Delrin Bushings

[montmill]

I've searched the topic but really haven't found what I was looking for. I have and use delrin bushings on a "A" mandrel. Unfortunately the pens I'm making now use a "B" mandrel and I can't find delrin bushings for a "B" mandrel. I bought a rod of delrin and will have to make my own I guess.

 

[magpens]

The "B" mandrel is of larger diameter than the "A".

Could you drill out the hole in the Delrin bushings so that they fit the "B" mandrel ?

 

[montmill]

I thought of that but I'm not sure how to get a good grip on the bushing without squeezing it out of round.

 

[KenB259]

I bought some delrin rod awhile ago just for the purpose of making my own finishing bushings. I finally got around to doing that today. Was pretty easy actually.


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[magpens]

@montmill
Possible method ... never tried, but it might work.
Put the Delrin bushing on an A mandrel held in Jacobs chuck in tailstock. . This would get the bushing aligned with axis of lathe.
After gripping in headstock chuck, withdraw the A mandrel and replace it with drill bit of appropriate size.
Drill (carefully and slowly).
The hole doesn't need to be enlarged by very much, so if you drill carefully and slowly, you don't need a "heavy" grip on the Delrin bushing.
The 4-jaw headstock chuck should compress the Delrin quite uniformly, so I'm betting there won't be any out-of-round.

To get down to specifics, the A mandrel has a diameter of 0.246", while the B mandrel is 0.291" (both +/- 0.002") according to my online source.

So you are enlarging the hole by only 0.045".

Probably drill with an M drill (0.295"). . An L at 0.290" is prob. too small. . Drilling with M, the hole will prob. be just about right by the time you retract the drill and the hole springs back down in size slightly. . You could do the drilling in two stages, if you want, to keep the stresses down and permit a "lighter" grip in the headstock jaws.

EDIT: But .... As Ken just said, making your own Delrin bushings is easy peasy so that's probably the better way to go.

 

[montmill]

Thanks, I may try drilling one since my rod is ordered from Amazon and I'm sure they have other more important things to ship.

 

[wolf creek knives]

Like ken, I made my own. However, I epoxied a 7mm tube into the Delrin and then turned it down just shy of the brass to a tip. Any pen I make that I use them on will easily stay below the blank being turned. I've yet to have any trouble with them and for bigger brass blanks (8mm+) I simply lightly set the tail stock, turn the lathe on at a high RPM and they center themselves.

 

[leehljp]

There are several places that metric bits can be ordered in tenths of a mm. 7.1, 7.2, 7.3, 7.4 7.5.

7.4 would be the closest I think.

 

[darrin1200]

I've searched the topic but really haven't found what I was looking for. I have and use delrin bushings on a "A" mandrel. Unfortunately the pens I'm making now use a "B" mandrel and I can't find delrin bushings for a "B" mandrel. I bought a rod of delrin and will have to make my own I guess.

Are you talking about the cone style delrin bushings used for applying a finish?

Like these?

If so, then you don't need a special set. You shouldn't need to use the "B" mandrel. It's the cone shape that works for these, not the mandrel.
Unless I'm misunderstanding, and you only have a "B" mandrel. If that's the case, it might be worth while to pick up an "A" mandrel just to add to your toolbox. There are a lot more kits that use the "A" mandrel, than the "B" mandrel.

 

[montmill]

Some interesting ideas. I thought I'd just put them between centers but ended up with the brass ends cupped out due to brass on metal. I do have an "A" mandrel and could certainly try that. At one time I made different sized inserts to go inside various non 7 mm brass out of white oak but I can't seem find them. Using them I only needed the "A" mandrel.