How To Turn A Round Groove?

[dieselshadow]

How can I turn a round groove with a radius of .063 on a manual lathe. Seems like round insert tooling is fairly rare for a lathe, let alone find one with the correct radius?

Any good ideas?

 

[T Bredehoft]

Round groove as in "O ring groove"?, grind a HSS tool. Yeah, it's a tiny thing, but doable. I made rollers for bending 1/8 wire hooks, they are .062 (or so) radius.

 

[JimDawson]

The normal way to do that is to just grind a HSS tool bit as needed.

 

[Cobra]

As Jim said, I would grind a HSS tool to the round nosed shape you show in the drawing and then plunge it into the piece.
I have done the same a number of times when making small v-belt pulleys. Just go easy because you are cutting over a large area as you go in.

 

[4GSR]

Once you hand grind the radius, take a oil stone and hone the edge to get a smoother radius. Then you will be ready to cut the groove. Use your favorite cutting oil to get a nice finish. After that, if you want, use a piece of very fine emery to polish the groove to 32 or better finish. Ken

Edit: after looking at your picture, If you have a Acme threading tool ground up, put a radius on the tip of tool. That way you can blend the radius in with the sides of the groove. Ken

 

[Bob Korves]

If it is for an o-ring, an o-ring groove is square cut, to close tolerances.
http://www.sealanddesign.com/category/O-Ring-Groove-Design/183.html

 

[Tony Wells]

I use full radius inserts when I need to cut a precision groove. They are also used for profiling. Many are available. Here's one example. Look at the A3 style in this Kennametal catalog:

https://www.kennametal.com/content/...9_MasterCat_stationary_groove_cutoff_inch.pdf

It starts on page D27.

 

[Eddyde]

+1 on the HSS.
The carbide would be fine if you had many parts to make but might be costly to purchase the holder and insert to for a one off part.

 

[dulltool17]

With care, you can grind a HSS tool blank to about any form you need. With a bit of patience (something I wasn't blessed with in abundance) I managed to grind an 0.042 square to cut threads in a 5/16 sq blank for threading a Marlin 336 barrel. 0.062 radius will be a bit more challenging, but is doable. HSS is very versatile.

 

[GA Gyro]

When I first played with machining... around 1970...
There were no CNC machines and few carbide tools (most were brazed onto blanks).

Custom grinding the end of a HSS tool blank to do specialty machining on a lathe... was the norm.
I have forgotten how to do it, however one time, under the leadership if a seasoned old guy... ground a tool to cut hard rubber bushings. Worked just fine!

If I remember... most of the information you will need... is in the Machinery handbook...
However I have no idea where... [grin]