Thread: Truing a diamond wheel - what to use ?

Nice work John.

That should keep you out of trouble.

I'll most looks like your machine could handle a bigger wheel. 7" or 8". I wouldn't be changing the diamond one yet.

I forgot to mention, that a single point or a cluster point dresser, like you would normally use on a surface grinder, will also refashion that wheel. Its just a matter of guiding it straight.

I think RayG from Shep, had a line on 7" green wheels in that face profile for the other end.

Regards. Phil.

You've inspired me to have a look at my stockpile

I must have 200Kg plus of assorted wheels I got with my T & C grinder, but only one green wheel

It's chipped but rings OK, I guess the chip will go away with wear, what do you think ?

Originally Posted by johntopp

It's chipped but rings OK, I guess the chip will go away with wear, what do you think ?

If I was to tell you publicly on a world wide forum that, that wheel was O.K to use. The Internet Police, would beat me home, change the locks, steal my car and pilfer my stockpile of Scotch.

A bloke I used to know, that looks a lot like me, would have given it a try, using caution. (Duck when you press the go button). It rings, so its not cracked.

Looks like its been chipped in storage, rather than having impact from a crash? Its a lot greener and fresher looking than the rest of the wheel. You normally get powder when a wheel has had a part go missing at 3000 f.p.m.

Regards Phil.

It's perfect, I was more worried about balance rather than instant death. In any case it's not doing a million revs and it's well guarded.

It runs much smoother than the old wheel, and I'm too lousy to buy a new one when I've got one in stock, just a little shop-soiled

Thanks for your help

Originally Posted by johntopp

It runs much smoother than the old wheel,

Do I take it from that you have all ready tried it? And it didn't explode.

I'd still lock your front door, it takes longer for the Internet police to get to Hastings.

You can dress that out, and just about anything will do it. I just checked EBay and they want $50 bucks for a Norton Norbide Stick. That must be something the Chinese haven't replicated yet. Norbide is near diamond hard. Eats green wheels.

Regards Phil.

I chucked it on as soon as I read your post.

Also had a little go dressing with the remnant of the diamond dresser, seemed to get into the wheel pretty well - lots of dust though

Suppose the $4 eBay diamond dressers will be more economical than Norbide

Have a look below - then again I suppose Blackwoods deliver for free

John

STICK DRESSING NORBIDE 4.78X13X80MM *

Part No.	00692201
Brand	Norton
Manuf. No.
Availability	Ready to ship

1+	EACH	$209.00 / EACH (Inc. GST)
3+	EACH	$188.00 / EACH (Inc. GST)
5+	EACH	$177.00 / EACH (Inc. GST)
7+	EACH	$167.00 / EACH (Inc. GST)

Originally Posted by johntopp

I chucked it on as soon as I read your post.

Heaven Help us John, we could go to jail together. I want the top bunk.

To the others: I'll explain my cynicism. This forum only has a small measure of that Hysteria. We are generally well grounded, but had you posted this exact same question, on one of the International (Read U.S) forums. You were about to kill yourself at best, or mess up the time / space continuum.

Where I have a really high horse, that pisses me of no end, is since the introduction of Inverters, especially around grinders. Adding invertors to what was a three phase drive.

Iv'e often read about a 15 -20 -30 second ramp up time. I've read that here, by members, so it is relevant to the Aussie contingent, and this forum.

Internet myth is so that it doesn't un-settle the wheel. Changing the dressing / balance. You have to keep in mind what a commercial wheel / commercial machine does.

Real 3 phase motor on an industrial machine, connected to real 415 - 3 phase. Get a real kick in the Guts, to do full RPM @ 50 Hz. That will spin up in 250-500 ms. That would be 1/4 to 1/2 of a second.

This 15 - 20 -30 seconds to get them up to speed. That's just weird.

This delay thing of more then 1 second upsets me. That would be more than half accel. Machine that takes 30 seconds to come on song. F.M That's just awaiting a wheel to explode when it finally gets to speed

Analogies are good. If I'd won Tattslotto last night. There be a Porsche in the drive way tonight. That might do 5 sec to 60kmh. Trim the accel to 1/60th and you would likely be beaten, by some pretty chick from Amsterdam, with a flower basket and bicycle.

Top bunk !!! - obviously you've done time before

Not sure why a VFD would upset things re balance, if the speed was slowly ramped up you think that the inertia of the wheel would be less likely to shift the wheel slightly on the arbour. Would be an interesting question for the physicists.

More of a concern I would think is that with a VFD you could drastically overspeed the machine. A 2800 rpm grinder is going to do 5600 if you run it at 100 Hz - that's even more of a problem for the safety Nazis perhaps.

I don't know that running that Waldown on VFD would be practical - there are only 3 leads coming out of the motor, so you'd be running it on 240V instead of 415V - you could still overspeed it as the rpm is determined by frequency, but you'd have no torque

I'm not too keen on VFD's anyway. There was one on my little Schaublin lathe when I got it, it'd take what seemed to be ages to come up to speed. I put it back to standard and the machine was "transformed". Up to speed instantly, lovely. The VFD is still screwed to the wall behind the lathe wrapped in its power cord, and that's probably where it'll stay.

Originally Posted by johntopp

Top bunk !!! - obviously you've done time before

I'll always regret that tattoo on my forehead.

Originally Posted by johntopp

Not sure why a VFD would upset things re balance, if the speed was slowly ramped up you think that the inertia of the wheel would be less

It doesn't upset anything Re: Balance. The quad root of that goes up with speed.

That's the thing. It makes no difference if you just kick it in the guts, and it takes half a second, but taking 30 seconds to get about it, via VFD. That would be 1/60th of the accel.

A second or two would be considered a soft start, but 15 -20 -30 seconds. That's the only point I'm trying to make. There are blokes here that do that. I'm trying to cut them off at the pass.

I thought all the "recommendations" about not stopping a surface grinder after the wheel was dressed was that the position of the wheel on the spindle was critical to balance / concentricity. E.g the wheel could rotate a smidge on the spindle and thus upset things. So in that case a slow ramp up would be less likely to disturb things. If Force = Mass x Acceleration then if the acceleration is decreased by the ramp up time being 100 times or whatever more than a rapid start, then the Force will thus be 100 times less and so less likely to shift the wheel on the spindle.

Then again, a quick start is more likely to lock the nut onto the spindle thread - but, I'm not sure I'd want to leave the motor running forever till I'd finished the operation, my speed is not exactly industrial.

Also I'm not sure that the balance problem is so great with the size of wheel the average hobbyist would be running, when you get 12 inches or over, then maybe

What would drive me mad is waiting so long for a machine to spin up, it'd be comparable to swapping the 3 phase motor for a rope-start (not recoil) Villiers.

I don't understand why you'd set a ramp up time longer than half a second or so, the only reason for a ramp up time would be to limit the inrush current on startup, so you don't pop a breaker. It's not like you're firing up a 500 KW motor.

You can't argue with using a VFD if there's no other way out, providing you can correctly match the motor to the VFD, but I don't see why you'd increase the agony by taking so long to get up to speed.

Originally Posted by johntopp

I thought all the "recommendations" about not stopping a surface grinder after the wheel was dressed was that the position of the wheel on the spindle was critical to balance / concentricity.

The "not stopping" thing is more about bearings and spindle - getting them up to a steady state working temperature and establishing the correct oil film in the bearings. Does that matter? Not sure but if you are chasing tenths it probably does, along with the temperature controlled grinding enclosure. Maybe for a plain bearing machine it has a greater benefit of wear reduction.

Phil is right - balance at speed is balance at speed. How long it takes to get there is immaterial to the actual balance.

I must admit to being lazy as I have not changed the default settings on the VFD's from a 10s ramp. I promise to fix it before you visit Phil.

Michael

Originally Posted by Michael G

I must admit to being lazy as I have not changed the default settings on the VFD's from a 10s ramp. I promise to fix it before you visit Phil.

Michael

I just turn mine on and it's at speed.....

A friend of mine has been busy fitting new motors and VFDs to my Hercus T&C grinder as he needed it for some projects and I didn't need it any time soon. I guess I'll find out what he used as ramp time when I get home.

FWIW I'm partial to the top bunk, too.....

PDW

John, I have my diamond grinder on a slow ramp up down, maybe 5 seconds, if I don't do that the wheel spins off. I have a heavy cast iron disk to support the diamond lapping plates. Turn it off too quick and the next thing you will be running across the yard trying to stop it.

I chased all over looking for recessed mount 6" green carbide wheels, in the end I got a steel plate backed one from this mob in the US. Klinik in NZ used to have them, but they are no longer a stock item. I could have ordered a carton but 12 weeks delivery and what would I want with a whole carton anyway.

The diamond lapping disks I got from a supplier that BobL put me onto, (Can't find the link at the minute) I also got some from http://www.cutandslice.com.au/specials the 1200 grit gives a pretty good edge to carbide.

http://www.travers.com/53-110-196

If Phil and PDW are sharing the top bunk, I want a different cell.

Spins off..... sound like you could do with a locking arrangement - the photo shows what Waldown have done

Re carbide wheeels, I came across these guys when I was looking up specs on google, their prices seem OK

But I don't know anything about them

http://coatedabrasives.test.hornetma...ide-green.html

Blackwoods also carry wheels

https://www.blackwoods.com.au/search?q=green+wheel