What geen grinding wheels for tools

[not done it yetParticipant @notdoneityet]

Regarding a diamond on a stick for wheel dressing. I am wondering why use diamond unless really necessary (green grit wheels as a example)? Why not use a carbide tip as a dresser for most wheels?

[SteviegtrParticipant @steviegtr]

Posted by not done it yet on 21/09/2020 22:39:15:

Regarding a diamond on a stick for wheel dressing. I am wondering why use diamond unless really necessary (green grit wheels as a example)? Why not use a carbide tip as a dresser for most wheels?

That sounds logical.

Steve.

[SillyOldDufferModerator @sillyoldduffer]

Posted by not done it yet on 21/09/2020 22:39:15:

Regarding a diamond on a stick for wheel dressing. I am wondering why use diamond unless really necessary (green grit wheels as a example)? Why not use a carbide tip as a dresser for most wheels?

Try it and see. The problem is grinding wheels and carbide are similarly hard, and neither has much advantage over the other. Some carbides are on the soft side, and they can all be defeated by Cermets, Boron Cubic Nitride and diamond. A carbide tip might do a good job, or the wheel might inflict a lot of damage on it. Or both!

Diamond is as hard as it gets, and can't be bettered. Industrial diamonds are cheap too. A small diamond is cheaper than a carbide insert.

Got to be worth trying though – a damaged insert might well make a decent dresser, and who cares if it fails!

Dave

[Rod RenshawParticipant @rodrenshaw28584]

Might I suggest you look at a Youtube video entitled "Diamond lap for sharpening tungsten tools" for use of a very low cost diamond disc for finishing carbide cutters. It's a homespun sort of solution which might suit.

Rod

[Simon Williams 3Participant @simonwilliams3]

Reference the comments above about "why use a diamond".

You can indeed use a carbide tip, or even another abrasive to dress the wheel, but it's horses for courses. I use a coarse carborundum stick for roughing the wheel but it leaves a crushed grit surface with a limited abrasiveness – it blunts the wheel grains and therefore the wheel loses some of its free-cutting properties. A wheel surface which is blunted in this way will cut as if it were a finer grit, but will generate more heat as the grains rub rather than cut. A carbide tip will have the same blunting effect as it crushes the grains it touches exposed on the periphery of the wheel.

Different wheel materials give different results – I have a white wheel I use for sharpening twist drills etc (HSS) and this is less susceptible to the "crushed grains" effect. Understanding the different effects of this means getting into the intricacies of the wheel construction – a green grit wheel for example is a hard grit in a relatively soft bond so the grit is renewed quickly as it cuts. A grey wheel is a soft(ish) grit in a hard bond so it survives the rigours of daily sharpening HSS with occasional (whisper it quietly) contact with bits of mild steel.

A diamond cuts the grains, and as a result leaves a much more free cutting wheel surface. It will cut more freely and cooler, and behave as a wheel of the designated grit.

If you want a really free cutting wheel – particularly if it is a fairly coarse grit wheel for coarse material shaping – then the old fashioned star wheel dresser is the thing. This pulls grit particles out of the surface of the wheel, creating a horrendous abrasive dust hazard, but the advantage is that the wheel will cut with a vengeance.

[SteviegtrParticipant @steviegtr]

One of the large factories i used to do contract work for, had a workshop for the maintenance guys.

Only a couple of fitters that had been trained were allowed to dress the grinding wheels.

Steve.

[not done it yetParticipant @notdoneityet]

Posted by Steviegtr on 22/09/2020 22:53:21:

One of the large factories i used to do contract work for, had a workshop for the maintenance guys.

Only a couple of fitters that had been trained were allowed to dress the grinding wheels.

Steve.

That seems, on the face of it, to be a waste of training. Once trained they likely needed to practise occasionally ‘to keep their hand in’?

[BazParticipant @baz89810]

NDIY, don’t understand the waste of training, in a normal engineering shop offhand grinders will be dressed nearly every day so they would get plenty of practice. The life of an abrasive wheel in industry is pretty short, a six inch diameter wheel will be worn out in less than six months. When I done my apprenticeship the machine shop had a communal grinding area, shared by the various sections, capstans, centre lathes, drills, mills etc, the wheels were dressed first thing in the morning and again after lunch, life of a wheel here was measured in days, of course that was in the days of HSS, I would imagine throw away tips have changed things a bit.

,

[not done it yetParticipant @notdoneityet]

Baz, don’t tell me – I was only commenting on the quoted post – where only two of the trained staff were allowed to practise that learned (and presumably suitably certificated) skill. Like having lots of trained first aiders but not letting most of them react in the case of an accident!

[BazParticipant @baz89810]

Always amazed me that everywhere I have worked there have only been a couple of people qualified to mount and dress wheels, it is only a one day course, I have done it at least six times, all for different employers, the course is a general chat in the morning and a bit of practical in the afternoon, followed by a quiz to see what you have learnt, the attitude of my instructors was that the students have most probably mounted and dressed more wheels than he had ever done and it was a tick box exercise, meanwhile back at work in a machine shop of about a dozen machinists only two are qualified to mount and dress a wheel so when a chap on the surface grinder wants to put up a new wheel it took two people, him to do it under my supervision, my job had to wait, and we wonder why this country doesn’t have an engineering industry anymore.

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