Dovetail Bits and their Sweet Spot

[Johnnyy Johnson]

I just bought a Rockler Dovetail jig. I did not have any trouble learning to do half blinds and through DT's. What I don't understand is the mystery around the depth setting for the bit on the H blinds. In my case it is 9/16". Since I cut the tails and the pins at the same time I want a larger DT. Lowering the bit to get the better looking tails will not work...Hence, the highten to tighten. It will not work. I hope someone can in simple terms solve this mystery for me. Do all dovetail bits have a magic number in the depth setting to get it in the sweet spot?

Thanks
Johnny

[Tom M King]

The number you're looking for is "several". That is....several test pieces until you get it right. That's why I have dedicated routers to my dovetail jigs. One has made probably 25 sets of kitchen and bath drawers in as many years, and I've never touched the router since I got it right. I have a digital depth gauge now, that would make repeating settings a lot easier than it used to be. I do have a list of settings that work for different things in a router box with the router, since having the digital depth gauge. It does work fine.

[Johnnyy Johnson]

Thanks Tom...But that still does not explain why each bit has a sweet spot for adjustment. I have 4 routers, 1 on a table and 3 for this stuff. I am just hoping someone can explain why a bit has to be adj. on the money to make a great fit. It's a mystery to me about the depth setting on half blinds to get them to work. If a length and degree can be set to a chart...I would really like to see. Someone please help.
Thanks
JJ

[Steve Wurster]

These DT jigs have fixed spacing. If you expose more of the bit then the part where its narrow section impacts the wood would be narrower compared to when the bit is at its "sweet spot". This would require different spacing on the other board, but you can't do that with these jigs. At least I think that's the answer.

[Lee Schierer]

I found the same thing with my Rockler jig. I used to have a lot of trial and error pieces getting the fit right. I tried using my digital calipers to get a reading for the proper height setting, but it was hard to get good readings. Last year I asked Santa for a Wixey™ Mini Digital Height Gauge and he came through for me. Now setting the depth of cut on the dovetail jig, dadoes, etc, is easy and repeatable.

[Pat Barry]

Do you use the dovetail bit with a collar on your router or with a guide bearing? I use the collar. My bit is 1/4" shank. The collar vs the opening size on the template determines the width / size of the dovetail. If you have a bearing and want a wider dovetail then you should try and switch to a smaller bearing so the bit can move a bit laterally in each template slot. DOes this make sense? I just used my Rockler jig today to make 8 sets of half blind dovetails.

[Johnnyy Johnson]

Hi Ted..Do you have a link to a site wher i can See the bit and collar?
Thanks
Johnny

[Lee Schierer]

Do you use the dovetail bit with a collar on your router or with a guide bearing? I use the collar. My bit is 1/4" shank. The collar vs the opening size on the template determines the width / size of the dovetail. If you have a bearing and want a wider dovetail then you should try and switch to a smaller bearing so the bit can move a bit laterally in each template slot. DOes this make sense? I just used my Rockler jig today to make 8 sets of half blind dovetails.

I use a bushing with my Rockler jig and a 1/4" shank bit. What the OP wants is dovetails with longer tails that approach through dovetails, which isn't possible with the Rockler jig. You would need a larger diameter cutter (not talking shank diameter) to get taller tails. So far all the bits I've tried have nearly the same diameter and give you the same half blind dovetails. There is one height setting (depth of cut) that gives you a it that isn't too loose or too tight.

[Steve Wurster]

Hmmm, perhaps you could get longer tails if you find a bit whose cutting area is longer, but has the exact same diameter as the Rockler bit in the areas where the two bits line up. And of course the same dovetail angle. That is, if you placed the two bits next to each other and lined them up vertically where the cutting area starts nearest the shank, they would be identical except for one bit being taller.

If this bit were setup correctly then all it would be doing is removing extra material. Everything else should be the same. The tricky part is setting up the bit correctly.

[Pat Barry]

I use a bushing with my Rockler jig and a 1/4" shank bit. What the OP wants is dovetails with longer tails that approach through dovetails, which isn't possible with the Rockler jig. You would need a larger diameter cutter (not talking shank diameter) to get taller tails. So far all the bits I've tried have nearly the same diameter and give you the same half blind dovetails. There is one height setting (depth of cut) that gives you a it that isn't too loose or too tight.

I see - you are saying the depth is limited by the bit itself, its not the jig

[Lee Schierer]

I see - you are saying the depth is limited by the bit itself, its not the jig

If you use the 14 degree 1/4" shank bits you are limited to a depth of cut to about 3/8" which makes half blind dovetails.
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If you go to a 7 degree bit you can get deeper cutting depths, but the overall diameter of the bit also increases from 1/2" to 5/8".
22-105.jpg
I'm not sure how a 7 degree bit would work with the 1/2" spacing that comes with the Rockler jig. The narrow widths of the tails might get too narrow to have any strength.