Truing a diamond wheel - what to use ?

[johntopp]

I've acquired a bench grinder with a diamond wheel. The wheel's got a bit of a hollow in it, but there seems to be a fair bit of meat left. I've had a look at the manufacturers website, but there's not much info re maintenance of the wheels. From what I can see by poking around the internet, you use a silicon carbide or aluminium oxide stick a couple of grades finer than the wheel grit. The wheel's a Kinik D180R75BD3X = Diamond 180 grit Hard 75% concentration, Resinoid for dry grinding, so I'd guess you'd dress dry too.

The wheel's just a plain ally disk with the abrasive stuck to the side of the wheel, so you grind using the flat side of the wheel, the grinder has an inclineable hanging off each side

Anyone got any clues ?

Seems like attacking the wheel with a SiC stick is a bit agricultural somehow

[dai sensei]

:? Diamond wheels are basically a thin coating of diamond matrix over a metal wheel, you don't dress it.

You say the abrasive is stuck to the side. Is it not on the face? Photo would help.

[johntopp]

The wheel is shape 6A2 in the attached link

http://www.kinik-abrasives.com/301E0507/img010.pdf

D=150, W=20, X = 3mm (thickness of abrasive

[.RC.]

Diamond wheels are trued with a brake dresser...

eg: http://www.dk-holdings.co.uk/engin/brakdres.html

[Machtool]

This is all I use, a selectively mined chuck of Alum Ox, smashed out of a 12 or 14 inch wheel.
353610

353611

353609

All of Marko's wheels come with an Aluminium Oxide Dressing stick about the size of one of those Norton pocket stones. They are soft as anything.

Those diamond electroplated dressing tools, work also. Especially if you need to lose some wheel to get a flat profile back. Its not diamonds dressing diamonds. That attacks the resin bond, Diamonds in the wheels just get lost with the resin. But exposing fresh ones.

http://www.ebay.com.au/itm/Diamond-Dresser-Tool-Grinding-Disc-Wheel-Stone-Dressing-Bench-Grinder-Strong-/351389559909?pt=LH_DefaultDomain_15&hash=item51d0732c65

Regards Phil.

[johntopp]

Thanks Phil,

I've got both, I bought one of those little eBay things years ago and have never used it, it looked a bit puny when it arrived. I've also got no shortage of old Alox wheels as victims, if an Alox chunk does it need to be fine ?

The wheel's a 6 inch 180 grit diamond to be used for scraper sharpening

Which would you use ?

John

[Machtool]

G'day John.

The diamond plated dresser, would probably be the best if you want to get the wheel face flat again. There's lumps and bumps on those, so you have to guide it across the face some what square. It will chew it up pretty fast, but they are so cheap now. I'd use that if you have a cavity in the face you want to get rid of. It might cost you that dresser. Not sure how bad the face of your wheel is.

Your diamond wheel will eat an Al- Ox chunk, regardless of the grain size or bond. Its a dusty job. See the flats on that rock I posted. They would have been ragged jagged edges. A few passes across the diamond wheel, and it will grind a flat, on the AL Ox piece

That's probably best once you feel the wheel has glazed up, or gone blunt. Pulling a bit of the bond out of the face, exposes new diamond grit.

Regards Phil.

[.RC.]

All of Marko's wheels come with an Aluminium Oxide Dressing stick about the size of one of those Norton pocket stones. They are soft as anything.



So that is what that very soft white square stick that came with a diamond wheel I bought is for..

[johntopp]

Talk about a timely response.

Just got the grinder back together after new bearings and rewire

Gave the little eBay diamond dresser a whirl, after what seems like about half an hour of dressing, I've got about 40% of the face flat, with a 0.2 mm or therebouts hollow left to go. The dresser stood up really well, but it's had it now. I'll have to get a new one or several.

FWIW the one I used was a Dongfang 36 grit P/no LX-8000

I like the minimal dust with the diamond, so I think I'll wait till the new diamond dressers arrive, I should be able to use the wheel as is, pro tem.

Thanks again Phil

John

[johntopp]

They do say "diamonds are forever"

[Machtool]

So that is what that very soft white square stick that came with a diamond wheel I bought is for..

That's the one. Seriously soft, almost like grinding chalk. I'm sure if you were hungry enough, you could eat them. Some of Marko's wheels, they will send 4 or 5 of them with it. His are virgin, as he doesn't use them. He gave me that chunk of rock.

[Machtool]

Just got the grinder back together after new bearings and rewire

If you get a chance John. A picture or two would be good. (Your'e welcome to email them to me, if your not up with how to host them here)

I'd like to see your set up, and there's a few of the other boys just getting into a machine like that.

Regards Phil.

[johntopp]

Here are a few snaps and a little about the initial maintenance

1. Grinder, Waldown picked up on Grays a couple of days ago

2. I must be getting old, or perhaps have too much time on my hands, but before I plugged it in, I grabbed the megger. First insulation, L1,L2,L3 all near infinity = good, then continuity, change to ohms, then with rotary switch at off, L1,L2,L3 all open = good, Earth low ohms =good, ...... then switch to forward/reverse, L1-L2 open, L2-L3 open, L3-L1 mid scale (about 25 ohms) = not so good. Looks like a new rotary switch or a rewind are in order. So have a look at the plug, it's got a clear cover, looks like red-L1, black-Neutral, blue-L3, green-Earth, would all be good if we had a white or some active colour in L2, and why would a grinder need a neutral? So off with the cover and swap black to L2, now L1-L2-L3 resistance are 25 ohms all round and same in both forward and reverse switch positions, so give her a whirl, runs, but noisy bearings, so what, easy to fix maybe.

Seems like the previous plug fitter decided that black=neutral, and there's a spot for all the remaining wires, so must be OK. I don't think that wiring scheme would have improved the power output. Without thinking it through too hard, one winding would have seen 415V, but the other two would have had 240V out of phase, so may have acted as brakes. Doesn't seem to have done any harm though , I had the machine running for a good half hour under pretty constant load while dressing and the motor was just a little warm, so doesn't look like a shorted turn or whatever resulting from being cooked.

Moral of story, the only colour you can trust is green (solid or with a yellow stripe) - all else question and test out

3. Now for the bearings, they sounded shot, so let's swap em. All came apart pretty easily, except for the diamond wheel arbor which need a bearing puller to get it off (after removing the actual diamond wheel)

The end caps slipped off a bit too easily, the bearings were an easy sliding fit. If you look at the photo, it seems that one at least has had a little spin in the housing, which may have something to do with the custom-made half moon shims between bearing and end-cap at one end. At first I thought I thought someone had cut a washer out of tin, which then broke in half, but when I reassemble it the two halves don't match, hard to fathom.

Down to SKF for a couple of bearings and a wave washer to replace the custom job.

So, fit the bearings to the armature and trial assemble the end caps to check end-float, one end bearing is a too loose fit in the housing, so a bit of green 609 loctite in that end, leaving the other end free to slide against the wave washer, all assembled - spins nicely, much better, nice and quiet, smooth

4. Wheels back on. Had a bit of a struggle to refit the diamond wheel and its arbor, very close fits. Now it's not so quiet or smooth, I suspect the green wheel on the other end, it's had a bit of a flogging, may have to change that

5. Table at one end rattles a bit, the pivots are worn, may need a resleeve or whatever - job for another day

6. After advice from Phil, had a crack at truing the diamond wheel with the little eBay diamond dresser. Took ages, and had to stop occasionally to let it cool down. It's knackered now, and there's still a hollow in the wheel, I'll probably destroy another to finish the job. I think I may have overkilled the dresser, at the end I seemed to be making no progress and the wheel was getting a mirrorlike shiny surface, maybe it picked up a bit of steel from a worn through section of the dresser

7. Trial sharpen. Grabbed my scraper and the wheel seemed to work OK. The shiny wheel surface disappeared a bit, maybe the carbide blade removes any steel pickup. A test scrape, and it cuts well. Not sure about the finish on the blade though, the original finish (maybe virginal from Sandvik) had a mirror finish, it now has obvious striations, but it seems to cut, maybe I need to look into what grit I should be using, finer than 180 perhaps ?

[Machtool]

http://www.woodworkforums.com/attachment.php?attachmentid=353667&stc=1&thumb=1&d=1437786834

John.

You want your table to be 5 deg the other way. Higher on the outside.

As it is now, you are sharpening from the centre where the bevel intersects, and the wheel is grinding down as it leaves the edge.

It will grind far better in compression. Starting at the edge, and leaving at the bevel.

Regards Phil.

[johntopp]

I remembered the 5 degrees, but couldn't remember direction, naturally given two choices, the guess is going to be wrong

For some reason the table's harder to adjust when pointing down, must be the way the adjustment screw misses the corresponding dimple in the table, might need to be scraped in - or the dimple elongated

[johntopp]

I was having trouble adjusting the table to 5 degrees negative, normally the adjusting screw locates in a dimple underneath it. It's an elongated depression, looks as though Waldown put it there, but if you set a negative table angle the adjusting screw sits on the edge of the hole and the angle won't stay set, it varies a degree or so both ways when you put any weight on the table.

Problem is solved with a little saddle, the slot is angled at 5 degrees, so when the table is at 5 degrees the screw is sitting perpendicular to its bearing surface, very easy to set now

I don't think I'll bother adding a dimple to the top of the saddle

[Machtool]

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.

[johntopp]

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 ?

[Machtool]

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.

[johntopp]

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

[Machtool]

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.

[johntopp]

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 * (https://www.blackwoods.com.au/part/00692201/stick-dressing-norbide-478x13x80mm-)

https://www.blackwoods.com.au/content/images/part/100/Norbide_Dressing_Stick_c.jpg (https://www.blackwoods.com.au/part/00692201/stick-dressing-norbide-478x13x80mm-)
https://www.blackwoods.com.au/content/images/part/66/Norton_Logo_new.jpg


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[Machtool]

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.

[johntopp]

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.

[Machtool]

Top bunk !!! - obviously you've done time beforeI'll always regret that tattoo on my forehead.


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.

[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. 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.

[Michael G]

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

[PDW]

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

[RayG]

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

[johntopp]

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.hornetmarketing.com.au/index.php/reinforced-abrasives/grinding-wheels/vitrified-grinding-wheels-silicon-carbide-green.html

Blackwoods also carry wheels

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

[RayG]

Hi John,

No problem finding green carbide wheels, there are plenty of them around, I was looking for the recessed center style Kinik GC60J8V5A 150x38x31.75 CG5556 If your's is a 7inch then I think it's the same as Phil's which is Kinik YWG52007003.

If you come across green carbide in a 6" recessed wheel I'm still looking.

I have Lock nuts on the end of the spindle that has RH thread, I haven't made a LH nut lock nut for the other end, easier to just dial down the acceleration. With reversible grinders like these, I don't know why you would bother with LH and RH threads anyway :)

[PDW]

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

You & Phil can share the cell, I don't smoke....

Might have some of those green wheels in a job lot I picked up some years ago. When I get home in another month, I'll take a look. If I remember by then.....

PDW

[jhovel]

Hi PDW,
there is no smoking in VIctorian jails any more - so yo0u can take your pick.
There are no drugs in victorian Jails either.....

[PDW]

Hi PDW,
there is no smoking in VIctorian jails any more - so yo0u can take your pick.
There are no drugs in victorian Jails either.....

Also, they're from the Government and here to help you.....

PDW

[eskimo]

There are no drugs in victorian Jails either.....

when did that stop.

[shedhappens]

when did that stop.

http://www.abc.net.au/news/2015-07-01/riot-at-melbourne-remand-centre-over/6585456

[eskimo]

http://www.abc.net.au/news/2015-07-01/riot-at-melbourne-remand-centre-over/6585456

no no...not the smoking bit.. the no drug stuff in Vic jails

[.RC.]

Hi PDW,
there is no smoking in VIctorian jails any more - so yo0u can take your pick.
There are no drugs in victorian Jails either.....

They will be banning soap in jails next..

[neksmerj]

No soap?........that's gunna make things a bit dry!

Ken