Dado Jig modification


johnnie52

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I watched Marc's video on the main page on his dado jig and this is in reply to his query on how to make the jig with the adjusting knobs on the top rather than the bottom of the jig. I didn't see any replies here at the forum, perhaps this idea has been discussed in the guild.

Anyway, this should be rather simple to accomplish. All one has to do is to make the sliding arm wide enough to allow the router plenty of clearance. Attach the screws to the bottom short arm and secure them in place so they do not fall through, cut the adjustment slots in the movable arm and secure with the knobs. The knobs remain in the same spot relative to the cross arms and the adjustable arm is free to move.

Here is a quick sketch of my idea.

dado-jig.jpg

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Maybe I'm missing something.

It seems to me that you need a wide arm to make sure that you have enough clearance between the inside edge of the wide arm and the knobs. But, by putting the slot in the wide arm, you allow the knob to move closer to the inside edge, which eliminates your clearance.

I think I'd put the slot in the cross pieces, so that there was a fixed clearance between the knob and the inside edge of the wide arm.

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This has turned out to be the most popular suggestion for beefing up this jig: using wider rails. But this is the first time someone sketched it up. I think there would still be some details to work out but no doubt, having wider rails should solve the problem. Thanks for posting Johnie!

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Johnnie, I'm in violent agreement! Of course, with a wider rail, the functionality of the jig would be more dependent on it's flatness.

I too had thought that a wider rail ( and a corresponding longer slot and guide bar) would allow both a wider platform to support the router, and the ability to position the locking knobs on the top of the jig. This would allow us to use it on the bench top instead of an overhang. I really like Marc's concept of having the jig independent of the router, and dependent on the bit arrangement.

Marc, question: Do you have any guidance about using a straight side of the jig and a top bearing pattern bit? Thanksunsure.gif

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Just before I saw this video I built a dado jig that is a similar but yet different.

post-336-0-55562600-1298167628_thumb.jpg

I made it to work with a specific router base and bit without a guide bushing as I don't have any.

The fence is not permanently attached to the rails allowing for angled dados. It also lets the whole thing be taken apart for compact storage.

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Just before I saw this video I built a dado jig that is a similar but yet different.

post-336-0-55562600-1298167628_thumb.jpg

I made it to work with a specific router base and bit without a guide bushing as I don't have any.

The fence is not permanently attached to the rails allowing for angled dados. It also lets the whole thing be taken apart for compact storage.

Nice Emm! I think the biggest advantage of Marc's version is that you can dial in the width by using the actual board you plan to house.

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Maybe I'm missing something.

It seems to me that you need a wide arm to make sure that you have enough clearance between the inside edge of the wide arm and the knobs. But, by putting the slot in the wide arm, you allow the knob to move closer to the inside edge, which eliminates your clearance.

I think I'd put the slot in the cross pieces, so that there was a fixed clearance between the knob and the inside edge of the wide arm.

Chip,

The knobs would not move in either direction. They would be attached to the cross arms below the movable guide, not to the movable guide piece. The slots would be in the guide positioned to allow that piece only to move as required for proper width adjustment. Basically its exactly what Marc already made, except the movable part is wide enough to allow the knobs to be located on top of the jig and still give clearance for the router to travel as needed.

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You can do that with mine too. I used it to make the half laps for my boom arm.

Oh yea, I can see that. You just place the router AND the wood to be housed, set the fence and that will give you the exact dimension. Sometimes I'm a bit thick. ;o)

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Marc, question: Do you have any guidance about using a straight side of the jig and a top bearing pattern bit? Thanksunsure.gif

Well I don't know that you can do both, unless you make the jig configurable where both fences can be flipped around so you can access the non-rabbeted face, its going to be a little tough. If you try to run the pattern bit using the rabbeted side, you better have a really stubby pattern bit. Honestly, its probably best to pick a method and stick with it.

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Well I don't know that you can do both, unless you make the jig configurable where both fences can be flipped around so you can access the non-rabbeted face, its going to be a little tough. If you try to run the pattern bit using the rabbeted side, you better have a really stubby pattern bit. Honestly, its probably best to pick a method and stick with it.

Marc, Thanks for the quick reply. Right, one could not do both. I was thinking that since I have a 1/2" pattern bit ( Katana 16509) with the bearing on top, the reach of the bit from the bearing to the end of the cutter is less than 5/8", I could use 3/4" material for the jig, add the hard wood guides, make them straight and square to the jig face, and use the jig like that, without needing the added step of the rabbet.

All of that being said, your design does make more sense, as it provides a more flexible solution to the depth function. Sooooo, I'll try it with the pattern bit initially, and if it works, great! Otherwise, I'll go for back to the drawingboard.....

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This has turned out to be the most popular suggestion for beefing up this jig: using wider rails. But this is the first time someone sketched it up. I think there would still be some details to work out but no doubt, having wider rails should solve the problem. Thanks for posting Johnie!

A wider rail is a good idea for stability of the router, but, would it not be better to make the long slot in the rails you have the bolts in? If you machined a recessed slot, one just wide enough for the bolt with a second recess beneath just wide enough to accept the flat head. This would sit quite happily on the bench. Once the first face is set it should be easy to slide the bolt and the wider face up to your piece and clamp with the knobs well clear of the router.

Just a thought.

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A wider rail is a good idea for stability of the router, but, would it not be better to make the long slot in the rails you have the bolts in? If you machined a recessed slot, one just wide enough for the bolt with a second recess beneath just wide enough to accept the flat head. This would sit quite happily on the bench. Once the first face is set it should be easy to slide the bolt and the wider face up to your piece and clamp with the knobs well clear of the router.

Just a thought.

I do not believe it would work as well. You need some way to capture the flat head of the bolt for the knob so that it will not be able to turn as you tighten the knob. Making it so that the slot is in the rail not only presents the possibility of the bolt turning with the knob, but also makes it necessary to make not only a wider spot for the head but that area must be continued the entire length of travel. It also presents the possibility of the bolt being able to twist in the slot and pull through without holding.

My way keeps the bolt and knob in one spot where the bolt can be held either by the widened area alone or with an epoxy to prevent movement.

Of course as in most things, there are many different ways to accomplish the same thing and its up to the builder which method he/she chooses.

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A wider rail is a good idea for stability of the router, but, would it not be better to make the long slot in the rails you have the bolts in? If you machined a recessed slot, one just wide enough for the bolt with a second recess beneath just wide enough to accept the flat head. This would sit quite happily on the bench. Once the first face is set it should be easy to slide the bolt and the wider face up to your piece and clamp with the knobs well clear of the router.

Just a thought.

Hi (Bonjour) WoodServant,

The idea is a good one to try, but I can tell you from experience with another similar jig, It does what Johnnie said. Keeping the bolt in one place on the jig is an advantage for setting the dado accurately.

Also, Marc, you were right, of course. I did try to use a pattern bit, and found the combination of the thickness of the jig and the reach needed to make the dado prevented me from being able to make a proper cut. Oh Well.........

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  • 3 months later...
  • 1 month later...

Here is my version of the jig:

DSCN1245.jpg

DSCN1246.jpg

You will see that the sides are wider to allow the 'knobs' to be on top. I do not use the guide bush but use the base plate of the router ensuring that I index it from the same side each time. I also use the same cutter in it. It works great and I have used it for a couple of years now without a hitch. It is made out of some plastic laminate I had lying around.

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