Herbert 2b setup

Steveng'14 · Nov 25, 2019

Hello all, I'm trying to set up a Herbert capstan to: Skim 30mm EN8 down to 28mm using a chip box tool on autofeed; Did that, no problem.

Next I need to skim down to 14mm on the same bar. This is giving me a problem. Tried using another chip box but it really struggles and auto isn't an option. It seems to get so far unhappily and then refuses to cut. Upon inspection, the tool is still sharp. I'm running it at full speed 2800rpm approx, loads of coolant.It's almost as if the surface has hardened. Or am I trying to take off too much in one go?

Any ideas? I'm stumped.

johnoder · Nov 25, 2019

EN8 is 0.36 to 0.44 % carbon content. EASILY work hardened by RUBBING instead of cutting. At your 2800 RPM and 8mm depth of cut you would need to be feeding along SMARTLY to avoid work hardening

Say the feed was 0.25 mm per rev. You would be traveling 25 mm in a little under TWO SECONDS

Unlikely the 2B has this sort of get-it-done power at that depth of cut

Steveng'14 · Nov 25, 2019

Thanks johnoder, your comment on work hardening certainly makes sense.

I think I'll slow it down and try again.

Limy Sami · Nov 25, 2019

What John Oder says, at 2800 rpm basically you haven't enough power on a Herbert #2

This might be a get over.

At 2800 rpm on 30mm dia bar you are pulling around 875 ft / min cutting speed - which is tramping on in anybody's language.

I'd try ''sorta'' halving that speed (say 1000 - 1400 ish)which will still give you <> 400ft a min (not slow!!) and should be outside the BUE zone, and run that @ <> 0.010 '' / rev PLUS - is in if it will pull more feed do it.

Why, - the reduced RPM should give you more torque, and less heat with the higher feed rate reducing thwe chances of work hardening.

You haven't mentioned coolant - but if you're trying to do this dry - all bets are OFF.

Steveng'14 · Nov 25, 2019

Thanks for that, and coolant was mentioned, positively jet washing the cutting tool with a good quality water soluable oil mixed to the recomended spec.

Will be back down the workshop in a bit and give it a try.

Limy Sami · Nov 25, 2019

Steveng'14 said:
Thanks for that, and coolant was mentioned, positively jet washing the cutting tool with a good quality water soluable oil mixed to the recomended spec.

Will be back down the workshop in a bit and give it a try.

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