Bright EN24T steel vs Black EN24T for cutting gears

Andrew many thanks - so 60 rpm, full depth "one pass" cut, but rate of table feed (I don't understand what you mean by 4 thou per tooth)?

Edited By Adam Harris on 10/10/2019 11:44:06

Multiply RPM x number of teeth on the cutter x 0.004" and that will give distance per minute feed.

Aha thank you Jason. 36T x 60RPM  x 0.004" = 8.6 inches/minute

Edited By Adam Harris on 10/10/2019 11:50:34

That seems quite a lot of teeth

I would have expected about 12, have you got a picture or link as teeth would be very thin

Edited By JasonB on 10/10/2019 11:54:39

Adam, read my reply again, it is teeth ON THE CUTTER not the gear

Aha that make more sense!! Thanks for the correction. Well the cutter comes from RDG and expect to receive it tomorrow so will know then, but probably as you say 12!

Edited By Adam Harris on 10/10/2019 12:00:33

There are 36 teeth on the gear being cut.

Just noted that the involute cutter is around 65mm diameter. My spindle speed of 60rpm was based on a 3-1/4" diameter cutter.

Andrew

so 12 x 60 x 0.004 = 2.9 inches/minute a much more sedate rate of feed!

Edited By Adam Harris on 10/10/2019 12:02:31

Andrew thanks I'll adjust the RPM and thus feed accordingly when I get the actual cutter dimensions .

Edited By Adam Harris on 10/10/2019 12:12:39

That's fine - Andrew

So, JB, are (almost) all involute cutters sold to hobbyists? Maybe most gears are cut by hobbing in the commercial sector these days, but I wasn’t thinking of David Brown Gears in this context - more like the commercial machine shops rather than high production manufacturers - like automotive gearbox suppliers for instance.

Adam,

Do compare your machine to that of Andrew’s. The feed rate may be restricted by your machine... I try to cut gears with my machine in horizontal mode rather than vertical, for instance, simply because the cutter has support at both ends of the arbor.

Ah I was thinking along the lines of HPC, Duval etc. I suppose a jobbing shop would use Involute cutters for a one off, would really depend on what equipment they have as it may be cheaper to sub it out.

As for hobbing a modern machine will drive the blank independantly by electronic means no need for gear trains so no need to run a particular way to get started unlike free hobbing and they seem to use climb cutting too. Though you probably won't find many bodging lodges with something like this.

Oil mist lubrication?

Fantastic video Jason!

Possibly turned off for the video, the two blue pipes clipped to those fan spray outlets probably supply flood coolant in normal use and there is what looks like a coolant pipe at the far end of the hob

Incidentally I make the OD of a 36 tooth 10DP gear to be 96.52mm.

Andrew

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Wow ... Do they have a Desktop version of that machine ?

MichaelG.

Yes Andrew 3.8" - not quite sure how 98mm slipped in but probably because i understand Black is only made to 2% tolerance so I was pondering about 100mm diameter, is worst case 98mm size enough to turn down to a perfect 96.52 and I have decided possibly not so bought some 105mm Black instead

Hi Andrew , cutter is 10T & 70mm diameter (made by HBM incidentally) so therefore feed 2.8 inches/minute (given my cutter circumference is 0.849 of yours)?

at 70 rpm