Saw Blades

[Jim Miller]

I need help here. If you don't want to read through the detailed explanation of my problem, just go to the bottom line.

I bought a pair of new 12" blades for my newly-acquired, used Pistorius miter saw, which are designed to cut both aluminum and wood. And they do.

Some say not to use the dual-purpose blades, but I don't have room for two saws, and I won't change blades twice a day. Besides, the makers of saws and blades say they should work. And they do.

From the first day I installed them, the right-hand blade tends to chew a bit off the miter after the cut, as the blades return up to their starting position. This saw is new to me, so I checked all the bearings, alignments, belt tension -- everything I could think of. It's all good. I also played around with the speed of the cutting motion. No change.

Then I switched the blades left-right. The problem stayed with the blade; now it chews on the left miter. That's less of a problem, because we can simply pull the moulding to the left, away from the cutting path, after the down-motion of the blades. (Can't do that on the right due to the measuring stop.)

Now that I know the problem is the blade, I went looking for a solution. One local maker suggests that particular blade wasn't "tensioned" properly for the high speed (3450 RPM) of the saw. Makes sense.

Another saw expert asked about the tooth configuration. On my new blades, every other tooth is beveled on both sides, with straight-cut teeth in between. He thought there should be three different, alternating tooth shapes: Right-bevel, double-bevel, left-bevel, double-bevel, etc.

I'll send the bad blade back to its maker with a warranty claim, and I expect a new blade will be forthcoming. But I need to buy another set of blades to use before I give up this one.

The Questions:

1. Have you heard of the "tensioning" problem, or is there another explanation for this blade's poor performance?

2. Which tooth configuration is best for cutting both wood and aluminum?

 

[Alan Sturgess]

We have been using Pistorius Combination Wood/aluminum blades for 16 years for all our customers chops. We have tried other manufacturers combi blades and NOTHING works like the Pistorius combination blades.

The Pistorius combination wood/aluminum blade is a combination of just two teeth. One angled right and one angled left and they alternate with no different tooth in between. Pistorius calls this their ATB or Altermative Top Bevel. I would never let any sharpener sharpen our blades without giving the manufacturers specs on the grind to them. We have used about 25 sets of these and they work like magic. Yes they cost more than other blades, but they work better.

We simply switch from wood to metal by turning the lubricator switch on or off. We even use the lubricator to cut oaks and maples with virtually no lubricant left on the wood. When cutting hardwoods with the lubricator on you prolong the life of your blades and no longer get any pitch build up on the saw blades. You also eliminate the burning you typically get from the blades.

Other blade manufacturers claim their combination blades are as good as Pistorius, but none have been able to prove it to me so far. Lots are cheaper, but none better.

From the sounds of it you have a faulty or out of balance blade but William at Pistorius is the best I know in the industry to solve saw and blade problems.

Phone him if you still cannot solve the problem. Tel 631-582-6000

Alan

 

[Rick Bergeron - CPF]

Jim

Does it really matter about the tensioning when you have proven that there is a problem with the blade? Other than personal knowledge aquired for future reference.

You didn't say that the defective blade was a Pistorius blade. I agree with Alan about only using a manufacturer provided blade. The manufacturer of a precision saw should know which blade is best for their saw. That is why I only use FrameSquare furnished blades on my FrameSquare saw. In addition to proper cutting, it reduces questions should there be an accident associated with using a generic sawblade without proper documentation that the generic blade is truly a satisfactory substitute. I tried another namebrand that is advertised to be equivalent but results were less than expected. The manufacturer would not/could not prove the blades were built to the same specifications.

Are you also using some form of coolant or lubricant when cutting metal and hardwood? Wax works for me, but spray sure seems to be less messy.

 

[gearold]

Jim
It sounds like it is the tentioning of the blade
blades are tentioned to make the blade stiffer so it wont wobble, the blade may just be warped,
most generic blades are tentioned to run at 1750 rpms so at high rpms like 3450 they will wobble,on
a correctly tentioned blade you cant bend it side to side when its on the spindle , dont worry about the warranty deal they will get you a new set pistorius is good about that.
a tip when you cut when you get thru the miter move the left frame away from the blade & press to the right on the right frame before you let your blades come up. dont baby that machine cutting slow that tends to heat up the blades then you will get a warping on the blade..........

gearold

 

[Jim Miller]

Thanks to all of you for the information.

I would like to learn more about tooth configurations, and how to determine which is best for the cutting we do here.

Alan, the blades I have aren't Pistorius, but came from a large Pistorius dealer that makes blades for their saws. The tooth configuration isn't as you decribed -- I'll ask about that when I call them about the replacement blade(s).

 

[John Gornall]

Blades just back from the sharp shop and installed in the double miter saw. First cut I can feel sawdust hitting my left hand holding the moulding. Not hitting the right hand. Inspect the cuts and the left cut is rough. Send blades back to the sharp shop. - What's wrong? I use a heavy duty, triple chip grind, 8 degree negative rake carbide blade. I'm lucky to have a talented saw guy that has guided me through all these years of framing with good blade advise - I just do what he says and have no problems - and blades are only 85 bucks each! Back to what's wrong with the left blade - A blade of this type has 10 different surfaces to be ground. The diamond wheel is set for each surface and the machine grinds every other tooth (every other tooth is a different shape) - 10 times around the blade with the angle of grind reset each time. So the operator must have been distracted and missed grinding 1 or 2 of these surfaces. My saw guy is embarrassed and mad at his operator. I have 2 sets of blades and a spare blade. The sharp shop truck comes by every Thursday so no big deal to get the blade sorted out. When a newly sharp set is installed I do a quick test cutting wood (hard and soft) and aluminium to make sure all is well. Ask other framers, finish carpenters, and others where the good sharp person is and get to know him/her! Now what do you use those miter sander things for?

 

[Warren Tucker]

There is no way a combo blade is going to work well. I gave up on 'en 20 years ago. BTW, there are no Pistorius blades, they're Forrest Blades and are over priced for what picture framers need blades. The Forrest Miter Masters are outstanding blades for cutting wood all day long. The problem is, most picture framers cut very little wood only frames; we cut plaster coated wood frames and the plaster will dull any blade in a few hours of use. Aluminiun won't and these blades will cut AL forever.

There is an inherent disadvantage in 12" blades and for that reason, we don't use them. Very little runout will cause major problems at the edge of a 6" radius. There is much less at 5" on a 10" blade.

There is a natural movement of the moulding into a blade when miters are cut. I think the main problem is one of clamping. I have no idea why this problem would follow the blade. Runout will not cause the problem; it only causes a wider cut, but once the blade has passed through the moulding, it should have removed all the material it's going to *unless* the moulding moved into the cutting path while it was being cut to be caught again as the blade cycles up and away.

Since we cut a lot of leafed and plastered moulding, we sharpen blades frequently, way too frequently to use industrial blades (blades designed for the woodworking industry, Forrest Miter Masters are a good example). We get excellent cuts with Freud LU85's and have about 20 of them. We use use industrial blades for hardwoods, though, probably because of habit.

We use a dedicated saw for metal because the process is so messy, oil and water on the tables. And we change blades on the wood saw depending on what we're cutting,, hardwood or "gessoed" wood. If I had to use a saw for both wood and metal, I'd go with blades designed for each. The three minutes it takes to switch blades is a non issue. I use Forrest blades for metal and Freud LU85 for wood. The Forrest Blade cutting metal will last forever before it needs sharpening (about a year for us and we cut a lot of metal); the LU85 will get dull fairly fast, but so would a Forrest blade.

When i mentioned the LU85's make excellent cuts I mean excellent with no chip out on the backs or on the top of coves. These are really good blades made by the largest blade maker in the world. The newer LU 85's are even better than the ones I'm currently using. Anyone who wants to discuss blades and blade changing should call Lynn, our frame maker (910 395 2953) and talk to her. She's been doing this for 14 years and is accutely aware of what it takes to make excellent cuts on a daily basis.

I don't think I've seen an ATB blade used as a combo metal/wood blade. The combo blades I've seen were thriple chip, an ATB with a raker between the two top bevels. That's an attempt to extend the life of the blade between sharpenings.

When you get a new set of blades or a newly sharpened set, listen to the cut; there's almost no noise through wood. After a while, the blades will make enough noise to be painful. When the blades get noisy, they're getting dull and they get dull fast cutting through plaster. Warren