Deep hole drilling + ball-end fillet? 1

[Jabberwocky]

Hey all,

I have a question as to whether or not this feature is (reasonably) machinable. I have a 8mm OD tube, approximately 180mm long, and I need to step down from a 6mm internal diameter to a 3mm diameter about 10mm from the tip (6mm ID for 170mm, then 3mm ID for the rest). I know this can be done, and we've specified a chamfer to make up the difference between the two IDs.

However, there is an interference issue and I'd like to propose a fillet instead of a chamfer - is this machinable? I'd think you can gun-drill or any other process to get your basic depth, then stick some kind of ball-end mill to get the radius - but can you do this at the bottom of an almost blind hole?

Thanks for your help.

 

[btrueblood]

Yes. Same way you'd make a counterbore, with a piloted reamer, and I've seen those with radii ground on either or both corners.

 

[TVP]

I agree with btrueblood that this is possible with a piloted reamer. The 180 mm length means that the fixturing will need to be rigid to prevent any distortion, eccentricity problems, etc.

 

[unclesyd]

If you need a very smooth transition you might want to look a the tools made Conical Tools.
We routinely made a part very similar to your requirements using a profile cutter to transition from one bore to the other. Ours was in a flow application where we used a ball in the taper as a backflow preventer.

These people were nice to work with.

http://www.conicalendmills.com/default2.htm

 

[Jabberwocky]

Thanks for the info guys. "Piloted reamer" did seem to be the magic word.

 

[SteveWag]

Sounds like a chambering reamer for a small caliber. Check out Manson Chamber Reamers on the web. He can make one, piloted or not.
Steve