# Fitting a clutch to lathe.



## Downunder Bob (Apr 29, 2017)

I have been considering fitting a clutch to my lathe. It occurs to me that often when using a lathe we take a small cut stop the lathe, measure, restart the lathe, take a small cut and stop it again. etc, etc. This constant stop start cannot be good for the motor, particularly the start caps, and switch gear.

Most of the lathes that I used when working had a clutch and the motor was left running. The clutch often incorporated a brake. I would also like to have a brake.

So I'm thinking would a clutch taken from an auto A/C unit be suitable, my lathe motor is 1.5 HP. I'm sure the auto A/C clutch can handle more than that. It also occurs to me that a second such clutch could be set up to operate as a brake.

I realise that it would require a 12v dc power supply, but that is not a problem, not sure how many amps it needs.

Would this work, has anyone tried this or something similar, or am I missing something obvious.


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## whitmore (Apr 29, 2017)

bobshobby said:


> I have been considering fitting a clutch to my lathe. ...constant stop start cannot be good for the motor, particularly the start caps, and switch gear.... I would also like to have a brake.



The shaft on the A/C in a car is not likely the same as the keyed motor shaft.
It might be easier to get a clutch/pulley prebuilt assembly,
with a mechanical engagement ( controlled through a bicycle's
brake-cable and pull-handle, perhaps).

Probably the cost of that clutch (and labor to install) greatly exceeds the
'wear' on a modern motor's parts when it starts/stops.   In my home
shop, the quiet after the motor turns off is a benefit...

Braking, on the  other hand: if you can wire the OFF position of
the AC motor to bleed just a trickle of DC into the windings, that should
stop it spinning.   A little doorbell transformer, a rectifier, and maybe
a time-delay relay, would be an efficient combination.  Or, just a
battery, resistor, and pushbutton.


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## larry4406 (Apr 29, 2017)

Electric PTO clutch from a tractor mower to engage blades has a straight keyed shaft.


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## Downunder Bob (Apr 30, 2017)

larry4406 said:


> Electric PTO clutch from a tractor mower to engage blades has a straight keyed shaft.



Yes I have looked at them about $250 on ebay, saw the keyed shaft but haven't been able to find out any tech details although I believe the shaft dia is 1"at least on some models. they should be able 1.5 HP easy. however I think they are somewhat larger than than auto A/C ones. Anyway I'm just looking info at the moment, I was hoping someone here had tried it.


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## Downunder Bob (Apr 30, 2017)

whitmore said:


> The shaft on the A/C in a car is not likely the same as the keyed motor shaft.
> It might be easier to get a clutch/pulley prebuilt assembly,
> with a mechanical engagement ( controlled through a bicycle's
> brake-cable and pull-handle, perhaps).
> ...



Yes I get that the shaft will probably need some kind of adapter , or maybe bore the clutch to fit , not a serious problem, isn't that why we have lathes etc.?

And I see the partial advantage of a hand operated clutch, but maybe don't always have a spare hand, I was thinking of a  simple on /off button, or toggle switch.

part of the desire to avoid constant stop and start use is  based on the well known fact here in Australia, we have a problem with asian electrics in that they are made in 110v for your end of the world, and they are made in 220v for Europe, but here we run 240v just to be different. most of the equipment we get is simply 220v stuff relabeled 240v and failures are common.

Projects don't always have to be cost effective, It's the challenge, to change something. the motor should be pretty quiet, the noise will be coming from the gears.  My personal philosophy tells me that everything is made to a price and or the makers process needs, so a smart person can always improve it.

Not sure if your trickle of DC is going to work, as in a quick stop, without damaging the motor and switch gear. My thought is to have a big red stop button which opens the clutch, and simultaneously slams the brakes on. The brake is only stopping the gearbox, shaft and chuck. the motor can just keep running.


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## mksj (Apr 30, 2017)

By going to a 3 phase motor, there are no start/stop issues to deal with. Using a VFD you get both controlled acceleration and deceleration to whatever degree you want. I have done a number of smaller lathe conversions, often go with a 2 Hp motor if it will fit. Alternatively you could go with a DC motor and controller with braking. A lot easier then adding clutches and brakes and the space it would take up. There are also brake motors for either single phase or 3 phase, but they are pricey. Expense wise, if you do both a mechanical brake and some form of clutch, a VFD and 3 phase motor would probably be similar in cost. 

Slamming the lathe to a stop, I would be less concerned about the motor and more concerned of the longevity of the gear train/drive. There is a lot of momentum in the system, a mechanical brake slammed on at speed generates a lot of braking force and something would eventually break. VFDs you can control both the time an slope of the braking rate, so would be a bit gentler on the system. I normally use 3 second braking with VFDs, 1 second only for slow speeds or emergency braking.


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## larry4406 (Apr 30, 2017)

I bought an electric PTO clutch from this company for $163 (US$) for my tractor.  Nice unit.
https://xtremeope.com/


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## rgray (Apr 30, 2017)

I don't know if amazons any good for your area, but there are plenty of styles of mag clutches on there.
These mower clutches are meant to run vertically....not sure if that would be an issue.
I did find some clutch/brake combination industrial units, but no pricing. I would imagine they are expensive.
Sounds like some release the clutch and apply the brake at the same time. Perfect 

https://www.amazon.com/s/ref=nb_sb_...ctric+clutch&rh=i:aps,k:mower+electric+clutch


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## Kernbigo (Apr 30, 2017)

vfd drive is the only way to go


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## rgray (Apr 30, 2017)

mksj said:


> Slamming the lathe to a stop, I would be less concerned about the motor and more concerned of the longevity of the gear train/drive. There is a lot of momentum in the system, a mechanical brake slammed on at speed generates a lot of braking force and something would eventually break. VFDs you can control both the time an slope of the braking rate, so would be a bit gentler on the system



If I was to attempt this I would install the brake on the spindle. Therefore not braking through the gear train.
The largest amount of momentum before that is the motor itself and it could probably just slip the belts if a sudden stop was done.
Mechanical braking on the imput would be a bad idea I think. It would have a different effect depending on what gear the lathe is being run in. 
I agree the VFD braking is very nice. Smooth and not harsh.


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## Downunder Bob (May 1, 2017)

mksj said:


> By going to a 3 phase motor, there are no start/stop issues to deal with. Using a VFD you get both controlled acceleration and deceleration to whatever degree you want. I have done a number of smaller lathe conversions, often go with a 2 Hp motor if it will fit. Alternatively you could go with a DC motor and controller with braking. A lot easier then adding clutches and brakes and the space it would take up. There are also brake motors for either single phase or 3 phase, but they are pricey. Expense wise, if you do both a mechanical brake and some form of clutch, a VFD and 3 phase motor would probably be similar in cost.
> 
> Slamming the lathe to a stop, I would be less concerned about the motor and more concerned of the longevity of the gear train/drive. There is a lot of momentum in the system, a mechanical brake slammed on at speed generates a lot of braking force and something would eventually break. VFDs you can control both the time an slope of the braking rate, so would be a bit gentler on the system. I normally use 3 second braking with VFDs, 1 second only for slow speeds or emergency braking.



I had thought of 3 phase and VFD etc., and even though I have  3 phase available I decided against it, I could yet go that way but just looking at alternatives.

The brake would rarely ever be used. it is strictly emergency use only. Just thinking out loud.[/QUOTE]


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## Silverbullet (May 1, 2017)

For the brake an electric solenoid with a brake band should work. Some of the electric MOWER clutches do brake the belt to stop the blades or other moving parts. You don't know if it will or don't work if no one tries to use one. I'd be careful with sudden stops and full speed starts. More damage will happen if done often. In my opinion anyway.
Just had another thought how about the manual clutch used on the big old singer motors , they held up well and easy to service .


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