minilathe speed reduction

Hi Micheal

Perhaps new fabricated pulleys using "Poly Vee Belts" can be made to fit in place of the originals.

Now assuming that this head stock has a two speed gear box and belt drive then increasing the belt drive ratio then increases the load on the somewhat flimsy gears breakage is a lot more likely.

My hobby over the last few years has been renovating repairing workshop machines and re powering with mainly DC Motors.

A bigger motor or increase the drive ratio to increase torque at the spindle with a loss of top speed.

Eric

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Michael,

Poly Vee Belts are much better performing than the conventional vee belt.

... at this size you could probably use 19mm motor pulley.

They've changed the rules of the game !!

MichaelG.

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I see that the standard drive is via 'timing belt'  ... What count are the pulleys ?

https://www.amadeal.co.uk/acatalog/CJ18%20Manual.pdf

Edited By Michael Gilligan on 25/08/2018 21:55:29

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31 ... That's surprisingly low [to me, at least]

Whilst you are checking the motor pulley, could you please also let us know details of the belt [hopefully marked on it]

I'm sure the team can come up with some suggestions

MichaelG.

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Edit: that was quick !! 

Let's dicsuss tomorrow.

Edited By Michael Gilligan on 25/08/2018 22:47:42

If the metal gears won't give way then something else like the control board will be the next down the line.

Also if you go much smaller that 18T on the motor you may have a job getting the belt to grip without chewing off the teeth. You want to go bigger on the driven pully not smaller to reduce the speed.

Edited By JasonB on 26/08/2018 07:29:08

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That's great, Michael ... it confirms what I found on the Amadeal site:

Here's an extract from the manual that I linked ^^^

What Eric and myself are proposing is to replace the two timing pulleys (27) & (148) with Poly Vee.

... I feel quite comfortable that 3 or 4 rib J section belt would work very nicely, and you could easily get a high reduction ratio in the same space as the existing arrangement.

An incidental advantage is that a poly vee belt can be tensioned such that it will slip before the gears fail

MichaelG.

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Edit: useful references to the original parts

https://www.amadeal.co.uk/acatalog/Drive-Pulley-for-CJ18---Part-27-533.html#SID=268

https://www.amadeal.co.uk/acatalog/400W-motor-for-CJ18A-Mini-Lathe-AMA_SP_CJ18_150_400W.html#SID=240

https://www.amadeal.co.uk/acatalog/Timing-Belt-AMA_SP_CJ18_029RB.html#SID=198

https://www.amadeal.co.uk/acatalog/CJ18-Metal-Gears-Set-AMA_SP_CJ18_2418MGRB.html#SID=11#SID=11

Edited By Michael Gilligan on 26/08/2018 10:22:05

The very first job on my lathe years ago was to machine the smallest pulley I could to reduce the speed of my lathe for single point threading. I managed to get the lowest speed down from 180 rpm to about 100 rpm. The pulley is still on the lathe, I never put the original back although I still have it.

Your lathe has a brushless motor?

They should advertise it better, because I can't see it on their website.

Here are a couple of ideas:

http://mikesworkshop.weebly.com/speed-reducer.html

http://www.toolsandmods.com/lathe/mini-lathe-motor

Many more by googling mini lathe speed reduction

As always depends on what you're doing with the lathe. But, as small lathes often turn small diameter parts, 2500rpm isn't ridiculous, even less so if you use carbide.

When I had a mini-lathe I would mostly use low gear (up to 1200 rpm) for anything over, say, 20mm diameter, and high gear (up to 2500rpm) for anything less than about 20mm diameter. I prefer carbide inserts which work better at higher speeds. Low rpm is essential for threading under power, which might make smaller pulley attractive. However, I used a spindle handle for threading on a mini-lathe and found manual threading easier to control all round.

Brushless lathes are still a relative novelty. Yours is the first brushless mini-lathe I've heard of and it's performance is likely an unknown quantity due to lack of experience with them on the forum. I'd expect it to be better than a conventional DC motor but not wildly so. Personally, I'd spend some time getting used to the machine before rushing to modify it. Sod's Law says you discover you need 2500rpm just after going to a lot of trouble altering the pulleys!

If you feel the lack of torque, beware you're not overdoing it. Mini-lathes aren't industrial metal munchers that can be pushed to the maximum. Think Fiat 500 rather than Humvee.

Dave

Cor Dave, you aren't paying attention! The earliest mention of the SIEG SC3 (brushless mini lathe) I can find on this forum is April 2011....

Neil

Just like being back at school! I didn't pay attention back then either...

Please don't tell mum I've been caught daydreaming in class again. She still thinks I'm wonderful.