Gallery, Projects and General > How do I??

Cutting internal gear teeth

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bogstandard:
Bernd,

As explained to me by John S, the cutter is made to the same profile as a small spur gear.

The central tooth on one side is the one that does the main cutting, and the teeth either side of it (depending how large the cutter is made) partially shapes the other teeth that are due to be cut either side of the main cut.

So basically to reduce the manual loading while cutting, you make a small cutter, so that say only one either side gets shaved, whereas if you made a large cutter with many teeth, you might be shaving say 8 or 9 at the same time (this will put more load on the cutter and of course the arm that is operating it).

I hope that is the way John meant it to happen.


Bogs

tinkerer:
This is a very interesting topic. I thought the cutter was shaped round like a gear, so it would turn with the piece you are cutting to cut the clearance profiles as it turned. Looking forward to your pictures of the process.

dsquire:
John

Here is a link on gear cutting that may or may not be of interest to you. It is on a site by a new member Joachim Steinke from Germany. There are lots of other goodies there as well.

http://www.metallmodellbau.de/GEAR-CUTTING.php

Cheers  :beer:

Don

bogstandard:
Don,

The method Achim is using on the mill is what I was describing the other day, only he is cutting teeth one at a time using a straight cutter, whereas I will be cutting the whole blank in one go by freewheeling the blank using a spiral cutter, and how he has explained the cutting of adjacent teeth is what I posted earlier, but mine was a lot less technical.

He is having some very good results there. If mine turn out that well, I will be a very happy chappie.

Unfortunately, that is all concerned with external tooth cutting, of which there are a lot of techniques to achieve the same results.

There is very little on the net for the home machinists about cutting internal teeth, which is what I am trying to solve as easily and cheaply as possible.

It seems that very few people have even tried, and lived to tell the tale.

Bogs

John Hill:
John,  I have just about scratched out the last few strands of hair on my head trying to imagine how a rotating cutter could be used to cut an internal gear without the axle of the cutter getting in the way, unless the gear were is to be very big. :scratch:

Maybe if the cutter had a very coarse thread it would be possible to swing the axle enough to clear the gear while keeping the cut parallel to the axis of the new gear.  Then maybe that was what you have in mind anyway? :coffee:

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