RockingRuralMo
starting to spend too much on rocks
Member since July 2022
Posts: 138
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Post by RockingRuralMo on Jan 17, 2023 18:54:50 GMT -5
I have a 16 inch slab saw that I got off of facebook marketplace. It was quite the job to rebuild, but there's not a lot of lapidary equipment in Missouri, so I was lucky to get it.
It only came with one weight, and that weight seemed really big and heavy to me for some of the cuts I was doing, so I hung some old concrete barbell weights on wire hooks so I could use those instead.
I tried to apply the same principle as with my trim saw and use less pressure and more patience, but my cuts are slow and sometimes the sled will stall altogether. When that happens I have to go put more pressure on the line, which will always let me finish the cut, but leaves a saw mark on my slabs.
So that whole situation inspired a broader question: How can you tell when you have too much weight (or not enough) on your gravity feed saw? I'd be better off to start with enough weight to prevent stalling. But is there some way to know how much is too much?
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QuailRiver
fully equipped rock polisher
Member since May 2008
Posts: 1,640
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Post by QuailRiver on Jan 17, 2023 19:25:12 GMT -5
Using a gravity feed saw properly is an art form within itself. One I admittedly never mastered so prefer a mechanical power feed system.
Too much weight can make your bearings, arbor and blade wear out faster and can also damage the blade by cupping it. Ideally It's better to start out with less weight and then ad more as needed. Instead of fixed weights try using a plastic milk jug and sand. Keep a bucket of sand, a sand scoop and funnel by your saw to adjust the weight as needed. Start paying close attention to how the saw sounds when slabbing various materials. And you will eventually be able to tell by the sound when the saw is under strain from being feed too quickly from too much weight.
Most mechanical power feed systems for mid-sized saws are designed to travel about 10" to 12" per hour. Which is a safe speed for slabbing most harder materials. So that may be a good speed to shoot for until you get a feel for, and ear for how your saw operates. Then experiment with adjusting the weigh for variuos materials and sizes.
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Post by vegasjames on Jan 17, 2023 20:33:42 GMT -5
I just saw a post on a Facebook rock board where in place of normal weights they attached a can they filled with sand making the adjustment of the weight much easier as you can easily add or pour out the sand for adjustment.
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Post by parfive on Jan 17, 2023 20:50:32 GMT -5
Since you rebuilt the saw, we can eliminate dirty oil and a dull blade from the slow cutting problem, right?
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RockingRuralMo
starting to spend too much on rocks
Member since July 2022
Posts: 138
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Post by RockingRuralMo on Jan 17, 2023 21:03:08 GMT -5
Since you rebuilt the saw, we can eliminate dirty oil and a dull blade from the slow cutting problem, right? Should be able to! I replaced the blade and took my time truing it up, and just recently changed out the oil. I also rebuilt the bearings and replaced the belt, one of the pulleys, and all of the cabling. The tank and motor are nearly the only original pieces left.
The first time I ran into stalling was with a big chunk of tiger iron that was cutting dead slow. It was about an 8 inch cut, but it took about 3 hours. I thought I may have glazed the blade, but I don't see or feel any indication of that.
I may just need to explore building it a mechanical feed.
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RockingRuralMo
starting to spend too much on rocks
Member since July 2022
Posts: 138
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Post by RockingRuralMo on Jan 17, 2023 21:11:21 GMT -5
Using a gravity feed saw properly is an art form within itself. One I admittedly never mastered so prefer a mechanical power feed system. Too much weight can make your bearings, arbor and blade wear out faster and can also damage the blade by cupping it. Ideally It's better to start out with less weight and then ad more as needed. Instead of fixed weights try using a plastic milk jug and sand. Keep a bucket of sand, a sand scoop and funnel by your saw to adjust the weight as needed. Start paying close attention to how the saw sounds when slabbing various materials. And you will eventually be able to tell by the sound when the saw is under strain from being feed too quickly from too much weight. Most mechanical power feed systems for mid-sized saws are designed to travel about 10" to 12" per hour. Which is a safe speed for slabbing most harder materials. So that may be a good speed to shoot for until you get a feel for, and ear for how your saw operates. Then experiment with adjusting the weigh for variuos materials and sizes. The and-and-jug system sounds useful. I appreciate you sharing that. I'll have to try it.
I try to listen to the saw and I can definitely tell when it's stalling, and the pitch goes way up when I use the big heavy weight it came with. That high pitch sounds like a problem to me, but I could be wrong. A table saw doesn't sound great cutting plywood either, even when it's doing fine. So maybe I'm just overthinking it.
I'll try the adjustable approach and see if that helps refine my ear. Thanks!
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Post by vegasjames on Jan 18, 2023 1:48:48 GMT -5
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Post by hummingbirdstones on Jan 18, 2023 9:58:43 GMT -5
We use a 1/2 gallon milk jug and water on our 10". Easy to add or subtract water.
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Post by Rockoonz on Jan 18, 2023 12:17:15 GMT -5
I am wondering about your carriage rails, never seen a setup like that. Is there something under the rails to hold the vice carriage down? Seems like sans rollers and adjustments you would see too much slop and binding of the carriage, all the square rail saws I've seen have at least one of the rails in a diamond configuration to minimize the side to side and binding. With all that contact surface the condition of the oil will also change the amount of resistance to movement. If you have the resources to do so, maybe build a round rail setup like a Mojave industries, Royal, or Jenkins saw.
I have photos and drawings from old Mojave plans for DIY saws taken from the lapidary journal article they used as a guide. If you would like the file PM me. The DIY vice is a bulletproof bookend style vice that is better than a clamping bar vice also.
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stefan
Cave Dweller 
Member since January 2005
Posts: 14,113
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Post by stefan on Jan 19, 2023 17:02:34 GMT -5
Those rails are an issue. Way too much friction. They need to be mirror polished clean and have a near friction-less pad under the carriage brackets. Get a little rock snot in there and that carriage is going to stick and bind. I would really investigate the power feed option or do something about those rails. Cool saw otherwise!
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