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Bench grinder

Grinder very noisy at start

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Michael Brett 114/10/2021 20:19:08
23 forum posts

Hi all

I have a Erbauer 8 inch bench grinder model ERB8DLC that has developed this fault. On switch on the grinder makes a very loud hum and struggles to get turning. This started about 8 months ago. I have found that if I spin the wheel by hand first then turn it on it picks up speed much quieter . Once it is up to speed it works just fine. Would this indicate a fault with the run capacitor, if so is it an easy fix. Or would it possibly be what I believe is called the run switch on the shaft.

As I say , once running its fine so reluctant to replace if its fixable.

Cheers Mike

noel shelley14/10/2021 21:41:16
770 forum posts
19 photos

It does sound like a start condenser that has gone low. Your lucky to have got away with it for so long. IF the windings have not cooked then it should be repairable. IF you can read the value of the capacitor and can check it's current value thats a good start, remember the tolerance may be as high as 20%, it should be marked. It will have a run voltage of possiblly 400V DO NOT use a lower voltage. Good Luck, Noel.

Andrew Tinsley14/10/2021 21:43:00
1488 forum posts

It could be the start capacitor that has gone faulty or the run switch is stuck in the run position and hence the motor is struggling to start.

Unless you have a capacitance meter and can check the start capacitor, I would simply change it out for a new one. If that doesn't cure it take the end plate off the motor and check the centrifugal switch isn't stuck.

If you are tight fisted, like me, check the switch first, you might save the cost of a start capacitor, at the expense of some disassembly work!


Steviegtr14/10/2021 23:21:22
2244 forum posts
311 photos

Many bench grinders do not have a centrifugal switch. They are just capacitor start & run. The capacitor being in circuit permanantly. Hopefully a cheap fix for you.


kevin laxon15/10/2021 07:07:37
9 forum posts

I agree with others,check the motor capacitor,you will probably have to remove a plate from the base & dont be supprised if it has bulged or even exploded.

Nicholas Farr15/10/2021 07:57:20
3001 forum posts
1371 photos

Hi, my Draper 200mm grinder has a capacitor, I guess it makes them cheaper and easier to produce than a centrifugal switch and probably gives a softer start, which puts less stress on start-up for the wheels.


Regards Nick.

not done it yet15/10/2021 08:23:21
6350 forum posts
20 photos

… Once it is up to speed it works just fine. …

That would indicate it is not a run capacitor.

That it needs help to start rather indicates a start capacitor, winding or centripetal switch problem.

You should hear a definite click as the motor runs down (close towards stopping). That generally indicates the switch is working (but not always).

Continuity through the switch can be readily proved by a quick resistance check. Open circuit would indicate switch contact problem or a break in the start winding.

The usual problem is the start capacitor has failed completely or has gone low on capacitance. A common issue.

noel shelley15/10/2021 10:22:24
770 forum posts
19 photos

The reason I did not mention the centrifugal switch in my first post is that many bench grinders do not have one. As others have said, Check the continuity of the start windings and if sound, then if you cannot check the condenser just replace it. Good Luck, Noel.

Michael Brett 115/10/2021 10:22:58
23 forum posts

Many thanks for all replies.

I could not find any sort of centrifugal switch so I assume it must be the capacitor. Although this component showed no sign of damage, when I put my meter on the terminals it measured zero volts. Anyway I have ordered a new one so hopefully that should sort it .

Cheers Mike

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