Taking a step back - Bit grinding

[Blogwitch]

If you couldn't grind on the side of a wheel, then very little would be done on commercial jobbing shop surface grinders, which mainly are the same wheels you use on an offhand grinder just a lot bigger at times.

Not only do you radius the edge of the wheels and the normal cutting face with a special rotary dresser, so that you can grind both external and internal radii, you also sometimes use an hand held square oxide stone to dish the side of the wheel leaving a cutting edge around the side periphery of about 1/8" to allow you to grind vertically down a face.

Sides are also ground when profiling wheels to allow cutting of profiles into very hard materials, how else are they supposed to do it?

Whenever I changed jobs, if there was any grinding machines in my new employment that I would be required to maintain or use, my grinding wheel certification wasn't transferable from job to job, a new 3 or 4 day course had to be attended to be re-certified each time, and at each one, wheel profile dressing was a major part of it.

John

 

[goldstar31]

Not only do you radius the edge of the wheels and the normal cutting face with a special rotary dresser, so that you can grind both external and internal radii, you also sometimes use an hand held square oxide stone to dish the side of the wheel leaving a cutting edge around the side periphery of about 1/8" to allow you to grind vertically down a face.

Sides are also ground when profiling wheels to allow cutting of profiles into very hard materials, how else are they supposed to do it?



John

John is right, I have such a jig- came with my Clarkson.
As a bit of 'All our Yesterdays' I did the testing of the modified rosins- in the early 1950's that made some of the wheels. There was too much dangerous stuff on free maleics and thallics and so on. Went back to 'bean counting' and retired with enough to manage some 31 years ago.

Well, I did read 'Ill Principe' amongst my other 'sauces' of information.

 

[Blogwitch]

Norman has hit the nail on the head.

Over the years, bonding on normal wheels have become much better, and to burst a wheel nowadays really needs to be worked at, like hitting it with a hammer or dropping it on the floor.

When I first started 50 years ago, wheels were really fragile, wheel ringing was a common place thing to check for cracks and too much coolant penetration, and this is where the no side grinding on a wheel came from.

I am not saying that you should disrespect bonded wheels and their safety precautions, far from it, but side grinding is an operation that can be allowed to a certain extent without causing major problems.
You are more likely to come to a sticky end if you try to fit a larger wheel than your grinder is designed for, smaller is no problem, but if you increase the diameter, the peripheral speed can easily go beyond the designed speed for the wheel.
I wince when I see people making up their own offhand grinder out of a motor that comes from goodness knows where and a wheel that has no history for it, most probably found in the back of their grandfathers old workshop, probably off a hand powered grinder.


John

 

[goldstar31]

Thanks John!

It's these newer washing machine motors which give me the willies. It was OK in a past decade with the old 1440 rpm 1/4HP things.
I've one- somewhere., which powered my Quorn until I got a proper 2880rpm one. I tell a lie because I have another on my Kennet and , oops, one on the little Stent.

'And one man in his time plays many parts'

Hope you are well

Norm

 

[BaronJ]

Hi Guys,

Re motors used to power grinding wheels...

Common induction motors are not a problem, they don't normally run at more than 3000 rpm (3600 @ 60Hz). Grinding wheels are commonly rated to 5000 rpm or higher.

Its universal motors that become dangerous with grinding wheels attached to them. Spindle speeds can often be in excess of 15,000 rpm. How many of you with Dremal type tools have blown up those tiny abrasive wheels at speeds much less than this.

The other motors that can be an issue with very high rotational speeds are DC motors, many falling into the universal catagory. Not that universal motors cannot be run from a DC supply.

Norman: Yes I was infering that Barry's ability to swap the tool rest from one end of his grinder to the other in order to make use of two very different grit size wheels was very useful.