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1 1/8" Groove Cut Jig- Need advice

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Forum topic by GerardW posted 208 days ago 522 views 0 times favorited 10 replies Add to Favorites Watch
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GerardW

35 posts in 324 days


208 days ago

I am working on a new router table top made out of 3/4 phenolic faced ply, which is going to be so much nicer than my current plywood tabletop. I’m also adding in t-track and, pertinent to this post, a mitre channel. For the mitre channel I need a 1 1/8” wide groove.

Lucky for me I just purchased a new dado set (my first!) and figured I could use some fancy shop math and diagrams to figure out a smart way to do this. My dado set maxes out at 7/8” cut, so it is going to be a minimum of two cuts to make this work.

My idea was to use a piece of 1/2” plywood as a secondary fence along my rip fence, and stack the dado up to 5/8”. After the first cut, I would remove the secondary fence, run it through again with the 5/8 set, , and end up with a perfect 1 1/8” groove.

Many of you are already aware of how this story ended. What with 1/2” plywood actually being 15/32”, in the end my groove was off by 1/32”. Searching through my shop with a caliper, I quickly determined that I had no true 1/2” stock in house (I also don’t have a planer to make any). Further, my dado set doesn’t have the flexibility to handle n/32”.

So- suggestions for how to get this groove right on the first try? I of course will practice with scrap wood first to make sure its working, but is there any better solution than running it through once, then jimmying the fence just a tad, running it again… and repeating until its done (or you’ve gone over too far?)

-- Gerard in Bowie MD


10 replies so far

View bpalmer60's profile

bpalmer60

11 posts in 1146 days


#1 posted 208 days ago

You get get some 1/2 in MDF and create a fence. MDF is actual thickness and very flat and conistant,

-- Bill, Missouri, http://billsgarageworkshop.blogspot.com/

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Woodendeavor

193 posts in 1108 days


#2 posted 208 days ago

use a router with a template guide. Take your 1 1/8” mitre channel and put a scrap piece of plywood on each side. screw another scrap to the end keeping the width set by the mitre channel. Use a bottom bearing router bit and cut the grove. This gives you the exact size of the mitre channel and will fit like a glove

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Nicky

628 posts in 2593 days


#3 posted 208 days ago

With your dado installed, and at the correct height….

Take a straight edge, and hold it against your dado blade. Draw a line on your insert plate to determine the line of cut for the dado blade. You can make your first cut, then use the line you drew as your reference to move your fence. You may want to use masking tape on your insert, and draw a line on the tape for clarity, and accuracy. A good straight edge, and a sharp pencil will be required. Be sure your straight edge touches a tooth in front and back. I’m assuming here that you will have a 5/8 dado installed.

You can practice on your scraps

-- Nicky

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firefighterontheside

1526 posts in 358 days


#4 posted 208 days ago

I may be oversimplifying this, but I would mark on the edge of the top the location of the dado, set the table on the saw and move the fence so that the dado set matches up with one side of the intended dado, of course set the height of the dado to the depth of your dado. Make this first cut with your full set. Then move your fence so that the dado set lines up with the opposite side of the the intended dado and run it through again. That’s what I would do.

-- Bill M. I love my job as a firefighter, but nothing gives me the satisfaction of running my hand over a project that I have built and just finished sanding.

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C_PLUS_Woodworker

385 posts in 1409 days


#5 posted 208 days ago

What “firefighter” said

View pintodeluxe's profile

pintodeluxe

3032 posts in 1314 days


#6 posted 208 days ago

Just sneak up on the cut by moving the fence. When the track fits in the groove, you are done.
Aim for an easy friction fit, otherwise you can chip the edge of the phenolic when installing t-track.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

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GerardW

35 posts in 324 days


#7 posted 208 days ago

Wow! All of these are great ideas, from the simple and effective to the more elegant and creative. I will probably be using the dado set as I just got it and need some practice. I’ll report back on what I did and how it goes.

-- Gerard in Bowie MD

View gfadvm's profile

gfadvm

9545 posts in 1191 days


#8 posted 207 days ago

I would use a hand held router and jig similar to woodendeaver’s comment above.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View Jim Jakosh's profile

Jim Jakosh

10248 posts in 1607 days


#9 posted 200 days ago

Set up a straight edge on the board for a guide for the base of your router and rout it in with a 3/4” bit- 2 cuts. It is easier than setting up dados. Check it out on a piece of scrap first because some of the router bases are not right on center with the bit so get to know what the router cuts and adjust for it after measuring the cut in the scrap piece…..........JIm

-- Jim Jakosh.....Practical Wood Products...........Learn something new every day!!

View GOOD LUCK TO ALL's profile

GOOD LUCK TO ALL

418 posts in 229 days


#10 posted 200 days ago

Make your first pass in your top and then also on a couple pcs of scrap.
Set your fence for the second pass, test it first on one of the pcs of scrap.
Re adjust if necessary, test again with second pc of scrap. After making sure the fit is correct, run the second pass on your top and it should be perfect.

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