Doesn't exist? -- 8 TPI threaded chuck to fit an 80mm HF faceplate (w/ picture)

[bcrimmins]

Probably not the drill but the tap. You will always get wobble like this. Drill and ream a hole (next stock size up) in your soft shank. Use green locktite to retain the new piece of stock(say 3/8 if your doing 5/16 threads). After it sets up for 24 hours cut the glued in shank down to 5/16. Cut threads single point but not under where the ring sets. Just like the unimandrel above. Even better, don't cut any threads under any part of the mandrel at max extension(smallest size ring you will do) and use spacers under the nut for bigger rings

Ah, good to learn. Makes perfect sense. Two questions...

What did you mean by "single point"?

Any tips on cutting threads? I've never done that. I've watched some youtube videos.

 

[Firebrick43]

single point is to cut threads with a single point 60 degree tool bit.

As far as tips, go as slow as you can, take small passes, and use a good cutting oil.

 

[rwm]

Single pointing the threads would eliminate the need for boring. You will still need a very small internal threading tool. I think boring and tapping would be fine. Single point is arguably harder but would guarantee concentricity.
R

 

[bcrimmins]

How deep did you drill the hole ? Could you just face off threads ?

All the way to the base shank. Ironically, I drilled it all the way in because I knew there would be some play in the threads and wanted it to wicked less. That was clearly the wrong thing to focus on!

 

[bcrimmins]

.020" is pretty bad. To get a hole dead center, it should be drilled undersized and finished with a boring bar. You would need one of those tiny boring bars for a hole this small.
You could start over with a new shank or loctite a plug in place as suggested above. Either way you should use a boring bar to center the new hole.
Keep this in mind:
Drilling is for making a rough hole.
Boring is for making a hole on center.
Reaming is for making a hole to exact diameter.
Sometimes you need to do all 3.

Great info, thanks!

 

[Firebrick43]

Single pointing the threads would eliminate the need for boring. You will still need a very small internal threading tool. I think boring and tapping would be fine. Single point is arguably harder but would guarantee concentricity.
R

Don't single point internal threads???? Locktite a 3/8 shaft into a 3/8 hole , turn to 5/16 diameter and single point the external threads on the end for a thumb screw.

 

[bcrimmins]

Don't single point internal threads???? Locktite a 3/8 shaft into a 3/8 hole , turn to 5/16 diameter and single point the external threads on the end for a thumb screw.

Yeah, that's what I thought you meant. I like it.

 

[Firebrick43]

Yeah, that's what I thought you meant. I like it.

Also if you mess up, or want to change things in the future, green locktite while "permanent" if heated to 400 degrees will let go so you can have a do over.

 

[bcrimmins]

What shape tool would you use the reduce the 3/8 stock down to 5/16?

 

[Firebrick43]

Any good right hand tool/holder that has a sharp cutting edge and has positive geometry would work. HSS would have the lowest pressure and therefore limit deflection of the shaft.

I personally would use a tangential tool holder but that is because I have one. A CCMT 21.52 RH tool holder (SCLCR) would work as well.

While I still don't know why they do it, a RH tool is meant to cut to the Left towards the chuck.

I personally don't care for triangle inserts most of the time.

I would use HSS for threading but you would need to learn to grind it. I also have a number 1 top notch tool that takes threading inserts that works well but probably more expensive than many want. Laydown threading tool holders seem to be much more reasonably priced but I have not really used them.