Making A Monkey Tool

I went through a phase where I made some grilles and gate and railing which used peened tenon joinery.  I made several monkey tools to true up the tenons and create a square shoulder for a nice fit.

I don’t remember who showed me how to make these tools but I remember he said to be careful to relieve the inner edge so there was a little radius at the takeoff point of the tenon rather than a sharp edge which may be a stress raiser.

I found one old handled monkey tool in a flea market and made all the others from jack hammer drill rod which was once abundant at my scrapyard.  I just drilled out the center hold to the sizes needed.

I remember using them once to put tenons on flat bar slats that made a table shelf.  After the round tenons were formed I flattened them into an oval and made a corresponding drift.  When assembled the slats stayed in the horizontal plane nicely because they could not rotate.

Here is one reference on how to make a monkey tool:

http://www.provos.org/index.php?/archives/65-Making-A-Monkey-Tool.html

And you can buy them:

http://www.blacksmithsupply.com/catalog.aspx?storename=blacksmith_supply&DeptID=147760&ItemID=8704197&detail=1

My Monkey tools.

In driving position.

Monkey seated.

Slight edge relief on Monkey gives the tenon base a stress relieving radius.