Adjustabel width width Zero Clearance Insert

mickyd · Post by **mickyd** » Wed Jan 27, 2010 8:40 am

Has anyone ever designed / made a ZCI where the opening was adjustable? Being a newbie, I don't even know if the concept make sense so if you rolling on the ground, consider the experience of the source.

Does the concept even make sense.I thought of this when reading Gene Howes post where he developed the sacrificial insert.

dusty · Post by **dusty** » Wed Jan 27, 2010 8:47 am

mickyd wrote:Has anyone ever designed / made a ZCI where the opening was adjustable? Being a newbie, I don't even know if the concept make sense so if you rolling on the ground, consider the experience of the source.

Does the concept even make sense.I thought of this when reading Gene Howes post where he developed the sacrificial insert.

I await the responses from the rest of the forum. This is an interesting question. With my very narrow breadth of experience (almost limited to a Shopsmith TS), I see no advantage to a variable width.

I cut all of mine for a thin kerf blade with the quill fully retracted. If I use a full kerf blade, I just sacrifice/dedicate the insert.

I cut multiple inserts when I make them with the idea that they are sacrificial.

mickyd · Post by **mickyd** » Wed Jan 27, 2010 9:14 am

dusty wrote:I await the responses from the rest of the forum. This is an interesting question. With my very narrow breadth of experience (almost limited to a Shopsmith TS), I see no advantage to a variable width.

I cut all of mine for a thin kerf blade with the quill fully retracted. If I use a full kerf blade, I just sacrifice/dedicate the insert.

I cut multiple inserts when I make them with the idea that they are sacrificial.

Maybe I need a better understanding of exactly what is meant by ZCI. I assumed that this meant is regardless of the dado width, the insert would have no space (thus zero clearance) anywhere around the cutter. Since the dado width varies based on how wide it is set up, the insert would either have to be a unique width for each width dado setup OR it would have to be adjustable to accommodate unique widths. Is my assumption correct?

Now I question the gap in the front and back of the dado also which varies based depth of cut.

Now I question why I bought the dado insert yesterday since it is a fixed width / length.

Hope to get clarification on my understanding soon. I must be missing something here.

heathicus · Post by **heathicus** » Wed Jan 27, 2010 9:55 am

Standard inserts are NOT zero clearance. Likewise the dado insert you bought is NOT a zero clearance insert. It simply has a wide enough slot to allow usage of a dado blade. For zero clearance - standard kerf, thin kerf, or dado - you have to make your own. Any changes after that - changing blades, adjusting dado width, etc - can result in your custom ZCI no longer being zero clearance.

I've never seen an insert with an adjustable slot. While it might be possible, the complexity of such a thing would make it impractical. Any time you needed to make a change, you would have to adjust the slot narrower than the blade and then re-cut the slot to maintain/remake the zero clearance. Eventually, you would need to rebuild the ZCI again (or at least part of it).

But I'm a newb too, so someone please correct me if I'm wrong.

shipwright · Post by **shipwright** » Wed Jan 27, 2010 9:57 am

Mike

Use the router. For small pieces like that dados can be dangerous and are always time consuming. use a bit of that time making a simple router table and get it done the easy, fast and accurate way.

Paul M

pennview · Post by **pennview** » Wed Jan 27, 2010 10:14 am

Mickyd, a zero clearance insert (ZCI) refers to an insert that is purpose built for one blade width and is meant to reduce splintering on the bottom of the wood being cut, as the stock is supported on both sides of the blade and right up to the edge of the blade. It also prevents thin cutoffs from falling through the opening and possibly jamming. As Dusty mentioned earlier, you'd need a separate ZCI for a thin kerf blade and another for a standard blade. On the Shopsmith, you need to ensure that you drop the table down over the sawblade in the same place each time to maintain the zero clearance.

If you wanted the support provided by a ZCI for cutting dados, you'd need one for each width. If you get tearout with the dado cutters and a standard dado insert, you might want to give a ZCI a try.

I don't think there is such a thing as an adjustable ZCI, or at least I've never heard of one. Something close thought, is one for a Delta Unisaw (and perhaps others) that accepts a strip of wood that slides into a metal insert and allows you to swap out that strip of wood for each blade you use.

Ed in Tampa · Post by **Ed in Tampa** » Wed Jan 27, 2010 10:18 am

Gene Howe started a new thread that contains pictures of his excellent designed new ZCI prototype
https://forum.shopsmith.com/viewtopic.php?t=5084

foxtrapper · Post by **foxtrapper** » Wed Jan 27, 2010 10:32 am

I can think of some ways to make an adjustable zero clearance insert, but I don't think it would be worthwhile. Having a few home made ones cut to different sizes would be sufficient. Gene's is nice for having a simple to make and replace center strip. For cutting the entire insert it a bit harder. Think I might make up a handful of Gene's design.

For much cutting, a zero clearance is superfluous. When you're whacking 2x4's to length, insert clearance isn't a factor. It's when you're making fine slices and other applications where you really need to support the wood right beside the blade. For many folk, that's not very often.

mickyd · Post by **mickyd** » Wed Jan 27, 2010 10:33 am

shipwright wrote:Mike

Use the router. For small pieces like that dados can be dangerous and are always time consuming. use a bit of that time making a simple router table and get it done the easy, fast and accurate way.

Paul M

Paul - My question wasn't related to my candle lantern project but rather the concept.

After looking at Gene's prototype, I envisioned the center sacrificial piece actually being wider AND being split in half lengthwise with each half having adjusting slots to move them either toward or away from the blade to provide zero clearance. You'd first mount the blade then slide each half inward until you have approximate zero clearance then tighten each half down.

JPG · Post by **JPG** » Wed Jan 27, 2010 11:54 am

mickyd wrote:Paul - My question wasn't related to my candle lantern project but rather the concept.

After looking at Gene's prototype, I envisioned the center sacrificial piece actually being wider AND being split in half lengthwise with each half having adjusting slots to move them either toward or away from the blade to provide zero clearance. You'd first mount the blade then slide each half inward until you have approximate zero clearance then tighten each half down.

As you have previously 'asked', What about varying blade height(depth of cut)? Adjusting to the sides does not resolve the 'length' issue.

IMHO an adjustable zci is probably impractical. Most are made from relatively inexpensive materials(NOT walnut!:rolleyes:).

Often overlooked is the length variation when the depth of cut is altered, as well as the effect of any set the blade may have.

Most of the time a zci is made for a specific project/cut. They are truly expendable(except by Ed in Tampa and Myself - I do not have a wood stove either!).

Having the ability to only change/replace/create the center section is a plus. Not having to match the end radii(radius(es)) each time is a 'time' saver. Gonna have to make one!

Thanks Gene!

My only 'concern' is the structural integrity of the 'bottom'. The blade(s) would also cut a major portion of the 'base.