Hi I am new here buy want to use this site for info on wood working.

I want to start using  box joints for some small boxes I want to build.

I plan on using my table saw. with a sled

Want to be able to do 1/4" and 3/8" joints.

So here is my questions.

How do I tell which size opening I need to use.

Related to the width of the wood.

All the videos I have watched no body says a thing about how they came up with the proper spacing on the last cut.

Jeff

 

Edited December 5, 20178 yr by Ron Dudelston
tags added

The easiest thing to do is to use over size parts, make the box joints, and trim to the look you want. And by the way, welcome to the Forum.

Jeff, It's easier to show than explain but here goes; First take a template board of choice and make you first cut with either 1/4 or 3/8 using your miter gauge. Then move to the right the same width as your first cut and then make a second cut, then put a peg in the first slot and glue it. Then you simply 

Place your board against the template and make your first cut on the box part, then place it over the peg and continue till; you reach the end of the board and you will have a perfect layout for each end.

I do it as Wally suggested, use stock slightly wider than you need and trim to size. Otherwise it's a calculation using the width of the board divided by the width of the finger.

Edited January 23, 20179 yr by Fred W. Hargis, Jr

Jeff, I'm not sure if I'm reading your question correctly, but here goes. My preference is If I have 1/2" thick boards, I use 1/4" box joints. If I have 3/4" thick boards, I use 3/8" box joints, etc. The table saw is a ok way to go, I did it that way for years with a jig attached to the miter gauge. But I've found that I get better results with a router and a dovetail jig that has a box joint template. A router bit produces a flatter bottom.

Edited January 23, 20179 yr by CharlieL

I would agree with what the others have said. Also, welcome to the forums!

3 hours ago, Jeff Peters said:

How do I tell which size opening I need to use.

Related to the width of the wood.

Welcome to the forums Jeff...

I believe the look/sizing is all aesthetics and what you like......

this is a case for experimentation...

 

https://duckduckgo.com/?q=pictures++of+box+joints&t=ffsb&atb=v47-7bs&ia=images&iax=1

 

Welcome to the PWW forum, Jeff. 

Width of your fingers is a matter of taste. Cutting them in an over sized board and trimming it is easiest. 

Accurate set up of the sled is paramount.

While I hand cut mine....I do use the size chisel to set the spacing.   1/4" fingers= 1/4" wide chisel.   I just mark along one edge, to test how the spacing is going to turn out.  

On this one. Every other space is a waste cut.   There is a knife line across the bottom of the fingers, set to the thickness of the mating board.

I usually chop out the waste from one side of the corner, and use those fingers to mark out the matching fingers.    I leave the lines on the second part.   I cut on the waste side of them.   Just a simple "X" to mark which finger will be the waste ones..

A little tune up, and the fingers will mesh just fine..

Takes about as long as setting up a tablesaw jig...

He guys thanks for the replies, I guess I need to build a sled looked at a sled on Woodsmith that looked pretty easy to build and use. 

Need to get some flat top blades also

Can a regular saw blade be converted to a flat top blade.

Jeff

Maybe, if you can find someone willing to do a re grind (I guess). Easier would be to get a blade to do it from the start. Since box joints are cut with the grain by nature, just buying a rip blade should do it, they typically have a flat top with their chisel style teeth. If you really want a combo blade that cuts a flat bottom, I understand that Forrest can grind a new one to that cpec for a price. there may be other options, someone will chime in with some.

1 hour ago, Jeff Peters said:

Can a regular saw blade be converted to a flat top blade.

an FTG blade will do that...

Woodsmith has a video on the TS sled/jig for finger joints.  It shows how to set the spacing, using a horizontal stop block with a screw adjustment.  I found that a non-flat cut can be squared up by using a chisel as a bottom-scraper.  Just don't get aggressive with it or you change the depth.  I also found that using a dado blade for variable width was handy.

Many dado blades produce bat wings. I had mine ground flat. I would discourage using a single blade to make the cuts. Too many adjustments to complete the cut. Frued makes the SBOX8 set expressly for box joints. One of our sponsors, Woodcraft, sells it. https://www.woodcraft.com/products/freud-sbox8-box-joint-blade-set?gclid=Cj0KEQiAk5zEBRD9lfno2dek0tsBEiQAWVKyuO7O8PBhoLlVceqRZY6T-llH1qHDeH_qypZgjecLiX8aArz48P8HAQ It's an excellent choice.

Edited January 24, 20179 yr by Gene Howe

3 hours ago, Gene Howe said:

Frued makes the SBOX8 set expressly for box joints

second that...

1 hour ago, Stick486 said:

second that...

I have the Frued  and it does an excellent job for the 1/4" and 3/8" wide Box joints. For the wider dadoes I use the dado set that I had sharpened for a flat top.

Herb

So in a box joint set of blades there are 2 blades.

Are they the same or is 1 thicker , or are do they use shims.

jeff

 

Jeff, you use both blades. The teeth are offset to one side. Face to face cuts one size, reverse one face for the other size. 

16 hours ago, Gene Howe said:

Jeff, you use both blades. The teeth are offset to one side. Face to face cuts one size, reverse one face for the other size. 

I also use them one at a time ,for various Rabbets. They are super sharp and cut fast,and a flat bottom groove.

herb

I am going to the Woodworkers show in Columbus this weekend and am goin to look at box joint blades.

I found a plan at the wood smith web site for a box joint sled that I am going to build soon.

Jeff