New mandrel problem!!!

[alscalls]

My brother in law helped me make a new blind mandrel

I tried it out last night and some today........

Something seems a little off so I indicated it in my four jaw and it was off a few thousants but not much at all......I tried it again and BANG!!!.........

Scared the crap out of me ........
It is chattering something awfull......I can not get a smooth cut at all.
I can not seem to get it to quit the chatter  Any thoughts on whats causing it?

[HaMeR]

What were your RPM's set at Al. You'll have more catches on a slower turning piece than a faster one. And are the bearings tight on the top & bottom pulleys?

Glad you didn't get hurt too!! 

[BigB]

Are ya supporting the cantilevered end with the tailstock?  Mine chatter some too when I don't support the end with the tailstock.


Brian

[Bills Custom Calls]

Take your belt off and look for a slight flat spot that will cause you problems also

[alscalls]

No tail stock.....That is why I made it outa stainless real hard stuff and it dont give much.
If I run my pen mandrell everything is fine....
I do not know the RPM's I will fool with that some.
I have more belts I will look.
Thanks guys

[BigB]

No tail stock.....That is why I made it outa stainless real hard stuff and it dont give much.

All metals have a natural frequency that make them vibrate.  Just like a tuning fork.  Without the tailstock supporting it, certain things can make the natural frequency come alive, and you essentially have a rotating tuning fork.


When is it chattering?  Does it only chatter when your tools are touching the wood as it is turning?  The tool touching the wood may be exciting the natural frequency.  A different turning speed may cure the chattering.


When did the chunk come off of the blank?  Did it come off while sanding, while a chissel was cutting on it, or just while the blank was turning?  The pin lock mandrels work on the premise that the pin will get lodged in the corner between the mandrel and the wood blank as the blank spins to secure the blank from spinning on the mandrel.  If the wood is a fairly soft wood, the pin will keep working itself into that small corner.  As the pin does this, the pin will start to try to make the hole in the call blank an oval shape if enough pressure is put on it.  If it creates too much pressure, the wood may crack or even blow out similar to your case.


Brian

[alscalls]

I only notice it when the tools are touching it.........I have not tried chaging speeds yet. The tool marks are strange, almost like wrinkles in a flag blowing in the wind on the inside dia. of the call and spiral on the outside.
I do see a big dent on the inside from the pin.
I got some sharpening to do and I may try it on my other lathe to get the RPM's a lot faster.....going to be a while I am on overtime and my truck is busted  too much to do....
Thanks 

[HaMeR]

Soft wood & dull tools can mess things up Al. I'm sure you know that. Hard woods & dull tools can make that pin dent the inside from too much pressure against the wood while trying to make them cut. I still think upping the RPM's will help once you get your tools sharp again. I've seen those same marks on this acrylic type stuff I'm turning too. I just run the tool across the blank slower than normal with a very light cut. Hope you get it figured out. Too bad about your truck too. I hope you get it fixed up & running again!! I've just dumped a bunch of $$ in mine this year too.

[alscalls]

I have spent a couple thousand on trucks here of late
I could have had a new e-caller but it will have to wait.