Zero Clearance Insert with Riving Knife - Woodworking Talk - Woodworkers Forum
 
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post #1 of 9 Old 09-11-2020, 12:08 PM Thread Starter
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Zero Clearance Insert with Riving Knife

In another thread, I'm thinking of adding a riving knife to my old saw.

Now I'm wondering, how would I cut a zero clearance slot in the insert? Do I cut from the back end and then drill and pin the two sides of the cut crosswise to re-inforce them? Could I fill the back part of the slot with epoxy (not sure epoxy would even bond to phenolic)?

How have you solved the problem?

BruceT
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post #2 of 9 Old 09-11-2020, 12:42 PM
where's my table saw?
 
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I just raise the blade into the insert .....

I make the insert, and level it flush all around. Using the blade I intend to use with the insert lowered all the way down and the fence locked down over the far right side of the insert, out of the blade path, slowly crank the blade up under power. It will be exactly a "zero clearance" insert. You can raise it up as far as you need it for now OR all the way up for future "full depth" cuts.



The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #3 of 9 Old 09-11-2020, 02:42 PM
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I needed riving knife slots in homemade inserts and scratched my head on the same problem. The solution I figured out is:

RIVING KNIFE SLOT CUTTING PROCEDURE

0. Unplug the saw as appropriate for safety.

CREATE THE ZERO CLEARANCE SLOT FIRST:
1. Remove or lower the riving knife out of the way.
2. Lower the blade below the table.
3. Place the new insert over the hole.
4. Clamp a scrap 2x4 on both ends across the saw table to hold down the new insert.
NOTE: You can use the rip fence, but be sure it doesn't cover where the slot will be.
5. Power on the saw, and raise the blade to cut the zero clearance blade slot in the new insert.
6. Lower the blade completely.

EXTEND THE ZERO CLEARANCE SLOT FOR THE RIVING KNIFE:
7. Remove the new insert.
8. Install an old insert. Any old insert will do.
9. Raise the blade above the table just a little bit.
10. Take the new insert and place on top of the old insert, with the slot over the slightly raised blade. 11. Move the new insert forward with the blade still engaged in the slot.
12. Clamp the new insert down with the 2x4.
13. Lower the blade.
14. Power on the saw and raise the blade to extend the slot backwards in alignment with the existing zero clearance slot.
15. Install the riving knife and test to see if it can raise it through the extended slot.
16. If yes, you're done. If no, then repeat steps 9-15 until yes.

Note: On some saws, the slot for the riving knife cuts through the back of the insert. That's how they are.

Here is an earlier solution that I didn't like as well.

ALTERNATE PROCEDURE:
1a. Create the zero clearance slot as described in steps 1-6 above.
2a. Remove the new insert.
3a. Install an old insert. Any old insert will do.
4a. Raise the blade above the table just a little bit.
5a. Take the new insert and place on top of the old insert, with the slot over the slightly raised blade.
6a. Bring the rip fence so that it touches the right side of the new insert.
7a. Carefully make a stopped rip cut through the back of the new insert, to create the riving knife slot. Done.
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post #4 of 9 Old 09-11-2020, 04:29 PM Thread Starter
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That's how I did my ZCI, but would not work with a riving knife in place.

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post #5 of 9 Old 09-11-2020, 04:54 PM
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Major typo here ......

Quote:
Originally Posted by woodnthings View Post
I make the insert, and level it flush all around. Using the blade I intend to use with the (insert) blade lowered all the way down and the fence locked down over the far right side of the insert, out of the blade path, slowly crank the blade up under power. It will be exactly a "zero clearance" insert. You can raise it up as far as you need it for now OR all the way up for future "full depth" cuts.
You probably can't do it with the riving knife in the saw.
I would also be leary of running the insert along the fence with a rounded end as the leading edge unless I had the insert attached to a longer straight board.

A safer way to do this is to extend the ZCI slot with pencil lines and saw the slot on the end for the riving knife with a bandsaw or hand saw. You want just a smidge more kerf width than the ZCI anyway to allow free movement up and down.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #6 of 9 Old 09-12-2020, 02:03 AM Thread Starter
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Hand saw, maybe a jigsaw, but no way with a bandsaw.

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post #7 of 9 Old 09-18-2020, 05:46 PM Thread Starter
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Shop-made is an interesting idea and I have lots of scrap baltic birch plywood. I could saw right through the end and then glue in a spacer to fill the back gap.

When you make an insert, how do you level it? Phenolic ready-mades come with leveling screws.

BruceT

Last edited by brucet999; 09-18-2020 at 05:49 PM.
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post #8 of 9 Old 09-18-2020, 07:03 PM
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Just use a coarse thread tap

Baltic Birch has close enough layers so it will tap just fine for a small set screw in 10-24 or 1/4" X 20 TPI.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #9 of 9 Old 09-19-2020, 12:36 AM Thread Starter
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Quote:
Originally Posted by woodnthings View Post
Baltic Birch has close enough layers so it will tap just fine for a small set screw in 10-24 or 1/4" X 20 TPI.
And do you find with a BB insert the stock slides easily? Maybe a couple of coats of poly to make it slick?

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