Cutting a SRBF gear

[JOHN KNIGHTParticipant @johnknight56112]

Gentelmen,

When time allows I have to cut a 16DP gear in SRBF. So far I have failed to find any useful information on the cutting speed that should be used and tool geometry. Should the tooth be cut in one pass? Any advice please.

Regards

John

[JOHN KNIGHTParticipant @johnknight56112]

[Michael GilliganParticipant @michaelgilligan61133]

John,

It would be worth you reading this thread … especially the Tufnol documnt that I linked.

MichaelG.

[Anonymous]

1. Geometry is set by using the appropriate involute cutter

2. I can't remember what cutting speed I used last time I machined SRBF, but the key to machining plastic is low speed and high feedrates. Too high a speed and the plastic melts. At a guess a 16DP cutter is going to be about 2.5" diameter, I'd run it at 100-200rpm, no coolant.

3. Cut to full depth in one pass

4. SRBF can chip where the cutter leaves the work, so it may be beneficial to use a sacrificial spacer of the same material on the exit of the cut

Regards,

Andrew

[Neil WyattModerator @neilwyatt]

Fast and sharp is my understanding. Try to cut in a direction that minimises the chance of causing delamination.

Some advice right at the bottom of this thread: **LINK**

Neil

[Howard LewisParticipant @howardlewis46836]

The advice given to me was always to cut the tooth to full depth in one pass. Multiple passes risks errors in indexing the blank.

As Neil says, to reduce the risk of chipping or delamination, use a sacrificial blank (aluminium?) behind the workpiece.

If you are cutting gears in a laminated material, use the material so that the laminations of the gear teeth are not in shear.

i.e use sheet for the blank, rather than rod. This may seem obvious, but many years ago, a motor manufacturer did not, and a lot of Idler Gears lost their teeth, because of this.

Howard

[BazyleParticipant @bazyle]

Look out for the dust. I once had to machine a lot of this, not for gears, and am still finding the martian red dust in corners 15 years later despite using a 1HP woodwokers dust extractor strapped to the cross slide and most of it coming off as chips.
Any comments on using flood cooling to wash down the dust?

[Author]

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