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Dressing a diamond wheel

implmex

Titanium
Joined
Jun 23, 2002
Location
Vancouver BC Canada
Hi All:
I'm looking for advice on dressing a diamond wheel.
Resin bonded 150 grit 100% concentration 4" diameter 1/16" wide running at 2800 RPM.
I'm having problems getting a decent finish dry grinding tungsten carbide.
Here's a picture:
DSCN5532.JPG

It's on a little home made cutter necking grinder (think miniature cylindrical grinder) I built for myself:
DSCN5530.JPG

I can dress an aluminum oxide wheel and grind HSS to a nice finish so I know it's not the spindle on either the wheelhead or the workhead.

Since I have both a powered wheelhead and a powered workhead both with variable speed, I've been faking the dressing with an aluminum oxide wheel in the workhead operating like a brake dresser.
It took the lumps off the wheel and made it run true but I cannot seem to dress it to a decent finish, so it's tearing at the carbide shank I've been test grinding.
The brake dressing wheel is a mounted point on a 1/8" shank and seems to be about 80 grit and maybe an "M" hardness 5/8" diameter.
I tried a coarser one too...no joy.
I'm running the diamond wheel at about 100 RPM and the aluminum oxide mounted point at about 5000 RPM.
I've been running a dressing stick over it after dressing it with the wheel.
Here's a picture:
DSCN5533.JPG
I want to do better and it seems my dressing setup is not doing it.
Any recommendations?

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
 
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eKretz

Diamond; Mod Squad
Joined
Mar 27, 2005
Location
Northwest Indiana, USA
Are you losing much off the wheel while you're grinding? Also, when dressing you power spinning the dressing wheel the same direction as the grinding wheel, yes? Generally the brake dressers do that but at somewhat slower surface speed than the grinding wheel, it sounds like you are doing that. You need to keep the diamond wheel taking light "cuts" on the dressing wheel and rapidly moving it back and forth across the dressing wheel - forgive me if you already know all this, I suspect that you do

Next, are you plunging straight in on your grind or trying to traverse across the part? For a wheel that thin and the amount of material it looks like you're taking off I would be plunge grinding as much as possible, only going to a traverse at the very end after a fresh dress for a light finish pass. You could try pressing a dressing stick into the diamond after the "brake" dressing also. It might also behoove you to try a wider wheel.
 

implmex

Titanium
Joined
Jun 23, 2002
Location
Vancouver BC Canada
Hi eKretz and Milling man:
Thank you both for weighing in.
eKretz, I did not make the setup I used originally, rotate the dressing wheel in the same direction as the grinding wheel...I ran it opposite rotation on the theory that I wanted to grind the wheel, much like I face grind the wheels on my Deckel cutter grinder using the surface grinder when I need to flatten them.

Now I have cobbled together a brake dresser that works like every other one on the market and we will see how well it works once I have made a mount for it.
Further bulletins as I make progress.

Cheers

Marcus
 

michiganbuck

Diamond
Joined
Jun 28, 2012
Location
Mt Clemens, Michigan 48035
I agree a green wheel would do much better, but not a point-mounted wheel with a 1/8 shank. Likely that is vibrating way too much to dress properly. Perhaps buy a real brake dresser wheel (1/2" stub wheel arbor needed).

I would say to home-make a short stub dresser wheel arbor to fit your largest collet and to fit a 1/2" to 1 1/4 " hole wheel.. Have the R or L hand thread that tightens with the wheel direction, and your dresser should work much better. The same way /other way doesn't make much difference, * but both spindles should tighten (R or L) when running/dressing.

A handheld abrasive wheel Crackerjack (brand name) can also be used on diamond and CBN wheels. You hold one at an angle so it only goes up to about 300 - 500 rpm.

Using your setup and if having a variable dresser rpm I would start with both at the same SFPM, intersect the wheel to be dressed, and then cut the dresser wheel to half speed. You might even shut the RPM of the dresser wheel and let the dressed wheel pull it (Doing this or not doing this I like to back away from the contact while running/dressing.

Grinding a long carbide I grind a short section to + .002 or so, then stick out some more and grind that using a slow plunge grind with no cross the part travel and move for my next rough in section. When I have the length roughed +.002 I would try to come in near the holding, plunge to take .0005 0r .001 and then slow feed travel away from the holding towards the out end. that keeps my at-the-step wheel-corner good.

Squeezing a slug/wad of children's modeling clay on the long part does wonders to reduce part chattering. yes, the part RPM is slow so the clay does not go flying.

You might grind the short stick-out method all the way to the+size, then grind the length.

You might have a tad over length for cut-off /or grind off, and use a female center on the out-end so to reduce part vibration.

Oh, you can also use a sacrifice diamond wheel as a dresser wheel if you might come across diamond wheels a give away price, Yes such a wheel will be a little noisy at first grind with diamonds being dull/rounded.

OT : Watch out for "D" marked diamond wheels as they are the berries for carbide grinding with vey sharp diamonds , often you can see and hear the difference. D = mined natural diamonds, MD = manufactured diamonds.
 
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eKretz

Diamond; Mod Squad
Joined
Mar 27, 2005
Location
Northwest Indiana, USA
I agree a green wheel would do much better, but not a point-mounted wheel with a 1/8 shank. Likely that is vibrating way too much to dress properly. Perhaps buy a real brake dresser wheel (1/2" stub wheel arbor needed).

I would say to home-make a short stub dresser wheel arbor to fit your largest collet and to fit a 1/2" to 1 1/4 " hole wheel.. Have the R or L hand thread that tightens with the wheel direction, and your dresser should work much better. The same way /other way doesn't make much difference, * but both spindles should tighten (R or L) when running/dressing.

A handheld abrasive wheel Crackerjack (brand name) can also be used on diamond and CBN wheels. You hold one at an angle so it only goes up to about 300 - 500 rpm.

Using your setup and if having a variable dresser rpm I would start with both at the same SFPM, intersect the wheel to be dressed, and then cut the dresser wheel to half speed. You might even shut the RPM of the dresser wheel and let the dressed wheel pull it (Doing this or not doing this I like to back away from the contact while running/dressing.

Grinding a long carbide I grind a short section to + .002 or so, then stick out some more and grind that using a slow plunge grind with no cross the part travel and move for my next rough in section. When I have the length roughed +.002 I would try to come in near the holding, plunge to take .0005 0r .001 and then slow feed travel away from the holding towards the out end. that keeps my at-the-step wheel-corner good.

Squeezing a slug/wad of children's modeling clay on the long part does wonders to reduce part chattering. yes, the part RPM is slow so the clay does not go flying.

You might grind the short stick-out method all the way to the+size, then grind the length.

You might have a tad over length for cut-off /or grind off, and use a female center on the out-end so to reduce part vibration.

Oh, you can also use a sacrifice diamond wheel as a dresser wheel if you might come acros diamond wheels a give away price, Yes such a wheel will be a little noisy at first grind with diamonds being dull/rounded.

OT : Watch out for "D" marked diamond wheels as they are the berries for carbide grinding with vey sharp diamonds , often you can see and hear the difference. D = mined natural diamonds, MD = manufactured diamonds.

I find that running the dressing wheel in the opposite direction of the wheel seems to eat the dressing wheel up a lot faster and take longer to get the wheel trued, but it will probably still work.

I agree with the rest of that, and as usual it's fleshed out a lot better than my reply! :)
 

michiganbuck

Diamond
Joined
Jun 28, 2012
Location
Mt Clemens, Michigan 48035
Ops, my bad...grinding wet does wonders for diamond wheel grinding carbide.

One might have a split 4" PVC pipe on an arm to be a quick coolant catch and a 5-gallon bucket with a $10 aquarium pump temporary coolant tank using homemade washing soda coolant.
(cut off soda bottle?)
 

Milling man

Aluminum
Joined
Aug 6, 2021
Location
Moscow, Russia
I was carefully looking at the photos from the first post, and it dawned on me - the cutting speed is too low! 5/8" in diameter and only 5,000 RPM - it would flake more than it would grind even on contact with something steel. And upon contact with the diamond wheel, the effect will, of course, be sad.
You need to either increase the speed, or increase the diameter of the grinding wheel with which you are dressing.
 

michiganbuck

Diamond
Joined
Jun 28, 2012
Location
Mt Clemens, Michigan 48035
I think the brake dressers run at about 1000 / 1800 surface feet per minute and with the wheel about 3" the RPM would be in the same ballpark, and then the brake weights expand and the wheel tries to slow. The diamond wheel commonly goes about 4500 to 6500 sfpm and roughly about 3400 to 6000RPM with Tc cups and the like perhaps up to 10,000 Rpm (if listed for that high)

The 4" wheel grinding at 2800rpm is very slow..

3450 would be about the slowest that I would run it. / 5000+ if the label says to that.

QTI've got some larger wheels on 1/4" shanks I will try too.):(

Still not stout enough IMHO. it takes some pressure to dress a diamond wheel.

I pretty much know how much pressure because I have hand roller-dressed diamond wheels. It takes two hands so I would guess about 10 to 12 pounds push. AO and green wheels take about 1/4 and 1/2 that much push.
 
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michiganbuck

Diamond
Joined
Jun 28, 2012
Location
Mt Clemens, Michigan 48035
Yeah, good point about wheel RPM too, didn't even notice that on first read. Running too slow will make the wheel act very soft.
looks like about 2900 or less SFPM with grinding drag down, when 5000 + would be better.

I would likely spin the part at a slow RPM, 350 to 600. Travel slowly for the plunge to rough, and then long travel walking out toward the end. Try to employ some kind of tail support or perhaps grid the out end to +.0005 first and then bring in a steady or a female center at the out end. Run the grinder wheel at 4500 or more.
Could run a rag wheel or sponge on the part with a rub of oil, or add coolant.

An oil rub or coolant cuts the grinding pressure about in half for less vibration, less wheel wear, and a better finish.
* I know it would be difficult to rough plunge to +.002 with a 1/16 wide wheel, just about impossible so if doing this kind of work a wider wheel would be good, also long travel with a 1/16 wide wheel would quickly beat up the wheel leading corner and OD so there is another reason for having a wider wheel.. 3/8 or 1/2" (*1/2) wide would be my choice.

I usually only use a 1/16 wide wheel for a plunge grind cut-off wheel.
 
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eKretz

Diamond; Mod Squad
Joined
Mar 27, 2005
Location
Northwest Indiana, USA
looks like about 2900 or less SFPM with grinding drag down, when 5000 + would be better.

I would likely spin the part at a slow RPM, 350 to 600. Travel slowly for the plunge to rough, and then long travel walking out toward the end. Try to employ some kind of tail support or perhaps grid the out end to +.0005 first and then bring in a steady at the out end. Run the grinder wheel at 4500 or more.
Could run a rag wheel or sponge on the part with a rub of oil, or add coolant.

An oil rub or coolant cuts the grinding pressure about in half for less vibration, less wheel wear, and a better finish.
* I know it would be difficult to rough plunge to +.002 with a 1/16 wide wheel, just about impossible so if doing this kind of work a wider wheel would be good. long travel with a 1/16 wide wheel would quickly beat up the wheel so there is another reason for having a wider wheel.. 3/8 or 1/2" wide would be my choice.

I usually only use a 1/16 wide wheel for a plunge grind cut-off wheel.

Yep, like I mentioned earlier, I definitely would use a wider wheel if possible also.
 

CarbideBob

Diamond
Joined
Jan 14, 2007
Location
Flushing/Flint, Michigan
150 grit? Say what?
How big is this part?
If of the small size I'd guess this looks about right for a 150 grit wheel. :eek:
To dull a diamond wheel take a piece of soft steel and use it like a wheel stick. This rounds off the points on the grains.
One can also use a round molybdenum stick like you would a dressing diamond. Very small infeeds and this leaves a very dull wheel which is what you want here.

I do not use a 150 grit for finishing any carbide.
Everything wet here but on smaller parts I'm into 400 and 800 grits. (in plated diamond wheels 400 is the finest grit you can get)
I run the dressing wheels with the wheel rotation most of the time but do run against sometimes depending on the wheel and stone and how they are matched.
I have dressing stones in silicon carbide and aluminum oxide. On a 150 grit wheel I'd be using a 60 to 80 grit dressing stone.

Lower surface footage leaves a rougher finish.
Harig use to sell a machine called the "Carbide Hogger" that ran the 3hp spindle at 1750rpm and used 6 inch wheels.
Bob
 
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eKretz

Diamond; Mod Squad
Joined
Mar 27, 2005
Location
Northwest Indiana, USA
150 grit? Say what?
How big is this part?
If of the small size I'd guess this looks about right for a 150 grit wheel. :eek:
To dull a diamond wheel take a piece of soft steel and use it like a wheel stick. This rounds off the points on the grains.
One can also use a round molybdenum stick like you would a dressing diamond. Very small infeeds and this leaves a very dull wheel which is what you want here.

I do not use a 150 grit for finishing any carbide.
Everything wet here but on smaller parts I'm into 400 and 800 grits. (in plated diamond wheels 400 is the finest grit you can get)
I run the dressing wheels with the wheel rotation most of the time but do run against sometimes depending on the wheel and stone and how they are matched.
I have dressing stones in silicon carbide and aluminum oxide. On a 150 grit wheel I'd be using a 60 to 80 grit dressing stone.

Lower surface footage leaves a rougher finish.
Harig use to sell a machine called the "Carbide Hogger" that ran the 3hp spindle at 1750rpm and used 6 inch wheels.
Bob

Bob, I'm guessing you are suggesting you'd want the wheel a little duller to get a better finish? That makes sense too. Sort of make the diamonds a little less jagged to compensate for the lower grit? I use a moly stick myself but figured he'd be a step ahead and freer cutting with the abrasive dresser.
 

implmex

Titanium
Joined
Jun 23, 2002
Location
Vancouver BC Canada
Hi Guys:
Some great input here...I'm getting a terrific quickie course on how to make this work.
One thing to remember; my goal is to be able to neck down small carbide cutters...mostly 1/8" and under.
I want to do it fast (a couple of minutes max) and I need it to be good enough that the roughness that's left on the spun down shank is smooth enough not to cause stress risers.
That's why I settled on a 1/16" wide wheel with 150 grit.
I need to be able to neck a 1/32" cutter 1/16" longer than stock so the wheel has to be skinny to be able to reach in behind the flutes.

I'm not trying to cylindrical grind a shaft to tenths...I just want to do better and faster than I can on a Deckel SO cutter grinder.
My smallest cutters are in the 0.015" range.
I've necked 1/16" cutters 3/4" long in the past, so I need to make up some steadies too.
I plunge those in 0.050" steps, just as michiganbuck has recommended.

So far I'm pretty happy with the ease of use and the speed with which I can take a 15 dollar Garr cutter and turn it into a 50 dollar "Harvey like" special.
Once I get the finish to be the best it can be, I'll be very satisfied, and that's going to be all about the quality of the dress.

It always pisses me off to buy a bunch of Harvey specials so I'll have spares if I bust one, and then run the whole job on a single cutter...this new toy fixes that.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
 
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michiganbuck

Diamond
Joined
Jun 28, 2012
Location
Mt Clemens, Michigan 48035
Oh , one thing I failed to mention. or a few things.
Making small step drills, reamers, specials and the like it is common to grind a 60* point on the tool out end and use that for fitting into a female tail center. The female tail center can be smaller than the tool Od so the tool Od can be ground. Making this female Thin boded on the close side and thicker on the away side makes it very stout to resist grinding pressure. This tail center can be .025 on the close side and 1/2" on the away side so being very stout..and still be out of the way.
Yes, the center point is ground away and the needed point added as a/the last operation

Grinding the clearance to a step tool can be done at a clearance angle, and then butterfly (radially) up a bit to make a radial relief-looking tool.

Having some quick stops on your radial swing can allow hand rotating a cutter OD for about half or 1/3 the OD with not bumping the end of grind and so breaking small carbide necking down., By hand radial travel can be better controlled (sometimes) than spinning under power.

Axial (end) feed cutter should have 9 to 15* primary clearance and have .0002 or so per inch back taper (getting smaller).

A 120 and a 220gt wheel are Ok for few-up specials. Often a 500 is too slow cutting and a heat maker.

I think altered standards are the best way to make specials, it just takes too much time to grind flutes and everything into a carbide blank.

Bushings can be angle ground at their back end(or front end) and when set screwed to a citter shank can roll and clear a axialcutteing edge. often a specoalmight be just corce groend the the step and the n this kind on bushing uses to bring the clearence up to tha cutting edge... like a harige step tool fixture. Darn, I cant find a photo on the net. I will take a photo of mine if I can find my camera battery charger.

Nowadays CNC Tc grinder make easy work of specials but they cost big bucks.

A very handy machine/grinder for specials is a Royal Oak. Using crushable wheels and homemade crushers it can do some very fancy work quickly.
The cincinnati #1 or #2 wth a work head and centers is a very handt , Hot rod for cutter making
 
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M. Roberts

Aluminum
Joined
May 11, 2021
Implex, Good morning...coming into this late, and admittingly, I haven't read all of the suggestions. We use nothing but diamond grinding wheels; when they need attention, I use a G2 spindle truing devise, equipped with a diamond truing wheel. The rule of thumb we go by is to run the surface feet of the truing wheel at 80% of the main grinding wheel; running CCW, and using coolant. Truing and dressing are two separate actions....I hope this helps
 








 
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