ZCI design question

[cham-ed]

To be a spoil sport,another solution. Fastcap makes a thick plastic tape for this problem. You lower the blade, tape over the normal opening, then raise the blade. It forms a perfect size slot. I haven't used it much on the saw but with my band saw. I cut a lot of pieces that have small cut offs the fall into the opening in the band saw hole and jamb. Of course with the band saw you must cut a slot into it first.

[benush26]

Your not being a spoil sport!

I have the FastCap strips and while they work well on my miter saw, they did not work well when I applied a strip to the SS table saw insert. I suspect two reasons-
First is the movement of the wood aka how wood is cut on that style of saw. On the miter saw the strip has little if any friction of the wood sliding on it, where as the table saw is constant friction on the strip.
Second is that thickness of the strip. On the miter saw it is negligible but when I tried it on the insert it stuck above the table so it caught the leading edge of the wood. That happened enough that if finally peeled up. On my miter saw (hitachi), the insert is actually below the level of the wings/ outriggers?? enough so the yellow "tape" makes all surfaces level.

For the miter saw it is a fantastic addition. On the table saw, not so much.

The one thing I do not like about the strips is they keep their "rolled up in packaging set" long after they are out of their package. Finally ended up placing the strip between two piece of MDF and leaving there for a couple weeks to get it flat.

Be well,
Ben

[dusty]

Ben, at the risk of being accused of steal ideas, I want you to know that I too am working on a ZCI redesign.

I would like to have a ZCI that can be changed out without using the screws to hold it in place. If the table was steel this would be a snap; magnets would work. But it is not. That, however, does not mean that magnets are out.

The answer is not on the top side of the table. You need to explore this from the underside.

It would also be nice to have incorporated something along the lines of what reible was doing; a replaceable strip that gets exchanged to renew the ZCI effect.

[reible]

Please keep in mind that if something were to go wrong what are the outcomes? A blade hitting a magnet or other object and having a larger hole to fly up and out of does come to mind. Remember the safety first thing.

Ed

[dusty]

Please keep in mind that if something were to go wrong what are the outcomes? A blade hitting a magnet or other object and having a larger hole to fly up and out of does come to mind. Remember the safety first thing.

Ed

Care will be taken. I have already spent more time in the hospital than any one person should. Caution will be exercised.

[benush26]

Here is a dado insert where the width of the opening has stayed the same, however I lengthened it to allow 10" blades. The lines about 3/4" shy of the opening ends is about where a 10" blade would strike. Anything past that should be safe from contact (note that the opening for the upper blade guard still needs some material removed)

IMG_0283.JPG (197.46 KiB) Viewed 8428 times

One the backside you can see where i will drill and tap from the sides. By using 3/4" length set screws it will cover the gap and still have a bit on the other side, but nothing that should interfere with the lower guard.

IMG_0284.JPG (200.88 KiB) Viewed 8428 times

What I had originally intended to do was epoxy or braze brass strips or pieces across the ends then drill a hole where the black dot is and use that to attach the ZCI.

IMG_0285.JPG (212.2 KiB) Viewed 8428 times

What you may be able to do is substitute a steel strip (how you attach it?? epoxy maybe or bend extra around the sides and attach to the ribs ). That would allow you to use a magnet embedded in the ZCI.
That will necessitate a precise thickness of ZCI.

I abandon the brass pieces that bridged the ribs for two reasons. First, they seemed to interfere with part of the lower saw guard (though a different placement may have eliminated that - I was first setting them as far towards the end as I could for support adn to keep the ZCI from dropping though), the second was I wanted to used many different materials for a ZCI without worrying how precise they were in thickness.

Hope this helps with your brain storming!!

With the set screws, I can cut a rectangle the width of that opening in a material whether it be MDF, cutting board or UHMW, turn the insert upside down, place the ZCI in it, tighten the screws and be up and running.

Be well,
Ben

[JPG]

This scares me and I am NOT a timid person!

[benush26]

So other than not doing it at all what would alleviate a portion of your fears?

Usually you have a specific and full description of why something will or will not succeed and I have come to trust those. Just that it scares you without any further explanation actually puzzles me. Care to clarify or is it a gut instinct?

Would you feel less fearful if I explained that I had full intent to use the setscrews to mark the side of the ZCI and then drill a hole to better hold the tip of the screw (say 1/8" deep?) because that is one of my thoughts so I don't have ZCI chunks flying around the room.

I will explain that I have less fear and trepidation but that is with the hope that the upper saw guard will take the brunt of any eruptions (or so I believe). Also if the perimeter dimension is a very close tolerance, I think that the insert itself will help to keep the ZCI from moving. If I am wrong. Oops - There goes another rubber tree plant!

I promise that initial tests will be done with safety gear and redundancy of said gear!

If your fears are more aimed at the plan I abandon with the brackets or whatever to cradle the ZCI..... let's just say I'm not certain they would be safe. And would echo your trepidation. I also figure Dusty would see the error of MY ways and find a much more realistic and reasonable direction.

I'm still digging out the garage so it will be weeks before I get to try this. however it I am absent from this forum with my pithy, urbane and occasionally maudlin comments - say the entire month of July, you might send get well cards to my local hospital.

Thanks for the concern JPG. It is truly appreciated!

Be well,
Ben

[JPG]

One of my concerns was the brazing of brass to aluminum. Not sure that works. Glad you abandoned that. Perhaps the side set screws clamping the brass pieces would work - if done precisely and loc-tite used.

The 3/4" set screws tapped into the very thin rib is not going to be very sturdy. The 3/4" length allows a great amount of torsion.
If they were more like 1/4 or 5/16 I would think would be more successful.

The 1/8" 'dimple' for the screws to interface to would help assuming the 1/8" begins very close to the rib. That would require either a rabbet or greater width of the dado slot.

There is not an ability to lock the setscrews(jam nut etc.) so they would have an ability to loosen due to vibration.

As I see this, your intent is to use the width of the dado slot as an area for the ZCI to be inserted. That is reasonable as long as the durability of the insert is adequate to preclude it disintegrating. MDF is likely a poor choice.

Controlling the height of the insert above(equal to) the dado insert is I think missing unless drilling/tapping/dimpling are done very precisely.

I like the brass pieces to support the ZCI better since they provide vertical support with greater strength. The set screws remain a concern, but locking them would alleviate that.

Guess my reaction was it just seems less robust than I would like.

I am not timid, but not foolhardy either.