rykk
spending too much on rocks
Member since September 2011
Posts: 428
|
Post by rykk on Feb 7, 2014 18:35:17 GMT -5
Hi, y'all. Firstly, the blade I'm asking about is the black, continuous rim blade that Covington makes. Mine is a 14 incher. It has started to cut very slowly like maybe it's dull. It's only maybe 5 months old and I'm, mostly, a hobby slabber and do maybe 15-20 slabs a week at the most.
First Question: After some usage, the painted-on white arrow that tells which way the blade needs to spin got worn off from slabs that got stuck in between the blade and the shelf they fall onto. Both sides of the blade have no paint left, probably due to something shifting in the vise. So, I've taken this blade off of the arbor twice to re-tension it after it got a bit dished. The second time I did it, I may have gotten confused which side was which, though I'm fairly sure I got it right. My question is, what happens if the blade were to get installed "backwards"? Does it just not cut at all? Or does it just not cut very well?
Second Question: I bought a "wheel dressing stick" a while back, maybe Harbor Freight or Ebay. It's a stick about 1 1/2" square and maybe 6 or 7 inches long. I "think" it's silicon carbide. It's very rough and porous with big pockets like pumice or something. Anyhow, I'd not cut a piece of obsidian for a good while and the thing was laying around, so I cut a slice off of it. My saw has a good splash guard, so I just held the dressing stick by hand. It seemed as though the blade wasn't cutting it as quickly as I'd expected and then a piece flew off, so I stopped. I, then, decided to "sharpen" the blade on my 10" saw. It has no vise and is just a hand held rock cutter. Thin blade. Anyhow, after cutting half way through, I stopped. The blade was cutting ok, I just figured to improve it a little. After doing that, the blade won't cut ANYTHING! And I'm afraid that I've ruined my big saw's blade, as well. I've read here about cutting a fire brick, obsidian, or even a silicon carbide wheel to "expose more diamonds", thereby "sharpening" your blade. Was this dressing stick the wrong thing to use? Thanks, Rick
|
|
|
Post by deb193redux on Feb 7, 2014 20:17:54 GMT -5
I don't know of a porous stick like that could ruin a blade. I am surprised the blades did not cut through easily though.
|
|
|
Post by johnjsgems on Feb 7, 2014 22:12:42 GMT -5
The wheel dressing stick may be metallic and meant to straighten SC wheels. You may have clogged the blades and might salvage them with a blade dressing stick. You won't hurt the blades by running them backwards if they are made like the MK/BD blades. Not too familiar with the black sintered Chinese blades but if like MK/BD they will cut better run in correct direction. You should be able to inspect with a loupe and see the diamonds looking like comets with leading end towards rotation.
|
|
rykk
spending too much on rocks
Member since September 2011
Posts: 428
|
Post by rykk on Feb 8, 2014 1:38:05 GMT -5
Ok, so I turned the blade around but after I ran a medium sized chunk of mahogany obsidian through. Fine tuned the tracking of the vise carriage, although it really wasn't off much. Checked to make sure the blade hadn't dished and now I'm cutting the almost-too-big-for-my-blade chunk of St Johns Flower Agate again. A thinner cut just to lop off an end so it isn't within a quarter inch of the top of the blade when I turn it back around.
I'll let y'all know the outcome. Even if it cuts well this time, I'm pretty sure that I took a lot of life out of the blade with that dressing stick because of how it totally hosed my - albeit old and used when I got the saw - 10" blade.
So, Question 3 - How often should you cut a grinding wheel or obsidian/fire brick? Can you do it too often and shorten your blade's life? And - Does it hurt the blade if you slab a lot of obsidian? C-ya, Rick
|
|
|
Post by johnjsgems on Feb 8, 2014 8:30:22 GMT -5
Obsidian would be very mild. The 60 grit aluminum oxide dressing sticks I use are more aggressive so would shorten blade life if over used. If cutting by hand you can readily tell when you need to dress the blade. With gravity feed the cut will get slower or less smooth.
|
|
|
Post by Rockoonz on Feb 8, 2014 13:30:10 GMT -5
I have been told that obsidian doesn't sharpen but merely cleans the blade surface, kind of makes sense that glass wouldn't be abrasive to steel. I use the 60 grit sticks but oh so sparingly and dependant on what I'm cutting. In my power feed saws I can identify when they need to be sharpened by the sound they make. Also feed speed is important, always use the slowest feed available for the saw, and if it takes less than 5 minutes to travel an inch find a way to slow it down. What kind of saw do you have Rick?
Lee #2
|
|
rykk
spending too much on rocks
Member since September 2011
Posts: 428
|
Post by rykk on Feb 9, 2014 0:46:55 GMT -5
Hi, Lee - My saw's homemade 98% from scratch - here's a link: forum.rocktumblinghobby.com/thread/60506/cyborgsams-super-slabber-homemadeI've run the saw as low as 3.3in/hr but usually around 5in/hour. Pretty slow compared to most commercial saws. My saw has a digitally adjustable feed motor due to some circuitry I designed for it. I read at Covington, Highland Park, or Barranca or somewhere like that that saw blades in the 14"-18" range should be run at 7in/hr so I reckon I'm good there. One thing I just rememberd I did a week or so before the dressing stick was to cut a 100 grit grinding wheel, though it didn't seem to help anything when cutting hard agate. Here's the results of the stuff I did, above. Tried running the blade in both directions. One way did seem somewhat better than the other but still, both hung up when the cut (St Johns Agate) got around 1.5-2" tall and the slip clutch in the feed motor started spinning. The blade is better tensioned and flatter than when I bought it - been studying/practicing. I then rounded up an old Covington Gold 14" that I was using for awhile when I first built the saw but had gone to the black sintered because of saw marks. Spent some time straightening it out - didn't know how before - and slapped it on the arbor. Sliced right through and just did a 4+ inch tall slice with no problems. I know lots of folks swear by the "cut a SiC wheel" bit but, as for me, I don't reckon I'll ever run anything at all like that through my saw ever again. Doing so basically ruined both of my blades. The 10" was old when I got the saw but still was cutting. After the SiC dressing stick, there was no diamond left at all. The 14" I'd done just because I figured "periodic maintenance" would be a good thing and it was almost new. After the wheel and stick it can cut obsidian and probably wonderstone but is absolutely unable to get through agate without falling behind on moving rock out of its way and the rock tries to ride up the blade and the feed clutch starts slipping. Expensive lesson but that's how you learn, I reckon. C-ya, Rick
|
|
|
Post by Rockoonz on Feb 9, 2014 2:18:25 GMT -5
Nice build on the saw, I remember it now.
The commercial sharpening stones are aluminum oxide not silicone carbide. Feed speed sounds good too, my 24 inch runs about 6 or 7 inch/hr, the rest all run faster, especially the hydraulic 18.
I have a feeling the dressing stick you used was intended to clean up aluminum oxide and SiC grindstones when they get gummed up with non-ferrous metals, the perfect thing to rip diamonds right out of sintered blades. You might consider trying a 303C, John can get you a good deal on one and the two I have in saws have about 4 years on the 18 inch hydraulic, maybe ran a stick through it 5 or 6 times so far, and a 1 year old 10 inch blade that has never had a stone run through it and both cut like new.
Lee #2
|
|
rykk
spending too much on rocks
Member since September 2011
Posts: 428
|
Post by rykk on Feb 9, 2014 18:15:19 GMT -5
Lee #2 - I think you're right about that dressing stick. Real bad mojo for diamond blades! I would absolutely LOVE to have a 303C but they're just too pricey for me right now since I'm still out of work due to defense budget cuts. I got all fired up and bought another black Covington just as soon as I found the blade to be shot. You can find them on Ebay for 120 to 125 bucks with shipping so I did one of those "Bill me Later" deals. I'm having to sell most of my literal ton of slabs there, so I'll be able to pay it off before 6 months. Just wish I could get the same $$ as a few of the sellers there - especially since I'm selling the same exact ones I bought from them. Sure wish I had their clientele or knew the magic trick to getting more than $6-$10 for one! BTW - I'm "rykksROX" there and my "name" is "cyborgsam". I know, at first glance, the cyborg name appears x-rated but Ebay jammed "Cyborg Sam" into one word without the caps. I'm a world known digital/fractal artist who goes by the name "Rykk" - an edgy, internet-ized spelling of "Rick". My website is down because my host got divorced and the wife got the server but you can find me at Renderosity.com and DeviantArt.com. Google Rykk, sometime, and you'll see my art and my wins in the annual international show/contest in NYC. The patterns in rocks/agates are actually patterns described by the fractal math equations and that's why I'm so into rocks these days. C-ya, Rick
|
|
rykk
spending too much on rocks
Member since September 2011
Posts: 428
|
Post by rykk on Feb 9, 2014 18:19:12 GMT -5
Just for info - How much could he get me a 14 or 16 inch for? PM me, ok? Thanks, Rick
|
|
|
Post by Rockoonz on Feb 10, 2014 0:22:33 GMT -5
|
|
|
Post by deb193redux on Feb 10, 2014 0:33:46 GMT -5
I don't think it was an SiC stick. Maybe like john said, it was one for dressing SiC wheels.
Anyway, I use AO grinding wheels and/or Ace Hardware fire brick. neither hurt blade.
|
|
rykk
spending too much on rocks
Member since September 2011
Posts: 428
|
Post by rykk on Feb 10, 2014 2:27:32 GMT -5
Ok, I reckon I'd give a fire brick a shot when I need to sharpen the blade. Are AO wheels the green ones? Rick
|
|
|
Post by deb193redux on Feb 10, 2014 9:46:05 GMT -5
no, green are usually lapidary (fine) SiC. AO are gray or even light red. SOme course SiC also gray.
|
|
rykk
spending too much on rocks
Member since September 2011
Posts: 428
|
Post by rykk on Feb 10, 2014 22:31:49 GMT -5
Thanks, Deb. The very used 5" wheel that someone in Oregon sent me is a light gray and seems to be a fairly fine grit. I'll have to ask him again what it's made of. C-ya, Rick
|
|