Diamond scrollsaw variable speed


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New member
12 Dec 2019
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I am new to UK WORKSHOP so hello from me. I have a diamond scrollsaw which I bought new, probably 20 or so years ago. It has been an excellent and reliable tool for me, but recently I have noticed the variable speed is not consistent. It will speed up and/or slow down as I am cutting, has anyone had this problem and any suggestions on what to about it.
Is it possible that dust has got into the switch?

If possible can you take the switch apart and clean it out, if not a decent hoover over and around the switch

As a second suggestion

Does the motor have replaceable brushes? they may have worn down over time
Have checked the brushes and they look good, plenty of carbon left, I have also checked and it looks cleen inside the variable speed control box. Are there any further things I can try?
Just a thought, have you checked the 2 drive belts are in good condition and not slipping, could be an issue
I don't know if it's a continuously variable speed, but if so the potentiometers get corroded with age, as well as dust. A squirt of a suitable contact cleaner may fix it.

Electrolytic capacitors age - if there are any in the speed controller, it could be the problem.