Spindle speeds

RandyWilson

H-M Supporter - Gold Member
H-M Supporter Gold Member
Joined
Aug 29, 2016
Messages
838
Speaking of carbide in the home shop... I have been working with the settings of my VFD. The question is how fast should I set the upper limit? The faster the better for carbide, so I don't want to be overly conservative. Here's the factory info, advertised speeds.

Mine is a 14 1/2. I have a VFD and a Reese drive so I can hit outlandish speeds if I choose.

16" 980 rpm on 2 7/8" bearings
14 1/2" 875 rpm on 2 5/8" bearings
13" 940 rpm on 2 1/4: bearings
10" 1400 rpm on 2 1/4" bearings


Obviously we don't want max speed while swinging an off-center part in the 12" four jaw, but y'all think 1200 rpm for collet work would be an issue?
 
Upper limit seems most likely impacted by a chuck; bearings’ limit depends on configuration and lubrication. Are they all oil lubricated? If so, I’d imagine 1500-2000 rpm wouldn’t be a problem at all.

For collet work, you’re talking smaller diameters so you may want even more than that.
 
Yeah, all the examples are like era with plain bronze bearings oiled via wicks. I suspect you may be right. Small work with little radial (cutting) loads could probably spin quite a bit faster. The open geartrain may be more of a limit than the spindle..

I briefly spun it to 1200 today with no load. It didn't explode.
 
I would be more concerned with the motor than the lathe.
I don't run NON INVERTER DUTY motors over 75 Hz.
Can it be done? Sure...anything can be done , it's just rolling the dice.
This is why the Engineers designed the machine with the usable RPM ranges that at least included the calculation of the surface footage of the spindle bearings. Lubrication pays a part in the RPM limitations of plain bearings..
 
With the Reese drive, I can easily hit over 2500rpm @ 60hz. With the sheaves cranked all the way down to the lowest setting, the drive ratio is still roughly 50% faster than stock. These are the cards I was dealt when I bought the lathe. I'm just tuning it to my best advantage.
 
Having a Reeves drive is a luxury not many of us are privileged to have.
 
Is your concern the bearings or motor ? Those a fairly small bearings so speed should not be an issue with that size. Are there two radial load plain bearings and a thrust or a different configuration using tapering bearings? With a Reeves drive I agree that there should be no need for much variation from 60 hz needed. 50-2500+ should be doable. My lathe runs up to 3000 rpm and I have the bearings adjusted so they start to get warm after 5 minutes at 3000. I seldom go higher than 2500 but spindle bearings should warm up a little to tighten the clearance and minimise the runout on the spindle. I usually run the spindle a little at high speed before turning stuff to warm up the bearings. Bearings of that size will have an upper speed limit much higher than 3000, even in grease. Oil is even higher. Precision bearings that should be in the spindle often have a speed limit up to three times higher than normal stamped steel cage bearings.

A 6 inch chuck or collets are a better choice when you get into the 2500 rpm range. I don't like my 8" at those speeds but it is an old chuck and 2500 was the limit when new. Dave
 
The Reeve(??) drive is not really a good thing. It's not one of the easily adjustable ones. You have to adjust the preload spring on the driving shaft, then adjust the motor sled to pull the belt down into the primary sheave. The driven sheave is fixed. All this is done while laying on your side between a tool cabinet and the lathe working through the side of the bell. Needless to say, I got it slowed down as much as I can within the constraints, and leave it. It's still about twice as fast as the stock system.

The spindle is held in bronze bearings with thrust taken by ball bearings The motor itself is the least of my concerns. If it fails, it would be replaced with something more VFD friendly. It's not original, so not a big deal beyond the cost. My main concern is the lathe itself. Have you priced used South Bend parts lately? Insane.
 
Whar lathe and has it been modified from original? sorry if i missed that. I run a TENV motor on my lathe to give it more adjustment and run it up to 120 hz. Dave
 
I should have realized the subforum this is in. I know next to nothing about plain bearings. Interesting to read though.
 
Back
Top