Making throat plates

[gwyneth]

First, thanks to everybody who gave specific advice in the first thread, as well as every person who's ever posted anything about throat plates, especially to Lee for the diagram of the stock throat plate on the Sharkguard site.

Making one when you're at least 65 miles from the nearest one and can't use the saw until you do is an interesting challenge but the diagram has been invaluable.

Before I discovered it, my best effort, with the big circular saw and the All-in-one had been about 3/8" too narrow, although I got the slot perfect. And I didn't have the dimensions when the local hardware store cut two beautiful piece of 'plexiglass'--both 3" wide, one 14" long and one 15" long.

Yesterday, I came sort of close with the 3/8" thick ash plywood and the 18v circular saw.

Today I sighed and pulled out the old little bandsaw with the broken-glued/rebroken-reglued table bracket.

Much to my amazement, the combination of its new Morse blade and using an All-in-one as a fence produced a perfect, straight 2 7/8" rip.

Realizing that the sun, moon, and stars might never again be in such perfect alignment, I ran the ash plywood, some hardboard, the second half of the UHMW cutting board, and some pieces of thin plexiglass through. (I also remembered the wise advice given in several old posts about making a bunch of plates once you have the setups...even better if it may not be repeatable.)

Happily, the #10 countersink/counterbore/pilot hole bit in the drill press is the perfect size for the three factory screws.

The adorable Dremel "router/shaper" table is set up with the microscopic 1/8" router bit for doing the edges (the set of 1/8" shaft bits actually has a 1/8" straight bit in with the cove, roundover, and unbelievably, dovetail bits.)

Here are my questions. I'm going to use one of the plexiglass blanks to make a screw hole template since I was too dumb to trace the throat plate that's somewhere in the Sears system. I can see through it, so I can get the exact locations of where the screws will go.

Do I need to worry about all seven screws or just one set of three (used on the factory throat plate) or one set of four (lower)? I have read and read about throat plates and still don't understand what the set of four is.

Also, though the plexiglass is probably too thin to use by itself, I was wondering if building a plate up of two layers, making pseudo rabbits at each end by cutting the lower layer shorter and using contact cement to stick them together, would be feasible. Or the same technique with a layer of plexiglass and a layer of hardboard?.

After dinner I'm going to attack the screw holes and then bandsaw the blade and guard slots. I am getting cautiously optimistic about achieving something workable.

Thanks again, everyone, it would never be possible without you.

[KomaToast]

Use the 4 hole pattern to hold down each corner.
That's the way the factory 0 throat plates are made.

I use stainless steel 1/4" washers to shim up the throat plate level with the table top being they are thin and I have like 10K+ of them.

Keith

[Stytooner]

Thanks. I would shy away from using plexiglas as a throat plate. It will work fine for a pattern, but not so good on the machine. It's easily cracked and shattered. Polycarbonate is a better choice if you want some transparency.
Any of the hole patterns will work. You have a little more meat when you use the four hole pattern. They require longer screws. The three hole patten will work. If you choose to use the four hole pattern, then the two rear studs that normally catch the clips on the metal throat plate will have to come out.
Good luck with it and let us know if you succeed or not.

[JimD]

I went back to read you first post now so I understand you do not have the stock throat plate to use it to make the zero clearance plate. In that case, I recommend cutting to rough dimensions on a bandsaw and use a plane to get the thickness right and the width right. A router in a router table is a good way to make the rabbets (if you have one).

If you do not have a plane or router table, then the plexiglass throat plate, shimmed up, should at least let you make a better wooden plate - if you are careful. 1/4 plywood shimmed up might be better.

Jim

[mpc]

What about this process:
* get some cardboard, like the backing from a pad of paper or those memo pads left on your front porch by realtors... cut that into the approximate shape of the throat plate opening.
* put screws into the saw opening. Run them down about as far as they're willing to easily go; the heads should be about even with the saw tabletop.
* Place your cardboard template into position, on top of the screws. Line it up with the saw opening and then press it onto the screwheads to leave an impression of them. Now you've got a drilling template. Just remember it's the screw head template, not the screw shank/body!
* Use your bandsaw to rough out a real wood blank, slightly oversized. Use the cardboard template to drill the screw holes. Then see how it fits on the saw, noting where you need to file/trim it.

mpc

[gwyneth]

The new blade is not going on the saw until it has a good throat plate, with slot wide enough for guard and knife.

I now have two plexiglass 'models'. I'm going to stick to the 3 factory screws because they're easier, without a known working throat plate, to control production for. If these test out for saw blade and guard fit, I will then be able to use them to mark screw holes and slot dimensions on the 1/2" UHMW blank and the 3/8" ash plywood plank.

Routing the 1/8" wide side rabbits will be very easy with the 1/8" straight bit for the, ahem, Dremel "router/shaper table" which even has a precision fence and calibrated thingy to adjust height. (How rare to have an appropriate weird tool for a sudden, infrequent task!)

The issue then will be routing the rabbits on the ends and whether to get out and set up the big router (no table yet) or make multiple passes with the 1/8" bit on the Dremel "router/shaper table", which will be set for the appropriate depth, having done the sides.

Seems logical to drill screw holes first, then rout sides and ends, then cut slot on bandsaw.

Thanks to everybody again for helping me get through this.

[JimD]

I route the rabbets first, before drilling holes. The rabbet up the long direction is less than 1/8 wide so your dremel tool should work. It will also work at the end if you are patient, I think. I ususally do this with the saw blade which removes only 1/8 at a time.

To mark the hole position (I use 4 screws), I have screws that I ground to a pointed shape that I put on upside down (unplug the saw first). That allows them to point up. Then I can put the throat plate in position and tap it over each screw and get a nice little mark where to drill. It is too much trouble for one throat plate but I usually make several at one time. I sometimes work too fast but I had repeated trouble getting the holes exactly where I wanted them before trying this method. If you miss, you can alway make the hole a little bigger.

Jim

[steve-norrell]

To mark the hole position (I use 4 screws), I have screws that I ground to a pointed shape that I put on upside down (unplug the saw first). That allows them to point up. Then I can put the throat plate in position and tap it over each screw and get a nice little mark where to drill. It is too much trouble for one throat plate but I usually make several at one time. I sometimes work too fast but I had repeated trouble getting the holes exactly where I wanted them before trying this method. If you miss, you can alway make the hole a little bigger.

Jim

I thought it was a law that you had to get the screw holes a little off during the first several attempts.

Your suggestion about upside down screws is a great one. Thanks.

Regards, Steve

[gwyneth]

Your suggestion about upside down screws is a great one. Thanks.

Indeed it is, and I can think of several other applications where the idea would be handy.

Throat plate project update: Last night, after routing the sides of the 3/8" ash with the Dremel "shaper/router" table, it did one side of the UHMW before conking out. I have no idea what its problem is--wouldn't turn on again for the other side, although it did have sitting a while (no, it wasn't hot). Did the other side once, conked out, hasn't started since. It's a good thing it's the second-string rotary tool, but the first-string one doesn't fit into the precious little router table.

Planed and rasped the UHMW, then did a very nice half lap (i.e., rabbit) on one end with the bandsaw but in the middle of the second end, the broken-glued/rebroken-reglued bandsaw table bracket broke again.

Today I observed that the UHMW plate is about 1/8" too high. The 3/8" ash plywood, in contrast, was completely flush except the ends, which are still not rabbited or half/lapped.

While I was trying to figure out a setup for routing the ash plywood without a router table. A little worried about the rate of tool breakage on the project, I decided to see if the hardboard was thick enough for a counterbore.

With care, it was. I drilled the holes in one piece, trimmed another piece to build up 'rabbits' at ends and sides, slapped a bunch of contact cement on both, and eventually stuck them together. To my amazement, not only did they adhere, they were still bonded after bandsawing the slot, and the lamination fit the table saw pretty well (i.e., flush).

By then it was too late to run power tools to rout the ash plywood. I've left the laminated hardboard plate screwed into the TS to 'set' the shape and am thinking of poly-ing or shellac-ing the raw edges, at least. I don't know how well the slick surface of hardboard takes polyurethane.

I am also seriously thinking about asking some of my sculptor friends about how cardboard works as a substrate for bondo resin. In theory, that would provide a way to make gorgeous throat plates with no power tools. (In my papermaking days, I built up cardboard with other kinds of resin to make serviceable, weight bearing furniture, so the idea may not be as goofy as it sounds.)