Author Topic: Radius Cutter  (Read 6795 times)

Offline MadNick

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Radius Cutter
« on: December 16, 2011, 12:06:21 PM »
Afternoon,

Im looking for some design advice please on a tool I am fabricating for use with my lathe.

The idea was to bolt this to the top slide and then via an arm attached to the turret, cut a radius.

Having looked around the web before starting and after two or three revisions I came up with the attached design.

Given my base is steel and the turret is ali, should I be looking at using  a bearing between the two or would this be over engineering?

I look forward to your suggestions.

Nick

Offline Lew_Merrick_PE

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Re: Radius Cutter
« Reply #1 on: December 16, 2011, 12:40:04 PM »
Nick,

The issue with steel on aluminum is that aluminum ends up with an oxide coating -- the same stuff normally associated with "sandpaper."  It is counter-intuitive, but aluminum will wear most steels long before the steel wears the aluminum.  In normal usage, this should not be an issue so long as you lubricate surfaces each time you use it.  A thin UHMW PE (Ultra-High Molecular Weight Polyethylene) washer is another cheap and easy solution.

To those who will say that I am being too conservative on this, I had a customer back in the 1970's who made parts that had to be cut and routed using long aluminum skate tracks.  The skate carriages were made out of medium carbon steel with a heat treated glide plate.  The carriages would be worn to non-compliance (tolerance) within 100 parts.  A simple UHMW PE insert solved the problem.  I have run into this exact situation with fair regularity, so I am sensitized to the more than most.

Good luck with your radius cutting attachment.

Offline DaveH

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Re: Radius Cutter
« Reply #2 on: December 16, 2011, 12:50:43 PM »
Nick,

Do you mean a bearing between the two flat pieces or a bearing between the shaft and the hole?

 :beer:
DaveH
(Ex Leicester, Thurmaston, Ashby De La Zouch.)

Offline MadNick

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Re: Radius Cutter
« Reply #3 on: December 16, 2011, 01:35:10 PM »
Thanks fellas,

@Dave, I would suggest either but if I have to use a bearing would favour a taper roller on the Turret shaft due to the lateral force when cutting.

Nick

Offline 75Plus

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Re: Radius Cutter
« Reply #4 on: December 16, 2011, 01:38:00 PM »
Hi Nick, May I suggest that you do a search for "Ball Turner". You will find many pages of discussion on this subject as well as some neat designs.

Joe

Rob.Wilson

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Re: Radius Cutter
« Reply #5 on: December 16, 2011, 01:41:19 PM »
Hi Nick, May I suggest that you do a search for "Ball Turner". You will find many pages of discussion on this subject as well as some neat designs.

Joe

Just beat me to it Joe  ,,,,,,,, :D

Nick ,,,,, this thread my be worth a look  http://madmodder.net/index.php?topic=3460.msg37064;topicseen#msg37064  :thumbup:


Rob

Offline MadNick

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Re: Radius Cutter
« Reply #6 on: December 16, 2011, 03:16:59 PM »
Beautiful :)

Many Thanks.

Nick

Offline rleete

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Re: Radius Cutter
« Reply #7 on: December 16, 2011, 03:40:49 PM »
I used a thin (.010") sheet of teflon between mating surfaces.  Works well, very smooth.
Creating scrap, one part at a time

Offline Fergus OMore

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Re: Radius Cutter
« Reply #8 on: December 16, 2011, 04:25:54 PM »
I hope that there will be no undue criticisms but in Model Engineering Clearing House we have just had a surprisingly similar discussion.

I raised the point that an adjustable boring head( the main subject) could be used just as easily as a very good ball turning tool. It does require a change of tool bit but that is all.

You might want to have Two for the price of  or building one.

Offline PeterE

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Re: Radius Cutter
« Reply #9 on: December 16, 2011, 05:37:02 PM »
I can only agree with Fergus above. The similarity between the two tools becomes very obvious when looking at the George H Thomas designs for each: (Links to the Hemingway kit pages for each tool.)

The Boring tool:
 http://www.hemingwaykits.com/acatalog/info_HK%201030.html

and the ball turning tool:
http://www.hemingwaykits.com/acatalog/info_HK1160.html

It also becomes obvious that with different shanks and different tool bits we get a very versatile tool with much use.  :headbang:

BR

/Peter
Always at the edge of my abilities, too often beyond ;-)

Offline Fergus OMore

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Re: Radius Cutter
« Reply #10 on: December 16, 2011, 06:01:23 PM »
I made mine out of scrap ends from George Thomas's Model Engineer's Workshop Manual and Jack Radford's Lathe Improvements and Accessories. So long as one can make a measuring thread- say 1/4" x 40 and have a dovetail cutter, it is fairly straightforward.

But you can have a third bite at the cherry and if you build GHT's small dividing head instead, you can divide as well, and if you build the small DH, you can be craftier still and use it to drill from the saddle and if you a collet user, you can sharpen slot and end mills as a sort of encore.

That is enough for me- at the moment.

Offline MadNick

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Re: Radius Cutter
« Reply #11 on: December 16, 2011, 09:42:18 PM »
Morning!

Ive been through some of the threads and the links within and found them very interesting - a rich source of information.

Thanks again.

Nick

Offline Bernd

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Re: Radius Cutter
« Reply #12 on: December 17, 2011, 09:32:46 AM »
Nick,

Here's a link to more than you'd care to know about ball turner's.

Ball Turner

Enjoy.

Bernd
You can't fix "STUPID".