vibration on run down

[The Artilleryman]

Just had a call from a friend - bench grinder vibrates when running down (power off), but none on power up or when running - my thought was bearings worn, just what to check I'm right ?

 

[Brad93]

Just had a call from a friend - bench grinder vibrates when running down (power off), but none on power up or when running - my thought was bearings worn, just what to check I'm right ?

Either bearings or worse it’s damaged the bearing seat in the shaft.

 

[nickk]

Or,lump out of the wheel ,causing out of balance forces,more noticeable on run down,without power and torque masking the effects.

 

[Robert Weaver]

The rotor may be unbalanced, causing resonance at a particular multiples of rpm. Could be one wheel is not symmetric or is tightened on the shaft all to one side, so is not concentric.
When powering up, it probably very quickly gets through the resonant range, but on run down it takes a while, so is more able to shake.
Check the wheels are not damaged, then try mounting centrally on the shaft.

 

[Brad93]

check the clamping rings too. Often they’re poorly cast and not holding the wheel concentric. Abom done a good video on this.

 

[pedrobedro]

Mine has done it for years it's just resonance. I've ignored it and it's never altered.

 

[brightspark]

one i had used to do it from new. no big deal . is it screwed down

 

[Brad93]

I rebuilt a Sealey a while back, old school Sealey not modern. It’s perfect, no vibration at all now. I had to use loctite 638 on one of the seats but it was only just undersized.
Put new low friction SKF rubber sealed bearings in. £20

 

[Spark plug]

Is it belt drive? Mine dose it, I always believed it was caused by the belt wiping around as it slows down.

 

[The Artilleryman]

Thanks guys, it's only a cheap bench grinder and we'd gone through the obvious causes, it hadn't been used in a while, but wheels are OK.
I've told him to screw it down to the bench and if it doesn't get any worse, it's OK to use. I won't get to see it till end of the summer, but he'll bell me if it gets any worse.

 

[Beeezer]

Plastic centres in the stones?

 

[brightspark]

Thanks guys, it's only a cheap bench grinder and we'd gone through the obvious causes, it hadn't been used in a while, but wheels are OK.
I've told him to screw it down to the bench and if it doesn't get any worse, it's OK to use. I won't get to see it till end of the summer, but he'll bell me if it gets any worse.

the one i had that did it was a cheap black and decker at the time and done it from new but ran perfectly

 

[Pete.]

Mine does the same. It sits on a steel plate on the bench and rattles like a good'un when it's running down.

 

[pedrobedro]

One of mine is screwed to a piece of plank and I G clamp it to the bench when I want to use it.

 

[Barking Mat]

I bolt my bench grinders to pedestals, as I hate benches vibrating when powering down.

I've always assumed resonance too.

 

[Pete.]

Mine is on a steel plate because there's another one the other end. I spin the plate around to use one or the other..

 

[graffian]

My polisher has done it for the last 40 years.
Some days it was run all day long doesn't seem to get worse.