off hand grinder

Should the RH wheel on an off hand grinder be held in place with a RH or LH nut.

Mine is held with a RH thread and keeps coming loose. I'm wondering if the armature has been put in back to front.

Looking at the wheel from the right hand side it should rotate anti-clockwise and therefore a RH nut should tend to tighten, the left hand end should have a LH nut. The wheel rotation should tend to push the work onto the rests.

Mike

Edited By Michael Poole on 21/09/2016 11:06:52

Hello Eric,

​Running the grinder the correct way as Michael Poole desscribes, sparking and grinding residues will be directed down below the tool rests as well. Incorrect rotation will fling that upwards straight at your face.

​As you describe matters it is all very odd. If the rotor has been fitted in reverse, the same effect should be apparent on the left hand side of the grinder and the nut loosening will have been a problem right from purchase.

​Brian

I would have thought that the RH wheel would have a LH thread so the anti clockwise rotation of the wheel (viewed from the side) would tighten a LH nut.

Eric, think about start up. The motor shaft spins and the wheel tries to stand still and resist it. That results in a torque on a right hand nut TIGHTENING the nut to make sure the wheel is secure. The same argument applies to the opposite end of the grinder which is why the left hand wheel (standing facing the front of the machine has a left hand thread.

The only time the right hand thread on the right hand wheel would tent to come undone is if the motor shaft suddenly seized and the wheel tried to carry on. Normal run down on switch off takes long enough for the loosening torque to be low enough not to have an effect.

I'm on my third grinder in around 45 years, and all have had a right-had thread on the right, and a left-hand thread on the left. I've never had a wheel come even slightly loose. Makes me wonder if Eric's grinding wheels have been fitted with the correct washers. I've just had a quick "Google", and a Health & Safety Executive document on grinding wheels can be downloaded free at https://www.staffs.ac.uk/assets/hsg17_tcm44-45519.pdf

To loosen any grinder nut it needs smacking in the direction of stone rotation. Doing 10 times a day on my disc cutter. Work it out.

Frank

Easy way to think about it is this - imagine holding a spanner stationary on the nut and turning the wheel. If this would tighten the nut, it is the correct hand.

Make sure you have both the proper card and metal washers in place.

Neil