Thread: My new DIY zero clearance insert plate.

One problem with Zero clearance throat plates (and in fact most throat plates) made in the manner you describe is they stop too close to the teeth of the blade. This prevents the dust in the air stream travelling along with the blade saw blade from being dragged down through to the underside of the saw table where the dust is collected. The dust in the air stream is then sprayed across the table towards the operator. To Improve the dust extraction and produce minimal interference to cutting it is better if the slot is as long as possible. At the back of the blade the slot should be as close as possible to the blade teeth.

BTW with a Bandsaw for some reason when I have yet to determine it's the other way around.

Just wondering why he didnt just measure off the old plate to make the new he sure did fart around a lot.

On BobLs suggestion, I drill a 20mm hole with a forstner bit at common blade heights, starting about 5mm behind where the gullet hits the top of the insert... 9mm, 18mm for mdf and 45mm for MGP pine. The hole improves dust collection, but does not eliminate it, but it's a vast improvement.

The holes have a slight chamfer and don't impede the function of the ZCI.

It works exceptionally well with dados.

I fully agree with your observations.
in fact I thought to make some holes so as to allow the suction of the dust

Here's the one I made for the rip saw at work in 19mm ply. All the holes have a 4mm round on them to act like a bell-mouth and help smooth the airflow and the slot has been slightly enlarged around the teeth but I think I'll give it a bit more clearance since we don't care about the quality of the cut on this machine. If you're wondering why there's a hole missing, that's where one of the supports for the insert is.
IMAG1546[1].jpgIMAG1545[1].jpg

Holes away from the line of the cut in a throat plate don't draw much air as they are way too small and are usually blocked by the wood.
They will pull a few chips away after the wood has passed but the overhead guard should grade the fines that the back of the blade pumps upwards from the cabinet.
The one hole that does help is a hole right on the end of the slot in front of the blade like this i.e. no gap between the hole and the slot.

ZTP1.jpg

This hole and to some extent any holes along the line out directly in front of the blade help reduce the spray and bounce of sawdust that is generated as the blade breaks through the back of the wood.

Even better is a finger wide groove about 100,mm long like this
ZTP2.jpg

The holes are actually more for catching dust from when the blade isn't fully in the cut (mainly for tapering cuts) than anything else and they do a decent job. I'll enlarge the bit where the teeth are though.

The overhead guard needs a bit of work to be made effective; the connection point is over the riving knife, so it's not catching nearly as much as a 4" hose should. One day when I have some time...

Originally Posted by BobL

This hole and to some extent any holes along the line out directly in front of the blade help reduce the spray and bounce of sawdust that is generated as the blade breaks through the back of the wood.

Even better is a finger wide groove about 100,mm long like this
ZTP2.jpg

I was going to ask how that can possibly work when the timber being cut is covering that slot too, then I remembered my old zero clearance insert, the one with the hole widened at the leading edge. This seems to indicate some sort of excessive chip action happening in that region!

Thanks Bob, I won't have to remake it now, just widen out the slot to tidy it up!

Cheers,

P

16-06- 15 at 21-55-28.jpg

Originally Posted by bitingmidge

......I won't have to remake it now, just widen out the slot to tidy it up!

And hook up the dusty...

Ummm ... Comments re overhead guard notwithstanding, if this is a zero clearance plate, isn't it used when the off cut is narrower than the throat plate to the left of the blade (as pictured) - in which case it may not ALWAYS be covered.

Originally Posted by Glenn.Visca

Ummm ... Comments re overhead guard notwithstanding, if this is a zero clearance plate, isn't it used when the off cut is narrower than the throat plate to the left of the blade (as pictured) - in which case it may not ALWAYS be covered.

Sure, but most folks I know put on a ZCTP and then rarely take it off, or only take it off when they need to next tilt the blade, which was for me back in about 2008.

Holes in any throat plate only typically pull a few CFM each anyway so although they help clear some chips thy do little for fine dust.
The reason for this is because the pressure differential generated by a DC is too low to pull air through the holes
A gap in front of the blade is much more useful because the blade itself will pull much more air through that gap than a DC can

Originally Posted by BobL

A gap in front of the blade is much more useful because the blade itself will pull much more air through that gap than a DC can

Excellent point as always ..

I was going to respond previously, but thought I might be quite wrong.... Since a great deal of my cutting is at specific heights, I've made a few plates to accommodate each height.

At the blade height I've used a 25mm Forstner to drill a hole, but it starts where the gullet hits the plate.

Also, I've found most uncaptured dust is ejected forward at 45 degrees. By putting the plate on the router table with a 1/2" bit, I make a tear-like cut about 30mm further to the front-left. This captures the ejecta very well. It looks odd, but it really does work.

WoodPixel, sound interesting, but I would be interested in a picture if your are able, as I can't fully follow.

Regards

Bauldy