Thread: What do the numbers mean on the Abrasiflex AO wheels?

The inside of the arbor hole should have a metal or hard plastic sleeve embedded in the wheel.
If it does and the wheel is a nice firm fit on the arbor you should be OK and you do not have to use the plastic bushes.
If it doesn't you can't use that wheel on that grinder.
It is really important that the wheel does not move around on the arbor.
A substantial amount of support is provided by the flanges on the sides of the wheel.
These help prevent the wheel rattling around and eventually destroying itself.
The flanges are designed to suit the wheel and grinder i.e. firm fit on the arbor and cover sufficient area of the wheel to provide the necessary support.
If you don't have the original flanges you should not just use any old large washer but either purchase or make proper flanges to suit.
The metal flanges should not be fastened down onto a wheel without some form of cushioning between the flanges and the wheel.
Thin hard cardboard can be used as a cushion, the other material that is useful to use is thin linoleum.
If you use new cushioning material make sure you periodically check on the tightness of the arbor nuts in the first few weeks of use.

Thanks Bob, thats what I thought/feared. Ah well, I'll have to wait a bit longer before getting the grinding station up and running.

Cushioning material under the flanges.
They may explain a lot.
I've been having trouble getting the wheels on my grinder balanced.
It was new from total tools about 18 months ago.
But never came with cushioning gaskets under the original wheels.
I have had to use the plastic bushes on a new wheel I brought
But even these were not the fit I expect.

Bob's on the money with this one.

I'm surprised a wheel marked for 25.4 won't fit in your grinder as the old wheel was marked for 25.4... It should just be a nice fit.. It's a hard thing to describe. Check the bushings are clean without any of the plastic edges protruding during the moulding process. Check the shaft is clean as well.

There is a chance that the wrong wheel was put on the old grinder a long time ago and just made to fit..You never know.
The flanges and nuts are not done up gorilla grip tight against the wheel. It's a firm pressure. I might google and find out what the suggested torque is for grinder nuts.

Expect to dress the wheel. They are rarely perfect from the factory and most grinders have some runout.
I just put on a green Norton on mine for carbide cutters. I was surprised norton would make such a wobbler!

If your new to pedestal grinders, don't forget they are pretty dangerous tools. You may already know all this but it's worth repeating.
Check the guards are in good order.
Always stand to the side while the grinder comes up to full speed.
Grinding Aluminium is a no no.
Safety gear is a must!
Don't forget your respirator ( don't cringe Bob!). Their is some nasty stuff in some of the steels and in the wheel. Cobalt is HSS is one of them.

A dressed wheel is a sharp wheel that grinds more efficiently with less heat. Keep your wheel dresser on hand as it only takes a few seconds to touch up a wheel. The old fashioned wheel type ones still work just fine..

Originally Posted by Ben Dono

Don't forget your respirator ( don't cringe Bob!). Their is some nasty stuff in some of the steels and in the wheel. Cobalt is HSS is one of them.

Regular HSS (M2) doesn't contain any cobalt. M36 (HSS-E) and M42 (HSS-Co) contain 8% cobalt.

Cobalt is known to be 50% lethal for mammals at the 6g/kg level for ingestion, so a 80 kg human would need to eat half a kg of the stuff which is unlikely.
However Co is also carcinogenic (lungs) and also a skin irritant.

I have a 25 mm long piece of 1/4" HSS-Co I use on my MW lathe. Touch up takes off about 0.1g of metal (I just weighed it before and after).
0.1 x 0.08 = 8 mg of Co is ground off.

Let's assume all of the ground off metal is turned into fine dust (unlikely) in a 6 x 4 x 3 m shed generating a concentration of 8 mg in 72 m³ of shed air = 0.11 mg/m^3.
The OHS long term exposure limit is about half that (0.05 mg/m³ ).
Of course it is unlikely that all the metal ground off forms fine dust, some will be metal flakes that fall immediately to the floor.
Eventually all the Co fine dust will fall to the floor or be ventilated out of the shed.
Either way it doesn't matter since a brief tool one-of touch like this up is not going to generate a long term health issue.
If some one was doing this all day, that would be another matter.

Tool forming maybe a bit more of an issue and fortunately this is usually only done one per tool. To form the tip of the cutting tool will require the removal of at least 10-20 times more metal than a touchup.
Now the degree to which fine dust is formed starts to become important and the higher concentrations generated will take longer to fall below recommended exposure levels.
Despite this I still doubt that for a DIYer, even tool forming is going to be a long term health issue as in terms of overall exposure it will contributes less than the many grams of metal ground away during touch ups over a year.

Anyway, even if it is a problem, just like wood dust just using a respirator is not the front line way to deal it.
Using a respirator only provides protection while the grinding operation is taking place so a respirator would need to be used for some time after the grinding. Not to mention that it is a skin irritant and that the Co dust will have settled out on hair skin and clothes. The best way to handle this is by dust extraction.

From the MSDS for Co

Engineering Controls:
Use process enclosures, local exhaust ventilation, or other engineering controls to keep airborne levels below recommendedexposure limits. If user operations generate dust, fume or mist, use ventilation to keep exposure to airborne contaminantsbelow the exposure limit.

After ventilation has been employed a respirator can be used for extra protection if required.

I have the gear for testing fine dust emission so I might get it out some time to see what sorts of dust levels are generated by various cutting and grinding processed. I suspect the vast majority will come from the wheel but it will still be interesting to see what sorts of levels are generated.

I also looked up the MSDS for grinding wheels and below is the data for typical grinding wheels.

The most carcinogenic component is the fibreglass used in any reinforcing.

The OSHA Personal Exposure Limits for most of the components are greater than or similar to that for wood dust.
For reference, softwoods have an OSHA (and Australian) limit of 5 mg/m³ and hardwoods a limit of 1 mg/m³
These levels should probably be lowered for all materials, especially Aussie hardwoods .

Ben Dono is right we should be aware of the stuff in grinding wheels, but unlike wood dust which is typically generated by wood workers by the kg for many minutes if not hours a day, a 30 burst on a grinding wheel half a dozen times a day is drop in the wood dust bucket

I don't know that it could be as simple as that Bob. I think your forgetting how it can all accumulate. Sure, a small amount of most things can be classed as a non event. I think the real issue is the daily, weekly and monthly exposure to many different substances over time that can become an issue.

I agree with a comment you made in another thread about proper dust extraction and air filtration systems in home workshops. I can't say I have seen more than one business in OZ that has even started looking at that. The yanks are leaps and bounds ahead of us in that regard.

Having said that, when I get the power tools out, mate....the mask goes on!
Any young tradie coming up should be hearing us older blokes say that.
I would not let an apprentice work with me without using one.

Originally Posted by Ben Dono

I'm surprised a wheel marked for 25.4 won't fit in your grinder as the old wheel was marked for 25.4... It should just be a nice fit.. It's a hard thing to describe.

Thats basically the conclusion I've come to.

We've (wife&I) decided to just get a new grinder. Hafco's upcoming sale makes it essentially free delivery on the A&A so thats "ok". She's more comfortable with that anyway, which means she'll be much more likely to do the sharpening as she needs it rather than turning, stopping, calling me, waiting for me to arrive to grind, then getting back to turning.

The machine is older than I am, and likely wasn't a great one back in the day given my dads tendency to opt on the cheap side.

Expect to dress the wheel.

Yup, picked up a wheel dressing thing with the trugrind jig.

Good to know about the airborne nasties. I'd love to have a proper dust extraction and air filtration system setup, but sadly its just not going to happen for awhile. Respirator is, however, worn most of the time I'm out there anyway because I got sick of jarrah flavoured snot.

Nice one mate! A new grinder will solve that problem! And the musses shares the workshop with you! Well done. I was just having that conversation with my better half this morning..

A lot of home workshops have also put the dust extraction and air cleaners on the back burner. I'm only just starting to look into that now.

Originally Posted by Ben Dono

I don't know that it could be as simple as that Bob. I think your forgetting how it can all accumulate. Sure, a small amount of most things can be classed as a non event. I think the real issue is the daily, weekly and monthly exposure to many different substances over time that can become an issue.

The OHSA limit would include a factor for accumulation. Co is an essential element for human/animal life as it forms the basis of Vitamin B12 - if we don't get some we will suffer all the problems associated with lack of Vitamin B12.
Estimated intakes of Co are in the tens of micrograms of Co a day. What we need to know is how much is too much.

Cobalt sulphate, and Co TC powders and hard metals containing Co are listed on the American National Institute of Health Report on Cancer which lists and details materials known to cause cancer. However the concentrations know to cause cancer are only experienced in work environments by workers who work directly making these materials. This is what they say about people who use these tools on a regular basis.

[Information on Co exposure from the end use of hard-metal tools islimited; however, exposure appears to be minimal. Pellet et al. (1984,as cited in Angerer and Heinrich 1988) reported cobalt air concentrations of 180 to 193 μg/m3 and a mean urinary cobalt concentration of11.7 μg/L associated with use of hard metal; however, no additionalinformation was provided for these data. No other information wasfound that directly demonstrated exposure to cobalt–tungsten car-bide powders and hard metals by end users of products containingthe material. The Washington State Department of Labor, in a Haz-ard Alert issued in March 1995, stated that there was no evidenceof substantial exposure to cobalt during the use of tools containingtungsten carbide or other hard metals (WSDLI 1995).

Remember this is for people whole use TC-Co tools as part of a full time job e.g. cutting tool steel etc. The levels a DIY would experience would be significantly less.

Having said that, when I get the power tools out, mate....the mask goes on!
Any young tradie coming up should be hearing us older blokes say that.
I would not let an apprentice work with me without using one.

I don't have a problem with people wearing masks especially where there is no ducting or fume hoods. What I don't buy is the idea that a mask will do in a static environment like a workshop where ducting and fume hoods can be readily installed.

Originally Posted by Ben Dono

And the musses shares the workshop with you! Well done. I was just having that conversation with my better half this morning..

Would you believe we only have a lathe (and thus looking into proper sharpening for turning chisels) because of her? Pops Shed run some neat turning courses, she did the pen course and was hooked, a month later was back for the bowl turning class. We even had to upgrade the drill press for one with a longer quill travel so that we could drill pen blanks out properly (little ryobi job we had did about 50mm travel). You can imagine the fierce fight I put up not to upgrade!

No such thing as a "typical grindstone." Read the code on the wheel and look it up.

For example: 38 A 80 - H 8 V BE
38 = Norton
A = aluminum oxide
80 = grit size
H = grade, based on the hardness of the binders
8 = structure, the grain spacing
V = bonding material
BE = bonding modification by manufacturer

Wasn't that fun? Memorize page 38/ch 4 The Complete Guide To Sharpening (Leonard Lee/Lee Valley's grand old man).