. And the other bushings I got to match the pen kits.

Could the RPM’s be too high or low? Could there be something wrong with the mandrel itself? Those are the only things that I can think of.

-- Fladdy

View cebfish's profile

cebfish

129 posts in 2156 days


#4 posted 11-04-2014 12:38 AM

Are you sure the the blank is glued to the tube. sometimes the glue fails and the blank spin on the tube

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fladdy

93 posts in 2481 days


#5 posted 11-04-2014 12:44 AM

Didn’t think of that. I’m using thick viscosity CA glue but I’ve read that a lot of people prefer epoxy. I do have some thin CA glue that I could try. But I am able to do some turning (3 secs) after tightening things before it spins again. It almost always lets me do some turning after tightening things so I don’t think the blanks are spinning, however it’s not something that I was considering.

I may have to try the epoxy once I get a new mandrel.

-- Fladdy

View Bill7255's profile

Bill7255

354 posts in 1752 days


#6 posted 11-04-2014 01:49 PM

You can straighten the mandrel. Put it on the lathe turn by hand and use a dial indicator to find the high spot and gently push. After a couple of times it should come back. Bent mandrel is from too much pressure from tail stock, however could be you have a bad mandrel. I also prefer epoxy over CA for gluing the blank to the tube. Thin CA will not work for gluing the wood to the blank. If you want to run a test cut a short blank leaving about a 1/4 inch tube exposed. Then turn to see if the wood is slipping around the tube.

-- Bill R

View gwilki's profile

gwilki

121 posts in 941 days


#7 posted 11-04-2014 04:33 PM

Fladdy: Can you post a link to the mandrel you are using? Pretty much all the ones that I’ve seen use a round brass thumb wheel to tighten against the bushings. You should not need to do any more than finger tighten it to make it work. It will not loosen. If anything, it will tighten because the lathe is turning toward you, so the nut wants to tighten.

Also, do not tighten the tailstock too strongly against the end of the mandrel. It will easily bend the mandrel. Even if the bend is not permanent, your blanks will turn oval, not round. Does the live center in your tailstock have a 60 degree point? Some of the stock ones do not.The divot on the end of the mandrel is drilled at 60 degrees. Ideally, you want the live center point to match it.

In the classes that I’ve taught, the major cause of the problem you are describing is that the student is jamming the tool into the square blank. Until you knock the corners off, it will take nothing to stall the blank. You need t start with very, very light cuts.

What tool are you using?

-- Grant Wilkinson, Ottawa ON

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fladdy

93 posts in 2481 days


#8 posted 11-04-2014 06:50 PM

Here’s the link to the mandrel I was using:

http://www.pennstateind.com/store/PKM-BL.html

Let me clarify one thing, the mandrel wasn’t bent when I got it or was using. It is now bent due to my frustrations.

The live center is a 60 degree point. I’m using a 3/8” gouge to try and get the blanks round. I just sharpened it prior to using it. The blank would stall if I touched it with a pencil or my finger.

The brass thumb wheel would come loose. I could watch it spin off slightly and that’s why I added a few nuts behind it to keep it from coming loose. Which is weird since it’s threaded to tighten when spinning. I think I’m going to have to get a new mandrel and try it again. It doesn’t seem right that the blanks would stall so easily.

-- Fladdy

View gwilki's profile

gwilki

121 posts in 941 days


#9 posted 11-04-2014 07:12 PM

No offence meant, Fladdy, but the lathe is not running in reverse is it? I ask because, as you and I agree, it does not make any sense that the thumb wheel is coming loose. In my course, I have the students stop the lathe from time to time to loosen the thumb wheel, as it tightens by itself and can cause problems.

I repeat; I am not trying to be a smart ass. I’m just trying to help out.

If you would like to take this off line, so to speak, just send me a private message and we can go from there.

-- Grant Wilkinson, Ottawa ON

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fladdy

93 posts in 2481 days


#10 posted 11-04-2014 07:16 PM

Ha ha! I’m not offended. The lathe is not spinning in reverse, I’m sure of that. It is a good thought and would definitely cause problems.

-- Fladdy

View Bill7255's profile

Bill7255

354 posts in 1752 days


#11 posted 11-04-2014 09:19 PM

I haven’t used that style mandrel. I do not understand the brass part near the head. But that mandrel should work. Like gwilki I do not understand the thumb screw coming loose. I only speculate the threads are incorrect on the mandrel. Since the mandrel is bent and guessing no value to you here are some off the wall possibilities; If threads are bad you might try deforming them slightly with a chisel to make the nut harder to move or you might try putting a small o-ring between the nut and bushing. Hang in there, this is solvable.

Bill

-- Bill R

View gwilki's profile

gwilki

121 posts in 941 days


#12 posted 11-04-2014 10:49 PM

OK, Fladdy, some more ideas – ‘cause this is really getting to me.

I am stumped as to why the thumb wheel is loosening. Physics would dictate this is impossible. However, if you snug it up and put a jam nut on the outside of it, there is no way it can loosen. Once that is no longer an issue, you can address the blanks spinning problem. (I am assuming that the blanks are spinning even when the thumb wheel is snug. If that is not the case, then nothing I say below here is relevant.)

Are the ends of your blanks nice and square to the ends of the tubes? If they are not, the bushings are not making good contact with the blank, and the blank with spin. (You will also have gaps when you press on the components, but that’s another problem entirely.)

Like Bill, I have never seen a mandrel with a brass fitting on the headstock end. What does it do? Could it be what is loosening? If it is some kind of threaded nut designed to accommodate various blank lengths and bushing lengths, it would have to be left hand thread to prevent it from loosening. Just for giggles, can you take it off, and simply add a dummy blank to make up for the added length? If you can, what happens?

Finally, if I’m causing you more grief with all these questions than your original problem, just say so and I’ll go away. I’ll be crushed, but I’ll go away. :-)

-- Grant Wilkinson, Ottawa ON

View mpax356's profile

mpax356

67 posts in 1960 days


#13 posted 11-05-2014 12:04 AM

So what speed are you turning at? Should be in the high range maybe 2000 – 3000 RPM. Use a light touch with the tool.

-- MPax, Atlanta

View JADobson's profile

JADobson

682 posts in 1579 days


#14 posted 11-05-2014 03:34 AM

I’ve had similar problems, not sure why. One thing I found useful was to remove the point from my live centre and the locking nut from the mandrel and then snug the live centre against the bushings. It has worked well for me. Only problem I have now is that one of my mandrels unscrews from the morse taper while the lathe is spinning. Can’t figure out why. Probably just loc-tite it in there.

-- James

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fladdy

93 posts in 2481 days


#15 posted 11-05-2014 07:25 PM

Thanks everyone for the thoughts. Sorry to cause so much frustration! Mine does not have a brass fitting near the headstock. This must be a new “feature” as mine doesn’t have that.

I do square the blanks with the blank squaring tool, maybe I’m taking too much off, or not enough. This could be something I experiment with.

My other thought was maybe just lock citing the brass nut to the mandrel and unscrew it the hole piece from the headstock and use the bushings to take up the slack rather than having the brass nut be the “tension” adjustment.
I should probably check my RPM’s as well.

Thanks for all the thoughts. Once I get a new mandrel (might be awhile) I’ll let everyone know if it’s working and what tricks helped.

-- Fladdy

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