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View Full Version : Making a radius cut in the middle of a bar



Mike Hunter
08-24-2009, 12:27 PM
Suppose I need to make a radius cut in the middle of a bar. Bar is 20 inches long, .750 Dia, cut is 1/16th width, using a 3/8 dia cutter, and cut is .060 deep. Cut is 90 deg to the bar.
Right angle attachment on the mill won’t work; attachment is larger than the cutter, Dremel mounted in a lathe…again same problem.
I know that there was a milling head/adapter I think it was referred to as a chain mill.

Thoughts, comments, Ideas welcome.

Jim Shaper
08-24-2009, 12:31 PM
I'm not following what you mean by a radius cut perpendicular to the bar...

Do you have a drawing? Picture of what you're trying to make?

JCHannum
08-24-2009, 12:51 PM
I am picturing a Woodruff keyway, but at 90 degrees to the long axis rather than parallel.

A quillmaster with a right angle attachment is the best I can come up with in a coomercial unit, but they do not come cheap for a one-off application, and might not work either;

http://www.lathes.co.uk/bridgeport/page5.html

Jim Shaper
08-24-2009, 01:01 PM
If that's the case, then EDM is going to be your fastest and cheapest method.

I can't think of a valid reason to have a woodruff key seated in such a manner though. There's nothing to be gained over making a key that seats flat in the bottom of the groove and you could make that with a simple end mill.

Now if you're talking about making a pocket that follows the radius of the bar, that's simple - a super spacer (preferred method) or even a couple v-blocks would do to situate the bar to machine the pocket.

JCHannum
08-24-2009, 01:05 PM
I suspect Mike is looking for a method of machining the cut Winchester used for the magazine tube end cap as used on 1892 rifles for instance. I don't think EDM was an option.

Mike Hunter
08-24-2009, 01:33 PM
Jim H

Right on target; the cuts on the end of the barrel are easy, just woodruff cutter mounted in a right angle milling attachment. It's ithe 1/2 magazines where the slot is in the middle of the barrel, and yes I can mill them straight, and that's what I've been doing.... but its not correct, they really need a radius to them.

Quill master looks interesting....

Mike

Hunter Restorations
WWW.Hunterrestorations.com

JCHannum
08-24-2009, 09:38 PM
Mike, The Quillmaster might not work either, and as I recall, it or the QRA only have 3/16" collets. Might be a bit difficult to get a 3/8" Woodruff cutter with that small a shank, and the QRA body is probably still too large.

I have been looking for these, and finally found them, one could be made to work, they are pretty simple and turn up on eBay occasionally. They are not cheap if purchased new, but probably cheaper than the Quillmaster & QRA attachment. It might be worthwhile contacting them.

http://www.keyseaters.com/

wierdscience
08-24-2009, 09:57 PM
Mike it's a simple process done with an endmill the width of the slot,but it will require a rotary table and a fixture to offset the barrel's axis.

The barrel is offset the RT's axis so it is for lack of a better term "rocked" or "swung" through the cut so the barrel describes the radius of the desired groove.

Doing it with an endmill means the bottom of the groove will have a slight concave to it.If that is undesirable it might be possible to substitue a single point cutter in place of the endmill and shave it out a half thou at a time.

Hope that helps

Evan
08-24-2009, 11:43 PM
Following Wierd's idea, do it in the lathe. Use whatever power tool you have to drive the right size end mill and clamp it to the tool post so the bit is on centerline. Chuck up the barrel off centre the right amount using the 4 jaw and a live offset holder in the tailstock, maybe a boring head. Swing the barrel past the cutter which may be advanced as required to obtain the correct depth.

[edit] Or use a ordinary tool as per Wierd and shave it out.

Evan
08-25-2009, 12:17 AM
Here is proof of principle. I had the luxury of putting it on the end of a part so I only needed to chuck it up in the 4 jaw so it orbited the correct radius. I cut the slot with a small internal acme threading tool which is why the sides aren't parallel.

http://ixian.ca/pics6/keyslot.jpg