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View Full Version : Myford ML10, How fast dare I run the mamdrel.?



David Powell
12-15-2017, 03:38 PM
I have an almost mint Myford ML 10. Until now I have driven it with an AC motor and had a maximum speed of about 900 rpm, I have now fitted a DC motor and controller and can now run it up to about 2000 rpm. if I wish. The mandrel runs directly in the cast iron of the headstock. Can any of you confirm whether or not I will do damage if I occasionally run at such speeds. It is a fabulous machine for making fittings for my model steam engines and the higher speeds would help especially in drilling small holes. regards David Powell.

larry_g
12-15-2017, 04:37 PM
Way to many factors/variables in play here. My suggestion is to pay attention to the temperature of the bearing area. When the paint starts to burn off you've probably exceeded the max rpm or load ;) . The variables you are dealing with is cutting pressure, lubricant used, condition of the current bearings/spindle, and others. Me I would not run a plain bearing to 2K.

lg
no neat sig line

boslab
12-15-2017, 05:08 PM
I had a new from works ml10, it's on plain bearings, assuming good lube 1000 for a time, 2000 is going to shed its oil and run dry unless you can add forced lube, somthing like a metering unit and oil pump.
Doable I would think.
I do have a soft spot for them as it was my first lathe, not the best quality wise, better than Chinese.
In my case putting it on a wheeled base was not a good idea, too easy to move.
I did have its predecessor, same bearings ( no9 from the factory)
Mark

Rich Carlstedt
12-15-2017, 05:29 PM
The Limit speed for plain bearings is a function of the surface feet per minute (SFM of Bearing circumferences ) , the load, the clearances ,the lubrication method and the surface finish of the surfaces. My recollection (please note ! ) is that Cast Iron plain bearings have a liimit around 200-300 SFM versus bronze bearing at 700

Rich

The thing to also be aware is if you spin a cast iron chuck--THEY HAVE RPM LIMITS !

bob_s
12-15-2017, 07:01 PM
Well if it was still under warranty, ...

Magicniner
12-15-2017, 07:17 PM
Some good info here -

http://www.lathes.co.uk/myfordml10/

Hydrodynamic bearings, given adequate oil supply, are no the limitation which many believe ;-)

J Tiers
12-15-2017, 08:57 PM
The Limit speed for plain bearings is a function of the surface feet per minute (SFM of Bearing circumferences ) , the load, the clearances ,the lubrication method and the surface finish of the surfaces. My recollection (please note ! ) is that Cast Iron plain bearings have a liimit around 200-300 SFM versus bronze bearing at 700

Rich

The thing to also be aware is if you spin a cast iron chuck--THEY HAVE RPM LIMITS !

Is there an oil adhesion difference between CI and bronze?

I always had understood the difference had to do with viscosity and oil shear, that the speed had to build up the "edge", and not overshear it so it failed. The material being mostly important at start where there is metal to metal contact.

Am I missing something?