Dovetails - Incra Jig Process Improvement

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Blog entry by ratchet posted 07-10-2009 07:29 PM 3970 reads 2 times favorited 6 comments Add to Favorites Watch

Had some trouble with getting the Incra Ultra to cut joints the way I wanted consistantly. Loose joints drive me crazy! Anyway, I set forth to tighten things up with a process approach towards improvement.

The system now cuts near flawless 1/2 blind and full dovetails about every time. I’m looking forward to progressing to some of the more advanced joinery thats possible with the Incra system.

Of particular note: I replaced the slightly chewed up runners on the base of the Horizontal fixture with custom made plywood/polyethylene replacements. Extended them another 2” out the back from the originals for added support. The polyetylene was cut from a large cutting board purchased from sams club. That stuff even joints nice! The fixture slides much better now.

Below are the steps I took to make what I think are marked improvements!:
DONE – Tighten all Screws on Fence and jig
DONE – Verify Incra Jig Fence is 90 to router table top – shim if needed
DONE – Remove jig from table and blow out dust – blow out and brush incra jig teeth
DONE – Adjust router Table plate to be level with router tabletop height
DONE – Verify Router Base Plate is tightly secured to router table plate
DONE – Measure dovetail router bits with calipers to ensure correct sizing
Mark with Sharpie the size and bit type on bit shaft.
DONE – Clean dovetails bits of pitch and touch up with diamond stone.
Make dovetail rabbeting standup push jig.
DONE – Make new Horizontal jig jig runners from UHMW or Polyethylene Cutting Board.
DONE – Make spares runner part for future use (both 5” and 7”)
Add Aluminum or Wood Cross Member to runner extensions.
Add Lead Weight to top of base of Horizontal Fixture.
Add a handle to Horizontal fixture to push with.
Install UHMW on inside of horizontal fixture Al slide.
Test cuts with an MDF backer board on Horiz. fixture?
DONE – Test locking the router height. Note: not needed
FUTURE – Install in the table dust collection?
FUTURE – Install a tabletop dust collection catch.

Hope this is helpful to somebody. Let me know if you have any questions.
I very much appreciate all that I’ve learned from you good folks here.

Life is too short…this is not a rehearsal.

6 comments so far

View dusty2's profile


323 posts in 3910 days

#1 posted 07-11-2009 12:30 AM

Did you replace the runners only because they were chewed up or do you feel that the shorter runners contributed to poor fit (instability)?

Cleaning the teeth on the Incra Jig (all of them) and checking everything for proper alignment is a must with the Incra.

Also, make sure that your template tapes don’t move (get moved) after you have done all the setups. I cut an old template into 2” pieces and when I do a setup I slide one of the 2” pieces under each end of the template. This moves the template tighter and less likely to be moved accidentally.

I would have laughed at your suggestion to mike your router bits until I got my digital calipers and was miking everything I owned. Much to my surprise, the router bits showed significant deviation from expectation. They were all well used.

New, quality router bits made a world of difference in both fit and repeatability.

I now have a router table set up dedicated to the Incra Jig.

-- Making Sawdust Safely

View DocK16's profile


1186 posts in 4568 days

#2 posted 07-11-2009 04:18 AM

Great Blog. I was just thinking the other day about replacing the chew up runners on my incra sled but the idea of adding the phenolic blocks is brilliant. The sled ought to slide like glass now. Dusty is right about cleaning and alligning the teeth on the brackets is critical to smooth operation.

View abie's profile


900 posts in 4252 days

#3 posted 07-11-2009 04:37 AM

Bravo… TNX for all the use full info
I’ve been making sawdust on my Incra for months and only now getting things close to right
again Bravo.

-- Bruce. a mind is like a book it is only useful when open.

View ratchet's profile


1391 posts in 4268 days

#4 posted 07-14-2009 04:31 PM

I just addeed a handle and a cross plate for the extended base runners. It feels like it adds control to the cuts by permitting more downward and right pressure to keep base of fixture on the fence. It also adds degree of safety as I use one hand to hold the stock to the top of the fixture to minimize any vibration, and the other hand to push the stock through the bit with the handle. This ensures to a degree that both hands are out of the path of the bit as it moves through the work.

View ratchet's profile


1391 posts in 4268 days

#5 posted 08-06-2009 04:19 PM

I’m back to using a set of parallel screw clamps to hold the pin boards vertical on the horizontal jig. I now believe these are my best bet for accurate DT’s.

View ratchet's profile


1391 posts in 4268 days

#6 posted 08-06-2009 04:20 PM

Also; I will not be adding any lead weight to the sled as indicated in the list above.

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