Box joint jig questions

[offthemark]

I've never made box joints before but I'm about to jump in this weekend. I am planning to use the plans for Lynn's box joint jig at the Leeway site (http://www.leestyron.com/lynnjig.php).

I am assuming that as the jig is used, the bottom of the jig support and the carriage are "eaten" by the saw. Is this correct?

Once you've made one pass, how do you bring the piece back for a second? Seems like you would clamp it down so you'd be forced to bring it back over the saw (a big no-no if running).

Any other tips for a first timer? I plan to practice on scrap until I've gotten the hang of it.

[LCHIEN]

You can backup with this or other box joint jig. Basically the jig keeps everything aligned. You only need to get the top of the blade past the workpiece, then you can backup. Since its held to the same path/groove, nothing bad will happen.

[scorrpio]

Geez, that looks way too complex for a box joint jig. I 've seen a jig that was essentially a long board clamped vertically to miter fence. Had two notches cut into the bottom edge, and into one of the notches, a square peg is glued in. Workpiece rides vertical on the board. First cut is made with edge of work butting against the peg. Each subsequent cut, the freshly cut notch goes over the peg. Can be made adjustable by not gluing the peg in, but by making it ride along a slot cut into the board.

[gjbivin]

I use an "enhanced" version of Lynn's Jig, and have had good results from it. Basically, the enhanced version adds a base and front brace across the width of the jig. The biggest problem is losing count of the turns DAMHIKT To help with this, I marked the sled position every 5 turns on the jig base, and I'm thinking of putting a disk behind the handle with turn fractions marked on it.

Yes, the sled back does get chewed up. You will want to use a sacrificial backer board behind the work pieces to prevent tearout.

But the advantage to this jig over the usual design is that you can make the "teeth" any size you need to come out even across the width of the joint -- or even vary the widths across the joint, if you're gutsy enough (I haven't tried that yet, but plan to some day).

The previous BT3 Central discussions on this seem to have evaporated. Here's a cached page with photos that may help:

http://72.14.203.104/search?q=cache:QHg9S3fXFcMJ:www.bt3central.com/forum/topic.asp%3FTOPIC_ID%3D12920+%22lynn%27s+jig%22&hl=en&gl=us&ct=clnk&cd=6&client=firefox-a

I've worked up an Excel (2000) spreadsheet to do the calculations and attached it in a zip file, if I've done everything right.

boxjointxls.zip

The green fields are your setup; these are Joint Length, thickness of the wood, saw blade (kerf) width, Jig turns-per-inch, and desired number of joint "fingers". All measurements are nominally in inches, but it should be OK if you use another unit (mm or cm) consistantly in the entries. I protected the sheet except for the input fields; choose Tools | Protection | Unprotect Sheet if you want to make changes or enhancements.

Good luck, and show us some pictures of your work!

[woodrowB]

......... nothing bad will happen.

Yikes!!! That usually means trouble!! ;-)

offthemark - He's right in that it is the normal method, but there are simple(r) jigs you could use.

[offthemark]

Gary, thanks for the info and pix. Very helpful.

there are simple(r) jigs you could use.

Simple? Why go simple when complex is so much more fun.