Saturday, May 12, 2012

Finger Joint Jig -- Final Version?

     I've spent the last two days working on making a permanent, easy to adjust and set up, finger joint jig.  This will used on the tablesaw with an 8" Freud box joint cutter set.  Usually, if you just have one project to do it's no problem screwing a temporary fence to your miter gauge, banging it with a hammer to get the right fit, and cut the joints.  That's always worked in the past but I'm about 75% committed to making a small run of pistol cases and renting a table at a gun show coming to Las Vegas in September.  
      Not sure if I've ever talked about the pistol cases on the blog so here's a link to the website:

    These cases will be assembled with box joints or finger joints.  The name of the joint is pretty much interchangeable since the corners have the appearance of interlaced fingers.  This design exposes a lot of face grain for gluing and is incredibly strong.  The trick is to consistently cut them and maintain the spacing.  A thirty-second of an inch one way or the other can make them too tight or too loose.  Before buying the Freud set I would use the dado blades but the width of the cut was apt to change each time depending on the positioning of the blades.  Hopefully, with the Freud cutter set, they will always be either 1/4" or 3/8" without any variation every time it's set up.  Time will tell on that one!
     Here's a shot of the jig I've spent careful time on:

Finger or Box Joint Jig for Tablesaw

     As you can tell, it rides in both miter gauge slots which will keep the cuts square and consistent.  The piece in the front is referred to as the carriage and it "carries" the material being cut.  The piece of MDF directly in line with the blade is a sacrificial piece to prevent blow out on the back side of the piece being cut. The MDF to the right of it is a mistake on my part!  Since the Freud set only cuts 1/4" and 3/8" wide joints I needed to make a carriage for each size.  The 3/8" one is off to the left side.
     The plans for this jig came from ShopNotes Tablesaw issue that I believe, was published in 2007.  The original plan called for using 3/4" plywood as runners in the miter slots with a platform between them that held the carriage.  This worked but I found that the plywood changed in thickness due to weather conditions and one time it would slide freely and the next it would bind.  I chose to re-engineer their design and use the ultra high molecular weight  polyethylene available from suppliers like Lee Valley.  I've used this for many sleds, fixtures, and jigs and love it!  It can be drilled and tapped and is stable and slick.  For this application it was tapped for 1/4" x 20 tpi machine screws.  Here's a better picture of the jig:

Side View of Jig

     The carriage is attached to the sled portion through slotted holes which allow me to adjust it to get the proper fit.  There are a two knobs and fender washers on the backside which tighten the carriage bolts used to keep it all together.  That's some 5/16" thick Walnut I used for the test set-up.
     As far as the pistol cases go, I was commissioned to make six of them a year or so ago for a neighbor.  He is an avid gun collector and used the cases for presentation, storage, and transportation.  Since the case will be built for a specific pistol it's important that I can accomplish that -- obviously!  I had a friend of mine make a tracing of one of his pistols and made this mock up for it:

Alder Pistol Panel

     For the final fitting all that's required is for the pistol owner to first place the pistol in the leather covered, foam recess.  You would then put the strap onto the snap, put a slight bit of pressure down on the pistol and mark the other end of the strap.  Once a pilot hole is drilled at the location the strap can be secured.  Repeat the process for the other strap and you know have an attractive and secure way to transport your pistol.  In time, the foam will conform to the ins and outs of the gun for a perfect, custom fit.
     Next weekend there will be a gun show at the South Point Casino here in Las Vegas and I plan to go and see what it's like.  I've visited a few other gun shows, scouting expeditions if you will, and think there is a market for the serious gun collector for pistol cases like mine.  I'll keep you posted -- wish me luck!

No comments:

Post a Comment