quahog13
off to a rocking start
Member since February 2012
Posts: 5
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Post by quahog13 on Feb 7, 2012 14:41:17 GMT -5
I'm new to lapidary and just purchased an old Highland Park machine. It currently has 2- 8"silicon carbide wheels (black and green) I'm assuming 80 & 220 grit? They are not labeled. The green one is badly grooved. I cannot afford the diamond wheels yet so I was going to just purchase new SC wheels for approx $30 ea. I read a little about dressing the wheels, I'm wondering is it worth trying to do that instead of buying new ones? I think the tool is $20. The groove on the green wheel is probably a good 1/4" or so deep. I'd have to take the wheel down quite a bit to get it flat. I assume SC wheels are useable until they are just too small? Part of me thinks I should replace them and start fresh. I have to invest in an expandable wheel to replace the one on it which currently has a seam in the belt. I'm assuming expandable drums weren't available at the time the machine was manufactured. any advice is greatly appreciated.
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Post by Hard Rock Cafe on Feb 7, 2012 18:15:08 GMT -5
Well, my advice is to save your money for diamond wheels. Rocklady1.com has the least expensive ones and they're pretty good quality.
I started with SiC wheels and found them to be very slow and very messy. I think there are still a few people on the board who use SiC with good results, they just weren't for me.
Do you have more time or do you have more money? Dressing 1/4" out will take quite a while. Another option may be to just gradually grind the ridges down as you cab.
You want to be careful that the wheels are not out of balance, or they could come apart on you. Likewise, spin your wheels for a couple of minutes without water when you're done so that they dry properly and stay balanced.
Yes, you can use them until they're too small to work with.
My 8" HP grinder had expandable drums, so it may have just been what it came with.
Chuck
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shermlock
has rocks in the head
Member since August 2011
Posts: 612
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Post by shermlock on Feb 7, 2012 18:20:10 GMT -5
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Post by johnjsgems on Feb 7, 2012 19:14:12 GMT -5
You can dress them with a T-Bar dresser. You can grind them down until you get to the label on the side. That is supposed to be the safe line. Even if you buy new wheels you will need a dressing bar sooner or later.
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Post by Rockoonz on Feb 7, 2012 21:57:51 GMT -5
Another difference between SiC and diamond is that SiC wheels can come apart while spinning, rare but it happens, a scar from 3 stiches on my jaw is proof enough for me. Always wear eye protection. Never stand right in front of a wheel when starting the grinder. When ready to stop grinding first shut off the water and spin dry the wheel for a half minute or so.
Lee
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Post by johnjsgems on Feb 7, 2012 22:08:38 GMT -5
I would spin dry mine for at least 5 minutes. Shutting off wet causes the water saturating the wheel to drain to bottom. If restarted while still damp the moisture in the bottom of the wheel can cause a severe out of balance condition. I learned to cut with them as did many without mishap but it never hurts to be too careful.
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quahog13
off to a rocking start
Member since February 2012
Posts: 5
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Post by quahog13 on Feb 8, 2012 12:30:22 GMT -5
Thanks for the advice, especially the safety issues! I had read about spinning them dry and the person who sold me the machine also mentioned it. Just makes me want the diamond wheels more...
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Post by Woodyrock on Feb 13, 2012 2:28:20 GMT -5
Well Ms big clam, a quarter of an inch is not really too much to take down on a SiC wheel, but you need either a wheel type dresser, or a diamond point dresser before you use the Tee bar. When dressing, the main key is to hold the dresser in place, and let it cut the grinding wheel. If you let it ride on the wheel, it will not take the out of roundness from the wheel, but actually make it worse. The wheels do not actually need to be flat, but they do need to be round. Some of the cabbers in days before diamond was more affordable, actually dressed their wheels concave. When dressing, use as much water as you can tolerate, do not dress dry.
All that said, diamond wheels allow more cabbing since you are not dressing them.
Woody
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Post by johnjsgems on Feb 13, 2012 11:40:22 GMT -5
Woody, my dad had three wheels. 100, 220, and something in between that had a perfect concave surface. I'm assuming he put it in for doming. The T bar dresser will take the wheel down flat pretty quickly. You need to use both hands and prop against the pan or something stable. Since they are wider than the wheel they work much better than the old wheel type dressers.
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