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slab blade warping and angle cuts

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Author Topic: slab blade warping and angle cuts  (Read 885 times)
Neural
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« on: June 09, 2010, 04:03:56 pm »

I'm a bit confused here.

First I noticed that the saw tends to not cut straight down.  As it progresses through the rock, it tends to slowly push away from the vice.

Second, when done cutting, the blade looks pretty badly warped.

Then I took the slab out of the oil, cleaned it off, and turned back around to inspect the blade damage, and...

...it was perfectly flat.

Thinking I was losing my mind, I tested this again, and the blade is *definitely warped when the machine is turned off after the slab falls, but within like a minute, the blade is perfect again.

Is this normal? o.O
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« Reply #1 on: June 09, 2010, 04:56:28 pm »

Jon, on my LS12, if the bearings under the carriage are out of adjustment, they need to be tightened, so the carriage does not move.
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Neural
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« Reply #2 on: June 09, 2010, 05:13:53 pm »

I'll see if they are tight enough, but it's brand new bearings and shaft, so there shouldn't really be any play in them.

Any idea on the blade warping/unwarping?
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« Reply #3 on: June 09, 2010, 05:18:38 pm »

It's the carriage moving. Mine had too much slack, right out of the box.
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« Reply #4 on: June 09, 2010, 06:16:31 pm »

Hulagrub's answer is the most likely cause, but it is also possible that the blade has been warped back and forth enough to tension the outside or skin of the blade while leaving the core soft.  This assumes that the warp you are observing is a cup shape.  If so, next time you observe the problem, don't remove the blade, just push on the side to which it is warped.  If it warps to the other sid, this is the case.  Get out your ball peen hammer and start experimenting.
Steve
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« Reply #5 on: June 09, 2010, 07:28:24 pm »

Neural,

Take one of the slabs you have cut and put it on a piece of glass.  It should be flat.  If it isn't your blade has cupped.   

Were you the guy who bent a blade and then strightened it with a piece of plywood and 2 by 4?  If yes, it may still be tweaked.

Some saws, mine included have way too much play in the vise carriage.   I tightened up all of the available adjustment screws and even shimmed one of the rods by hammering a small finish nail really thin and hammering it into a bearing area on one of the supports to tighten it.

I own a Covington 16 inch saw and since I tightened everything it does cut a lot straighter and faster.
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« Reply #6 on: June 09, 2010, 08:12:11 pm »


That was me Mike not Jon.  My blade is still good and straight after the 2X4 trick but my carriage is out of whack.  I have a Lortone 12 with a 14" blade in it.  The carriage tends to wobble around a lot.

TOG
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« Reply #7 on: June 09, 2010, 09:22:03 pm »

Something else I haven't seen anyone else mention is that the ways on which the carriage rides must be exactly parallel with the blade.        Is this not so, Little Grasshopper?
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« Reply #8 on: June 09, 2010, 10:37:23 pm »

gregorgr8 - Has a point if this is a new saw and the blade being pushed to the side by the carriage if it is not running straight.  Pretty easy to check though.  Move the empty carriage as close to the blade as possible.  Measure how close the front corner of the vise nearest the blade is to the side of the blade at the point it would first start to pass by the blade.  Push the carriage all the way to the rear and see if the measurement remains the same.

Don't worry if the front of the vice distance is a bit different that the rear part of the vice as they are bolted to the frame and could be a bit off in their slotting or bolt holes.  As long as the front part remains the same distance it is running straight.
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« Reply #9 on: June 09, 2010, 10:41:12 pm »

What kind of saw is it?

Tony
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Neural
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« Reply #10 on: June 10, 2010, 01:19:53 am »

yeah.. was just about to mention.  This isn't a carriage type saw.  Its a Lortone 14" drop saw. 

The blade and motor are on an arm that basically is balanced so the weight of the saw and arm are what provide the force to cut downward through the rock
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« Reply #11 on: June 10, 2010, 07:32:50 am »

.  Pretty easy to check though.  Move the empty carriage as close to the blade as possible. 

an easy way to do this is with a pencil. Put it on vise when it is as forward as it will go. have the pencil just touch the saw.  Push vise back and the pencil shoud stay equally on the saw as you push the vice back.   I just wanted to give this tip.

However,  as you said a drop saw is different, but perhaps the same principles apply and could be checked.  eg  the blade probably needs to be truly vertical - plumb as it is called.
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« Reply #12 on: June 10, 2010, 09:20:47 am »

Be sure to make the first bit of the cut very slowly to be sure the cut starts straight.....
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Neural
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« Reply #13 on: June 10, 2010, 11:26:44 am »

Well.  Everything looks solid on the arbor. 

Is it possible that one side of the blade edge is cutting faster than the other?
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« Reply #14 on: June 10, 2010, 02:41:02 pm »


The alignment check between your drop saw and a carriage saw is similar to the alignment check between a radial arm wood saw and a table saw (for wood).  The drop saw is going to be harder to align but that has to be the problem.

TOG
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« Reply #15 on: June 10, 2010, 05:43:35 pm »

You have to start a cut that is on an angle very, very slowly.  And I think this is going to be harder to do with a drop saw because its weight wants it to keep on drawing.

another thing I do when starting a cut on an angle (not on a drop saw) is to hold my finger against the saw blade as I start the cut very slowly and then when it is in deep enough letting it go.
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« Reply #16 on: June 10, 2010, 07:36:19 pm »

I read an article in Rock and Gem and they discussed how to cut a sloped stone.  Their way was to let the blade contact the stone for a short time so it just started to nick the stone.  Then say 15 to 30 seconds later, stop the saw and pull the stone away from the blade.  Now push it back into the starting cut and do it again.  Repeat this process 2, 3, 4 times until you can see a rectangular channel cut in the stone.  Now the blade will no longer try to slide down the stone as it has a slot to hold it straight.  Since I started this on sloped stones, i have not had a single problem and have been finally able to cut sloped stones.  A sloped stone is what caused me to warp a $275 blade a couple days after i first got my saw.  This may take an extra minute or so, but its well worth the effort.

Mark
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Neural
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« Reply #17 on: June 10, 2010, 08:38:06 pm »

The sloped stone issue is most certainly part of the problem. 

The drop saw is operated by lightly setting the blade down on the stone and holding it steady until it has a start, then smoothly releasing until the full weight of the arm is in action.

I will try the method Mark mentioned, as I'm betting that will solve the problem.

Thing for me is that something is ever so slightly off balance, so when I'm trying to set the blade down gently, I don't get a slight zzzzzzzzzzzzzzzzzzzzzzzzzz sound, I get zzz zing zing ting zzzzzz zing zzzzzzzzzz   because my muscles can't adjust fast enough to compensate. 
Might just take some practice. 
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« Reply #18 on: June 10, 2010, 09:43:34 pm »


Another trick I have tried with good success ..  as soon as the blade starts to contact the stone take it out of gear (carriage movement) for 30 seconds or so then put it back in gear for 10 seconds or so ... keep doing this and keep checking the stone (shut off the saw so you don't get oily face).

TOG
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-Gary

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« Reply #19 on: June 11, 2010, 08:16:01 am »

I think that Gary's method does pretty much the same thing as the one i got from Rock and Gem magazine.  You let the saw make several short contacts with the stone, until a channel is cut.  The channel will then tend to keep the blade cutting in a straight line.

Mark
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« Reply #20 on: June 11, 2010, 09:02:36 am »

I think the feed on my old Lortone is sooo sloowww That I do not have this problem. I went to look at the 18" HP yesterday. I am buying it. The seller also has a saw exactly like Neurals, which is also for sale and we actually discussed the blade starting into the rock. Paul (the seller/owner) uses a thicker than normal blade and actually eases the blade into the rock. He says that it is messy business and  he avoided cutting Montana Agate (usually round and slippery)with that saw. Bob
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« Reply #21 on: June 11, 2010, 09:15:45 am »

Congrats on the new saw Bob..

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Neural
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« Reply #22 on: June 15, 2010, 12:12:57 pm »

Well, one thing I have to make clear is that this is a drop/chop saw. 
I can post pics if needed, but there is no carriage of any sort.  the rock is held in a vice that is part of the base, and you literally set the running blade down on the rock, let it groove a little, then release.

I've not had a chance to try Marks suggestion yet of taking a few grooving swings at it before letting it fully rest on the rock, but will see what results I get there.

Lortone seems to think it's a blade issue, but hard to say there.  The blade is perfectly flat, far as I can tell.  I keep thinking that maybe it's something to do with the blade edge being sharper on one side, but beyond that, this is an oddity.

Everything is clamped down tight, and the thumbscrew that keeps the side to side adjustment is tight when the saw is in use (it locks a long threaded shaft that, when rotated, moves the entire saw arm side to side, this is how you adjust to make cuts).
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« Reply #23 on: June 15, 2010, 07:32:25 pm »


Let us know when you get this figured out.  I wish someone close by had a drop saw that I could look at.

TOG
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-Gary

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Neural
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« Reply #24 on: June 15, 2010, 07:48:23 pm »

I'll take some pictures tomorrow and post them.

According to Lortone, they say that it sounds like the saw blade has lost "tension", which apparently results in the warping like this.

I can only assume that they are eluding to some sort of metal fatigue due to heat over time, since the blade has been used for a while.

They told me to buy a new blade.

Honestly, if that is the case, then what I want to know is what's the danger of using the blade as it is currently?  It doesn't warp real far, and the stones are in the vice nice and solid.   Just want as much out of it as I can get.
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« Reply #25 on: June 15, 2010, 08:10:41 pm »


I would continue to use it.  It doesn't sound like it is causing any real problems.  You might try bigger washers.  I don't know if you have one or two but if they are bigger it will make the blade more stable.  I do that on my wood saw.

TOG
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-Gary

Of all the things I've lost..I miss my mind the most.

Whether you think you can, or you think you can't, you're probably right.
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