Thread: Mitre Mayhem

The blade is pulling/twisting the work into itself through the cut; it's not unusual on angled cuts, especially in thick/hard material and/or if you're running a blade that isn't as sharp as it should be.

The fix is to cut stuff 1-2mm over size, then re-cut to size. This reduces the pressure on the blade and prevents the work being pulled in.

Originally Posted by elanjacobs

The blade is pulling/twisting the work into itself through the cut; it's not unusual on angled cuts, especially in thick/hard material and/or if you're running a blade that isn't as sharp as it should be.

The fix is to cut stuff 1-2mm over size, then re-cut to size. This reduces the pressure on the blade and prevents the work being pulled in.

Thanks Elanjacobs however I am not convinced that is the case.

The recuts I mentioned above have only been set to take 2mm off per cut and the result is also the same.

I also have featherboards setup holding the slab hard against the fence

What kind of blade are you using and when was it last sharpened?

Do you have anything set up to stop the board twisting at the back end as it leaves the cut?

Originally Posted by elanjacobs

What kind of blade are you using?

Do you have anything set up to stop the board twisting at the back end as it leaves the cut?

Its a Freud 60T general purpose blades. It is a couple of years okd but still feels sharp to the touch.

i just have the 2 featherboards set up in front of the cut. As mentioned, the issue seems to be with the start of the cut (first 150mm) while the remaining cut seems fine

I'll bet if you had it sharpened the problem would be gone. "Sharp to touch" isn't a useful indicator with carbide, you have to check it under high magnification to see if the edge is actually good.

I had to deal with the same thing a lot at work and a fresh blade fixed it every time. No amount of featherboards will stop the piece twisting into the blade; the saw is much stronger than they are.

Thanks Elanjacobs, i will see if I can get a new bkase tomorrow

I didn't understand "mitre" until I saw the blade angled in the saw for a "bevel"...
So the following is quite possibly your problem...

If you've set your saw up, and checked that the mitre slots are in line with a vertical blade...that's only half the job as it only confirms the left/right alignment of the slot to the blade.

This step is often missed in setup tutorials, but you also need to check the slots with the blade set at 45deg as this will tell you if the front/back edge of the blade is higher/lower, which in turn affects the cut whether it's being made from the mitre gauge/slot or (aligned) fence.

You adjust the table height accordingly, recheck the vertical setup, recheck the 45deg setup, then rinse and repeat until it's within acceptable tolerances between both vert/45. It can be a complete pain in the butt to do, but by golly it's worth it.

Unfortunately the absolute best resource I had for this...tablesawalignment.com is now defunct. Specifically it had the calculations for how much to raise/lower the table by when testing at 45deg.

I'll try to find something similarly detailed for you tomorrow, but I reckon that is the source of your problem.

This vid loosely explains how to do it with a TS Aligner (basically a dial indicator jig), but doesn't provide the calculations for how much to shim the front/back of the table so it's just guess work.
It might pay to watch the whole thing, but I've linked to the 45deg section. It's pretty dull watching.

https://youtu.be/gLTVFrNZIHw?t=319

Is it possible that the panel is twisting as you push it through and not staying hard up against the fence. Being a fairly long panel it would be easy to drift away from the fence which would give you an uneven cut at the opposite end.
Do you have a mitre gauge with a long fence that you could put up against the trailing edge as you push it through and check that it stays against the gauge fence.

Is the panel being held flat against the table surface during the cut, any lift will change the width of the bevel.

Originally Posted by elanjacobs

I'll bet if you had it sharpened the problem would be gone.

Turns out I did need a new blade as the previous one had a bow in it. I could see it when I lined my 45 degree angle against it however I had just assumed that was the norm. The new one sits flush.. after all these years (6+)... go figure.

Either way, the new blade made the problem worse. I am now getting a wavey (is that a word) edge. I think it is an issue with the flattness of my board. Regardless of the issue I glued the top to the mitred/beveled legs and then with 11 Bessy clamps and bucket loads od pressure I actually achieved a half decent finish.

Now just need to work out why my board was .... wavey....