Cutting a worm wheel

[Ramon WilsonParticipant @ramonwilson3]

HI guys, in the coming days I intend to have a go at something I’ve not attempted before and that is to cut a worm wheel using a tap as a hob.

Just wondered if anyone has carried this out using this method and with what  level of success as a result. I can see that the equal (in form) number of teeth wil define a diameter but can’t quite see how one arrives at that save from a cut and see basis.

Any tips or pointers both to do, or avoid, would be much appreciated

 

Best – Tug

[Andy StopfordParticipant @andystopford50521]

It’s a bit random, the diameter makes a difference, but not predictably, +-10% maybe.

I’ve tried gashing the blank at the appropriate angle, but it didn’t seem to make any difference.

I did see someone doing it on quite a large scale in one of those Pakistani safety last videos on YouTube a while back. He turned a half round groove, about equal to the radius of the tap first, then fed it in very gently. It seemed to work well, and I got the impression it was for something which would require a predictable result (though this wasn’t specified). Unfortunately I can’t remember which YT channel it was on, but it was this year, in the summer maybe, so might be reasonably easy to track down.

[JasonBModerator @jasonb]

If you work out the circumference it will give you an idea of how many teeth you will get on the wheel for a given TPI but could go a tooth either way.

There was a long thread a while back which I will look for but this was the video I posted at the time.

Tell a lie it was gear cutting where I moved the tap along rather than just feeding in the gear blank.

[bernard towersParticipant @bernardtowers37738]

Yes Tug I did it for the steam launch feed pump and its still working. Did a few others at the time to work out tpi to circumference and it does work out. Plunged in not like the prev vid.

[FulmenParticipant @fulmen]

I’ve only done it to test the concept, but it seemed to work OK. There are a couple of challenges to watch out for though. One is the need for constant engagement on the tap, which can be problematic on certain hand taps. Spiral fluted machine taps might work better. I also think you should feed to full depth in one go to get the pitch right.

[Pete RimmerParticipant @peterimmer30576]

Remember that the cutter which cuts the teeth on the wormwheel should be the same pitch diameter as the worm you are using. If not, the engagement will be either only in the middle or on the edges of the teeth.

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