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I have an older set of LMI 1/4in aluminum dovetail jigs meant for a classical guitar, that I would like to use . I have them seperately mounted on a frame, The alum mortise jig will accept up to a 5/8in guide bushing, my problem consisits of matching the correct bushing size to a matching router bit calculating the offsets makes my head spin . I have 4 large routers and 3 med routers and a host of laminate trimmers . I would prefer to use either the med size or large routers for this job. Has anyone out there calculated the right combo of straight bit/dovetail bit / guide bushing. I have two 5/8in guide bushings on the large routers. The med size bosch router needs a sliding adapter to mount the bushings currently 6 weeks backordered . Any suggestions would be much appreciated. Thanks ernie

I would think as long as you use the same bushing for both cuts it should work with whatever dovetail bit you use, but maybe I'm misunderstanding here. I know I can "over think" at times and must remember the principle of KISS.

here's my dovetail jig. Works for me. Not even sure what size bushing I use in my Porter cable router.
Hope that helps.

_________________
"Preoccupation with an effect gives it power and enhances the error"
from "Your Owner's Manual" by Burt Hotchkiss.

I want to use 2 seperate bits the first 3/8in wide by 1/.2 in shank to hog out 1/2 in of waste and then use a 1/2in shank/1/2 in dov bit to make a slightly lower cut by 1/16in of my target depth 1/2in and then cut a final pass with the dov bit at 1/2in. depth The slightly lower 1/16in is for future neck removal ?? Is this how you do it ?/ or do you just use one size bit to do the mortise and tenon ?? PS all done with a 5/8in OD collar

What bit/guide does the jig recommend to use ??? .. I doubt you can just change to whatever you want because the bottom of the female template will dictate how large a dovetail will drop to the bottom after routing the male side. If the bottom of the female template will take a 5/8,and its afarily tight fit, then the bottom of the route will be the size of the dovetail bit, not much larger, correct - so in your case, 1/2 inch. But when you use a larger guide on the male template, you get a much wider, rounded dovetail end .. the angles will be correct , but no way will the male bottom out into the female pocket ... do you understand ??? Take a look at the dovetail jig shown above .. there is no way a larger guide will give you the pointed narrow tip in the male to fit into a tight bottomed pocket - the neck will sit way too high, above the top of the block.

_________________
Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

Your right Tony I am flying blind and trying to guess the sizes , and that is what happened. the male dovetail was too high, but I was using 1/4in bits on that try. The female dovetail will accept up to a 5/8in collar. I called LMI where I purchased the templates , and they had no clue of which router bits to use with their 1/4in alum. dovetail templates and I don/t have a copy of the original data sheet (lost). My dilemna is figuring out which combination of straight and dovetail bits will work to create the joint . I would like to use the straight bit to hog out most of the waist, and then use the dovetail bit to make one pass at 1/16in below my targeted depth of 1/2in and then a final pass at 1/2in. Your thoughts please . thanks ernie

I think this is a case where I'd experiment on scrap. Dovetail geometry gives me a headache - perhaps that's why I shifted to M&T bolt ons.

Will a couple of test cuts on scrap blocks work for you?

Ernie,

Watch those videos I sent you and you will find what you are looking for. Anyone else interested in making this jig, LMI has plans and a hardware kit that includes the templates.

Setting up the jig


The dovetail joint


The M&T joint

Thanks robbie I already bought the plans from you. ernie This old LMI template is 1/4 in alum

Hi robbie watched the video . I learned a lot thank you . First problem is that the LMI jig is not adjustable therefore one needs to make the tenon jig as close as possible to the target length. Secondly. I have an older makita router with a 5/8in collar the I.D. of the collar is 14mm O.D.is 16mm I believe you used a 1/2in width and depth dov bit on 1/2 in shank ?? coupled with a 3/8 in st bit with 1/2 in shank. I have perhaps the same bits, but because your I.D. is 17/32 your offsets are much smaller than the setup I just used on a dummy piece. I need to find a bushing that is 17/32 in order to make a complete dovetail mortise ?. When I looked into the mortise cavity about 4mm at the top had not been cut. MY dovetail bit is 7 deg 1/2in wide and 1/2 in length with 1/2 in shank . The st . bit is 3/8in wide by 1in long on 1/2 in shank. Do you think changing the guide bushing to 17/32 will help ?? . I only one one mid size PC router circa 1976. It has a 1/4 in collet on it , and it/s a pita to change settings. The male tenon was way too big , probably too much offset ?? Your suggestions Robbie would be appreciated thanks again ernie. I am determined to solve this ____ problem.

OOps just checked again. The dovetail is 14 deg . not 7 as per your video . Thats probably why there is a 4 mm st ledge on upper mortise cavity.