zero clearance insert start/finish blade

[FINER9998]

when making a ZCI for ridgid table saws, is there a consensus about finishing the blade opening cut in the ZCI with the same blade that starts it (usually one blade of a stack dado set) or should the opening cut be started with the single dado blade and finished with whatever 10" blade is uaually in the saw? comments appreciated.

[cpw]

when making a ZCI for ridgid table saws, is there a consensus about finishing the blade opening cut in the ZCI with the same blade that starts it (usually one blade of a stack dado set) or should the opening cut be started with the single dado blade and finished with whatever 10" blade is uaually in the saw? comments appreciated.

You should use the blade that you are going to use with that particular insert. If you finish it with the outer blade of your dado set, you'll likely create an opening that is too wide for a regular blade and leave a small gap which is undesirable.

[BadgerDave]

One of the primary purposes of a ZCI is to customize the insert to fit a particular blade so yes, finish off cutting the opening with the blade you'll be using with the insert.

[FINER9998]

and for those who have used MDF for ZCI or any other shop application, what type of finish have you used to extend the useful life of your MDF jig, fixture or other shop application??

[TheChucker]

and for those who have used MDF for ZCI or any other shop application, what type of finish have you used to extend the useful life of your MDF jig, fixture or other shop application??

I made several ZCI's for my R4511 out of 1/2" mdf. I put a couple coats of primer on each and two coats of spray on polyurethane. They're holding up really well for me.

[FINER9998]

what did you use for primer?

[TheChucker]

I used some oil based Kilz primer. The water based primer could potentially have an adverse effect on mdf.

After each coat dried, I sanded it down smooth to get rid of any rough spots.

[FINER9998]

would that be the same type of kilz that one would use to prime problem walls and ceilings? and regarding the kerf cut in the insert, i understand that it should be made with the blade that will be used with that insert. but how high should the blade be elevated when making the kerf cut? the full height of the blade or should there be inserts for a given blade with differing "height" cuts ( which determines the length of the cut in the insert, assuming that teh insert does not have a built in splitter and that the kerf cut in the insert was made by raising the blade up into the uncut ZCI. e.g., for 1/2", 3/4", 1", etc. material)

[rofl]

If you can afford, or keep up with, ZCIs for every possible blade height in a variety of possible blades more power to you.

I just match them to blade width and live with the rest of it.

[Bob D.]

One of the primary purposes of a ZCI is to customize the insert to fit a particular blade so yes, finish off cutting the opening with the blade you'll be using with the insert.

Agree with Dave, cpw, and others. It's also helpful to label the ZCIs with the balde they were married up with. Just use a sharpie and mark the blade on the underside (or topside if you're not fussy). This is why so many say to make your own. You need about a half dozen or so to be covered. I have two for my better blades, one at 90° and another at 45°.

[cpw]

would that be the same type of kilz that one would use to prime problem walls and ceilings? and regarding the kerf cut in the insert, i understand that it should be made with the blade that will be used with that insert. but how high should the blade be elevated when making the kerf cut? the full height of the blade or should there be inserts for a given blade with differing "height" cuts ( which determines the length of the cut in the insert, assuming that teh insert does not have a built in splitter and that the kerf cut in the insert was made by raising the blade up into the uncut ZCI. e.g., for 1/2", 3/4", 1", etc. material)

I wouldn't raise it up until I needed to, but eventually it will get cut at the full height.

[hewood]

Most 10" saws don't drop a 10" blade low enough to start the kerf, so you typically need to use a 7" or 8" blade to start, but once you've cleared enough kerf depth to accommodate a 10" blade, use the blade that'll be in the saw so you get your "zero clearance"....hopefully it's a real nice blade! ;)

[formware]

Agree with Dave, cpw, and others. It's also helpful to label the ZCIs with the balde they were married up with. Just use a sharpie and mark the blade on the underside (or topside if you're not fussy). This is why so many say to make your own. You need about a half dozen or so to be covered. I have two for my better blades, one at 90° and another at 45°.
I'm about to make some ZCIs. I understand I will fasten it into place and raise the blade. But how do you make one for a 45 degree cut??? When you raise the blade you'll wind up making a very wide cut, won't you?

[rofl]

I'm about to make some ZCIs. I understand I will fasten it into place and raise the blade. But how do you make one for a 45 degree cut??? When you raise the blade you'll wind up making a very wide cut, won't you?
If you only intend to use it for 45s then it will be a skinny cut also.

If you intend to use it for a wide range of angle then it will no longer be a ZCI

[Gofor]

I'm about to make some ZCIs. I understand I will fasten it into place and raise the blade. But how do you make one for a 45 degree cut??? When you raise the blade you'll wind up making a very wide cut, won't you?

Make sure the bevel is set to the angle you want (ex: 45 degrees) BEFORE you raise it through the new insert. The blade will follow the angle, giving a ZCI. Trying to move the bevel adjustment with the blade up through the insert will result in a lot of bad things happening!!

Go

[3rdtime]

I have used MDF ZCI's for years on several different saws, and never put a finish on any of them. They have always held up very well. As to making the kerf the full height of the blade, this can help if you are doing a quick or non repetative dado cut. You just line up your pencil/scribe line with the side of the kerf and you're good to go.

[3rdtime]

Most 10" saws don't drop a 10" blade low enough to start the kerf, so you typically need to use a 7" or 8" blade to start, but once you've cleared enough kerf depth to accommodate a 10" blade, use the blade that'll be in the saw so you get your "zero clearance"....hopefully it's a real nice blade! ;)

Another way to do this is by routing a narrow groove deep enough to clear your 10" blade in the bottom of the ZCI along the blade position. Usually a 1/4" deep is enough clearance. Then you can mount your ZCI using the correct blade and just run it up through to make the kerf slot.

[carbonBased]

Another way to do this is by routing a narrow groove deep enough to clear your 10" blade in the bottom of the ZCI along the blade position. Usually a 1/4" deep is enough clearance. Then you can mount your ZCI using the correct blade and just run it up through to make the kerf slot.

Yep; I actually make my ZCI's out of two pieces of 1/4" hardboard. The lower half has the rear locking tab in it, and a hole around where the blade will raise. When glued to the top half, I've got a perfectly sized locking tab, and a 1/4" recess for a 10" blade... works pretty well (I do generally have to sand down the bottom half by tiny amount (maybe 1/16th..?) to ensure it's perfectly flush, but otherwise it's a perfect fit.

--Jeff