Squaring a blade in my tablesaw

[Collie1956]

How do I square the blade? My blade runs out by 2mm .

[John Rumm]

There are three different "squares" you can check. The vertical square - i.e. is the tilt 90 degrees to the table surface in the full upright position. Most saws have adjustment screws on the limits of the tilt mechanism to set this.

Next thing is to get it parallel to the slots on the table surface. Many saws will allow the bolts retaining the table to be slackened and the angle of the table shifted slightly. To check this place a bit of wood in the slot and slide something about the right width up to it, and align the blade so it looks parallel to the wood. Then use a dial test indicator so that you can run it along the blade against something in the slot. Again tapping the table gently until they are properly parallel.

Last thing it to align the fence. There are usually adjustment screws for this - you can line that up with a table slot to start with, and do a final check against the blade. (if you did the previous step right, then the blade and the slot should be parallel anyway).

[newshound]

I guess the other possible fault that could need "squaring" is swash in the blade, caused by poor seating in the washers or distortion of the blade itself.

[John Rumm]

True, but that is not something that you can typically "tune out" so easily.

[Reentrant]

It took me a while to visualise it, but if the fence isn't parallel to the blade you still get a parallel cut - just one with a wider kerf.

[John Rumm]

Its also potentially very dangerous - since if the fence is closer to the back of the blade than the front, it will cause the wood to pinch at the back where the blade is rising from the table. That has the habit of grabbing the wood and throwing it up and at you! The other way round is slightly less dangerous, but still best avoided for a number of reasons.

[TimW]

Don't ask me where I got it from but I am certain that I read in a manual or text book once to set the fence so the blade was just ever so slightly toe-in. eg the front of the blade closer to the fence than the rear.

TW

[newshound]

I've seen that too, I always assumed it was to help to keep you just clear of the more dangerous case.

[John Rumm]

Best you can say of that is if you are going to have an error in alignment, then that is the safer direction to have it.

[Thomas Prufer]

Eh... depends?

I know of a table saw, large, cross slide over a meter, and the cross slide and fence were not a 90° to each other, but very slightly off. It bothered me, but the machine was new, and rather than fool with it myself, I asked when it was first serviced by the manufacturer:

This saw was (also) used for melamine-faced chipboard, generally using many-toothed carbide blades with specialized tooth shapes.

It is set assuming that the "good" piece from a cut was either between the fence and the blade, or against the cross slide. Cutting against the fence, the saw blade enters into the material from the top, leaving an unchipped edge on the top. At the back end of the kerf, where the blade comes up, there is a bit of clearance. This keeps the edge unchipped. The clearance was below 1/10th of a millimeter. Cutting with the material held against the cross slide, the clearance was on the other side, i.e. the piece on the fence side got the teeth where they came "up", with more noticeable chipping.

(Some of these table saws have a pre-cutter to avoid tearing on the underside of the chipboard, but this machine was also used for solid wood, where the pre-cutter is in the way...)

The machine was a similar model to this one:

Cutting with material against both the slide and the fence is a no-no, for one because the two are not at 90° to each other. (Also because there is no place for the wood to fall away freely, and scrap can get caught between fence and blade, and shoot out the back...)

Thomas Prufer