Shopsmith Forums

I just posted a set of plans for an ingenious box joint jig. It is based upon a Improved Lynn's Box Joint Jig I found while surfing the net and looks to be able to produce very accurate joints. Enjoy...

Viewed the new plans with interest. I have several questions and comments:

Although I love your work in making all of these plans - I find myself questioning the reasoning of doing all of the work to make this jig. Unless a person were able to fashion a dial indicator into Lynn's Jig - simpler jigs can be made that will yield more accurate work.

Although a single crank twist of 1/16' seems accurate enough, my recent experience with fingers show that even a .005" error can be disastrous over just a few fingers. Trial and error set-ups can be made with a single finger/slot jig, but each finger on this jig would be unique - there is no chance for trial and error.

If a person were making a small box the slight errors in this jig would be O.K. as all slots are cut during the same pass. However you couldn't use the set-up as shown in your 3D drawing. In that drawing, the sides would have to be flipped over in order to make a box with even edges. The flipping likely wouldn't work because slots cut on one side of a piece would be placed on the other side.

All that is not even considering the fingers MUST be the exact width of the slots.

One way to set up this jig would be to put a spacer (equal to slot/finger width) on one side of the longer pieces (shown in you drawing). That way the fingers and slots would be off set (by a slot width) to make a flat bottom/topped box.

Does Lynn show a project made with this jig? - or is it just an idea? Can you post a link to Lynn's site?

charlese wrote:Viewed the new plans with interest. I have several questions and comments:

Although I love your work in making all of these plans - I find myself questioning the reasoning of doing all of the work to make this jig. Unless a person were able to fashion a dial indicator into Lynn's Jig - simpler jigs can be made that will yield more accurate work.

Although a single crank twist of 1/16' seems accurate enough, my recent experience with fingers show that even a .005" error can be disastrous over just a few fingers. Trial and error set-ups can be made with a single finger/slot jig, but each finger on this jig would be unique - there is no chance for trial and error.

If a person were making a small box the slight errors in this jig would be O.K. as all slots are cut during the same pass. However you couldn't use the set-up as shown in your 3D drawing. In that drawing, the sides would have to be flipped over in order to make a box with even edges. The flipping likely wouldn't work because slots cut on one side of a piece would be placed on the other side.

All that is not even considering the fingers MUST be the exact width of the slots.

One way to set up this jig would be to put a spacer (equal to slot/finger width) on one side of the longer pieces (shown in you drawing). That way the fingers and slots would be off set (by a slot width) to make a flat bottom/topped box.

Does Lynn show a project made with this jig? - or is it just an idea? Can you post a link to Lynn's site?

There is a link referenced to the page I found this on page 1 of my plans, and yes that site does show photos of it's use. The link is http://www.leestyron.com/newlynnjig.php

Thanks for the link, Tom!

I see the maker did use the setup as you showed in your drawing. What I didn't anticipate is he didn't care about the uneven edges of each board that he would have to cut off. He simply made oversized box sides than cut to size after assembly.

I see Lynn cuts the slots - lines up the fingers without flipping two boards (the only way the finger/slots will align) - then cuts off the protruding sides (all 4 of them) to get a box. (Lynn's last 2 photos) This method ends up with a narrow finger as well as a narrow slot. IMHO -Looks a bit sloppy.

Before one tries to make something other than a stand alone box using this jig, he should recognize the height of the box will be unknown until the sides are trimmed. It would be really tricky to make finger jointed, fitted drawers using this method. You'd have to make them big and then trim to size. Chances are great you'd end up with uneven fingers near the top and/or bottom. (UGH!)

Like I said above - there are much easier and precise methods/jigs for making fingers on already sized pieces.

While I like the idea of being able to stack several pieces to be able to make multiple cuts at the same time, what is the advantage of the crank over a more typical pin or bock to index off of?

charlese wrote:Thanks for the link, Tom!

I see the maker did use the setup as you showed in your drawing. What I didn't anticipate is he didn't care about the uneven edges of each board that he would have to cut off. He simply made oversized box sides than cut to size after assembly.

I see Lynn cuts the slots - lines up the fingers without flipping two boards (the only way the finger/slots will align) - then cuts off the protruding sides (all 4 of them) to get a box. (Lynn's last 2 photos) This method ends up with a narrow finger as well as a narrow slot. IMHO -Looks a bit sloppy.

Before one tries to make something other than a stand alone box using this jig, he should recognize the height of the box will be unknown until the sides are trimmed. It would be really tricky to make finger jointed, fitted drawers using this method. You'd have to make them big and then trim to size. Chances are great you'd end up with uneven fingers near the top and/or bottom. (UGH!)

Like I said above - there are much easier and precise methods/jigs for making fingers on already sized pieces.

Charlese,

Did you read this part prior to the pictures?...

In these photo's I didn't take the time to cut my stock to the proper width. You need to do that for the tops and bottoms to line up correctly. This was just some stock I had left over after making another box. That is easy to do though. When designing your box, simply let your width dimensions fall on 1/4 inch or even 1/8" increments, depending on how large your fingers joints are. I really like them at 1/4" on small boxes and 3/8" to 1/2" on larger ones. The width of your stock should be considered as well. This is just a personal preferrence.

foxtrapper wrote:While I like the idea of being able to stack several pieces to be able to make multiple cuts at the same time, what is the advantage of the crank over a more typical pin or bock to index off of?

I would imagine the fact that you could make fingers of infinite variable sizes/spacings without having to have multiple block/pin setups.

Hi George!
Yes, I read that text. When the maker said, "...didn't take the time to cut my stock to the proper width..." I think the maker was pointing out it is rather useless to have the box stock cut to width.

Let's say that you DO cut your box stock to the proper width (actually height of the box) before making fingers. Then before cutting fingers with this jig - you must align the pieces in the jig so they are offset by the width of a finger/slot. One point I'm trying to make here is all pieces of a box MUST be slotted during the same setup (using this jig) or they will not fit. This is because each finger/slot combination will be unique, and they will only fit precisely in one configuration. The pieces will not be accurate enough to be interchangeable.

This inaccuracy doesn't matter and is perfectly acceptable, if you are only going to build a stand alone box. - - - However, there are two issues: 1) There are many simple jigs available that will help a woodwoker make boxes that are more accurate. Efforts to construct this jig are extraordinarily extreme for what you get. and 2) Even by offsetting two of the four sides of a box in the jig, there will very likely be some offset between the sides and the front/back when assembled. This offset must be trimmed before the box has even edges.

The "link" showed me that flipping two of the four side will not work because of inaccuracies in turning the crank. This was not said, but what other reason would exist for having to trim off a 1/4" from all box sides?