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Can't get finger joint jig right

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Forum topic by SouthFloridaSun posted 09-23-2013 12:09 AM 1613 views 0 times favorited 18 replies Add to Favorites Watch
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SouthFloridaSun

14 posts in 554 days


09-23-2013 12:09 AM

Topic tags/keywords: jig purpleheart pine tablesaw joining

After deciding I wanted to start learning a few wood joints to use rather then my Kreg pocket hole jig all the time I settled on the finger joint as a first. I looked over lots of jig plans and decided to make this one because it was in the middle of the road between plain and fancy

I wont go into the details of the jig but I had scraps of 1/4” purple heart which as you can see I used for the key. The key is absolutely 1/4” from the blade and the blades are 2 stacked 1/8” dado blades equaling 1/4”.

Here is my issue. If the blade cuts 1/4” and the distance from the blade to the key is 1/4” a 1/4” finger isnt going to fit in a 1/4” hole so what is the general rule of thumb? Should I make the distance from the blade to the key 1/32 less then 1/4”?

P.S. I am going to bolt the removable fence to the back fence after I am confident its all good.


18 replies so far

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JustJoe

1554 posts in 761 days


#1 posted 09-23-2013 12:30 AM

If the blade cuts 1/4” and the distance from the blade to the key is 1/4” a 1/4” finger isnt going to fit in a 1/4” hole

Huh? I’m not following the math. A 1/4” finger will fit in a 1/4” slot.

If your blade cuts a slot (X) wide, then you want your key to be (X) wide and to be (X) from the edge of the slot that the blade cuts.

-- This Ad Space For Sale! Your Ad Here! Reach a targeted audience! Affordable Rates, easy financing! Contact an ad represenative today at JustJoe's Advertising Consortium.

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SouthFloridaSun

14 posts in 554 days


#2 posted 09-23-2013 12:34 AM

A 1/4” finger fits in a 1/4” hole sure but with a bit of force. My questions is what is “too tight”

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JustJoe

1554 posts in 761 days


#3 posted 09-23-2013 12:41 AM

You want it to be a nice slip fit. You shouldn’t have to force it. And to keep it accurate, you want the distance between the key and the blade to be as close to perfect as you can get. So if your blades are 1/4”, make that slot between the blade and the key 1/4” and then take your block plane and just wave it in the air at the other side of the key until you’ve scared away 1/1,000,000th of an inch, so the key is maybe .2499999999999” and then when you’re cutting the fingers your board should slide right over the key. And then take the same blockplane and relieve the two top edges a bit, that will make it easier to lift/drop the board over it.

-- This Ad Space For Sale! Your Ad Here! Reach a targeted audience! Affordable Rates, easy financing! Contact an ad represenative today at JustJoe's Advertising Consortium.

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unbob

439 posts in 626 days


#4 posted 09-23-2013 01:22 AM

If this photo does not work, I will try another.
My jig looks much like yours, but I have bolts instead of clamps to hold it.
These are guitar amplifier boxes. the joints are long. To make this work, I add .004” shim for the mating part. This gives .002” per side of the slot. If it did not have this clearance it would not go together.
I have a bunch of other tips, if you are interested.

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juniorjock

1930 posts in 2488 days


#5 posted 09-23-2013 01:27 AM

I’d listen to unbob. He knows what he’s talking about. If your boards move any when making the cut, the joint will be off.

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bowedcurly

495 posts in 452 days


#6 posted 09-23-2013 02:23 AM

hold the board tight and do it the same way every time and you will get good joints, the trick is in the setup make sure to mark your boards and cut one corner then the other, the way I do it is cut the front of the box then the back of the box, the real key is shimming your box joint set to get really great joints

-- Staining killed the wood<<<<<>>>>>Dyeing gave it life

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bowedcurly

495 posts in 452 days


#7 posted 09-23-2013 02:24 AM

I think this is another pic

-- Staining killed the wood<<<<<>>>>>Dyeing gave it life

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bowedcurly

495 posts in 452 days


#8 posted 09-23-2013 02:26 AM

I made these joints with the Forrest box joint set and use 2 shims to make them perfect fit that’s perfect for me best joints I have dome to date but the Box joint set really makes it easy

-- Staining killed the wood<<<<<>>>>>Dyeing gave it life

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bowedcurly

495 posts in 452 days


#9 posted 09-23-2013 02:28 AM

the second pic is from the forrest box joint set, the first is with a Frued safety dado you can tell a big difference

-- Staining killed the wood<<<<<>>>>>Dyeing gave it life

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bowedcurly

495 posts in 452 days


#10 posted 09-23-2013 02:32 AM

I don’t really measure I just pick a look and try to get a good slip fit not tight but not loose either shimming is the way I do it

-- Staining killed the wood<<<<<>>>>>Dyeing gave it life

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unbob

439 posts in 626 days


#11 posted 09-23-2013 02:32 AM

I did these a few years ago, this photo shows some progression in quality. I read about all I could find, some not so helpful. Many ways for error to creep in, get one slot off the following ones will be off, induce accumulative error on every slot, with long joints the end ones will be way off. The box on the right is how I want them to be, the wood looks stitched together.
I have it now where I can put 40 or more 1/4” slots together near perfection.

View Skippy906's profile

Skippy906

101 posts in 710 days


#12 posted 09-24-2013 03:03 AM

I found this plan on the net and made perfect box joints. I kinda amazed myself at the ease of this project.

This is Lynn’s box joint jig. There are are few plans out there of this jig, but this is the one I chose.

Here is the box I made and the fingers matched up perfectly.

This is the only box i have made with this jig, but it is another tool in the toolbox for another project.

-- Making progress

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comboprof

277 posts in 457 days


#13 posted 09-25-2013 01:44 PM

Get out your caliber’s and measure the actual width of the dado that your 2 stacked 1/8” blades make.
Mine don’t make 1/4” instead its 15/64”. I adjusted my keys to also be 15/64”, but I will admit my joints are very tight and I may try shaving the fixed key as JustJoe says. Alternatively my jig has micro adjustment so I may try that first. BTW I made two 15/64” keys one fixed in the jig and the other loose to help with the alignment of the “mate” to the first board. Also if you cut two sides at once you can use the loose key to lock them together once you have
a free finger hole.

-- -- Cheers, Don K. (Michgan's Kewenaw peninsula)

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MrRon

2933 posts in 1966 days


#14 posted 09-26-2013 08:48 PM

I understand your problem. It is a common one. What I do is taper the sides of the pin slightly so the work you are cutting fits firmly over the pin, but easily due to the tapered sides.

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DaddyZ

2419 posts in 1763 days


#15 posted 09-26-2013 09:00 PM

Even modified box joints are cool
Click for details

-- Pat - Worker of Wood, Collector of Tools, Father of one

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