Zero Clearance Throat Plate Inserts

[Neil Bosdet]

I had an aluminum insert made for my craftsman TS a few years ago by a friend. It has a slip in replaceable piece of wood similar to the what you did; however, I tapered the sides of my slot with a dovetail bit so the insert is held down by the throat plate and completely captive once the plate is in place on the table.

I guess I should have put more info in my post. I expected people to read the article that I copied from. I too used a 14 degree dovetail bit on my edges to retain the disposable insert.

[Mike OMelia]

This is a great idea. And as soon as I can figure out who carries phenolic inserts for my Jet Super Saw, I will make one. My current insert is made of cast metal. Not going to touch that one.

Thanks for sharing that!

Can you see your process working with this insert? http://www.amazon.com/gp/aw/d/B00028...736678-8065767


Mike

[Noah Katz]

the phenolic should be more temperature stable than aluminum.

That didn't sound right, as all plastics have a much higher CTE than even high expansion metals like aluminum, though the reinforcement will lower it.

I looked it up in my materials reference and the ones listed were all in the range of aluminum, so better than I thought but worse than you thought

[Neil Bosdet]

This is a great idea. Can you see your process working with this insert? http://www.amazon.com/gp/aw/d/B00028...736678-8065767


Mike

Yes. It looks ideal. Very similar situation to what I had with lots of relief cuts on the underside which makes this idea work so well.

[Mike OMelia]

So, mill out a slot using a dovetail type bit, keep much of the undercarriage stuff as structural support, the angle of the slot edges serve to hold the wood insert in
Place. Round the end to match curvature. Have I a good understanding?

Mike

[Norman Hitt]

That didn't sound right, as all plastics have a much higher CTE than even high expansion metals like aluminum, though the reinforcement will lower it.

I looked it up in my materials reference and the ones listed were all in the range of aluminum, so better than I thought but worse than you thought

Hmmmmm, guess I 'forgot' to NEVER assume anything, eh? I guess the assumption was because I have noticed some aluminum Items expanding on occasion, but never had noticed any phenolic items doing that. I guess they could have, but in their application it wasn't noticeable to me. Not all, but most of my experience has been with Aircraft Quality linen impregnated phenolic used for mounting spacer blocks and insulators, and the type used for older electrical ckt boards and mounting insulators. I do have a couple of solid phenolic router plates with no impregnation and I don't know if the chemistry of that phenolic is the same as the others or not.
Interesting question No less, and thanks for your response.

I have had or used a few Saws that came with Inserts that fit pretty well, but more that were a sloppy fit and or warped, (which I hate). I once made 3 out of HDPE, but they all warped/sagged and 2 of them bowed up like Borg lumber after a while. Since my shop gets VERY hot in the summer, and a short time of very cold in the winter, I just want a material that I can get a snug fit that won't get tight or loose with the change of the seasons.

[Neil Bosdet]

So, mill out a slot using a dovetail type bit, keep much of the undercarriage stuff as structural support, the angle of the slot edges serve to hold the wood insert in
Place. Round the end to match curvature. Have I a good understanding? Mike

Yes. The depth you make your insert is arbitrary. I made mine about 1/4" thick x 1 3/4" wide. I hogged out the bulk of material with a 1/2" carbide spiral upcut bit. Then I put in the 14 degree dovetail bit and increased the depth a smidge. Grooved the edges (wider) and passed over the main area to smooth out the bottom of the finish.

[Mike OMelia]

Yes, I figured that about the major hogging, and finishing with the 14 deg bit. Just wanted to make sure that the depth of the cut was intended to be supported by the stuff underneath.

Again, great idea.

Mike

[Mike OMelia]

Is this concept the same as the Betterly Tru Cut system?

[Rick Lizek]

Is this concept the same as the Betterly Tru Cut system?

It's actually based on the Wood Dynamics system which came before the Betterly Insert. The WD and dovetailed insert was the best ZCI designed but was too pricey and or not marketed well enough. The WD with the dovetailed insert was quicker to swap inserts and better in the long run.

I am amazed at how some folks think having one ZCI is all you need. We would always make up a couple dozen at a time so we would have them for dado blades, moulding heads and such. The idea is to continually swap them out as they wear so one puts the next compatible size in the appropriate application.

One can also fab up a dovetailed insert holder from pieces of plywood, phenolic or what ever instead of a solid piece. The limiting factor is creativity and resources at hand. The WD inser sold for around $125 and was $50 better in cost than the Betterly insert.

[Mike OMelia]

I think I will go the inexpensive phenolic route. The Betterly is expensive, and so are the inserts. One other question: before routing out the slot, should I run the blade up through the ZCI?

[Neil Bosdet]

I don't know why it would matter either way. I don't think I'd bother myself. If you're insert is new you could use it as is for a while and make up the inserts when it gets worn.

[george wilson]

I don't know why the Saw Stop throat plate needed to be made so complicated. I made one for the SS I bought for work. Being a machinist I was able to do so. But it did take a milling machine. Would be MUCH nicer if their throat plates were like most others. Maybe its done so you are forced to buy their stuff? I like just being able to make one out of plywood for my 1964 Dewalt/Clausing table saw.

The dovetailed routed wood replacement insert sounds like a good idea.

[Noah Katz]

I just want a material that I can get a snug fit that won't get tight or loose with the change of the seasons.

Put in a ball plunger or two on the side to spring load it.

I just did a quick calculation to see how much clearance should be allowed; assuming a 20" long throat plate, the differential expansion between cast iron and aluminum for a 25 C temp change is .006".

[Neil Bosdet]

I don't know why the Saw Stop throat plate needed to be made so complicated.

Me too. Some of it seems unnecessary but I think it's to allow the blade to get as high as possible and to allow the blade to angle easily.