After seeing how bad the tearout from cross cutting the veneered MDF for the TV stand project was and some advice from Olly via the comments, I created a simple zero clearance base for my Bosch PKS46 circular saw from 6mm ply.
I decided I wasn’t going to plunge the saw through the ply (it’s not a plunge saw and the depth adjustment doesn’t allow for the blade to be lifted clear of the material), but instead just cut a slot most of the way through, with the stopped section ending up in front of the blade.
After one abortive attempt with the ply held by the plastic dogs of my folding workbenches
, I decided it would be easier to make it using the saw mounted in my Wolfcraft mastercut 1000 powertool table.
I’ve mentioned before that I think the fence is inadequate, but now I have some pictures to show what I mean
In ripping mode, the fence is only attached at one end and is fixed to the mitre gauge, which is pretty loose and inaccurate.
(I know the short fence not being able to project past the blade is an anti-kickback measure, but the slop in the mitre gauge makes it pretty hard to use accurately).
For crosscuts the mitre gauge runs in the slot on the MDF workbench section, visible to the right of the above picture.
As I was in a hurry (it looked like it might rain) I just clamped a straight board parallel to the blade and relied on the riving knife and the saw being too weak to kickback in any meaningful sense.
The structure of the bench is such that I can’t clamp anything to the left of the blade (at least not with my current arsenal of clamps), but I was able to clamp a wide board to the MDF section on one side and one of the brackets for the fence slot on the other.
I ended up with a piece of ply with a slot in it, which I attached to the base of my saw with some double sided tape (I think it’s carpet tape – thin fabric based and very very sticky)
The blade guard is held up by the base, which isn’t ideal from a safety point of view and the sticky tape has its work cut out fighting the spring of the guard, but it’s good enough for now.
I think if I was to do this again I might make it in two pieces, so that the slot behind the riving knife could be closed, which might add a little extra strength to resist the blade guard spring.
It may also be possible to make the slot wide enough to allow the blade guard to close at least partially, since the zero clearance section only needs to be where the teeth are exiting the material – i.e. at the front of the blade.
The nearest edge in the above picture is only slightly less tidy than the far one – no sign of the previous tearout