Strange problem

[monophoto]

I got my start in woodturning making pens, but I've sort of wandered away, and now only occasionally make a pen using a commercial kit.

The lathe I started on had an MT1 spindle. I have since upgraded to a lathe with an MT2. That's significant to the problem I just encountered. Rather than purchasing a new pen mandrel, I opted to purchase a sleeve that allows me to use my MT1 mandrel in an MT2 spindle.

To the best of my recollection, I've made two pens since I upgraded lathes. The first used a typical two-blank 10mm pen while the second was a 7mm stylus that only had one blank.

So this afternoon, I went into the shop to make another pen using that same 10mm kit that I used last year. I got to the point of mounting the blanks on the mandrel, and found that I couldn't extend the rod in my adjustable mandrel far enough to accommodate the blanks and bushings for the 10mm kit. After fussing a bit, I eventually concluded that the end of the rod was mushroomed very slightly - just enough to keep it from sliding into the body of the mandrel. Now I could understand how that could happen if I had been using the mandrel on the MT1 lathe - repeatedly using the knockout bar with the mandrel adjusted so that the rod protruded slightly from the end of the taper could easily cause it to deform. But what I can't understand is why I didn't have this problem when I made that last 10mm pen, and it how it could happen I was using the mandrel with a sleeve - the knockout bar only comes in contact with the sleeve, it never touches the mandrel itself, much less the rod.

The solution was simply - carefully grind the mushroom from the end of the rod.

But how did it happen?

 

[Rockytime]

I got my start in woodturning making pens, but I've sort of wandered away, and now only occasionally make a pen using a commercial kit.

The lathe I started on had an MT1 spindle. I have since upgraded to a lathe with an MT2. That's significant to the problem I just encountered. Rather than purchasing a new pen mandrel, I opted to purchase a sleeve that allows me to use my MT1 mandrel in an MT2 spindle.

To the best of my recollection, I've made two pens since I upgraded lathes. The first used a typical two-blank 10mm pen while the second was a 7mm stylus that only had one blank.

So this afternoon, I went into the shop to make another pen using that same 10mm kit that I used last year. I got to the point of mounting the blanks on the mandrel, and found that I couldn't extend the rod in my adjustable mandrel far enough to accommodate the blanks and bushings for the 10mm kit. After fussing a bit, I eventually concluded that the end of the rod was mushroomed very slightly - just enough to keep it from sliding into the body of the mandrel. Now I could understand how that could happen if I had been using the mandrel on the MT1 lathe - repeatedly using the knockout bar with the mandrel adjusted so that the rod protruded slightly from the end of the taper could easily cause it to deform. But what I can't understand is why I didn't have this problem when I made that last 10mm pen, and it how it could happen I was using the mandrel with a sleeve - the knockout bar only comes in contact with the sleeve, it never touches the mandrel itself, much less the rod.

The solution was simply - carefully grind the mushroom from the end of the rod.

But how did it happen?

I use a plastic mallet.

 

[KenV]

There are two mandrel to MT mounts I have seen. One has the mandrel threaded into a mating threat in the MT. The other uses a collet schema where a nut compresses the collet to hold the mandrel. Sounds like you have the latter


1. Do you have a cat? At our house, all strange outcomes are attributed to the Cat being involved.


2. Could the mandrel have been dropped onto a hard surface -- like a concrete floor. That force is enough to raise a burr or distort the end if that is where it hits first.

There are a lot of things that could be speculated

 

[flyitfast]

TBC !! Turning Between Centers. All you need is a dead center for the headstock end and a 60 degree live center for the tailstock and a inexpensive Harbor Freight digital calipers to measure the hardware. Don't need bushings any more. Put the blank between the centers. Turn blank down until the ends match the hardware measurements, allowing for sanding. Then finish the middle part anyway you want to.
Works for me.................gordon

 

[79spitfire]

If you have ever removed the adapter sleeve from the mandrel, they often use a wedge to pop the MT1 from the MT2 adapter. How many times have you changed which piece is in the adapter? The shaft is not hardened steel, and if the wedge is hitting the end it could mushroom it.