Re: [CAD_CAM_EDM_DRO] Re: what is your max feed rate

Hi Fred.

I've just looked up the max feed rates on a couple of lathes :-
Microkinetics basic conversion kit at 8 ipm, advanced package at 20 ipm.
Compared to an OEM machine - Boxford 240TCL at 16 ipm.
I must admit, I'm quite suprised at the low speeds acheived with these
machines when compared to my lathe, which I had considered to be slow.
Max feed rate on mine is 5m/min or ~197 ipm.

Looking at the available specs, I would accept 100 to 200 RPM to be a
realistic speed for threading. But whilst many things affect surface finish,
with carbide tooling - assuming the correct grade and adequate coolant, a high
cutting speed is required.
From the Sandvik guide for a TCMT110204 insert - which I use as a general
finishing tool - in a grade GC4025. Typical values are given as :
Depth of Cut 0.4 (0.2 - 2.0) in mm
Feed rate 0.1 (0.05 - 0.20) in mm/rev
Surface speed 480 (415 - 505) m/min

Based on the figures quoted for machining BSi EN1A (or SAE 1115) given a
diameter of say 2 inches - Using a DoC of 15 thou, 3000 RPM and 11.6 ipm feed
based on a tool life of 15 min. Adjusting the cutting speed for a more
realistic tool life of 60 min results in a speed of 2250 RPM.
This is about the sort of speed I would use myself. One thing to note from the
Sandvik guide - "The surface finish can often be improved by higher spindle
speeds." - For those with variable spindle control, try taking a cut at low
speed, and gradually wind the speed up as the cut progresses.

Agreed, these speeds are probably a bit extreme for HSS tools, But I still
stand by my original assertion that a high spindle speed using carbide tooling
and coolant helps in giving a good finish.
To which I will add - IF your maximum feed rate and response times are fast
enough, then use the highest practical speeds.

Regards, Paul.

On Wed, 12 Jul 2000, you wrote:
> >For example - Spindle speed ~1100 RPM, 24 TPI thread = 46 ipm feed approx.
> > Within the capabilities of most lathes I would have thought.
>
> Paul many things come into play when threading. A poor finish at 200 rpm will not get much better
> at 800. A good tool will cut well in steel at a very wide range of RPM's.

> Just out of curiosity, what are the top feed rates on the Sherline-MaxNC-Taig, 3 in 1, etc., cnc conversions, either mill or lathe?
>
> Please everybody DON'T post your answers with my entire text re-quoted!!!