Mill spindle speed, how important is it?

I am thinking of buying a new mill. My current mill has six speeds from 110 - 1600 RPM. My current candidates are all have variable speed motors, and the top ends are between 1750 on a larger mill and 2250 on the smaller mills.

At some point I will want to use small cutters e.g. 2mm, how important is the spindle speed. Should I go for a smaller mill with the possible loss of rigidity but faster spindle, or the larger more solld mill with a slower spindle.

Adrian

What do you sort of work do you plan to do with your Mill Adrian?

Regards,

IanT

A 2mm HSS cutter would be looking for 4000rpm for steel so unless you have a high speed spindle to fit then most general purpose mills will be a bit slow. This is a cross that most of us have to bear with small cutters. If you plan on a lot of work for small cutters then a speed increaser or a high speed spindle may be worth it. Brass aluminium and carbide cutters will all want even more speed for maximum productivity but running slow and for hobby purposes it should be ok. Carbide tips can sometimes not give their best performance if the are not run hard enough but at 2mm this problem will probably not occur.

Mike

Ah the age old question, what will I do with it all.

So far I seem to spend my time making tools to make tools to make things. I have just completed my first wobbler. I would like to make some more complicated engines, hence the thought of small cutters for steam ports. I don't think I will make large models at most I would guess 1" bore.

It seems unless I want to spend many thousands I cant get a mill that runs at the speeds that the size of mill would infer. Ie a small mill for small things but they all run too slow.

I was wondering how others deal with it, what do owners of Sieg SX2.7, Seig SX3, Warco WM 16, Chester Champion 20v handle the low speeds.

Adrian

I have seen high speed motors with er collets on them on ebay, I wonder if one could be attached to the head or quill of a mill when the very small cutters are used? I found this on ebay with an er11 collet which goes from 2000, to 12000 rpm.

https://www.ebay.co.uk/itm/400W-CNC-DC24V-52V-High-speed-Air-cooled-Spindle-Motor-for-Engraving-Milling/221839037678?hash=item33a6a314ee:g:V2cAAOSw3ydVuEMh

Edited By old mart on 26/04/2020 18:50:15

Here's another more sophisticated one with an er 20 collet, even more power and speed.

lUAAOSwYVRcxsD4">https://www.ebay.co.uk/itm/EU-2-2KW-ER20-220V-Air-Cooled-Spindle-Motor-2-2KW-HY-VFD-Inverter-Driver-400HZ/383501508816?hash=item594a78a0d0:glUAAOSwYVRcxsD4

Small cutters will work OK at less than optimum speed, you may loose a bit of tool life and the job will take longer as you can't feed as quickly, I have no problems using 1.5-2mm cutters on my X3 or the SX2.7

I think I would rather have a benchtop will that has a bit more low end grunt than one with the motor belted up to give a higher top speed with the loss of low end torque. 

The only one that springs to mind that will do both is the SX3.5 which has a toothed timing belt for low range and a polyVee for high speeds upto 5000rpm

Oldmart, plenty of mills with high speed spindles mounted on the side of them about be they manual or CNC

Edited By JasonB on 26/04/2020 19:18:35

I rarely use small cutters on the Bridgeport. It's too darn easy to get the feedrate slightly wrong and ping goes the cutter, even at several thousand rpm. On the CNC mill I'd be running a 2mm cutter in steel at 5100rpm, and that's limited by the machine. For really small cutters (<1mm) I have a high speed spindle on the CNC mill which goes up to 24000rpm. One of the big changes due to improved cutter materials and coatings is the rise in spindle speeds.

On a manual mill a slow top speed would be a PITA for me. Of course the cutter will work, but you're very reliant on being able to create a steady feed. Overdo it with a bigger cutter and you'll stall the machine. With a small cutter it's ping and a trip to the local tool emporium.

Andrew