Mitre Saw Tension

[David Cefai]

I have a hand mitre saw that up to now has always given me beautifully precise cuts.

Today however I used it to cut the cheeks off a tenon in 3 x 3" oak. The blade twisted in the cut so that by the time I realised that things were going wrong the cut line had drifted by almost 1/16" in a 1" cut.

I am assuming that the blade tension needs to be higher. Could somebody give ma a few pointers on how to set the saw up? Google was not my friend today.

[Jonathan McCullough]

Sawmakers of yesteryear hammered hand and panel saws to put tension into them so that they would not bow or kink. Saws with backs, like your own, and dovetail saws, carcass saws, mitre saws, back saws, etc. use the steel or brass back to provide stiffness instead of hammer tensioning. So you will not want to be putting tension into your back saw. If your saw is drifting on a consistent basis, and you're satisfied that it's not operator error (my own usual first culprit), you may want to gently "stone" the saw by drawing a file or abrasive against the side it's favoring. That way, if you or a previous sawyer has set one side of teeth further over than on the other side, you'll correct that without messing with the set.

[David Cefai]

I should have been more specific!

The saw is a frame type and can be adjusted.

[Jim Koepke]

There looks to be an tension adjusting bolt or wing nut below the handle. Does the top rod have any adjustment? This looks like it could be designed like a bow saw.

The blade could still need some work if it has somehow come into contact with part of the mitre frame and effected one side of the teeth.

This is where you need to determine what kind of drifting occurred and then what is the cause.

It could be a loose stop on the mitre guide.
It could be teeth that have been damaged.
It could be the blade tension needs to be tightened.
There could be other causes.

jim

[David Cefai]

The top rod can be adjusted to vary the tension.


It could be a loose stop on the mitre guide. No, that was the first thing I checked.
It could be teeth that have been damaged. Not that I can see. The blade is bimetal, with fine teeth.
It could be the blade tension needs to be tightened. I think that this is the cause.
There could be other causes.

I am quite convinced that the problem is blade tension. Up to now the hardest wood the saw has seen was 3/4" by 1" maple. Now I've turned it loose on oak.

What I am hoping for is some sort of "rule" for tensioning the saw because I din't want to risk overdoing it and stripping a thread and because it's hard work making test cuts :-(

[Jim Koepke]

What I am hoping for is some sort of "rule" for tensioning the saw because I din't want to risk overdoing it and stripping a thread and because it's hard work making test cuts :-(

Finger tight is usually the rule.

Set a piece of wood on the saw and make a 90° cut. Check with a square and you should be done.

Life is full of hard work that never gets done just because.

If it is real hard, the saw may need sharpening. That is hard work that makes the work to follow easier.

jim

[David Cefai]

Thanks Jim,

I shall have to go down that route. I don't think the blade can be sharpened - bimetal and fine teeth - but I can get replacements. I already have one and can actually test with it.

[Roger Bell]

I prefer the older "real saw" set ups, like the Stanley/Millers Falls/Langdon boxes with a heavy spined saw, especially for the harder furniture grade woods...but my wife has a Nobex for her picture framing. This unit is designed for lighter duty work....like molding cuts, for starters.

Usually, when poor cuts result on the Nobex, it is time to replace the disposable blade. But my guess is that the Nobex is simply not up to the task in terms of size and weight.

In any event, I don't think I would overtighten the tension. I would try a new blade before I monkeyed around with anything else. And you might also consider eventually trying an older style miter Quality miter box if you see one priced right. In Stanley, I would go with the Model 358 or 460 and not their cheaper offerings. A cheap older miter box will not have the accuracy of your unit. A good one will...and then some.