Practical way to true a Diamond grinder wheel?

[chale4incolo]

Hi grinding gurus,
I’ve got a 7” dia, 1/8”-wide Diamond surface grinder wheel that has become “crowned” I guess you could call it, i.e. the wheel is its largest dia in the center of its 1/8” width, and it tapers off a bit to either edge of the wheel. I need for it to be good and flat across its width. Is there a “practical” way to achieve this condition? I don’t have a fancy/$$ abrasive dressing tool like you see at MSC and such, and can’t really afford to buy one at present. I do have some white “sticks”, and I’ve got a good single point Diamond dresser for my abrasive grinder wheels. Is there a sensible way to go about this problem “in house”? Thanks—Charley in Colorado

 

[chale4incolo]

By the way, by “fancy/$$” tool, I mean the “brake-type” dresser tools, that I see out there for $400 type level of expense. Hope to avoid that…thanks—

 

[michiganbuck]

I have dressed a diamond wheel by wet grinding a piece of mild steel, and a piece of brass. Soft material sucks the diamonds out of a wheel.
Guess I would long lay up a 1/16 x10"(or what length) steel solidly between two parallels and grind on it with the center section of a 1/8 wheel.
*Put some card paper under the set-up so to not score the chuck.
After doing this the wheel will be loaded up so sticking will be needed.

I have a free spinning Crackerjack minie, abrasive wheel dresser that will hand dress a diamond wheel, but it may be tough to narrow dress a 1/8 wheel with it.

One can grind-dress a diamond wheel with a green wheel, but that really takes a lot of green wheel to take just a little off a diamond wheel.

Sometimes one can save the last of a plate-mounted wheel to vise it and then grind on it with the wheel needing dressing with incremental cross grinding a tenth down feed at each pass.
It is not uncommon for a plate-mounted wheel to wear off in one place, so no longer good for grinding, good to cut up such a wheel and use the remnants for hones..and a hack dresser..

Incremental cross grinding both in and out directions likely wore the wheel to be crowned, high in the center. Cross-grinding in only one direction may make the wheel's flat last longer.

1. Good to keep a diamond wheel on it's own mount.
2. Indicate it to .001 or so at its first use.
3. have a lineup mark wheel-to-mount , and mount-to-spindle.
4. run it wet.
5. clear away any steel or brass from being ground.
6. make it plenty tight on the mount.

 

[jkopel]

Here is video about dressing a diamond wheel with a molybdenum stick. The format is hard to watch but the information is interesting. I see 3/8" molybdenum rod on ebay for cheap so if it works it's a lot less then buying a brake truing tool.

 

[eKretz]

Yeah a molybdenum stick works much the same as the steel or brass, but a bit faster. Still gotta open up the wheel after.

 

[jkopel]

That is just hitting it with an abrasive stick, right?

 

[eKretz]

That is just hitting it with an abrasive stick, right?

To put it simply, yes.

 

[chale4incolo]

Here is video about dressing a diamond wheel with a molybdenum stick. The format is hard to watch but the information is interesting. I see 3/8" molybdenum rod on ebay for cheap so if it works it's a lot less then buying a brake truing tool.

Wow, that IS an interesting video, for sure, thanks. I’m definitely going to look into this. He’s dealing with a ($$$) metal-bond wheel and I’ve got a (~ $150) resin-bond wheel, but I’m figuring that’s ok? And my little old #2 B&S WW2-era grinder doesn’t exactly have as many bells/whistles as his marvelous machine, but, surely I could do that (at full 3200 RPM, that’s all it does…), too. Any further thoughts on this?

 

[chale4incolo]

By the way, by “fancy/$$” tool, I mean the “brake-type” dresser tools, that I see out there for $400 type level of expense. Hope to avoid that…thanks—

Um, correction on my “$400 above”; that’d be like a steal on eBay for a used one…Norton “Pacesetter” 3597 seems like kind of a leader in these things, and they’re more like $800-900 looks like…arg.

 

[chale4incolo]

Wow, that IS an interesting video, for sure, thanks. I’m definitely going to look into this. He’s dealing with a ($$$) metal-bond wheel and I’ve got a (~ $150) resin-bond wheel, but I’m figuring that’s ok? And my little old #2 B&S WW2-era grinder doesn’t exactly have as many bells/whistles as his marvelous machine, but, surely I could do that (at full 3200 RPM, that’s all it does…), too. Any further thoughts on this?

Quick update, bought a couple of 3/8”dia rods of molybdenum off ebay last PM, so I’ll see in a few days. I may try a similar rod of brass I’ve got on hand today “for practice” and tooling setup, who knows, maybe it’ll do a nice job of it, too?

 

[michiganbuck]

I hack-dress a diamond wheel coming down on a piece of brass or steel to only grind /dress on the high place of the wheel with down feed..if hack cross-travel dressing, I will come down .0002 or so to just hit/take wheel from the high place.

I think the molybdenum method would be best served with .0002 or .0001 down feeds and crossing...seems like .002 would put a taper/convex high in the wheel.

 

[eKretz]

Wow, that IS an interesting video, for sure, thanks. I’m definitely going to look into this. He’s dealing with a ($$$) metal-bond wheel and I’ve got a (~ $150) resin-bond wheel, but I’m figuring that’s ok? And my little old #2 B&S WW2-era grinder doesn’t exactly have as many bells/whistles as his marvelous machine, but, surely I could do that (at full 3200 RPM, that’s all it does…), too. Any further thoughts on this?

Yes, that's fine. Works great on resin bond. 3200 isn't optimal but yes it will still work. You may chew through the molybdenum faster.

P.S. Looks to me like the guy who made that video is in dire need of a mag chuck regrind. See the shiny spots (they look dark or black) every 2 or 3 mag bars on the top of that chuck? It's not flat. I've noticed that electromagnetic chucks seem to do that (start to hump a bit between the mag bars) after a while.

 

[michiganbuck]

OT: (other topic)
Another vid from that fellow..He has a company called kinetic Precision.

 

[luke8888]

I'm very interested if those molybdenum bars work for you once you test them.

In the meantime my method (before I got my rotary brake dresser) to true a resin bond diamond wheel is to use up a crappy Chinese combination bench stone that is unsuitable for anything else (with sand and brick dust in the mix).

Aluminum oxide or a silicone carbide stone will do, but it should be quite flat (flattened on a diamond bench stone flattening plate, or unused).

Use the coarse side if your diamond wheel needs s lot of truing, fine side for finishing. Use a grinding vice, parallels and some copper foil to hold the stone.

I did this with flood coolant on. I touched off on the stone and then dialed in depths of cut up to 20 thou (half thou towards the end). Just plunge into the stone full wheel width. Every time traverse the entire length of the stone and move not to overlap the cuts. You need "new" piece of surface to cut every time.

Once you've cut ridges one next to the other the whole width of the stone you can rotate it 90 degrees and d the same from the side.

Do measure your diamond wheel frequently. You can always take off more... Also if you finish by shallow cutting the fine side there is no need to stick the wheel afterwards.

It all depends on the stone of course. Perhaps I was lucky in the crappy stones I got.

 

[chale4incolo]

Thanks, this is a really interesting approach, too. Harbor Fgt ought to have crappy enough ones I would think : ) , I might make a quick trip up there and get 1-2 crappy stones and try this. While waiting for my molybdenum rods, I tried a 1/2”dia rod of brass…didn’t much seem to work for me (took off about 0.04” off the rod length, certainly made a nice pretty cylindrical-concave end on the rod…)…but didn’t appear to me to help my wheel face flatness much (a little, maybe). Brass too “wimpy” compared to moly For this diamond-sucking-out process?
—what rotary brake dresser did you spring for? My whole deal here has to do with dicing/grinding features in fused silica optics (mirrors, splitters, filters etc.) , and I’m pretty decently able to at this point. I’ve had a couple of word-of-mouth folks who’ve paid me to do some simple dicing, and if I could gin up a few more, I wouldn’t feel so bad about getting a $$ brake-type dresser…ah well, TBD!.—

 

[LexD]

Quick update, bought a couple of 3/8”dia rods of molybdenum off ebay last PM, so I’ll see in a few days. I may try a similar rod of brass I’ve got on hand today “for practice” and tooling setup, who knows, maybe it’ll do a nice job of it, too?

Could you post a link to the 3/8 molybenum rods please, I can't seem to locate any.

 

[michiganbuck]

I think crossing over a soft material Moblyb, mild steel, or brass with .002down feedsd would put a dome/ a convex bottom to the wheel...down feeding one or two tenths might be ok so just taking the wheel where it was one or two tenths high.
A diamond on an AO dresses flat..and a brake wheel dresser makes a diamond wheel flat..
But do test the method and give a report.

 

[dalmatiangirl61]

Could you post a link to the 3/8 molybenum rods please, I can't seem to locate any.

https://www.ebay.com/sch/i.html?_from=R40&_nkw=molybdenum+rod&_sacat=0&LH_TitleDesc=0&_sop=15

What is molybdenum rod used for? I see it also comes in an all-thread version.

 

[LexD]

I suspect that the threaded rod you are referring to is an alloy steel with molybdenum and other alloys included, sometimes referred to as Chrome-Moly steel or Nickel- Chrome- Moly, not pure Molybdenum.

 

[dalmatiangirl61]

I suspect that the threaded rod you are referring to is an alloy steel with molybdenum and other alloys included, sometimes referred to as Chrome-Moly steel or Nickel- Chrome- Moly, not pure Molybdenum.

Direct link, there are other sizes available in the link in my previous post too.
https://www.ebay.com/itm/1940381409...Bd6BVgEYw1C7WHPAUFFuB7LqFSxFvvrjNqdq1fUsq4psJ

So, short of dressing diamond wheels, what are other applications for molybdenum round stock?