technique for "straightening" a warped saw blade?


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Old 12-05-08, 08:03 PM
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technique for "straightening" a warped saw blade?

Greetings!

While giving my DW744 table saw a tune up, I found that a couple of my blades are *very* slightly warped. It seems to be a few teeth on each side of one expansion slot.

Is there some technique for tapping a blade so as to true it up, and compensate for a little warp? The warp is barely noticeable as you rotate the blade next to the fence.... 7 or 8 teeth barely graze the fence while the rest do not touch.

I guess I could give it a whack, but I thought I'd ask first.
 
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Old 12-06-08, 08:14 AM
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Here are my thoughts for what they are worth.
If all 7 or 8 teeth are in a row then I would just whack below them with a hammer to correct them. But if there is a space of straight teeth between the 7 or 8 I would use a blunt 1/4 inch punch and strike the blade just below the tooth while the blade is resting on a vise or anvil with the tooth not touching anything. Striking near where the gullet ends on the blade. My thought of the gullet is the cut out places between the teeth. My thoughs are that the blade got a little hot and this is where the weakest place would be.
Only thing is after disturbing the metal in this way it may be more supseptible to warping more next time it get hot.
 
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Old 12-06-08, 08:19 AM
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I'd pitch them. The metal on the convex side of the warp has stretched and will not ever return to its previous condition.
 
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Old 12-06-08, 04:41 PM
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Xsleepoer - Wow. A red letter day. I think this is the first time I've read a post where you asked - not answered - a question.

I wish I could provide an answer, but I would probably just toss the blade and ***** about having to buy a new one.
 
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Old 12-06-08, 05:33 PM
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LOL @ cwbuff! Contrary to what you may have heard, I'm not a know-it-all.

Just to follow up, I put on a brand new finish blade today, and it does the exact same thing. I believe this means that the motor shaft or bearings are slightly worn, allowing the shaft to dip in one spot as it rotates.

When I set the fence right next to the blade and then slowly spin it, all the teeth of the blade miss the fence until the shaft gets to a certain spot where it (or the bearing) must "dip" inside the motor, allowing the top of the blade to also dip slightly, causing the blade to graze the fence momentarily (not quite 1/4 of a turn).

So I guess maybe this will be a good excuse to start thinking about selling the saw and getting a new one.

Thanks for the replies!
 
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Old 12-07-08, 06:52 AM
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You can replace the armature and bearings if you think the saw still has some life left in it. Then again, what better excuse to buy a new saw?
 
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Old 12-07-08, 06:56 AM
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Does that saw have the washers that clamp the blade? Could it be something as simple as that? Could always put a dial indicator on the shaft to see whats up. And if you don't have one of those, maybe 2 new tools!
 
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Old 12-07-08, 03:02 PM
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cwbuff, That thought crossed my mind, but I did that exact thing on an older 1994 model DW744 where the bearings actually shelled out, and I was not too pleased with the results. Perhaps its because I'm not factory trained in refurbishing tools, but after the repair it just wasn't 100% reliable for use as a "finish" saw. I'm kinda picky when it comes to blade vibration and wanting to achieve smooth cuts. When a saw starts getting worn to the point where it can't be tuned up, you are right- it's time for a new saw!

Gunguy... yes, it's got a heavy washer on one side that's flared to fit the motor, and a flat washer on the other, and yes, it's possible that one side is worn (the side that is away from the blade). I hadn't considered that possibility. I did clean off the faces of the washers by rubbing them on a glass top w/sandpaper... since any gum or goop on the washer could cause some wobble.

After all this, I put the blade back on... no change. So I did a little "persuasion". I rotated the blade to the point at which it tips toward the fence, and then gave the blade a whack with my fist (blade was fully extended 3 1/4"). I checked the rotation, and it was a little better. After doing this 3x, the blade now runs true and straight with much less vibration than it did before. I'm not sure exactly what changed, but I'm pleased with the results. We'll see how long it holds up once I run some wood through it. The wife doesn't want me sawing anything in our living room for some reason. Since it's cold out, I've been working on the saw where it's nice and warm.
 
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Old 12-07-08, 04:26 PM
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It sounds like you did an old school fix - "if it don't work, hit it. If it still doesn't work hit it again only harder".

My guess is that the bearings are shot. I can't see a bent armature shaft getting straightened like that. Is there any slop in the washers or between the blade and the shaft?

If you have any flange head friends borrow a dial indicator and check the runout on the shaft. I'm sure that the DeWalt customer support guys will give you the specs.

One thing though. If the only warm place you have to work on your saw is the living room - it's time to build a new shop! Blow a bunch of sawdust on the living room carpet and the wife will agree. Either that or you'll be sleeping in your truck.

My shop was once in my basement until my wife got tired of the noise and the dimming lights whenever I lit off my table saw. When I offered to build a new shop out of the house she agreed.
 
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Old 12-08-08, 01:37 PM
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Did someone say "NEW TOOLS"??!!!
 
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Old 12-08-08, 01:50 PM
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Yeahhhh Babeee...NEW TOOLS!!!
Dial Indicator, micrometer.....hmmm what else...OH Yeah....a table saw and a new shop!
 
 

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