Thread: Truing a diamond wheel - what to use ?

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.

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

Diamond wheels are trued with a brake dresser...

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

This is all I use, a selectively mined chuck of Alum Ox, smashed out of a 12 or 14 inch wheel.
P1010296.JPG

P1010297.JPG

P1010298.JPG

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-D...item51d0732c65

Regards Phil.

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

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.

Originally Posted by Machtool

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..

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

They do say "diamonds are forever"

Originally Posted by .RC.

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.

Originally Posted by johntopp

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.

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 ?

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.

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