circle mill blade question

[HPPDRoss]

I finally got my husk clamped down on the h-beams and now need some advice. I put a level on the blade and it appears to be off about an 1/8 inch. I then put the level on the arbor shaft and its dead on. I put a plumb on the blade and there was a small gap at the bottom. I know the husk is level, and the steel beams its resting on. Seems that the closer I put the level to the center of the blade it was real close but no cigar. I want it to be right.

[reride82]

HPPDRoss,

Is the blade out of level from top to bottom, or just top to center? When a circle blade is at rest, it has a concave, or dish-like shape. It doesn't straighten out, or stand up, until it is up to operating speed. If the Mandrel, or arbor shaft, is level, once the blade is up to speed, it will run true as well. Hope this helps.

Levi

[beenthere]

HPPDRoss

Here is a good publication on circular saw setup and operation. If you don't already have it, this online version may help you sort out some things.
http://www.fpl.fs.fed.us/documnts/misc/circsaw.pdf

[bandmiller2]

If you have the arbor "dead nuts" level prehaps theirs a problem with the saw.Saws are tapered from the center to the rim and sometimes cupped slightly.Unless its a large diameter it should be Danged close to plumb on the log side.I would say be sure your arbor is perfectly level and try it.Sometimes saws will get a kink or bent slightly.A common carpenters level is not really close enough better a machinest level used to setup machine shop equipment.I use a Starett with a very accurate vile and base that will align with a round shaft.If you just have a carpenters level check it agenst outhers or buy a good new one.Its also possible theirs a problem with the collars. Frank C.

[GeneWengert-WoodDoc]

For a large circle saw (over 48"), it is common to have it dished so much that it will appear to be not vertical when stationary.  As it spins, the centripetal force (like the force when you spin  a ball tied to a rubber band) wants to make the edge of the blade fly off and this means that the force wil make the rim a bit longer as the metal stretches.  If the blade were perfectly flat and vertical when stationary, when it spins and tries to get longer, it would have to get wavy.  But if it is dished when stationary, then when it spins and lengthens, it will stand up straight.  The amount of dish depends on the rpms.  This is why each blade will typically have an rpm stamped on it...to know what speed the saw was designed for.  A saw can be retensioned for a different rpm.  Incidentally, you can buy a straight edge that is actually curved on one edge, with the curve being correct for a given rpm.  The rpm would be stamped on the curved edge.

In addition to dish, the saw is tapered, as mentioned, with the thickest being near the center.  The taper on the log side is hard to measure as the saw is made with the taper mainly on the lumber side.  This is why they make blades for left hand mills and right hand mills that are different.  If you check with your level, you should be able to see one side is different (more non-vertical) than the other.

The collars are usually of two types.  The collar attached to the mandrel is called the flat, fixed or tight collar and should be perfectly flat.  The loose collar is not flat but has a slight taper with the outside rim protruding.  This means that the outside rim will contact the saw blade first as the collar is tightened.  In this way, when you tighten the collar, the pressure from the rim of the loose collar on the fixed collar will not cause the blade to move or deform. 

The larger the collar, the more stable the blade, but then the smaller the log you can saw. 

The tight collar also will typically have a hole or two so you can insert a pin into the collar and into the saw.  This pin is what holds the saw in position with the mandrel so the saw will not slip when it is sawing.  Without the pin, the blade might slip between the collars...there is a lot of cutting force on the outside rim of the saw and so the leverage or lever arm principle means that this force on the small contact area of the collar is huge and can make the blade slip even when the collars are really tight.

Hope this is not re-hashing what you already knew; hope it helps you understand, even if it is a bit wordy.  Maybe my coffee this morning was a bit to strong?

[lyle niemi]

Im not an expert but I would think if your mandrel is true your saw should hang true unless you have debris between your collars and saw, best way is try it and see how it cuts.

[Thomas Ruga]

Ross: All these thoughts are correct. When you start the saw the blade will look like a raw pizza crust until she gets up to hammered speed. When you first experience it, it may be a bit disconcerting, but when she's at speed she will stand straight as the Statue of Liberty. Then enjoy the sawdust...

tom

[Seaman]

I love hanging around (so to speak ) with so many smart people!

[dblair]

the arbor should lean a couple thousands per foot towards the log according to my book the blade may be true or not but will straighten out when spinning . set the blade to the carriage using the same tooth rotating the blade 180 degrees and measuring to the same spot . the lead should be 1/32 to 1/16 inches . mine is 1/16 and it cuts good . take the guides away from the blade in setup . hope I've helped .