Yea as long as oil is getting to those bearings you should be fine. Bearing in lathe spindles are way better than they need to be in my opinion. They named to add some qaulity to other stuff before going into super precision bearings.
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Maximum Safe Rpm For A Grizzly G4003g
- Thread starter Xiansheng
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- Mar 8, 2014
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Hi Everyone,, To respond to the several responses that have been made in the last 10 hours, I realise there might be issues with the headstock gears and bearings, and I believe more risk with the gears. I simply will replace the bearings with the best I can buy if they fail, and likewise with the gears, that said, I repeat my previous comment that I don't intend to use 2500 RPM except on rare occasions, for small jobs. I also would not use a chuck or faceplate at such speeds, because there is too high a risk that they will disintegrate. Collets would be my only choice at 2500 RPM. I remember as an apprentice using a high-speed Chaublin lathe for small work and it was only used with collets (a very nice lathe, I must say!). Another reason for the 2500 upper limit is my opinion that the present maximum RPM of 1440 RPM is limiting. Many jobs will not be machined at their correct cutting speed at this limit. Coolidge's suggestion to use a proximity sensor and vfd electrical brake is interesting and thought provoking.
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FYI: VFD proximity sensor stop
http://www.hobby-machinist.com/threads/vfd-proximity-sensor-stop.32816/
Regarding safe operating speed, although the bearings may be rated for higher speed, lubrication to the bearings is probably the rate limiting issue when using splash lubrication. Most lathes in this size/type limit out at around 2000 RPM. It may do higher, for short periods, but if the bearings go it could cause additional damage. I would use an ISO32 oil (which is the standard for most Grizzly lathe gear heads), as higher viscosity oils cause too much frictional drag.
http://www.practicalmachinist.com/v...eadily-available-oils-will-work-pinch-278701/
"Most of those small lathes will do 2,000 RPM. It's not the gears, its the bearings. An oil that's too viscous will heat those bearing up in a hurry if you run a very fast RPM. Almost all the lathes that I've seen in 15" and under take ISO-32 in the headstock. IMO, Vactra would probably wipe out a set of bearings if you ran very fast. It just doesn't squeeze out of the way like hydraulic oil does. Somewhere, if I haven't thrown it out, I've got a calculation sheet from one of my lube schools. You put in all of the bearing data plus the RPM and do about 20 calculations an end up with a maximum film thickness of the oil/grease you can use."
http://www.hobby-machinist.com/threads/vfd-proximity-sensor-stop.32816/
Regarding safe operating speed, although the bearings may be rated for higher speed, lubrication to the bearings is probably the rate limiting issue when using splash lubrication. Most lathes in this size/type limit out at around 2000 RPM. It may do higher, for short periods, but if the bearings go it could cause additional damage. I would use an ISO32 oil (which is the standard for most Grizzly lathe gear heads), as higher viscosity oils cause too much frictional drag.
http://www.practicalmachinist.com/v...eadily-available-oils-will-work-pinch-278701/
"Most of those small lathes will do 2,000 RPM. It's not the gears, its the bearings. An oil that's too viscous will heat those bearing up in a hurry if you run a very fast RPM. Almost all the lathes that I've seen in 15" and under take ISO-32 in the headstock. IMO, Vactra would probably wipe out a set of bearings if you ran very fast. It just doesn't squeeze out of the way like hydraulic oil does. Somewhere, if I haven't thrown it out, I've got a calculation sheet from one of my lube schools. You put in all of the bearing data plus the RPM and do about 20 calculations an end up with a maximum film thickness of the oil/grease you can use."
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- Dec 2, 2012
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- 1,721
If your vfd can have more than one ramp up duration that might be nice to the gears to give it a less harsh acceleration period or manualy ramp it up using the speed pot.
Sensible about the no chuck at high rpm , i cant even imagine a Big 3 or 4 jaw at that speed. Wow
The other thought, as was said about oil and stuff is how does it move the oil in the head stock? If theirs any kind of impela it will be under more load at the higher rpm, if its just the gears flinging the oil thats probably a non issue.
With the low rpm side i have managed to heat up my bench mill motor quite significantly hot doing some extended work at a much lower rpm due to the cooling fan not running fast enough (its 0.75kw and gets warm to the touch in normal 50-65 hz range) threading would probably be running the motor for reasonably long times, although i suppose it would generally be short threads you would want to do at that speed.
Stuart
Sensible about the no chuck at high rpm , i cant even imagine a Big 3 or 4 jaw at that speed. Wow
The other thought, as was said about oil and stuff is how does it move the oil in the head stock? If theirs any kind of impela it will be under more load at the higher rpm, if its just the gears flinging the oil thats probably a non issue.
With the low rpm side i have managed to heat up my bench mill motor quite significantly hot doing some extended work at a much lower rpm due to the cooling fan not running fast enough (its 0.75kw and gets warm to the touch in normal 50-65 hz range) threading would probably be running the motor for reasonably long times, although i suppose it would generally be short threads you would want to do at that speed.
Stuart
- Joined
- Mar 16, 2016
- Messages
- 14
If you run the lathe at low RPM's, the oil will not reach the spindle bearings. Rev the speed up to sling the oil to upper part of the gearbox. It then flow into the holes for the spindle bearings.