Author Topic: Diamond wheel question  (Read 833 times)

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Kent

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Diamond wheel question
« on: January 23, 2016, 01:37:15 PM »
About a month ago I purchased a real heavy 60/80 grit "sintered" diamond wheel from Covington Engineering which has over 1/8" thickness of diamond and I figure at the cost would be a long term user. When I got it it could grind anything fast. Today I started a petrified wood piece and I can hardly see the rock diminish. Its like the wheel just stopped grinding. I don't think I'm pushing too hard. Do these wheels need to be dressed for time to time ? If so with what ? a hard rock ?

Cheers,

Kent
 

Ranger_Dave

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Re: Diamond wheel question
« Reply #1 on: January 23, 2016, 02:12:44 PM »
I'm pretty much a beginner, but I'm sure the wheel could clog up if you don't use enough water and/or have been grinding on some soft material.

PhilNM

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Re: Diamond wheel question
« Reply #2 on: January 23, 2016, 02:28:21 PM »
Might just be you're not used to grinding a really hard stone like pet wood. Make sure you have lots of water and keep at it.

slabbercabber

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Re: Diamond wheel question
« Reply #3 on: January 23, 2016, 02:36:24 PM »

Dress with a piece of old grinding wheel or sharpening stone.  It doesn't seem to pull out any diamond.

bilquest

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Re: Diamond wheel question
« Reply #4 on: January 25, 2016, 08:55:04 AM »
I have the same wheel and have a few comments...

Having bought various diamond wheels over the years I've noticed that they all cut like a mofo when they're new, but then their cutting aggression tends to taper off. Even my 360 grid diamond wheel did crazy shaping for the first couple hours. I don't think it's a glazing issue, I just think a freshly manufactured wheel has a break-in period. I remember when I first purchased my sintered wheel (about 3 years ago) I was giddy with how fast it shaped stones. But then, as you mention, it seemed to stop cutting. Further inspection revealed that it hadn't stopped cutting, rather it just wasn't cutting very fast. Also note that sintered wheels are actually a grit finer than advertised. For example, your 60-80 grit should actually be considered a 100 grit (or even 200 IMHO) once it's broken in. In summary, you can't set the expectation of a wheel based on initial cutting ability.

I feel your pain. I too was looking for a good shaping wheel that would last awhile, and the sintered variety seemed to make that claim. Once I accepted that my sintered wheel wasn't going to 'cut it' (pun intended) I continued my search.

I found the answer with a 60 grit Sachi Perfect diamond wheel (mine is an 8x2). Brand new it was too course and would shred a hard piece of petrified wood, essentially unusable. I dressed it with a hard piece of junk agate, probably eating through 2 or 3 pounds of the stuff before the wheel smoothed the knobs of diamond/metal left over from manufacturing. Once the wheel was properly dressed, it cut like a charm, and has continued to cut like a new wheel for the past 2 years that I've owned it.

My dream team consists of:

- 60 grit Sachi (shaping)
- 60-80 grit sintered (shaping, beveling, remove sachi scratches)
- 360 grit hard diamond (remove sintered scratches)
- 400 grit SC expando (wet) remove flat spots, scratches

I have all these mounted on an old HP combo unit, and I can complete the shaping of a dopped shape in 10-15 minutes if I'm in a hurry.

So, I guess my advice with your sintered acquisition is not to despair. Rather discover its capability and where it fits in with your process -- rest assured that the wheel will probably outlast you. I've found it's a great wheel for shaping preforms, as well as beveling the dome and finalizing the shape of the cab. It's probably my most used wheel, as it should be.

As for dressing the sintered, I've never done that, nor would I even know how to. I've read about services where you can send it for dressing but costs as much as a new wheel. I try to use the entire face of the wheel for even wear, and after 2.5 to 3 years of daily use, it's still as flush as the day it came in the mail. I've been curious if anyone has ever worn out a sintered wheel, and what that looks like. Maybe sweat shops in China manage to get through all those diamonds, but I can't imagine a hobbyist wearing out such a wheel in a single lifetime.

Hope this helps, I know those wheels have a killer price tag.

slabbercabber

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Re: Diamond wheel question
« Reply #5 on: January 25, 2016, 09:30:09 AM »
When I suggested dressing with grinding wheel, it was from experience.  I got the tip from Micheal Hoover.  It turned my 60-80 grit wheel back to new condition.  Dressing this way is simply running the sic piece over the face of the wheel as if you were grinding any other stone.  It doesn't take much.