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post #1 of 7 (permalink) Old 08-14-2013, 05:14 AM Thread Starter
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Default Dovetail Bit Bushings

My dovetail jig says to use a .40" guide or bushing, which I can't find. If I use a 3/8" one, which I don't have, what am I going to need to do to compensate?

Also top edges of parts are misaligned by about 1/64" - 1/32". Not sure if this is from bit being off center or not. Shank looks centered to me. Grrrr!

Thanks for help.
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post #2 of 7 (permalink) Old 08-14-2013, 06:31 AM
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Which Dovetail jig are you using, Bob.

0.40" guide seems a strange measurement for the US.

Some jigs use a proprietary set of guides and cutters.

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post #3 of 7 (permalink) Old 08-14-2013, 09:04 AM Thread Starter
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It's the Craftsman "Industrial Dovetail Fixture" #25450. Very good user manual, if you ignore the errors! It appears to be virtually identical to the Vermont American "Industrial Dovetail Jig" #23461. I can't find any sign of it's current availability.
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post #4 of 7 (permalink) Old 08-14-2013, 09:18 AM
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Originally Posted by nancysbob View Post
My dovetail jig says to use a .40" guide or bushing, which I can't find. If I use a 3/8" one, which I don't have, what am I going to need to do to compensate?

Also top edges of parts are misaligned by about 1/64" - 1/32". Not sure if this is from bit being off center or not. Shank looks centered to me. Grrrr!

Thanks for help.
Hi Bob - IIRC one of Sears dovetail jigs did require a .400 guide bushing. The Ridgid guide bushing set has a 25/64" bushing which translates to 0.390625 which may be close enough. You could probably order one through Home Depot but it would be kind of a spendy way to go at $42 for the set.
You might also try http://www.searspartsdirect.com/part...FZCe4Aod_VQApA.
You may/will need the model number to get the part number out of them. There are some phone numbers at the bottom of that page that may help also.
As far as the top edges being misaligned, it sounds like the left and right fences may be off. I haven't got that jig but on mine the fences are plastic and like to twist when tightened down which throws the alignment off. The incorrect bushing doesn't help much. As far as centering, eyeball isn't usually good enough. A 5/16 bushing will typically have a 1/4" ID so you can use a 1/4" straight bit and 5/16" guide bushing to center. Otherwise, a centering pin/cone need to be employed.
Good Luck

EDIT - I just noticed that Home Depot has discontinued that set. Here is one from Amazon
http://www.amazon.com/RIDGID-Univers.../dp/B008AW9RQI

John Schaben

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Last edited by jschaben; 08-14-2013 at 09:22 AM.
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post #5 of 7 (permalink) Old 08-14-2013, 11:41 AM Thread Starter
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I spent hours yesterday - and about seven feet of wood on trial & error routing. That included shimming left and right stops (mini fences), which are fixed and not really getting consistently repeatable results. Since those stops easily allow misalignment, this morning I super glued extended stops in line with the factory ones. That seems to reduce the top/bottom edge misalignment. Now if I can figure out why joint tightness isn't consistent.
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post #6 of 7 (permalink) Old 08-15-2013, 08:15 AM
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Bob,
Another thing to consider is the bit you are using. Not all dovetail bits are the same so you need to use the correct bit for the jig you are using.

Mike
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post #7 of 7 (permalink) Old 08-18-2013, 08:40 AM Thread Starter
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Bit is the 25505 which fortunately or not, is the "right" one. I finally gave up yesterday, spent half an hour with owner of local Woodcraft store getting pointers. One of his comments was essentially, that you have to use the same bit/guide bushing size specified for the template. No telling what will happen otherwise. OK to use different shank size. Finally bought PC 4210 / 4212. Much better gripping of boards. Also started making a hidden knife mark 1/2" from edge of board to align with mating board which assures (almost) that the tops of the parts will align exactly.
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