Internal chamfer

[Weldingrod1]

Oh, great fount of machining wisdom

I need ideas on how to generate a 15 degree O-ring lead in chamfer around an internal hole.

I've got a roughly 1.5" bore with four, 1/2" holes crossing it (all in one plane). I need to copy what's in the photo, but in PTFE. I can't buy it... that would be too easy!

I need those four holes to have a decently uniform lead in around them so that a plug with O-rings rotating in the big bore does not have its O-ring bitten off by the holes. It's NOT a 45 degree chamfer.

The challenge is that I can't just rotate a shallow angle countersink at one position; the path is curved.

It's OK to spend real $$ on solving this...

Ideas?

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[Ischgl99]

Something like this should work for you.

https://cogsdill.com/products/deburring-tools/burraway/

 

[Jim F]

Something like this should work for you.

https://cogsdill.com/products/deburring-tools/burraway/

We use these at work on smaller holes, up to 5/16/
Our use is in a u shaped handle with a .250 opening.
Not sure how it would handle the radii.

 

[Firstram]

How many parts? If you need one, you could you rough bore it and use an abrasive flap wheel to ease/radius the intersecting holes. Once they are rounded, finish the bore. For production, I think a custom cutter and a rotary table on the mill would be the way to go.

 

[Weldingrod1]

I need to make 4 parts and I want fairly uniform width all the way around the funny curve.

Cogsdill has a tool to do this on an external hole. Ellipti-bur IIRC. Not suitable for soft stuff and for internal like I need.

Thinking about a 3DP cam surface that I put on the outside, with a tool assembled into the bore with a pilot on the cross bore.
Or maybe a tiny roller to follow the bore and limit the depth of cut?
I'm hoping to do better than "freehand it"

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[Weldingrod1]

It looks like a spherical cutter could come pretty close, maybe with a little Axial motion. Or a ready funny shaped cutter that just gets traversed out from the centerline and into each opening.

Approximating the straight taper with a spherical profile....

They are clearly cut; you can see a bit of chatter marks. The included angle is 60 degrees.

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[Jimsehr]

Oh, great fount of machining wisdom

I need ideas on how to generate a 15 degree O-ring lead in chamfer around an internal hole.

I've got a roughly 1.5" bore with four, 1/2" holes crossing it (all in one plane). I need to copy what's in the photo, but in PTFE. I can't buy it... that would be too easy!

I need those four holes to have a decently uniform lead in around them so that a plug with O-rings rotating in the big bore does not have its O-ring bitten off by the holes. It's NOT a 45 degree chamfer.

The challenge is that I can't just rotate a shallow angle countersink at one position; the path is curved.

It's OK to spend real $$ on solving this...

Ideas?

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After you break the inside edges of the cross holes I think you should look into using a guad style o-ring . They are commonly available and in my opinion a much better seal.

 

[eotrfish]

This is a common problem that can be solved by correct design of the part.

Increase the bore diameter by the amount of o-ring squeeze and add an entry and exit chamfer. 20 to 30 Deg chamfers will do the job.



The easiest way to measure the squeeze is to install an o-ring on the male part and measure the OD of the installed o-ring. Then add about 0.010" to get the required bore diameter across the cross drilled hole portion of the part. Parker lists 16-23% squeeze for a 1/8" cross section o-ring although you can get away with 10% for a relatively low pressure seal.

 

[Weldingrod1]

@eotrfish I agree that the chamfers you should would be radically easier! The problem is that this is a 4 position radial valve. The internal part rotates to select which hole it's going to seal around. If it reciprocated then your bore would work grrat!

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[Weldingrod1]

I actually ran across a tool on fleabay to do this task manually! It's on the way to test out

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