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ZCI Inserts #1: MDF and Garolite

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Blog entry by Jason Peabody posted 03-25-2014 04:10 AM 730 reads 0 times favorited 6 comments Add to Favorites Watch
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Thought I’d post a few pics of the latest incarnation of ZCI that I made for my Craftsman 113 series table saw. These saws are a little frustrating for someone looking to make his own ZCIs, since it is necessary to rabbet a very thin lip (3/32”) around the outside of the insert for it to rest flush against the table. This is in contrast to most saws nowadays, which use inserts that are simply like extrusions of a basic 2-D shape, easily duplicated with a straight router bit and guide bearing.

I at first tried using plywood for the insert, but I did not have a piece whose flatness could rival that of the steel table of the saw. Perhaps if I’d gotten some baltic birch I would have had an easier time of it.

I then considered making the whole thing out of MDF, but the thought of having such a thin lip made only out of MDF worried me for structural reasons.

Eventually I bought some garolite (phenolic) and used that as the top part to form the thin lip, while using the MDF for the underside of the insert to provide stiffness. I tried gluing and screwing, but it turns out that glue alone (3M spray adhesive) is plenty strong enough to hold the materials together.

I used epoxy underneath to form “shims” in place that would keep the garolite level with the table saw surface.

These inserts worked very well, until the humidity changed and the MDF shrank a bit, causing the insert to bow upwards in the middle. It was enough that I could feel a bit of rocking while cutting small pieces on the saw, since small pieces are mostly registered against the insert and not the table.

The other issue I ran into is that when the insert flexed a bit, it introduced a tiny bit of mismatch between the insert and the table at the ends, so that workpieces (especially small ones) would catch a bit as they transitioned on or off. This did not feel safe like a safe condition.

My next plan is to try making some one-piece versions out of 1/2” thick, UHMW polyethylene. I will post to let everyone know how it goes.





-- When you begin to coast, then you are on the downgrade.



6 comments so far

View lepelerin's profile

lepelerin

335 posts in 1078 days


#1 posted 03-25-2014 06:05 AM

I made mine of 1/2 UHMW, it stay flat and is very strong. I do have a R4512 and the “lip” around the outside is very thin too. I never felt a security issue, Stays strong and secure.

View NDakota's profile

NDakota

34 posts in 299 days


#2 posted 03-25-2014 07:02 AM

I have a old makita with the same small lip and cant find a way to make inserts work. Could you explain what garolite and UHMW are? Thanks

View Roger's profile

Roger

15368 posts in 1557 days


#3 posted 03-25-2014 11:36 PM

Nice going Jason. I used 3/4 mdf on the ones I did. I did cut that rabbit around the top of it on the router table with a straight bit with a bearing. I just kept creeping up on the depth until I got it just right. They seem to be holding up fine. I did use an 8” dado set to begin the initial cut from the bottom to be able to get a 10” blade in there. When I made mine, I didn’t think of taking pics along the way… duhhh me. :(

-- Roger from KY. Work/Play/Travel Safe. Kentuk55@bellsouth.net

View Iamjacob's profile

Iamjacob

8 posts in 1379 days


#4 posted 03-26-2014 12:20 AM

I have an older Ridgid ts2424 that has the same mounting style. I make my ZCIs out of 1/2” thick corian. I stopped by a counter top installer in the area and asked for a scrap sink cutout. It was free and big enough to make like 10 inserts.

The material is plenty rigid not to bend from stuff going across the blade and it taps well so I am able to use the stock leveling feet to get the plate absolutely flat.

It’s dimensionally stable to boot so it doesn’t warp with seasonal changes.

View tomd's profile

tomd

1810 posts in 2523 days


#5 posted 03-26-2014 12:36 AM

I bought some 4/32” hobby aircraft ply and used that. Very strong and if it rises too high a quick light sanding will take it down to 3/32”.

-- Tom D

View dschlic1's profile

dschlic1

184 posts in 723 days


#6 posted 03-26-2014 07:46 PM

I too have a 113 style Craftsman TS. I make my ZCI out of 1/4” tempered hardboard. Very close match for thickness. I just have to shave a small amount off the rear part of the ZCI. I have had no problems so far. Add is a lot easier that routing lips etc.

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