Zero Clearance Insert for R4512

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Project by JohnMcClure posted 10-23-2016 11:53 PM 1465 views 1 time favorited 7 comments Add to Favorites Watch

This is my first ZCI for the tablesaw. I started with 1/2” MDF, traced a throat plate and scroll-sawed close to the final shape, leaving about 1/8” extra. Then I used a flushtrim bit on the router table to remove the excess.
The throat of the 4512 has 5 cast iron protrusions of irregular shape and depth, in which are 5 leveling points. I needed the ZCI to clear all the protrusions and to be exactly 0.1” thick above all the leveling points.
Back on the router table, I rabbeted the edge all around to clear most of the obstructions, then removed material more precisely where the leveling points are.

The blade wouldn’t go low enough to clear the ZCI, then turn the saw on, then raise the blade, so I routed out a groove to give me just enough room first.

Two questions for those who have gone before:
-Should I try to reproduce the “safety tab” that’s on the bottom of the factory throat plates (in picture)? Is it really important?

-Do you apply paste wax directly to MDF, or should one shellac it first?

Thanks for looking!

-- I'd rather be a hammer than a nail

7 comments so far

View robscastle's profile


5633 posts in 2446 days

#1 posted 10-24-2016 10:33 AM


Looks like good work to me, The thickness may be a bit on the hefty side.

Now if its a exact fit maybe a finger hole to get it out again, as for applying a finish I would leave it unfinished its a sacrifical item anyway.

-- Regards Rob

View nomercadies's profile


590 posts in 2580 days

#2 posted 10-24-2016 02:03 PM

I saw where a person used car polish on the leveling tabs on the saw, then put dabs of hot glue on the tabs. Before the glue got too soft, he pressed his insert into the opening to the flat level he desired. If he messed up, he just knocked off the hot glue and tried again. Seems like a reasonable way to solve a problem.

I did the double thickness on mine, made two of them while I was at it. I painted mine with some paint I had around. The paint scuffs of at first, but doesn’t transfer onto my projects. I think the paint was a latex also, unusual as it didn’t effect the size with swelling.

I think it has to be finished with something as the moisture might mess with your fit over time.

-- Chance Four "Not Just a Second Chance"

View Ted78's profile


401 posts in 2241 days

#3 posted 10-24-2016 05:19 PM

If you have the shellac handy wax over shellac seems like the way to go. As far as the safety tab, I would just make sure that the insert does not pop up no matter where you push on it from the upper side. Zero clearance inserts can sometimes see saw on the little tabs they sit on top of and cause rather spectacular flinging and mangling of projects, push-sticks and inserts.

On an unrelated note, things flying into mercury filled fluorescent light tubes and raining little pieces of glass down on oneself and the still spinning saw is exciting, but not recommended.

And never mind how I know this…

-- Ted

View HokieKen's profile


7648 posts in 1380 days

#4 posted 10-24-2016 09:02 PM

Regarding the tab, you really just have to decide if the insert is able to pop up or not without it. Personally, I make mine a tight fit so the tab isn’t needed but where you’re levelling points are can have a big effect on it.

Just a FYI for in the future, I put a circular saw blade on my TS to make the initial cut in my ZCIs. The smaller blade gives you the clearance to seat the insert fully then raise the blade into it. Then I put on a 10” blade and raise it up to finish the opening.

-- Kenny, SW VA, Go Hokies!!!

View robscastle's profile


5633 posts in 2446 days

#5 posted 10-24-2016 09:46 PM

Opps,... I didnt consider leaving the ZCI in permamently, as I have a few blanks made and cut clearances to suit at the time the job I am doing then remove them, and they get disposed of.

So if this is in fact a permanent installation the case I agree with sealing it and fixing in place permanently along with modifying to be able to refit your splitter and saw guard.

We dont need a repeat of Teds star shower in the workshop

You can do your drop saw as well.
it then provides an exact track as to where the blade will cut

As you can see it must be permanently attached.
The clearance at the back can be closed up as well.

Just screw a continious piece straight across.
Then carefully lower the saw running to cut the clearance.
This stops little offcuts scaring you and shows exactly where the blade will cut.

-- Regards Rob

View woodbutcherbynight's profile


5837 posts in 2650 days

#6 posted 10-25-2016 01:57 AM

I finished mine in Brilliant Red, oil based paint. reminds me to be careful, protects the wood, etc etc. Do let it dry in sun for a week to keep from rubbing off on the wood you cut. The safety tab I would duplicate, can’t hurt.

+1 HokieKen saw that tip on youtube before I made mine, was a breeze to get done one time.

-- Live to tell the stories, they sound better that way.

View Matt1475's profile


59 posts in 1738 days

#7 posted 10-26-2016 05:37 PM

I have an r4512 as well. For my throat plate i put a tape measure clip on the end. It squeezes pretty tight, and because the cast iron top is chamfered behind the throat plate, it allows for the tab to not interfere. Works really well for me

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