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February 17, 2019, 01:05:57 pm
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dished - NO BENT - the blade, pics added

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Author Topic: dished - NO BENT - the blade, pics added  (Read 1176 times)
deb193
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« on: February 25, 2011, 09:55:18 pm »

I have been using inexpensive Kingsly North generic 12" crimped blades on my LS12.

But I put about as big a piece as the vise will hold, and I cut hard agate and jasper. It starts to cut crooked, then shreds the belt before I can turn it off. Then I find the blade is dished. Second one in 6 weeks.

I ordered a 301 GemKIng and I hope it cuts faster and I have better luck with it. Looks like a fine blade.

Maybe I can back down on size just a bit too.

Sigh.
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hulagrub
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« Reply #1 on: February 25, 2011, 10:03:12 pm »

My LS12 came new with I believe it is a MK302 or 300 something. 5 years later and many big rocks later, still sweetly cutting.
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deb193
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« Reply #2 on: February 25, 2011, 10:26:56 pm »

I have over a year on the blade in my LS10, I can only hope the 301 lasts 5 years in the LS12.

On my Star trim saw I go through 2 blades a year.
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« Reply #3 on: February 25, 2011, 10:31:00 pm »

Keep turning the blade around, it will cause it to dish the other way and self correct itself.
Dishing is caused because the rock pushes on one side of the blade and not the other, which is exactly how they make tuba's by spinning a flat disc and applying pressure to one side. If you are dishing you are very slightly out of alignment. You can either fix the alignment or you can keep turning the blade around, of course this will not work if you have a directional blade.

Have a great day...........Tony
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« Reply #4 on: February 26, 2011, 06:02:52 am »

Keep turning the blade around, it will cause it to dish the other way and self correct itself.
Dishing is caused because the rock pushes on one side of the blade and not the other, which is exactly how they make tuba's by spinning a flat disc and applying pressure to one side. If you are dishing you are very slightly out of alignment. You can either fix the alignment or you can keep turning the blade around, of course this will not work if you have a directional blade.

Have a great day...........Tony

I found out the hard way this week that dishing can be caused by not dressing the blade often enough. My blade dished when the autofeed on my saw kept pushing the stone into the blade before the blade had cut enough.

so this leads to a question for the more experienced users...how often do you dress your blade?

Thanks!
Tom
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deb193
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« Reply #5 on: February 26, 2011, 09:04:15 am »

if the blade slowly acquired the dish, I would be right with Tony. And the crimped blade could have been turned around.

But when you find the blade crooked and stalled in a large chunk of rock and the belt is shredded, and the blade worked fine on the prior cut - well that is not going to be fixed by turning it around. Sadly.

possibly if I had dresed the blade and changed the oil sooner, it would have made it through the cut. BUT, I knew I was pushing it. The biggest rock I cut so far, and it was a very hard lizzard agate. jut plain my fault.
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« Reply #6 on: February 26, 2011, 09:59:38 am »

if the blade slowly acquired the dish, I would be right with Tony. And the crimped blade could have been turned around.

But when you find the blade crooked and stalled in a large chunk of rock and the belt is shredded, and the blade worked fine on the prior cut - well that is not going to be fixed by turning it around. Sadly.

possibly if I had dresed the blade and changed the oil sooner, it would have made it through the cut. BUT, I knew I was pushing it. The biggest rock I cut so far, and it was a very hard lizzard agate. jut plain my fault.

deb, when sawing large size and hard materials the feed rate needs to be slowed down to decrease the chance of overcrowding the blades capacity to cut. Is your feed rate variable? If not then you might want to see if there is possibly a way of slowing it down.

Don
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deb193
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« Reply #7 on: February 26, 2011, 02:13:53 pm »

the only variabiality in the feed rate is when the clutch slips. lol.

I need to stop putting rocks suited to an 16" or 18" saw on my 12"

also, the more agresive blade is "like" slowing the feed.
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« Reply #8 on: February 26, 2011, 03:52:09 pm »

Just a thought. Would speeding up the blade by changing the pully help if you can't slow the feed?

Fred
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« Reply #9 on: February 26, 2011, 05:36:39 pm »

There are really only two things that will cup a blade.  One is misalignment and the other is slipping sideways instead of starting the cut properly.  If the problem is misalignment, then reversing the blade will only work once or twice before the center of the blade becomes larger than the rim can work with and the blade will become a cymbol.  I have a few.  I never dress a blade.  My saws are set up at optimum blade speed and oil is pressure fed directly to the rim.  Rim speed is controlled by step pulleys.  I believe optimum speed is actually faster than normally recommended, but that definitely requires really good lubrication.  It also really throws a lot of oil around.  My saws tend to drip oil at the seems.  I use the cheapest thinnest blades I can find, but then again I enjoy doing a lot of maintenance.  Way better than bending over a car engine.
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« Reply #10 on: February 26, 2011, 06:00:40 pm »

Quote
I use the cheapest thinnest blades I can find, but then again I enjoy doing a lot of maintenance.

slabbercabber, why the cheapest? or have you tried the better higher priced with not so good results?

I'm up for a new blade real soon but I want to cut reasonably fast but with little down time/maintenance time.
The blade that I have now cuts slow but little down time. It came with the saw when I picked it up used. I have no idea what brand or cost of the blade. I've had it going 2.5 years now. I upped the blade RPM by 370 RPM's and slowed down the feed rate using a 5" pulley instead of the 4" pulley. It's a Lortone 18".

I agree, no fun bending over a car engine. If I have to work on a car then I had rather work under it. It's much better laying on your back anyday.

Don
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deb193
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« Reply #11 on: February 27, 2011, 01:51:49 pm »

I may have caused some confusion, I should have said I BENT the blade. Dishing is a cupping and affects the whole circumference. I bent the blade where one section, about 30 degrees of arc, does not lay flat.

Apologies for being imprecise in using the term dished.

You can see it is bent in this pic:



and you can see how the rock has the nuts on the vise all the way up. Except for overwhelming the blade, I do not know why it started cutting crooked. It cut the sister slab with no problems. Possibly the blade slid a little at the start, don't know. Possibly the oil was a little gritty and there was too much friction.





I think I should get a thermally protected motor however, given my habits and track record. You can see from the shredding of the belt that it must have been pulling a lot of amps and heating up before I shut it off. The belt actully melted onto the pulley.




Is there such a thing as an in-line kill switch that could be triggered by an amp spike? Like a circuit breaker, but not at 15 or 20 amps.
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mirkaba
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« Reply #12 on: February 27, 2011, 02:36:55 pm »

Is that a rubber or neoprene belt? I have never melted a rubber belt .
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hulagrub
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« Reply #13 on: February 27, 2011, 03:09:51 pm »

Daniel, to me,after seeing the pix, it looks like the rock slipped. Kind of squirted backwards. Wood wedges, to keep the vise faces parallel to each other is important. I can tell you this because of what I have gone through, on our LS12.
Myself, I need to replace the wooden, or are they masonite, pieces that are part of the vise. Mine are getting rather roughed up, and I believe, that I occassionally have some slippage issues because of that
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deb193
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« Reply #14 on: February 27, 2011, 03:23:23 pm »

it is the link belt that harbor freight sells

I find they vibrate less if the pulleys are slightly out of line, and I never had a problem with melting before.

http://www.harborfreight.com/vibration-free-link-belt-43771.html

I am also looking closer at the pulley sizes. using what was there when I got it, but the drive is 2.25 and the blade is 4, with the motor at 1725, this menas that have a ratio for .56, or a blade RPM of about 970, which is at the lower end of the 301 recommendations, and below the lower end on the 303 recommendations. Don't know the recommendations for the KIngsly blade, but I think it was likely turning too slow.

possibly it was rigged this way because the motor is 1/3 and not 1/2, but I am going to get a 3" pulley for the drive, and that will give me about 1300 RPM, which is in the middle of the range recommended for the MK 301.

I would go over to ACE right now, but we have a severe thunderstorm going on. Anyway, I have enough of the belt material to rig another one, and I should be able to get the pulley tomorrow, and I have a brand new 301 blade, and lots of rock to cut. Think I might change the oil while I am at it.

Hope to have the saw up again by Wed. Meanwhile I am going to cut a lot with the LS10 tonight, and probably change the oil in both saws early in the week. May as well do both while I am getting dirty.

---------

as for the vice, it is almost like leather rather than masonite, but whatever, mine seem in good shape.

I checked the tightness of the wingnuts and tried to move the rock. it seemed tight, but maybe it did slip a mm or so.

I often have the top metal plate at an angle that follows the rock. I am not clear about wood blocks to keep the top plate level. more contact, and the front end lower than the back end seems more secure. maybe I miss your point.
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