Stem Jig

Making A Stem Jig

6/2010 - A project by Tom Porter

After making a few stems without a specific jig I decided to do something about the difficulty of getting two opposed 90 degree angles to be accurate. Here’s the solution.

The larger base plate is 4” x 4”. All parts are made from 6061 either 3” or 4” wide. The other piece is 2” x 4” and is the piece that is clamped in a vise. First a 3/8” x ½” slot is milled in the base.

The base plate is scribed and centered punched for the Ό” holes for the mounting bolts to the vise clamp.
Holes drilled and tapped and the two parts are bolted together.
This is the adjusting arm plate and is machined as same as the base plate.

This shows that the two plates are at 90 degrees. The angle has to be precise to have the whole line up properly.

Next the adjusting arm plate is laid out and the corners sawed off and rounded to scribe line a disc sander.
Adjusting rounded off and ready for next step.
Layout on base plate for adjusting slot for the stem post.
Layout on the adjusting arm plate for pivot bolt and angle adjusting and clamping
Adjusting arm plate is now drilled with a Ό” through hole for pivot bolt and drilled with a #7 drill and then tapped for a Όx20 bolt.
Base plate is now set in the drill press vise and a series of Ό” holes drilled to remove as much material as possible.

 Ό” mill is now used to remove the necessary material to make a Ό” slot. It’s 1.5” long.
These three pieces now have all the necessary machining and are joined with Ό” 20 x 1” /cap screws.
This is the adjusting are for riser angle and length. I forgot to take photos of this but is similar to what was done on the other plates.

 Riser tube clamp is made from a 3” piece cut 2.75” to maintain center line alignment. 1” hole saw is used for clamping riser tube.

Two holes are drilled with #7 drill.
Plate is inverted and two more #7 holes are drilled for mounting bolts to adjusting arm.
After riser tubing clamp end is separated into two the top clamp is drilled to accept Ό” cap screws.
Lower riser tube clamp is now tapped for Ό” 20 bolts. These holes were drilled about 1 1/8” deep.
Lower clamp is inverted and tapped to Ό” 20 for adjusting arm mounting bolts.
This is the riser tube clamp completed and with a piece of 1” tube inserted to illustrate concept.
 A series of parallel Ό” are drilled in the adjusting arm for mounting the riser tube clamp.
All pieces joined together in vise.
With a piece to 1” tubing in clamp just give an idea of how it is used.

 Next are the two jig tubes for the stem clamp and bar clamp. I didn’t have any stock big enough out of steel so had to cobble together two pieces. The jig tubes are then brazed to these and holes drilled and tapped for joining to plates.

Here is everything mounted and bolted together. We’re now ready to go. Now to finish the lowracer and test drive this beauty.

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