Cutting an angle in a bore
 

Simple question. If you bored, say, a 1" diameter into a part mounted on
your lathe, and then wanted to do an accurate chamfer, how would you go
about measuring it. Say you want to chamfer out at 10° and the resulting
slope is to extend 1/4" into the bore. I know how to set up the tooling,
BUT, how do I precisely measure the 1/4" "daylight point".
Alternatively, I could simply figure the increase in diameter at the working
end. (tan 10°x0.25)x2. Okay, so now I know that the new diameter should be
1.088". How do I measure that. Seems like measuring this larger diameter
would end up to be an 'eyeball' job. My eyes are old.

Ideas with how to proceed would be greatly appreciated.

Thanks,

Ivan Vegvary

Cutting an angle in a bore
 

On Mon, 19 Jan 2009 19:11:41 GMT, "Ivan Vegvary"
wrote:

Simple question. If you bored, say, a 1" diameter into a part mounted on
your lathe, and then wanted to do an accurate chamfer, how would you go
about measuring it. Say you want to chamfer out at 10° and the resulting
slope is to extend 1/4" into the bore. I know how to set up the tooling,
BUT, how do I precisely measure the 1/4" "daylight point".
Alternatively, I could simply figure the increase in diameter at the working
end. (tan 10°x0.25)x2. Okay, so now I know that the new diameter should be
1.088". How do I measure that. Seems like measuring this larger diameter
would end up to be an 'eyeball' job. My eyes are old.

Ideas with how to proceed would be greatly appreciated.

Thanks,

Ivan Vegvary

Same way you measure the diameter of a countersink. Put a ball into
the hole and measure the height of the ball above the face of the
bore. Do a bit of trig and you can derive the diameter of the
countersink.

Regards, Marv

Home Shop Freeware - Tools for People Who Build Things
http://www.myvirtualnetwork.com/mklotz

Cutting an angle in a bore
 

On Mon, 19 Jan 2009 19:11:41 GMT, "Ivan Vegvary"
wrote:

Simple question. If you bored, say, a 1" diameter into a part mounted on
your lathe, and then wanted to do an accurate chamfer, how would you go
about measuring it. Say you want to chamfer out at 10° and the resulting
slope is to extend 1/4" into the bore. I know how to set up the tooling,
BUT, how do I precisely measure the 1/4" "daylight point".
Alternatively, I could simply figure the increase in diameter at the working
end. (tan 10°x0.25)x2. Okay, so now I know that the new diameter should be
1.088". How do I measure that. Seems like measuring this larger diameter
would end up to be an 'eyeball' job. My eyes are old.


You can do it with a 1-1/16 diameter bearing ball and a little trig.

If I didn't have a ball handy, I think I'd turn a hat-shaped gage. The
small diameter corresponds to the diameter of the chamfer at depth
equal to the length of the small diameter over the brim. Use a feeler
gage under the brim of the hat as you approach full size to figure the
final cut.

In other words, if the cham is to size, the brim will contact the face
of the part while the small diameter is touching the chamfer.

--
Ned Simmons

Cutting an angle in a bore
 

�Seems like measuring this larger diameter
would end up to be an 'eyeball' job. �My eyes are old.

Ideas with how to proceed would be greatly appreciated.

Thanks,


Ivan Vegvary

Start by setting the compound rest very accurately. Then cut the
chamfer deeper than needed. Determine with the Z axis feed the
distance you cut the chamfer. Trim the oversize from the face of the
piece you are cutting. Then the chamfer that you cut was precisely
done and you have the dimensions. Or mesaure the dimensions with a
dial indicator and do some math.

I would probably do the latter.

Bob AZ

Cutting an angle in a bore
 

On Jan 19, 2:11*pm, "Ivan Vegvary" wrote:
Simple question. *If you bored, say, a 1" diameter into a part mounted on
your lathe, and then wanted to do an accurate chamfer, how would you go
about measuring it. *Say you want to chamfer out at 10° and the resulting
slope is to extend 1/4" into the bore. *I know how to set up the tooling,
BUT, how do I precisely measure the 1/4" "daylight point".
....
Ivan Vegvary

You could make a male plug with the 10° chamfer on it, put it in the
bored hole and measure the protrusion, then stop cutting your chamfer
when the plug goes in 0.250" further.

Rough out the plug and part in to 0.9" or so on the left end before
setting the compound to 10° so you can taper the plug and chamfer the
hole without moving the compound.

JW

Cutting an angle in a bore
 

Ivan Vegvary wrote:

Simple question. If you bored, say, a 1" diameter into a part mounted
on your lathe, and then wanted to do an accurate chamfer, how would you
go about measuring it. Say you want to chamfer out at 10° and the
resulting slope is to extend 1/4" into the bore. I know how to set up
the tooling, BUT, how do I precisely measure the 1/4" "daylight point".
Alternatively, I could simply figure the increase in diameter at the
working end. (tan 10°x0.25)x2. Okay, so now I know that the new
diameter should be 1.088". How do I measure that. Seems like measuring
this larger diameter would end up to be an 'eyeball' job. My eyes are old.

Ideas with how to proceed would be greatly appreciated.

Thanks,

Ivan Vegvary

Simple answer.

Set the compound to 10 degrees.
touch off on the bore.
touch off on the face.
put a dial indicator on the Z axis ,, (carriage)
mave the carriage into the chuck the amount that your lathe can handle
on a cut and feed in the compound.
Keep cutting until you move a 1/4 inch on the dial indicator.

If you have a carriage stop, set it while touching off the face with a
1/4 inch shim (allen wrenches work fine) between it and the carriage.
Then do the same as above until you hit the carriage stop.


John

Cutting an angle in a bore
 

Ivan Vegvary wrote:
Simple question. If you bored, say, a 1" diameter into a part mounted
on your lathe, and then wanted to do an accurate chamfer, how would you
go about measuring it. Say you want to chamfer out at 10° and the
resulting slope is to extend 1/4" into the bore. I know how to set up
the tooling, BUT, how do I precisely measure the 1/4" "daylight point".
Alternatively, I could simply figure the increase in diameter at the
working end. (tan 10°x0.25)x2. Okay, so now I know that the new
diameter should be 1.088". How do I measure that. Seems like measuring
this larger diameter would end up to be an 'eyeball' job. My eyes are old.
Set compound rest for 10 degree angle. Adjust carriage until cutting
tool JUST barely touches sharp inside corner, at closest approach with
compound slide. Take a few cuts, advancing toward work with carriage,
using dial indicator, DRO, or whatever, until carriage has moved 1/4"
toward headstock. The chamfer should reach exactly 1/4" deep in the
bore. Make sure not to move cross-slide during this procedure.

Jon