Greetings to all!
This post will be useful for those who have a saw or table saw.
Table saws supplied to Europe are not equipped with zero inserts or DADO disc support (grooving discs), because according to some standards they do not meet safety requirements. And they do not correspond due to the inability to use the standard riving knife.
For those who do not know why a riving knife is needed: it serves to prevent the saw blade from being pinched by the material (wood) being sawn. If it is absent and the disk is clamped, two options are possible:
1) The saw is weak and the material is very heavy: it will jam the blade, damage the gearbox and damage the board for sure.
2) The option is worse: the board will be thrown, like a catapult, at the master and will certainly lead to injuries. This effect is called Kick Back. There are many videos on this topic on YouTube.
But, a riving knife is needed not only when cutting wood, but also for such stable materials as plywood / MDF and the like. A kickback can occur with them, if, with inaccurate sawing or incorrect feeding, the workpiece is unrolled and it comes into contact with the back of the disc …
And if it is so dangerous to work without a riving knife, then why is it removed? ..
There are situations when he really gets in the way. For example, when sampling grooves: manufacturers often make the knife higher than the disc (safety and the ability to install upper dust collectors, again more for safety). And in the case of installing the “zero clearance” insert, the standard knife is also impossible to use, because it’s too long …
Now let’s get back to the insert. Why is it needed?
It is needed for cutting veneered, i.e. veneered) panels (including plywood itself). It acts as an anti-splinter spacer that prevents the edges of the fibers from chipping off during the saw.
To make an insert for your saw, the easiest option (except for ordering from the aftermarket: so, by the way, on the Amazon there is an insert for the American version of my saw and it costs \$ 35) – take a standard spacer and attach it to the plywood of the required thickness (for my saw it is ideal 10mm plywood came up) and circle with a pencil.
With a jigsaw or band saw, we cut around the perimeter, with a slight indent.
At radii, you should take a smaller canvas.
When cutting with such an inaccurate tool as a jigsaw, it is better to make a small stock than cut out the excess =)
When the excess material is cut off, we fix the standard spacer on the cut plywood (you can use double-sided adhesive tape or, as I did, screw the spacer with self-tapping screws.
With a milling cutter with an overrunning milling cutter, we give the workpiece a shape exactly that repeats the standard product.
Because the disk is in the lowest position quite close to the table surface; it is not possible to place the insert to obtain the groove. You can put it on top of the standard one and press it with something from above, or make a groove with a cutter along the entire insert. Leave at least 5m in order not to significantly weaken the structure.
I made a groove 8 mm wide and 5 mm deep.
It would be nice to choose a quarter at both ends for the plywood gluing … I did it only on the back side, in order to make an emphasis that protects from the throw of the spacer itself.
I just cut out a piece of 4mm plywood and glued it into the groove.
And cut off the excess at the end. The laser is not tuned, I do not use it for precise work, but approximately where it will cut it shows.
Since I do not have a planer, and leveling the surface with a router is a chore and dusty, I use the same method to level the spacer as the manufacturer of the saw – leveling with screws.
I drill 10mm holes for nuts and 7mm holes for 6mm screws so that they fall through freely.
I press in the nuts.
Everything for installation in the sawing machine and the first cut!
It is imperative that before cutting, the liner must be aligned flush with the tabletop and pressed with something from above, otherwise you can get it on the forehead =)
I pressed against the parallel stop.
Thanks to the “zero gap” insert, I was able to cut the plywood without chipping for one of the projects, but that’s another story!
Thanks for your attention!
Hope the post was helpful to you =)