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Post by sheltie on Jun 12, 2013 14:38:26 GMT -5
Ever since I started using the BD 303S segmented blade on my 16" saw (after two previous BD301 continuous rim blades proved to me to be defective), I've been unable to get a good, clean, through and through cut. As the picture shows, there is a part of it ALWAYS, EVERY slab that doesn't cut all the way through. Is this normal or is there something wrong that I can correct? While the 301s kept losing their theeth, at least I got a good, clean cut on the two months or so each worked before going belly up. Any suggestions? Oh, if you're interested, that's a red Cary plume jasper in the picture.
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Post by deb193redux on Jun 12, 2013 16:02:04 GMT -5
Some tab is normal, because the weight of the slab causes it to drop before the last little bit is cut. But that much is not. I think you have some alignment issue. This is causing the blade to be pushing slightly against the slab (instead of just into the cut), this cause the break sooner because more than gravity is stressing the uncut portion.
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Post by sheltie on Jun 12, 2013 16:27:01 GMT -5
What you say makes sense but when I examine the saw from any angle, I can't see anything untoward. Any suggestion as to how to correct the problem? The blade runs straight and true and the vise works as it should.
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Post by deb193redux on Jun 12, 2013 17:00:10 GMT -5
it could be slight. aside from pencil in vise/carriage method, you could check w/ smaller rock. in my theory, offset is a moment arm. shorter arm should avoid issue more often,
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QuailRiver
fully equipped rock polisher
Member since May 2008
Posts: 1,640
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Post by QuailRiver on Jun 12, 2013 17:15:12 GMT -5
Aside from the already mentioned possibility of an alignment problem, the only other two suggestions I can think of is to slow your powerfeed rate down. And keep your blade well dressed. A 303 blade is not as aggressive cutter as a 301 blade and can't cut as fast. So if the feed rate is moving faster than the blade wants to cut then when the remaining area to be cut gets narrow it will just break off under the stress.
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Post by sheltie on Jun 12, 2013 18:47:06 GMT -5
Aside from the already mentioned possibility of an alignment problem, the only other two suggestions I can think of is to slow your powerfeed rate down. And keep your blade well dressed. A 303 blade is not as aggressive cutter as a 301 blade and can't cut as fast. So if the feed rate is moving faster than the blade wants to cut then when the remaining area to be cut gets narrow it will just break off under the stress. Very interesting, I didn't know that. My saw has three speeds that are dictated by the belt on the pulleys. I've always used the middle one because it was recommended to me for jasper and agate and, to be honest, I've never changed a belt. Knowing my luck, I'd never be able to replace it! So you recommend that I change the belt to the slowest speed? On my 301a, I used to dress it at least once a week (I normally cut 4-6 hours a day), cutting through a grinding wheel. Should I do the same with this blade? I also have obsidian if necessary.
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Post by sheltie on Jun 12, 2013 18:49:23 GMT -5
it could be slight. aside from pencil in vise/carriage method, you could check w/ smaller rock. in my theory, offset is a moment arm. shorter arm should avoid issue more often, I'm not familiar with this method. Could you please explain? Both the pencil and small rock aspects. And what do you mean by moment arm, shorter arm? So much to learn, so little time left to learn!
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Post by deb193redux on Jun 12, 2013 19:20:24 GMT -5
the pencil in the vise is set to barely touch blade at front. Then run vise (if possible w/o running blade) and see if it draws a nice line, skips, or bears down. I think this is poor man's pressure gauge. there are devices that can be clamped in vise and set to touch blade with some pressure. then as it moves, you can see if the pressure changes. pencil is much cheaper.
moment arm is just physics for lever. if there is lateral pressure pulling slab away form rock or pushing into rock the distance of pressure from point that breaks is the moment arm. if you cut all but last 1/4" and backed rock off of blade, it would be easier to break slab by pushing with finger tip at the far edge (longer moment arm) than pushing only 1/2" from end of cut.
other possibility is not alignment problem, but some runnout in blade. this could make blade push on walls of cut.
just thinking out loud. lets see what others think.
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I think you use the same belt and just change pulley. dose your saw have an idler pulley to tension belt?
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Post by deb193redux on Jun 12, 2013 19:25:05 GMT -5
also, usually the slab falls and leaves tab on rock. by letting it run a little longer, the tab gets ground off.
if your feed is too fast then there is forward pressure causing break with tab on slab.
in addition to slowing feed, you could try softer rock and see if problem persists. alignment or runnout would persist. speed problem would not happen w/ softer rock
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QuailRiver
fully equipped rock polisher
Member since May 2008
Posts: 1,640
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Post by QuailRiver on Jun 12, 2013 21:15:10 GMT -5
Sheltie Wrote: ...So you recommend that I change the belt to the slowest speed? Yes, I would recommend changing to a slower speed. If it doesn't help you can always change it back. Since i can't post photos on this site at the moment, I've attached a link to a photo bucket page with a photo of a 14" frantom saw's belt and pulley system, and a freehand sketch to illustrate. s1367.photobucket.com/user/QuailRiver/library/?sort=2&page=1Just loosen the bolt on the tension arm that holds the idler pulley to relieve the belt tension. Then slip the belt to the desired pulley positions and move the tension arm back to where there is slight tension and re-tighten the bolt that holds it in place. You DON'T want the belt so tight that it will strum like a musical instrument's string when plucked, just tight enough to keep friction contact with belt and pulleys. The only other adjustment you might have to make is loosen one or more of the set screws on the pulleys and line up the pulleys so the power feed belt travels in an absolute straight line as shown in the sketch. After you've done this a time or two it's a quick and easy process. Hope this helps. s1367.photobucket.com/user/QuailRiver/media/frantom7a_zpseda451cf.jpg.html?sort=2&o=1
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Post by deb193redux on Jun 12, 2013 21:19:02 GMT -5
why can't you post images?
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QuailRiver
fully equipped rock polisher
Member since May 2008
Posts: 1,640
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Post by QuailRiver on Jun 12, 2013 21:28:33 GMT -5
The last few days when I try to post photos I'm getting a message saying the site's memory space is filled and my photo can't be posted.
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Post by deb193redux on Jun 12, 2013 21:32:36 GMT -5
you cannot attach because the space is full
but these images are hosted in photobucket space - not here - you can use img tags to show them, like always
you can set photobucket to give img tags, but even if that setting is off, just put image URL inside tags
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QuailRiver
fully equipped rock polisher
Member since May 2008
Posts: 1,640
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Post by QuailRiver on Jun 12, 2013 21:35:06 GMT -5
Okay thanks for the tip!
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Post by Rockoonz on Jun 12, 2013 23:15:03 GMT -5
When you finish a cut your blade should be parallel with the end of the cut edge of the rock left in the vice. If there's a gap more than just like a paper thickness or the gap is wider at one end of the cut you alignment is off and you may be starting to cup the blade.I run all my saws at the slowest feed speed, nicer cut surface and longer blade life.
Lee
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Post by jakesrocks on Jun 12, 2013 23:38:48 GMT -5
One other possibility I haven't seen mentioned. Your rock might be shifting in the vise slightly. Always make sure the rock is very tight. After tightening the vise, grip the rock with your hands and try to forcefully move it. Use small wooden shims between the rock and vise jaws at points where the jaws don't touch the rock.
I use a 16" 303 S, and my cuts are very smooth.
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Post by sheltie on Jun 13, 2013 8:09:11 GMT -5
I'll run the pencil test this morning, thanks for the info. I'll also try to set the speed to the lowest speed which should be an interesting task seeing what a mechanical whiz I am! After I've finished slabbing a piece, I let the blade finish the job on the rough and it does grind the rest off. However, there is a gap of more than a sheet of paper between the rock and the blade when done so I guess my alignment is off. Will changing the belt speed correct that? Thank you deb, qualiriver and rookoonz.
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Post by deb193redux on Jun 13, 2013 8:33:40 GMT -5
If the gap is uniform, it is not as bad as if the gap is uneven.
if the feed is too fast and the blade is walking a bit to the side or cupping slightly, the lower speed should help. if the blade is a bit cupped, that may not go away by itself.
sometime I like to turn my saw off mid-cut. I watch/listen for how much time to stop. instant stopping and feed is way to fast or alignment way off. some spin down and you are likely OK. blade should be movable w/o too much difficulty, and should be able to restart w/o motor problems. the point is that there is not supposed to be a lot of pressure. consider how much pressure a few bricks on a gravity feed gives. you want the blade to grind, not be pushed through the rock.
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Sabre52
Cave Dweller
Me and my gal, Rosie
Member since August 2005
Posts: 20,487
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Post by Sabre52 on Jun 13, 2013 9:07:06 GMT -5
My ten inch saw almost always leaves a little spur at the end of the cut. If you use a shut off switch, it's actually better to leave the last little bit and break the slab off the spur yourself as it's easier on the blade. Cutting clear through the rock until the slab drops off is a good way to damage a blade but I'm very prone towards doing that because i don't like to mess with the cut off and am always multitasking while I saw so don't watch the saw that closely. That's probably why I wreck blades fairly often *L* Damn it's hard to type on a laptop when you're used to a separate keyboard!.....Mel
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Post by sheltie on Jun 13, 2013 15:11:45 GMT -5
If the gap is uniform, it is not as bad as if the gap is uneven. if the feed is too fast and the blade is walking a bit to the side or cupping slightly, the lower speed should help. if the blade is a bit cupped, that may not go away by itself. sometime I like to turn my saw off mid-cut. I watch/listen for how much time to stop. instant stopping and feed is way to fast or alignment way off. some spin down and you are likely OK. blade should be movable w/o too much difficulty, and should be able to restart w/o motor problems. the point is that there is not supposed to be a lot of pressure. consider how much pressure a few bricks on a gravity feed gives. you want the blade to grind, not be pushed through the rock. Ok, after lunch I made some checks and did some changes. There is no gap between blade and rock, it's uniform. I did the pencil test and you can't tell where the pencil began or stopped, it's a perfect circle. I changed the speed by putting the belt in the MOHS hardness 6 slot (slower) rather than the 7 I had before. Based on only two slabs, it may be better. Too early to tell. The instructions for my saw specify, agate, quartz, topaz and jasper the belt should be in the largest pulley (the fastest one), MOHS 7; the middle pulley is for Orthoclase, Feldspar and Onyx, MOHS 6, and that's the one I'm using now. The slowest pulley is 5 MOHS or below and is meant for Apatite, Fluorite, and Calcite. Do you recommend that I change my belt to the slowest pulley or leave it where it is? Will this apply as well when I change back to a continuous rim blade?
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