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[ToTheSummit]

When I built my custom cabbing machine I bought a set of Diamond Pacific wheels.  The set designed for a Titan (8" wheels).  The set consists of two galaxy (hard) wheel in grits 80 and 220 and four Nova (soft) wheels in 280, 600, 1200 and 3000.

My machine has always worked well and I love the wheels, but I noticed a problem with my 220 galaxy wheel early on.  I thought it would work itself out but instead the problem seems to be getting worse as the wheel breaks in.  The problem lies in the fact that somewhere on the 220 wheel there is (what I am assuming is) a bit of contamination that was introduced during manufacture.  Whatever it is it creates scratches that are deep enough that they do not come out as I continue on through the grits.  I can actually grind out these scratches on the first nova wheel (280) but only if I have identified where they are and have left enough meat in the stone to work them out.  And the problem is they are very hard to see until you get into the polishing stages.  When the stone is wet they cannot be seen at all and when the stone dries out I usually cant see them until at least after the 600, and thats only on stones that already start to take a shine at that grit.

I have taken to jumping from shaping on the 80 grit to going directly to 280, especially on things like obsidian where these scratches are devastating to the finish.  I have to assume the offender is a small diamond particle embedded in the 220 wheel because it is hard enough to scratch even the hardest things I have ever cut.  I thought maybe it would pop out or wear off, but it seems to be getting worse as the wheel wears in.  I don't cut lots of rock so I expect my wheels to last for years.  In fact I've already been using them for a couple years and they are just getting broke in nicely, but I can't continue with this one.  I have tried inspecting the wheel meticulously under magnification but I cannot identify the spot.

The scratches are small so I know the contamination is small.  In hand on most stones where I still have scratches after finishing them it is very hard to see the scratches with the naked eye.  The exception is darker stones in uniform colors with a high gloss finish.  Things like bruneau and obsidian are terrible unless I can find the scratches at the next stage and remove them.  Lots of my finished stones I haven't even noticed the scratches until they were done and I started trying to take macro photos of them.  Then I'm like "Awww Damnit!!"

So has anyone ever had a problem with a wheel like this in the past?   Is there a way I could identify the offending spot and possibly remove it?  Do I need to bite the bullet and just buy another wheel?  Any help or suggestions would be appreciated.

Here is a stone I finished today to illustrate.  This is a piece of agua nueva agate.  The cab is large (about 56X43mm) so the dome is fairly low.  In hand the scratches are all but invisible.  You have to look at a reflected light source shining off the stone where the scratches are to see them with the naked eye.  But in the photos I took they are very apparent and it drives me crazy.  You see them as the small white streaks crisscrossing the center of the stone.

[Kaljaia]

It's a gorgeous stone and I can imagine how frustrating that would be. I don't know the equipment but would hand-turning the wheel against a soft material let you narrow down where on the wheel the offending particle is?

[lithicbeads]

I have had exactly the same problem with that brand wheel of that and only that grit.One was so bad that there were 5 patches of carbonized super aggregations of diamond which collectively cut at about 30 grit. I argue with DP and sent the wheel back . They replaced it but would not reimburse shipping. Exactly the same problem!!! This time I called at lunch time when the brass were out and they let me talk to a manufacturing employee who said this defect was very common. He picked me out a wheel and sent it to me and it was fine.

[ToTheSummit]

Thanks Frank.  Good to know.  I may have to place a call to DP and see what I can do.  Don't think they'll wanna help out since I've used the wheel for so long though.  Still a lot of life left in my wheels though and its frustrating.

[lithicbeads]

Beautiful stone!

[Gergis]

Have you or could you try to dress the wheel a bit to see if it takes the imperfection/s out?

Sent from my LGLS990 using Tapatalk

[wampidy]

I have no idea if this will work on the wheels but it worked on my diamond velcro pads several times.

I was frustrated like you because I could not get it to stop and I had used every kind of stone and grinding wheels I had with no luck. I have a row of tools stuck to a magnet close at hand so I grabbed a  pair of side cutters made of hard steel and rubbed the side of it on the pad for ten or fifteen seconds.

Common opal is the worst especially on the side of the cab so I tried a piece that had visible scratches on the side and went to work on it. The scratches disappeared and I was one happy duck.

My contamination was caused by me and I finally figured out where it was coming from but I used this method several times and it worked every time.

You pointed out scratches in the center of the stone and I have noticed that if there are scratches only in the center of the stone I have worked it down to a smooth dome but not quite deep enough to get all the scratches at that final doming point. It might help if you work the next grit up double time and see if there is a difference because the tiny scratches are like the very bottom of larger scratches.
Jim

[vitzitziltecpatl]

Good call Jim. Lose a little life dressing them, but if it's worthless as is that's the way to go.

If you have a good tool rest sometimes you can sneak up on the wheel with a straight-edged stone or tool and find if it "ticks" as it goes around. Have also worked problems out by doing that with a steel tool. If there's just one little spot that's a tiny bit high, sometimes the steel will knock it outta' there.

[Slabbercabber]

Be careful using steel on diamond.  The iron has a chemical affinity for the carbon and will burn it off very quickly.  Obviously that will allow you to dress the wheel.

[vitzitziltecpatl]

Absolutely agree with slabbercabber. Have only used steel as a last resort, and then only to find and (hopefully) fix a small trouble spot. Dressing sticks specifically for diamond wheels are available for more normal conditions.

Here's one link (of many) with info on dressing sticks.

http://www.inlandcraft.com/uguides/use_dressing_stick.pdf

Good luck with your problem.