Long thin taper update
 

Some months back I posed a question for the group regarding how to make
a long thin tapering rod. The taper being from 0.25" (6.35mm) to 0.080"
(2mm) over about 6" (150mm). From kicking various ideas around I came up
with the solution shown in the dropbox. It works very well. Many thanks
for all the help.

http://metalworking.com/DropBox/longtaper.txt
http://metalworking.com/DropBox/longtaperfront.jpg
http://metalworking.com/DropBox/longtapertop.jpg

On Thu, 26 May 2005 19:33:11 +0100, David Billington
wrote:

Some months back I posed a question for the group regarding how to make
a long thin tapering rod. The taper being from 0.25" (6.35mm) to 0.080"
(2mm) over about 6" (150mm). From kicking various ideas around I came up
with the solution shown in the dropbox. It works very well. Many thanks
for all the help.

http://metalworking.com/DropBox/longtaper.txt
http://metalworking.com/DropBox/longtaperfront.jpg
http://metalworking.com/DropBox/longtapertop.jpg

Clever!

David Billington wrote:

Some months back I posed a question for the group regarding how to make
a long thin tapering rod. The taper being from 0.25" (6.35mm) to 0.080"
(2mm) over about 6" (150mm). From kicking various ideas around I came up
with the solution shown in the dropbox. It works very well. Many thanks
for all the help.

http://metalworking.com/DropBox/longtaper.txt
http://metalworking.com/DropBox/longtaperfront.jpg
http://metalworking.com/DropBox/longtapertop.jpg

What keeps the end of the rod from just lifting up at the tip, from the
cutting forces? - GWE

Its not clear from the picture, the groove in the brass is about .150"
deep so the rod is supported above and the cutter is like a threading
tool so resultant forces keep it in the groove. On the initial 2 runs I
used a piece of wood levered against the inside of the front way to push
lightly against the rod but it seems stable and not required. Tomorrow
i'll check the cutting speed and try it at a recommended SFM, the test
run was at 800RPM which is probably too slow even with HSS and EN24T,
feed was 0.002"/rev.

Grant Erwin wrote:

David Billington wrote:

Some months back I posed a question for the group regarding how to
make a long thin tapering rod. The taper being from 0.25" (6.35mm) to
0.080" (2mm) over about 6" (150mm). From kicking various ideas around
I came up with the solution shown in the dropbox. It works very well.
Many thanks for all the help.

http://metalworking.com/DropBox/longtaper.txt
http://metalworking.com/DropBox/longtaperfront.jpg
http://metalworking.com/DropBox/longtapertop.jpg


What keeps the end of the rod from just lifting up at the tip, from the
cutting forces? - GWE

David

Clever. I've been thinking about making long tapered reamers for making
woodwind bores, but I hadn't come up with a setup I liked. Your setup is
a considerable improvement over anything I'd thought of. Gonna have to
remember that one.

Jim

Glad its some help. If I had a taper turning attachment and travelling
steady I would use that but unfortunately I don't at least not yet.
Keeping an eye on ebay.

Jim McGill wrote:

David

Clever. I've been thinking about making long tapered reamers for
making woodwind bores, but I hadn't come up with a setup I liked. Your
setup is a considerable improvement over anything I'd thought of.
Gonna have to remember that one.

Jim

David, maybe I just need new glasses but I couldn't quite figure out how
that turning setup worked. Any chance you could describe how it works? - GWE

The rod rest in a semi circular bottomed groove in the brass bar which
is about .150" deep horizontally, the bar radius being .125" so a little
above and below forward of the vertical centre line. The groove depth
vetically is about .252", a little clearance for lube. Because the bar
is only .25" diameter it is flexible and the brass guide forces it
forward towards the front of the lathe at the tailstock end so producing
the required taper. The brass guide supports all the rod length from
close to where it leaves the chuck. The tool grind is basically a
threading tool so the resulting cutting forces should keep the rod in
the groove in addition to the force due to it being bent once it leave
the chuck. The taper is small so the bending is within the elastic limit
of the material. The cutting is done towards the chuck so the initial
cut on the current items is 0.085" reducing to 0 nearer the chuck.
Luckily the rod is happy to transmit the cutting torque and the EN24T
(4340) machines very nicely.

I hope that clears up any issues, if not I shall try and get a job
writing chinese machine tool instructions.

Grant Erwin wrote:

David, maybe I just need new glasses but I couldn't quite figure out how
that turning setup worked. Any chance you could describe how it works?
- GWE