Are kit transmissions true/concentric?

[underdog]

I seem to have noticed that after a pen is put together that the pen gets "banana shaped".

Am I doing something wrong, or are these kit pen trannies a little bent?

 

[mredburn]

I have actually chucked the 8mm tranny up and use it to hold and turn the tranny coupler. Rarely do they runout of round beyond a couple of thousandths. Which trannies are you refering to. It is possible to press them in crooked. Doesnt take much.Generally I give the tranny just a gentle start and then release the pressure so it can seat in the tube and them push it in the restof the way.

 

[Fibonacci]

I had that problem on one pen (that comes to mind), but it was because I bent the transmission while installing it.

 

[underdog]

I don't think I'm cocking or bending them when pressing them in. I s'pose I could be wrong..

Here's how I do it:
I generally try to start the transmissions by hand, then set the barrel on a piece of MDF mounted in the drill press vice, and push the transmission in the rest of the way with the flat part of the drill press chuck.

You can sort of "feel" when it's going right. 14 years working on mechanical things gives you a good feel for when things are threaded correctly, and I think also gives you a good feel for when the press fit is right...

Does it make a difference if the transmission is retracted or extended?

 

[flyfishermanmike]

I've had the same thing happen with a few, cheap slimline kits. Only when looking closely does it look like the pen it bent at the middle. I've started lightly sanding the ends of my pens before assembly and that seems to help the overall fit and this problem. I just made a little sanding mill so I can do it on the lathe now. Much quicker than by hand. I patterned mine off the guy here who sells them. His are much prettier than mine...

^^ike

 

[ed4copies]

Jim

I'm guessing you are referring to the 7mm tranny.

Lots of things contribute to "how that goes". I did hundreds one Christmas where they were ALL VERY tight in the 7mm tube. I have a one ton arbor press, so I know I WILL conquer it--but several bent.

Then, I realized I could use a chainsaw file and file out the inside of the 7mm tube a little, BEFORE seating the tranny. They became easier to install and I didn't bend any more.

You may want to try this. I have a full set of chain saw files now--5 different sizes.

 

[Sylvanite]

My experience is that there is a little play present in 7mm transmissions. If the pen upper and lower barrels are not colinear, then the problem is likely to be out-of-square barrels.

Try pulling the barrels apart slightly and see if you can wiggle the halves.

Regards,
Eric

 

[76winger]

One other thought I have is the possibility of a small amount of glue on the inside of the tube where you press the transmission in. It wouldn't take much to skew the angle ever so slightly. Do you check for, and remove any glue inside the tubes prior to assembly?

 

[hunter-27]

Jim

I'm guessing you are referring to the 7mm tranny.

Lots of things contribute to "how that goes". I did hundreds one Christmas where they were ALL VERY tight in the 7mm tube. I have a one ton arbor press, so I know I WILL conquer it--but several bent.

Then, I realized I could use a chainsaw file and file out the inside of the 7mm tube a little, BEFORE seating the tranny. They became easier to install and I didn't bend any more.

You may want to try this. I have a full set of chain saw files now--5 different sizes.

Another thing that makes them easier to install:

 

[ed4copies]

Landon,
That helps AFTER the chain saw file. The ones I did needed to be adjusted farther down into the tube than a chamfer tool would reach.

But, after filing, the chamfer tool WILL remove any burr you may have created--it's a good habit with ALL kits.

 

[hunter-27]

:wink:

 

[okiebugg]

banana shaped....

Landon,
That helps AFTER the chain saw file. The ones I did needed to be adjusted farther down into the tube than a chamfer tool would reach.

But, after filing, the chamfer tool WILL remove any burr you may have created--it's a good habit with ALL kits.

What they said. plus

I used to have the same problem once in a while. Took a long time to figger out.

Lightly retouch the ends of the finished blank/tubes to your end mill before fitting the parts together. I've noticed that on a few pens that use straight bushings that don't fit inside the tubes but secure right to the end of the wood/tube you can actually have the bushings indent the wood and cause a slight loss of the tube being square to the blank. Thus the pen mill
No glue in the tubes

 

[ed4copies]

Good observation---makes sense, to me!!