My new Norton 3X grinding wheel - advice needed

[Routermonster]

Dear All

My long-awaited 46 grit 25 mm Norton 3X stone arrived yesterday. So I rushed into the garage thinking about all those lovely chisels waiting to be ground ... alas, I ended the day frustrated.

The first problem is that it didn't fit. My fault - my ancient grinder only takes 3/4"/20 mm wide wheels, and I hadn't checked before I ordered it. Duh - what a Muppet!

So I sneaked out to Screwfix and bought an Erbauer branded one with 25 mm wide wheels (quite nice for the money). With the supplied 'grey' wheels it runs quietly and smoothly, with very little vibration.

The trouble started when I installed the new Norton wheel. It's supplied with a set of plastic bushings to reduce the wheel's 5/8" bore to 1/2". The trouble is, apart from the smallest one, which is a tight fit, all the bushings are a fairly loose fit, and the wheel wobbles around a fair bit on the largest one before the washers are tightened. The result is that when it's all finally tightened up, there is a fair amount of vibration when the grinder is switched on.

Should the 5/8" bore of the wheel be drilled straight and true so that it's a tight fit, or is that asking for the impossible?

I've checked the edge of the wheel and it spins about 1 mm out of round and has a similar amount of run out. I'm reluctant to tighten the washers too much, as I'm afraid of cracking the wheel. I'm hoping that by using a dressing tool I can restore concentricity, square up the edge, and get rid of the vibration. Or will I?

Any thoughts anyone?

Thanks for your help.

Muppet Les

 

[CHJ]

I would not recommend mounting the wheel without a reasonable fitting bush so that it is running concentric with the shaft, sooner or later a catch or knock will move the wheel and any truing you have done will be rendered null and void. (besides any shaft play will result in a measure of vibration dependant on amount of offset regardless of trueing the outer)

How true are the side washers locating on the spindle, are they machined from solid or pressed plate? the latter often do not locate square on the spindle, causing wobble.

 

[9fingers]

Grinding wheels are moulded and so the bore is normally true especially with quality makes such as Norton.

If you don't have a suitable bush without play, then you can wind layers of adhesive tape until the correct OD is achieved. Don't forget to rotate the wheel as you fit it in the same direction as the tape has been put on.

The flanges should also run true and as you say the machine does not vibrate with the original wheels, I expect they are OK.

Always ensure that the flanges bear onto paper/card washers. Never, ever allow them to bear direct onto the grit surface. If need be make some washers from dense card (not corrugated etc).

If you have to dress the wheel to achieve balance, then mark the shaft and the wheel so you can put it back on in roughly the correct alignment.

hth

Bob

 

[dickm]

If you've got access to a lathe, why not make some wooden reducers? That way, you'd be sure of concentricity. The tape solution would probably work, but would depend on getting a whole number of turns of tape around the bush, and not stretching the tape unevenly.

 

[ivan]

The industrial standard wheel bore is 1.25"/32mm and bushes in both metric and imperial are widely available. They are asked for and usually provided free at the time of sale. Unfortunately there are a lot of "made for the USA DIY market" cheaper wheels on sale here now. US diy grinders have imperial shafts of 1" or less and the wheels have a 1" bore and are supplied with a nesting set of imperial bushes. Norton has its diy range of wheels (and maybe others too) made for it in China. You may have difficulty in getting hold of suitable metric bushes, something the vendors appear to have forgotten (unless you have a "made for the USA diy market" grinder!) Why do people sell them? They're about 2/3 the price or less than a similar wheel made for the industrial market.

DO NOT use a badly fitting bush, as both your body, and your family may be adversely and permanently disadvantaged if you do.