Running motor at higher hz to achive more rpm

[Cheesie]

Anyone run their standard motor at a higher hz through their hfd to achieve more speed not looking to go mega fast even 250rpm would help my harrison 140 is limited to 750rpm, its more of a limitation on smaller aluminium parts

 

[Hood]

You may need more than 250rpm on the motor to get 250 more on the lathe.

As to your question, yes it is done often but the motor will dictate how safe it is to overspeed. If a modern VFD compatible motor then it shouldn't be an issue.

As an aside, 750 rpm is, for me, fast enough for most things.

 

[Brad93]

Anyone run their standard motor at a higher hz through their hfd to achieve more speed not looking to go mega fast even 250rpm would help my harrison 140 is limited to 750rpm, its more of a limitation on smaller aluminium parts

Swap the pulley.

Problem is you'll have the same motor as mine which is 1.5hp and really when you start overclocking the motor your torque drops off.

Fit a bigger motor and a bigger pulley

 

[optima21]

also when you run them faster the power losses through the transmission also increase.

 

[Scalarocco]

Also, be aware that while the spindle bearings may take the extra rpm the lay shaft bearings in the work head may not like it.

 

[Chippie]

My Warco wm290 lookalike, originally fitted with a 1.5kw dc motor whose speed was around 4200rpm, was swapped out with a 3 ph frame 80 motor, rated speed on that was 2800rpm…So to get back to the headstock spindle speed of 1000 rpm on low belts, I raised the motor speed by increasing the vfd freq. to 70Hz….gives me around the original motor spindle speed…If I remember rightly…

 

[fizzy]

Anyone run their standard motor at a higher hz through their hfd to achieve more speed not looking to go mega fast even 250rpm would help my harrison 140 is limited to 750rpm, its more of a limitation on smaller aluminium parts

Try one of these tools - really helps and you get a lovely finish. Also use them on steel.
Even small aluminium parts are great at 500rpm.

 

[Cheesie]

first batch of production work I done on it 12mm cut to length drilled then tapped doing them got old fast my fault for not charging enough, I'll have a search for that tool fizzy thankyou

 

[Brad93]

Also, be aware that while the spindle bearings may take the extra rpm the lay shaft bearings in the work head may not like it.

all harrison 140 runs the same bearings regardless of speed

 

[winchman]

We used to increase the conveyor speeds in a previous job if we where behind by increasing the HZ on the drives, but we had to provide additional cooling ( Air Line) to keep them going.
Personally I would change the pulleys as Brad suggested

 

[daleyd]

Assuming that as you want higher speeds the diameter of the parts you will be turning will smaller I don’t see any reason why you couldn’t try and use a higher speed. I don’t think I’d go mad and set something like 100hz but maybe 70-75 hz would be achievable (take it up in steps, and monitor the bearings and motor temperatures and listen out for anything that sounds a bit strange) - one thing to be aware of as said above is that the torque will drop off as you go above 50hz so I wouldn’t expect the same performance above this. But for light cuts on smaller diameters then it’s probably going to be ok.

 

[Cheesie]

Assuming that as you want higher speeds the diameter of the parts you will be turning will smaller I don’t see any reason why you couldn’t try and use a higher speed. I don’t think I’d go mad and set something like 100hz but maybe 70-75 hz would be achievable (take it up in steps, and monitor the bearings and motor temperatures and listen out for anything that sounds a bit strange) - one thing to be aware of as said above is that the torque will drop off as you go above 50hz so I wouldn’t expect the same performance above this. But for light cuts on smaller diameters then it’s probably going to be ok.

That was kinda the plan try it at 70hz leave the base at 50hz and only ramp up if I'm on small aluminium parts

 

[daleyd]

That was kinda the plan try it at 70hz leave the base at 50hz and only ramp up if I'm on small aluminium parts

Give it a whirl, costs nothing (providing the mechanicals and the motor itself are sound) as long as you are aware of any unusual noises/vibrations etc. You’ll notice if things aren’t right and it starts bogging down.

 

[Kram]

Correct that torque drops off, but on small alu parts you dont need torque and its fine to run in constant power mode. Realistically the same power spread over 5000rpm would be more than adequate torque for under 30mm work.

My warco has a 3:1 reduction and a 6 pole motor (roughtly 1000rpm at 50hz). So thats 333rpm spindle as standard. I run motor upto 2400rpm as, for bearings, its not really all that fast, it would probably take 4000rpm all day long, I just havent needed it enough to experiment.
The fan will spin faster so cooling wont be an issue and I've never had a problem with heat, running it slow either.


Check what pole motor you have, if its a fast one already, you'll have less headroom on motor bearings to increase speed.

 

[Agroshield]

...its more of a limitation on smaller aluminium parts

What is the actual limitation?

You cannot remove metal fast enough? You cannot get a good finish?

For the second, the suggestion above of a high positive rake, polished insert is good (note that the shape fizzy shows is a size 16 V-insert, but the non-ferrous inserts are available in all shapes, and for the size of those parts a smaller CCGT06 might be cheaper).

If metal removal is needed, consider a rear toolpost with an upside down tool. Rough with that (as it is less easy to set a precise cut depth) and then follow at the same time with a finishing cut from the front tool. Tie the tailstock to the carriage and drill the tapping hole at the same time as doing the OD turning.

If you are doing repetition work, the more things you can do simultaneously (parallel processing in computer-speak), the quicker the parts will be finished.

 

[Pete.]

Motor/layshaft/spindle bearings are never going to be the limiting factor on a workshop lathe. Ball type bearings that is. I don't know why people keep churning out the same warnings about bearing speeds. They don't fit different bearings to a 2-pole motor than they do a 4-pole motor of the same type because neither will even come close to approaching the bearing's design limit.

 

[daleyd]

Motor/layshaft/spindle bearings are never going to be the limiting factor on a workshop lathe. Ball type bearings that is. I don't know why people keep churning out the same warnings about bearing speeds. They don't fit different bearings to a 2-pole motor than they do a 4-pole motor of the same type because neither will even come close to approaching the bearing's design limit.

Quite so - I’d keep a cautious ear out the first time you do it being a (presumably) older used machine as you don’t know the condition of bearings etc at higher speeds but ultimately as long as they don’t sound/feel rough they are very unlikely to be a limiting factor.

 

[mike os]

Short term occasional use it’s fine to probably 150% … or 75hz

I wouldn’t want to run it long or often above that

If it’s a regular thing change the gearing … and watch bearing temperature on the headstock

 

[roofman]

The good ole USA run 60hz, plenty of English machinery including lathes went there...so we know 60hz does no harm anyway

 

[RWD3M]

I did this the other way round. I bought a 6.5hp 240v compressor in the USA and shipped it back here. It ran well for a good while but eventually the motor burnt out, likely due to the increased current of running at a lower frequency.