Ball seat drills?

[chucketn]

I've seen the name "ball seat Drill" used on HSM refering to a drill similar to a center drill but round on the end instead of a 60° pint. Are these called something else? I can't find anything with a google search. Was searching for info on using a boring head to turn tapers.

Chuck in E. TN

 

[pwasbury]

I think the center drills are called Bell type, not sure of a regular drill.

Here is a pix of my attempt at using the ball bearings as centers cutting a taper.

Cheers, Paul

 

[bentprop]

Are you perhaps thinking of a ballnose end mill?
I don't think you would use one to drill a ball seat though.You might use a 2 flute slot drill to drill a flat seat.Then fit a spare ball,and hit it to make an impression on the seat.This should give a good seal.Remove the ball,and replace with a new one for service.
John "bogstandard" had made a special piece of tooling ,which gave an angled seat,e.g.,the edges were lower than the center.Can't find it now though.

 

[tel]

A 'D' bit, shaped thus (angles exaggerated) is the best way I've found to cut ball seats

 

[n4zou]

I just drill leaving the 60 degree chamfer, drop the ball in, and then use a punch to drive the ball into the chamfer. I've never had any leakage problems using this procedure.

 

[peatoluser]

I think what chuck is asking about is what Paul refers to.
It's a special form of centre drill, that has a curve or radius instead of a 60 degree cone.
Although I don't think they are called bell type. These have two cones, one 60 degree and another at about 120 degree.
The type chuck is asking about is a radial centre drill.
Why exactly do you need it? I know a lot of people use them for taper turning with an offset tailstock because they think it gives better support instead of two mis-aligned cones, but if the taper is gentle, a standard centre drill is fine.
Funnily enough i've only ever seen them used on production machines for parellel turning. They are supposed to give more accurate support than a standard centre drill.

 

[chucketn]

peatoluser,
That's exactly why I'm looking for such. I want to turn tapers with a boring head to offset the taper instead of offsetting the tail stock. I'll try without and see how it goes.

Chuck oin E TN

 

[pabird]

http://www.use-enco.com/CGI/INPDFF?PMPAGE=60&PARTPG=INLMK32


Take a look at this Chuck.

 

[Omnimill]

Also here, bottom of page:

http://www.arceurotrade.co.uk/Catalogue/Cutting-Tools/Centre-Drills

Vic.

 

[Mainer]

One thing you can do for turning tapers is put a standard center hole in both the workpiece and the tailstock, then capture a ball bearing between them to act as a pivot.

 

[DICKEYBIRD]

One thing you can do for turning tapers is put a standard center hole in both the workpiece and the tailstock, then capture a ball bearing between them to act as a pivot.

Yup, that works very well.

In the internet article I read, the author stated that you center drill to a depth that leaves the "mouth" of the opening at 88 to 90% of the chosen ball diameter. This puts the ball at the the best compromise position for load carrying and offset ability. I've used his method numerous times and it's always worked great.