# Dado jig questions



## HawaiiBob (Dec 2, 2013)

I am a tad confused regarding the making of a dado jig.

I watched a vid on The Wood Whisperer, where Marc made a jig with one fixed side and one adjustable side that relied on the use of a particular size of straight bit and a guide bushing.

139 – Exact-Width Dado Jig | The Wood Whisperer

But also on this site, on a different project, he uses a parallelogram jig that uses a pattern bit and doubles as a cove cutting guide for the table saw.

http://www.thewoodwhisperer.com/videos/weekend-wall-shelf/

To my questions, which style of jig would be better (if at all)?

The jig in the first link has a hardwood facing on the inside, would this be better even with a pattern bit rather than the bearing running on the edge of ply?

I am leaning towards the idea of a jig that can use ANY size pattern bit rather than being stuck with a certain size bushing/bit.

Maybe a combination of the two?

What are you using?
TIA


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## jw2170 (Jan 24, 2008)

Bob, one is for making dados, one is for making coves ONLY.

If you are going to cut dados, make the dado jig....

http://www.routerforums.com/jigs-fixtures/30181-can-man-have-too-many-jigs.html


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## HawaiiBob (Dec 2, 2013)

Thanks James, but the cove jig is what was used in the project to cut dados…not only for coves.

Please look at the edited 2nd link.


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## FreeTime (Dec 2, 2012)

Bob,

I guess I would lean towards the first one. I’m not sure what cutting lengths are available with top mounted bearing / pattern bits and initially I thought this would seem to limit the depth of cut to the thickness of the jig but maybe not. For deeper cuts, the dado itself would be the guide after the first pass but you won’t be able to make a shallow cut with a longer bit.

I found similar plans for an exact width dado jig that was constructed out of ¼” hardboard that used the router base against a top “rail” as the guide / bushing (no bushings, no bearings). The positive side - I didn’t lose too much on cutting height. Having just finished quite a few dados on a recent bookcase project, I used most of the available height on a 2” bit cutting through (notching) the 6/4 frame. But unfortunately the constraint is the same – I need to use it with the same diameter bit and router (and the baseplate needs to be centered). I did not find any more of a universal design when I looked.

The jig I made was 24” inches long – the length only got in the way. The adjustment knobs are on the bottom on mine – another marginal design. I’m not sure why it was designed that way – clearance for the router perhaps. The setup worked ok if the work piece was mounted on bench cookies and if the jig could span the piece but I’m finding other uses for it (slots, etc) that I wish the configuration was slightly different.

The parallelogram configuration would seem to have the distinct advantage of forcing an even width dado cut for the length of the jig. I did get burned initially using the "adjust at each end" jig configuration ... if you set the thickness of the dado using a board something less than half the length of jig, it is hard to garantee parallel sides which becomes noticeable if you are not making all the cuts in the same area of the jig.


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## jw2170 (Jan 24, 2008)

Marc has used his jig for a second purpose, which is good to see. Some jigs are like that.

One jig uses a guide bush and the other uses a bearing guided bit.

As he said in the video, you could simply clamp two straight pieces of timber to the work piece.

Having a jig designed to use a specific patter bit or guide bush/cutter combination is no issue. Many dovetail jigs are very specific.

You appear to be leaning toward the "cove" jig, so I would make that.

You could also make the dado jig to use any bearing guided cutter, not a guide bush.

I prefer guide bushes....


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## HawaiiBob (Dec 2, 2013)

Not leaning either way at the moment, but looking for the most versatility in whatever jig to make.


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## MT Stringer (Aug 15, 2012)

I made a jig similar to his only my knobs are on top. Much easier to use. You can use the bushing or simply use a flush trim pattern bit. Set your boards at the desired width and run the pattern bit around the sides. Length stop blocks may be needed.


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## neville9999 (Jul 22, 2010)

Bob this question has been asked a few times, if you have a jig where the pilot guide fits into a groove snugly then you can run a groove, now the grove will not be the thickness of your material so rebate the underside of the, shall we say shelf so that what is left will fit into the groove, there is a detail on my thread called, Grooving and Tennoning Joint Construction so read that and have a look at the dado detail and you will see that if you do the dado's that way then you don't need an adjustable dado jig. NGM


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## skyrat (May 26, 2013)

I made the exact dado jig and it works as as advertised. Make perfect dadoes. I made mine a little longer so it could handle longer dadoes. Over all I am very happy with the results with out a lot of fussy test cuts.


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## Quillman (Aug 16, 2010)

"I am leaning towards the idea of a jig that can use ANY size pattern bit rather than being stuck with a certain size bushing/bit."
****************************************
Facility with algebra I will show that (nearly) any collar, and any cutter* whose diameter <the dado width can be used to produce any practical width dado. Clearly the cutter must fit through the collar, right?

I use 2 templets square to the front edge of the work.
The gap between them determines the net dado width.

The gap for a dado = N is = 1 collar diameter + (Collar diameter - cutter diameter). That is for an exact fit.
I'd add a few .001's for a slip (no-hammer) fit.
The gap is set precisely with adjustable parallels.
(*not a pattern bit but a bearing-less straight bit.)
Routs everyday!


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## Dejure (Jul 27, 2009)

I just posted my jig, if it will help. Here is the location: 

http://www.routerforums.com/jigs-fixtures/44539-kellys-new-router-jig.html#post365366


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## Dejure (Jul 27, 2009)

*I Believe It's the Best Dado Jig Out There*

In the video, he mentions a template, but that would throw off the "exact width" claim, unless you jump through the hoops of rabbiting, as set out in the video, for a specific template, which you do have to use each time. A pattern bit, on the other hand, would give you the exact width of the opening he set up with the piece he dropped into the jig. As long as the pattern bit is smaller than the opening, you can use any size you want.

If you are going to build a dado jig, look at mine. I have gotten no feed back on it at all, but I think you'll be glad you went that route.

(http://www.routerforums.com/jigs-fixtures/44539-kellys-new-router-jig.html)

It, is a "what you see is what you get," but does not require any clamps. Using it, I can cut the dados for a six foot shelf in under fifteen minutes, after initial set up, which is done the same way as this one. Among the key differences is a front clamp and the free floating back.

[SIDE NOTE] I missed details because, though I have high speed, I have an old system with only a meg of ram and so many "geniuses" want to load every page with videos, it slows my system to a crawl missed part of the video trying to follow the jerky flow of things. Grumble, gripe, moan.....



HawaiiBob said:


> I am a tad confused regarding the making of a dado jig.
> 
> I watched a vid on The Wood Whisperer, where Marc made a jig with one fixed side and one adjustable side that relied on the use of a particular size of straight bit and a guide bushing.
> 
> ...


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