Gallery, Projects and General > How do I??

Cutting a concave hole

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No1_sonuk:
mklotz (just recently joined this forum ) has something on his web site that calculates the steps for you for making balls.  You'd probably just need to modify the numbers a bit to make a socket.

http://www.myvirtualnetwork.com/mklotz/  Look for ballcut.zip

I'm only going by the description there - I have no idea if it's suitable for your application.

Divided he ad:
As the maker of the first "very badly designed" bit shown in that there post I'll say this.... Please be very, very careful with this idea....

The spinning one would not work as I'd centred it incorrectly, also the speed would need to be down to very low.

The stepping of the work piece is required to get the approx' size and then the re-designed tool was used to finish it off..... Bogs was the man who saved me from my own lack of knowledge  :thumbup:




As most people say.... What it is for will help with the answer.... Maybe a C-o-C ?






Ralph.

mklotz:
Arnold beat me to it but I'll expand a little.

Assuming that you want to create a hemispherical cavity, one way to do it would be to rough it out and then mount it on a rotary table.  Then, with a ball mill take cuts around the inside surface of the cavity, each cut adjusted in radius and depth so the ball cutter was just tangent to the desired hemisphere.

What would result would be a cusped surface with the cusp height dependent on the number of cutting steps used.  Polish out the cusps and you're done.

If this method appeals to you, I can write a program that will generate the radii/depth pairs needed for the incremental cuts.

Mike K:
Yeah, I guess I should have mentioned what I'm making.  I don't have a scanner to post the picture, but it's the "simple grinding rest" from Harold Hall's "Tool and Cutter Sharpening".

The one part is too long for me to spin in the mini-lathe to make the suggested 30 deg. cut.  So I figured I should be able to do something on the mini-mill.  Don't have much choice, though. Heh heh.

Ralph, I'm always careful.  Okay, usually. :)  First, I have to attempt the roughing steps.  And to be honest, I don't think I could do that D bit right now anyway...My mini-lathe is apart and the only drill rod I have is too small.

Marv, thanks for the offer.  I managed to work up a spreadsheet of offsets.  Although I may come knocking if this doesn't pan out.

Now that it's been suggested a few times, I'm dying to try this stepped cut thing.

Mike

Raggle:
This is bigger than a 1" pocket but a pretty good description of the procedure

http://translate.google.com/translate?hl=en&sl=fr&u=http://romubricoltout.canalblog.com/&ei=sH-USrEYmcqMB7_RkPMN&sa=X&oi=translate&resnum=1&ct=result&prev=/search%3Fq%3Dromubricoltout%26hl%3Den%26client%3Dopera%26rls%3Den-GB%26hs%3D0zl

I hope that link works. It's a google translation  -  should keep everybody busy with the rest of the site, a superb 5" gauge DeCauville loco. Scale is 2.5" to the foot.

Warning: This site contains strawberries, the occasional onion and I'm sure I saw a greenhouse. I rather hope no-one submits too many "better translations"

Ray

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