nik
spending too much on rocks
Member since May 2019
Posts: 315
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Post by nik on Dec 23, 2019 2:00:12 GMT -5
Hello again. I just tried out a used 60 grit sintered wheel that I picked up on ebay. It looks good, with plenty of thickness left in the diamond layer, and what looks and feels like a reasonable amount of exposed diamond. The problem is that it just does not cut nearly as fast as I would have expected, almost like the diamond is dull. It is slower to remove rock than my sintered 120. I know the wheels can be dressed, and I was hoping someone with a bit of experience with this type of wheel could give me some pointers as to the best way to accomplish this task. Thanks in advance. IMG_20191222_144821 by nik1924, on Flickr
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Post by As I in does tries! on Dec 23, 2019 4:03:41 GMT -5
Greetings Nik, the best way to sort this, basically you need mark the inside of the hub with a permanent marker, un-do the nuts in order to remove that wheel, remove the wheel and turn it over so the mark you made is now on the inside of the wheel, re-tighten the nuts and try it out is should cut better.
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nik
spending too much on rocks
Member since May 2019
Posts: 315
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Post by nik on Dec 23, 2019 4:39:36 GMT -5
Thank you for the tip. I tried reversing the wheel, and it was slightly better. Still not what I'd expect from a 60 grit wheel.
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Post by hummingbirdstones on Dec 23, 2019 10:52:53 GMT -5
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nik
spending too much on rocks
Member since May 2019
Posts: 315
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Post by nik on Dec 23, 2019 18:37:05 GMT -5
That is pretty much what I thought. Any tips for actually dressing the wheel, I'd be pretty sad if I destroyed it.
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Post by hummingbirdstones on Dec 23, 2019 20:24:15 GMT -5
Run your wheel with water and lightly hold the dressing stick touching the wheel. You don't need to do it for very long. You'll be taking off some diamond, so test the wheel on a rock and do it some more if you need to.
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nik
spending too much on rocks
Member since May 2019
Posts: 315
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Post by nik on Dec 24, 2019 5:22:50 GMT -5
Well, I tried dressing the wheel with an 80 grit aluminum oxide stone, and it is marginally better, but still nowhere near the 120 wheel.I have tested it on obsidian, agate, and boulder opal matrix, on every material, the finer wheel outpaces it at least 3 to 1 in terms of rock removal. Could it be that I just got a junky wheel with dull diamond, or are the old Soviet wheels just that good.
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Post by hummingbirdstones on Dec 24, 2019 10:00:20 GMT -5
I would try it again. Try without water this time. Wear safety glasses. If that doesn't work, maybe it's an inferior wheel?
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nik
spending too much on rocks
Member since May 2019
Posts: 315
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Post by nik on Dec 25, 2019 7:06:15 GMT -5
Still no luck with this wheel, I've tried aluminum oxide and silicon carbide dressing stones, both wet and dry. I have reversed its rotation, varied speed, and I'm running out of ideas. All of the other sintered wheels that I run just cut better with less effort.
Might there be any bennefit to trying a diamond dressing stick? Or would that just eat the wheel.
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Post by hummingbirdstones on Dec 25, 2019 11:25:47 GMT -5
I really don't know.
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QuailRiver
fully equipped rock polisher
Member since May 2008
Posts: 1,621
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Post by QuailRiver on Dec 25, 2019 15:32:23 GMT -5
I would not use a diamond dressing stick on a sintered wheel. The whole point of dressing a sintered wheel is to remove the softer matrix and leave more exposed diamond. A diamond dressing stick would remove both plus could damage remaining surface diamond particles. A sintered wheel that has been dressed properly will have lots of visible diamond particles with a ridge of bronze matrix, or tail, behind the diamond particles (see photo). The bronze matrix ridge behind the diamond particle helps support the diamond particle and helps keep the particle bonded to the wheel surface. So in reversing the direction of the wheel then all of that bronze matrix would be on the lead cutting side of the diamond particles and shield most of the diamond from making contact with whatever you are attempting to grind . So while it may be beneficial to reverse a plated wheel it is not beneficial to reverse a metal sintered wheel. If doing so you would have to remove so much material that you now have all newly exposed diamond particles with visible matrix tails running in the opposite direction from originally. Which is no more beneficial than having left it with the same rotational direction and dressed the wheel to the same state. Except when reversing the wheel you would just have to remove more material to get the surface to that same freshly dressed state. The type of abrasive, and the grit of dressing stick being used matters just the same as it does when using an abrasive stick to dress a diamond blade. And dressing sticks come in various hardness's. Too hard of a binder in the dressing stick can cause some of the diamond particles to be ripped out of the surface of the blade or wheel which can drastically reduce performance. Also like the bronze matrix used on diamond blades, there are different metal alloy compositions used by differing manufactures of sintered wheels. I have both HANS and Neosint Sintered wheels, and JBL sintered laps and am still working on figuring out which dressing sticks work best for each. And dressing sticks come in various hardness's too. See the "Spec Check" section near the bottom of page 2 at the following link: georgiagrindingwheel.com/Catalog/Norton/T199-T200%20-%20Dressing%20&%20Finishing%20Sticks.pdf Originally I was using slices of 100gt and 220gt SC lapidary wheels left over from dressing my slab saw blades to sharpen my sintered grinding wheels. But wasn't happy with the final result, especially on the 220gt sintered. So I'm now trying various aluminum oxide sticks. The 100gt and 220gt SC slices of old lapidary wheels works okay for dressing my sintered 30gt Neosint wheel. And they work okay for a preliminary dressing on my HANS 80gt sintered followed by final dressing with an AO 150gt dressing stick. And am currently using 220gt AO to dress my 220gt HANS sintered with decent results. The AO dressing sticks I'm currently using are Norton's type 54 HVBE sticks which work well on my JBL sintered laps but they are soft and my sintered grinding wheels eat them up quickly. So the next time I order I am going to try the Norton NV and KV hardness AO sticks as suggested in the Spec Check section linked above. The best deal I've been able to find on dressing sticks is at AA Abrasives. www.aaabrasives.comNow all of that said, it is possible that the bronze alloy matrix in your 60gt sintered may be much softer than that used on your other wheels and may require a softer bindered dressing stick. Or if your 60gt is a Chinese made wheel, their manufacturing standards are often low, so I guess it is possible that an error was made in the bronze matrix alloy in your wheel that makes it too soft for it's intended purpose. Also I remember hearing several years back that some Chinese sintered diamond product producers had been caught using crushed quartz mixed in with their diamond to save money. So if true you may had the misfortune of acquiring one of those products. But you could probably determine that by using high enough magnification to see if the particles show crystal structure as diamond will. Larry C.
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hummingbirdstones2
fully equipped rock polisher
Vince A., 1958-2023
Member since August 2018
Posts: 1,461
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Post by hummingbirdstones2 on Dec 26, 2019 8:00:26 GMT -5
Excellent info on dressing wheels, and links to sources too! Thanks.
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nik
spending too much on rocks
Member since May 2019
Posts: 315
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Post by nik on Dec 26, 2019 17:55:46 GMT -5
Thank you Quailriver for the info and links. I've got a few pictures of the wheel face under magnification. The diamond particles and bronze tails are pretty easy to see. I will put them up once the home internet starts working again. I had a Guam moment and some mud wasps built a nest in the conduit and corroded the wires.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,154
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Post by jamesp on Dec 27, 2019 15:33:10 GMT -5
Abrasive diamonds have a wide range of aggressiveness for a given size. 60 grit diamond(cubic,octahedron?) crystals verses 60 grit crushed diamond particles can be many times less aggressive. Particle shape is a deep subject and depends primarily on the hardness and/or toughness of the material being ground. Life, heat build up, etc are other controlling issues. A good example is a diamond knife sharper. Drag your finger across one of them and you will experience sharp. They usually have the sharpest diamonds because the grinding pressure is low, temp is low and knife steel is relatively soft. On the other hand powerful tool and die grinding machines would use a stronger rounder duller diamond on tough/hard tungsten carbide for instance.
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zarguy
fully equipped rock polisher
Cedar City, Utah - rockhound heaven!
Member since December 2005
Posts: 1,791
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Post by zarguy on Dec 27, 2019 16:10:13 GMT -5
nik With all of the work you've gone through to improve performance on the 60 grit wheel, I'd say you just got a lower quality wheel than your 120. There's probably no way to improve its performance. Lynn
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Post by stardiamond on Dec 27, 2019 18:08:59 GMT -5
I don't have any sintered wheel and understand the grit number compares to a higher number non sintered. I bought a 60 grit crystalite/crystalring wheel either new or barely used very cheap some time ago on ebay. I mounted it once and then took it down. When I got a new right hand arbor for my Genie, I mounted it an tried it out again. Way to chippy. The TOP 80 grit wheel I bought is far more aggressive than DP or Jadecarver. It seems like it will stay aggressive for quite a while and wes inexpensive.
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nik
spending too much on rocks
Member since May 2019
Posts: 315
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Post by nik on Dec 28, 2019 5:29:49 GMT -5
Thanks to everyone for the input. I have pretty well given up on the 60 grit wheel, it was just too good a price to pass up, even though it turned out to be a bust. The exposed diamonds, while plentiful, are basically round. I'll post some photos once I have proper internet again, more island time problems...
The price and cutting speed of plated wheels, is quite tempting, but I'm trying to keep with my design philosophy for this grinder of being as low maintenance as possible. I ended up ordering an 80 grit sintered wheel from Kingsley, mostly for heavy stock removal and removing agate rinds. I've got their 220 sintered, and really like the way it cuts, plus 6mm of diamond depth should last me basically for ever.
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hummingbirdstones2
fully equipped rock polisher
Vince A., 1958-2023
Member since August 2018
Posts: 1,461
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Post by hummingbirdstones2 on Dec 28, 2019 11:06:34 GMT -5
If you ever set up another arbor, maybe you could use this "slow" wheel for softer or chippier materials.
Robin and I both have Genies, and we typically keep newer wheels on hers.This gives us the option of using the less aggressive older wheels on rough that doesn't play well on new wheels.
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Post by stardiamond on Dec 28, 2019 13:01:31 GMT -5
If you ever set up another arbor, maybe you could use this "slow" wheel for softer or chippier materials.
Robin and I both have Genies, and we typically keep newer wheels on hers.This gives us the option of using the less aggressive older wheels on rough that doesn't play well on new wheels.
I'm doing the same. I call my top 80 the bulldozer and then finish off with a worn 80 grit DP on another arbor. It is getting more worn. I had bought some new hard 8 inch wheels that I have been waiting to mount, but I think I'll try the old wheels after the top 80.
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nik
spending too much on rocks
Member since May 2019
Posts: 315
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Post by nik on Dec 28, 2019 16:01:32 GMT -5
I do have a poly d-14 that is currently unused, but I have other plans for it. I'm thinking of getting rid of the 60 wheel, but feel bad about passing a problem to someone else. It seems like it should be useful for something though. There is still about 3mm of diamond on it.
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