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Variable Speed Bench Sander Conversion

Legs

ADC
Book Reviewer
I have a Clarke brand bench sander/disc sander combo thing. TBH, it's pretty pants, but it's what I have and I can't afford to replace it with a decent one - I spent all my cash on a professional lathe.

This POS machine has a simple on/off button. Much of the wood I use burns at the speed this thing runs at. Can anyone tell me how to take the thing apart and convert it from the on/off button to a variable speed controller. I'm no electrician, but I know how to do the basics of electrikery.


Oh, and never, ever by 'Clarke' branded stuff. It's crap.
 
Put a dimmer switch in line?

Not sure how it would handle the current though.
 
I have a variable speed belt sander mounted vertically While I wait for a decent bandfacer to turn up on marketplace...
 
I believe most of these simple on/off devices have an induction motor and speed is determined by the AC frequency (UK = 50 Herz). Probably not possible to easily make it variable speed.
 

Joe_Private

On ROPS
On ROPs
I have a Clarke brand bench sander/disc sander combo thing. TBH, it's pretty pants, but it's what I have and I can't afford to replace it with a decent one - I spent all my cash on a professional lathe.

This POS machine has a simple on/off button. Much of the wood I use burns at the speed this thing runs at. Can anyone tell me how to take the thing apart and convert it from the on/off button to a variable speed controller. I'm no electrician, but I know how to do the basics of electrikery.


Oh, and never, ever by 'Clarke' branded stuff. It's crap.
If it's an AC motor, which it probably is, then its speed of rotation is governed by the frequency of your electricity supply, so the first option is to go down to the power station and adjust the speed of the generators. Your second option is to buy an inverter, ensuring it is a variable frequency inverter, and use that to power your sander.
 
Pair of mole grips on the motor spindle. The tighter they are, the slower it goes.
 
A dimmer switch will just reduce the torque. It either needs to be done mechanically, via gears, or electronically with a speed controller.

Whichever way, it's not viable on such a budget machine.

Sent from my neocore_E1R1 using Tapatalk
 
Modify by adding an Off / Half-speed switch which has a suitable Amp & Volt rated rectifier diode in series with +240v supply
eg 1N4007 for up to 1 amp
 
Modify by adding an Off / Half-speed switch which has a suitable Amp & Volt rated rectifier diode in series with +240v supply
eg 1N4007 for up to 1 amp

1597703668238.jpeg


(with thanks to @MrBane for the use of his avatar)
 

Legs

ADC
Book Reviewer
This is the newer version of the POS I have: Crappy tool on-line catalogue

I've looked around the web. All the ones that say they are variable speed only seem to have "on" and "off" buttons and no speed adjustment. Maybe they mean it's two speed: xxx rpm or zero rpm...
 
This is the newer version of the POS I have: Crappy tool on-line catalogue

I've looked around the web. All the ones that say they are variable speed only seem to have "on" and "off" buttons and no speed adjustment. Maybe they mean it's two speed: xxx rpm or zero rpm...

That's a direct drive induction motor, so mechanical schemes are out. To change the speed of induction motors, you really want to change the frequency, but that's not going to be cheap. You could change the applied voltage, like @pcar964's suggestion, but that's a) going to fvxk with the start capacitor and b) still a pain in the arrse.

There are other more esoteric methods of motor control with ever more exotic semiconductors (diacs/triacs), but that's going to cost even more.

I'm afraid my assessment is "you're shit out of luck". Perhaps try either different grits, or even different wood.

Perhaps there's some residual value in the machine and you can find a different sander used?
 
There's a very simple method to reduce the speed of the belt. Note that when I say simple, that refers to the principle. How simple it would be in practice would depend on how handy you are in the workshop.

Substitute the drive wheel with a smaller one.

That's the principle sorted. Now you've just got to source or make a new drive wheel, come up with a belt tensioner and adapt what you have to keep it all together. There are probably no end of people capable of doing the work inside a couple of hours but are you one of them?
 
There's a very simple method to reduce the speed of the belt. Note that when I say simple, that refers to the principle. How simple it would be in practice would depend on how handy you are in the workshop.

Substitute the drive wheel with a smaller one.

That's the principle sorted. Now you've just got to source or make a new drive wheel, come up with a belt tensioner and adapt what you have to keep it all together. There are probably no end of people capable of doing the work inside a couple of hours but are you one of them?

Indeed, but that particular machine would be difficult to adapt, looking at its schematic.
 
Indeed, but that particular machine would be difficult to adapt, looking at its schematic.
Doddle, now I've looked at the exploded diagram. Remove the belt, start the machine, apply a file to part 54 (drive pully) until it's sufficiently reduced in diameter*, switch off, refit belt, adjust tension**. Done.

*It's not clear how much this can be filed down. It may require a drive pulley made from scratch. Also might need to remake part 60 and one or two other minor bits although part 54 shouldn't need to be filed down in this area so part 60 should be OK as is.

**May require a bit of tinkering if there isn't enough adjustment. Probably just need to extend a couple of slots and use longer bolts or something. It'll be obvious what's needed.
 
Splash a bit of old camouflagey looking emulsion on it and then get it for sale on eBay...

*** Rare *** Ex SAS Combat Sander as used by Sgt Sandy McNob


Give it a bit of absolute bollox fake provenance / back story and before you know it you’ll have the funds to buy any workshop tools you desire plus some left over for a new workshop.
 
My leccy drills and routers have variable speed triggers/adjusters, can these be transplanted?
 

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