ZCI design question

[benush26]

I've been reading Dusty's posts but rather than hijack one of the threads I thought I'd start this one which "sort of" fits, but just to be on the etiquette safe side....

Why, when making a ZCI is it necessary to allow just the blade width (kerf) to come through for the entire length of exposed blade?

Would it not be just as effective is the kerf cut went only as far as a point even with the arbor opening[half the blade diameter]?

If the point is to reduce tear out, none is occurring after the initial teeth contact. If you are trying to prevent narrow pieces from falling down on either side of the blade. unless the piece is REALLY short (less than the diameter of the blade), wouldn't the support only need to be as far as the mid line of the saw blade so as you push it through the other side of the throat would keep it from dropping.

As far as dust control.... and I am REALLY spitballing here... Would the extra opening (aka what exists now for the standard insert or even more) be better at causing the dust coming out of the blade gullets to stay in the lower area? I ask this because I "think" that the narrower opening of the back of the ZCI might actually cause more of a vacuum action as it pulls the from the back of the blades rotation, therefore causing the dust to stay in the gullet longer (another few revolution ? hundreds of revolutions??) before it is expelled or pushed out by more dust?? Which I would think is causing less effective dust control. Yep, just spitballing, but I am curious.

Why am I curious?? Because I think I have my dado insert modified enough (aka cut the heck out of it ) so I can make rectangular drop in ZCIs and am wondering if I can just have the kerf width {blade or dado} at the front half and widen out the rear (which would make the upper guard easier to accommodate) [[Sorry but as I was playing with this drawing I forgot to extend the existing removed area as far back as the upper saw guard but in theory that opening would go back far enough to accommodate the guard attachment. ]]

Okay, I will go with "it is just easier to plunge the blade into an insert and not fiddle with anything more, however, if I can... I would just place the ZCI in the leading edge of the opening and let the back end be a larger opening.

partzci.jpg (16.93 KiB) Viewed 11950 times

As I think of it I am trying to get all the engineers, mentors, gurus and forward thinkers in the group to come up with all the faults in my design before I do any more work!!

Anyway, if anyone of the brain trust wants to weigh in....

Be well,
Ben

[masonsailor2]

It would probably work. Try it and let us know. How are you adhering the ZCI material to the dado insert ?
Paul

[reible]

Well I'm sure I would not want to go this way.

Several points, think cross cutting and the ends you don't want falling in.... even ripping shorter lengths where the rip is thin and the size is less then "x" will/could tip in.

Huge amounts of saw dust comes up with the blade, zci on the back side cuts down on some of it.

A regular zci is really easy to make and is pretty well established practice.

I'm made a table insert with inserts but it was a lot of work.

See:

http://www.shopsmith.com/ss_forum/gener ... 16607.html

I believe someone else here also has a design like this as well.

Ed

[dusty]

I think you could make this work but I don't believe you will be happy with the final results. Yes, you will have minimized tearout (the primary function of a ZCI) but I believe you will be very unhappy with the dust that comes through that larger than necessary hole. I am also concerned about how secure that insert will be. How do you plan to attach the "half insert"?

I have toyed with an insert that requires no screws but have abandoned that for this same reason.

[benush26]

Thanks for the input.

I had looked at Ed's dovetail system a while back and it did cover most of the bases I wanted, (no accommodation for the upper saw guard but a simple use of a router slot made in it, which would be no big deal), but I wanted to use an existing SS insert. modified. Why, I don't really know , just thought it would be an easier modification or maybe look more factory?? Who the heck knows what goes on in my mind. I'm even scared to go exploring in there!!

Regarding how the ZCI is held in place....
(abandoned idea number one??)
I'd first thought of adhering brass pieces (epoxy, brazing ??) to the rim that protrudes on the bottom of the factory insert. they would be just long enough to hold the ZCI to keep it from falling through and without protruding around the blade space, then drilling a hole in each that I could use to screw the underside of the ZCI to keep it from popping out, but that got to be too fiddly.

**[[[First please excuse using the 500 insert but I could not quickly find a picture of the underside of a 510/520 plus I really don't have a good idea of where my prototype is hidden in the garage ]]**
My new thought is to drill 4 holes into the side of the ridge on the bottom (two on each side front area and near the middle (or rear if I use a fuller length insert), tap them and use set screws to hold the ZCI in place but still allow easy removal. I will still probably do that, but make the inserts of various lengths to see what kind of dust storm I create. If I turn the insert upside down, then set the ZCI within the open space of the insert to keep them flush and use set screws with points, I think it should keep it in place.

The green is where I would drill and tap. There will be a gap between the side of the ridge and the ZCI. Not happy about that, but trying to not have to do anything like a mod to the ZCI before a blade makes its first cut.

insert.jpg (10.43 KiB) Viewed 11856 times

Still tight on garage space and no cousin in sight to help clean up the friggin mess he made let alone start on the new space!! , but I keep believing. I still have jigs and things to make, but no idea where the crap weasel put anything so I can't even start!! Oh well! All I can really do is laugh.

Thanks for the input, insight and ideas. When I get it going I'll post the various outcomes. If you have more ideas, keep them coming!!!

Be well,
Ben

[beeg]

Seems to me that just using a regular ZCI wood be MUCH SIMPLER.

[dusty]

Seems to me that just using a regular ZCI wood be MUCH SIMPLER.

Why does everyone look for "what is simpler". Is no one else into mental challenges?

[jsburger]

Seems to me that just using a regular ZCI wood be MUCH SIMPLER.

Why does everyone look for "what is simpler". Is no one else into mental challenges?

[JPG]

Easier (as in less effort) might be a more accurate term.

[jsburger]

Easier (as in less effort) might be a more accurate term.

Yes, but Dusty likes a challenge once in a while as do I and you also I suspect. Of course everything does not need to be a challenge.