Thread: Finger joints - any good techniques?

Originally Posted by Gunnaduit

I've got some machine tools I want to make boxes for, I'll make them from some scrap hardwood I've got -- I'm talking boxes around 4 inches x 6 inches, that sort of thing. It'd be good to do finger joints on the corners, maybe 5mm joints.

What's some good ways to get accurate joints? I don't have a commercial dovetailing jig, but I do have nice router and ok table saw. Anyone got a trade secret?

Cheers

Hi there. Sure there are techniques...techniques galore. The boxes you have described are quite small, so I take it that you are looking to create something that's only a couple of inches tall? Anyway, all you need to do is to lay out the parts and make mating "fingers". You need to lay it out first. Equal spacing of the cuts is the key.

Hard to describe here, but basically the go is (for either a router table or table saw) to create a "key" that will be fixed to the table or fence that will provide the spacing. You would make a piece that will fit into the first cut you make at a distance from the blade or cutter for the next one. Get it?

Then, you would start with the alternate cut on the 90 degree member.

It's all about the setup and measuring it out. It may be a good idea to determine the height of the box based upon how many "fingers" it will take to get two males or two females at the end of the boards.

You'll also want a tall fence to push the work through, as you'll be cutting things on their ends. Hope that sketchy information gives you some ideas!

Michael

I have done a couple of items using finger joints, and did them on a table saw with a wooden carriage or jig, sliding in both mitre slots. The tricky bit is indexing the fingers and gaps to be exactly the same, but once the key is finally in place its relatively straight forward...just repetitious. I hate repetition!
The main problem with using the tablesaw is the end of the slot has a "V" from the very tip of the blade teeth, where one points one way, and vice versa. Either wear it; clean up each slot at that point; or modify the blade.

Cheers,

G'Day Gunnaduit

Try reading this, nice and simple http://www.lowes.com/lowes/lkn?actio...ld/boxjnt.html

Cheers
Bernie

I use a 3mm drill bit turned around for indexing 3mm fingers, The reason for this is the saw kerf is 3mm. so it works just great, ideal for small boxes. Guess a 1/4 " drill bit would do the same thing if using a 1/4" straight router bit for the fingers. Using the drill bits is very accurate.

If you can wait 'til Tuesday I'll post some pics of how I do it on the bandsaw. Basically involves marking out the widths of the fingers on a bit of scrap and using that to set the fence. Then you make the cuts.
It's easier to explain with pics.

Originally Posted by AlexS

If you can wait 'til Tuesday I'll post some pics of how I do it on the bandsaw. Basically involves marking out the widths of the fingers on a bit of scrap and using that to set the fence. Then you make the cuts.
It's easier to explain with pics.

Look forward to seeing the pics.

Sorry the pics are out of order. Also, although tis shows how to make wooden hinges, the technique is applicable to finger joints as well.

Cut two pieces of wood the same width for the hinges. Each piece will later be cut in two to form the two pieces of a hnge.
Photo 2: Cut a piece of MDF the same width as the hinges, for the template. Mark a face edge on the wood for the hinge and the template.
Mark the positions of the fingers on the template using a marking gauge, and highlight them with a fine pencil. It's best to have an odd number of fingers. Set a cutting gauge to the thickness of the hinge pieces, and mark this distance from each end of both pieces of the wood.
Using the template against the bandsaw fence, adjust the position of the fence so that the blade just cuts on the 'outside' of the first line. You should be able to see half the pencil line remaining.
When you're happy with the position of the fence, make a cut on each end of one hinge piece, to the depth marked. Be sure that the face edge is against the fence.
Reset the position of the fence, and bisect the 1st line on the template, this time on the 'inside'. When you're happy with its position, make cuts at each end of the other piece of wood.
Continue to reset the fence using the template, and then make the cuts on the appropriate piece of wood. The main problems to avoid are a) turning the wood the wrong way to cut the 2nd end. Flip it end for end so that the face edge is always against the fence. b) cutting the wood in the wrong order. If the wood pieces are numbered 1 & 2, they are cut in the following order: 1,2,2,1,1,2,2,1. This would give 3 fingers on one part of each hinge, and 2 on the other.
Chisel out the scrap between each finger.

Select a piece of bamboo kebab skewer for the hinge pins (for small hinges, you can use toothpicks). These are rarely perfectly round or exactly the size of a drill, so they can be smoothed and sized by sanding.

Photo 3: Insert one set of fingers on one piece between those of the other, and mark them as a pair, keeping the face edges on the same side. Then reverse the pieces and mark the other ends as a second pair.
Photo 4: Mark the location of the hinge pin using an awl on each end of the 'outside' finger piece, and place an assembled pair in a drill vice. Before drilling, be sure the table of the drill press is perpendicular to the drill post, and the hinge pieces are perpendicular to the drill. Drill the hinge pieces using a spur bit.

To be continued later. Any questions so far?

hand cutting isnt a bad way to make box joints. Just leave extra timber to make it snug fit and chiseling. However ts with a box jig on a sled is also great.

I was going to start a thread to mention this book but I'll just do it here. It has full plans and instructions for using the best box joint jig I've ever seen!
It also has lots of other excellent plans for other table saw jigs and fixtures and every one includes very detailed plans and instructions for use.
Here's a link to the web site where I bought the book.
http://www.woodsmithstore.com/w0811.html

An article on my micro-adjustable box-joint jig, described in this thread http://www.woodworkforums.ubeaut.com...ad.php?t=29446 , can be downloaded free from my blog (see below).

Rocker

A few years back I was a bit obsessive about box joints, & made a few jigs for the router table that ran in the mitre slots. They were the "standard" type, ie. a high fence backing the workpiece, and a "key" that was the exact thickness of the cut of the router bit, that was micro adjusted to the same measurement away from the router bit....ahh, that is confusing as hell. Google is your friend here & a bit of research for homework.

What bears mentioning, though, is a different, simpler type of jig that I came across on the website for the US show, Router Workshop. This is just a flat piece of material (they use UHMW PE) with a long "key" set into it. To use, one end is clamped onto the router table, then the other end is pivoted around to get the spacing correct from the key to the router bit. Once this is done, it looks like cutting the joints would go quickly.

The advantage I see in this jig is the speed of making it and of setting it up & finetuning. You wouldn't need to use the UHMW, regular materials (masonite, mdf, hardwood for the key" would do the job, with a slather of wax so the workpiece slides easily.

Note also they use a spiral router bit, this would give better quality cuts than the normal straight cutters most have.


Cheers...................Sean