Drill size for 1 1/4 tap

[larrystephens]

I am making a vacuum fixture for my 1 1/4 headstock and have a 1.25x8 tap. Chart says I need a 1 11/64" drill bit. Wondering if anyone has done this and what range of drill bit would work. I am drilling into HDPE material.

 

[Dieseldoc]

I am making a vacuum fixture for my 1 1/4 headstock and have a 1.25x8 tap. Chart says I need a 1 11/64" drill bit. Wondering if anyone has done this and what range of drill bit would work. I am drilling into HDPE material.

Hey Larry: I have made several adapters with using a beal trap and drilling with 1 1/8 bit in HDPE material . Go slow and use lot of lube

 

[greenacres2]

1 11/64 converts to 29.77 mm, so a 30 mm may work as well. That said, since you have a lathe…how about hollowing a blank on the lathe? No need to buy a bit that way.
Earl

 

[rherrell]

I agree with Earl, for a hole that size you don't need a drill bit.

 

[JimB]

I use a 1-1/8 forstner bit for wood and other materials. I've never done it on HDPE.

 

[larrystephens]

In making my vacuum chuck, I was planning on glueing 6 pieces of HDPE to make a block that I would turn round, tap a 1.25 thread, and fashion a vacuum cup on the other end. Well, as I started trying to round the block, the glue gave away and the pieces went everywhere. Luckily I was wearing my helmet even though I didn't need it. I had the pieces glued horizontally, would it work if I had them vertically, or should I use wood to make my fixture?

 

[Dieseldoc]

In making my vacuum chuck, I was planning on glueing 6 pieces of HDPE to make a block that I would turn round, tap a 1.25 thread, and fashion a vacuum cup on the other end. Well, as I started trying to round the block, the glue gave away and the pieces went everywhere. Luckily I was wearing my helmet even though I didn't need it. I had the pieces glued horizontally, would it work if I had them vertically, or should I use wood to make my fixture?

Larry; What I use if from Taps plastic 3 inch round stock of HDPE also you can find HDPE on eBay.

 

[duncsuss]

... the glue gave away and the pieces went everywhere ... would it work if I had them vertically, or should I use wood to make my fixture?

I don't think you'll be successful gluing HDPE in any orientation; if you want to use a man-made material, both HDPE and acetal (Delrin) can be threaded easily and are available in 2.5" or 3" diameter round rods.

For the threaded glue-blocks I've made from wood, I've drilled 1_1/8" for my 1_1/4" x 8 tpi Nova 1624 lathe.

 

[dogcatcher]

Recycle hdpe.