Pen Mandrel keeps coming loose

[Dan Jansen]

I came across a deal the other day, 19.5” Lathe and a whole bunch of unopened pen blanks, parts, etc. According to the seller, it came from a guy who was going to try out turning and never started. The chisels were still covered in wax. I don’t think anything was ever used.

I decided to give pen turning a go with all these new toys and am running into a problem. Most components are Penn State and I’m guessing the Lathe was part of a kit at one time. My mandrel (7mm) threads onto an adaptor. The Lathe has what I think is 3/4” 16 tpi threads and I screw on an adapter that is 1” - 8 tpi threads. The mandrel mounts to this adapter. The long 7mm bar of the mandrel is working loose every time I start to hit the blank with the roughing gouge. I try to tighten it but it’s like it’s spinning the wrong way and working loose. It’s coming loose on the headstock side. I attempted to use a jam but but there isn’t enough threads to make that work. I just thought of trying thread locker as I type this but I’m wondering if I just have the wrong mandrel?

Link:https://www.pennstateind.com/mm5/mer...e=pen-mandrels

[Kyle Iwamoto]

Reverse?
Use your tailstock.

[John K Jordan]

I attempted to use a jam but but there isn’t enough threads to make that work. I just thought of trying thread locker as I type this but I’m wondering if I just have the wrong mandrel?

Do you mean a jam nut? You might easily use a die to extend the threads. But your problem sounds very odd. The mandrel in the picture looks fine.

Have you tried very light cuts with a freshly sharpened tool? (I prefer a sharp skew for roughing small diameter spindles.) Perhaps you can ask a local turner in your club to take a look at what you are doing. Or take a video.

JKJ

[Paul Williams]

With a right hand thread and the lathe running in the normal direction shouldn't the mandrel rod tighten with use?

[Richard Coers]

You aren't turning on the back side are you?

[Dan Jansen]

One thing I found on another site is misaligned centers can cause it to come loose. I definitely have that and mine are a 1/4” off when I’m out the length of the mandrel and about a 1/16” when touching. Looks like my bargain is going to take some shimming. I’m going to attempt to adjust the headstock and see what that does.

[david privett]

there is a # 1 and#2 pen mandrel so you might not have the correct one for the spindle and I would suggest picking up a mandrel saver vs using a live center in the tail shaft to the pen mandrel end cone.

[Dan Jansen]

My lathe (no MT taper, no name 500mm Chinese lathe) was the likeliest culprit. I added locktite to the headstock side of the mandrel then leveled out the lathe and just like that, I turned my first pen! The third thing is it was possible the super glue didn’t cure quickly in 40 degree shop and that the wood was spinning on the barrels but cured properly over the 24 hours that it sat while I was troubleshooting. I’m not really sure but thought someone else may come across this and find it useful.