Thursday, May 28, 2015

A Bit of Blacksmithing - Inside/Outside Calipers (Dividers)

Here is the coal forge I was working on for this project.  An 1890's style rivet forge.  I started the fire with a bit of wood chips and ran the forge with coal.

Today's project would include 2 tools which are very much the same in their construction.  Inside and outside calipers.  Calipers are a device used to measure the distance between two opposite sides of an object. The inside calipers (number 1 below) measure the inside of a closed space such as the inside diameter of a pipe.  Outside calipers (number 2 below) can be used to measure the diameter of the outside of the pipe.

Inside Calipers

I started by making the inside calipers with some scrap metal from the shop.  I began like I begin many projects by sketching my idea on the face of the anvil with soapstone.  Eventually I will be placing hot metal on the surface of the anvil but the sketch will last long enough for me to make both halves the same size and shape.  I started with rectangular stock about 1/8th by 1/4 inch thick.  Rather than working two separate pieces I simply drew out and shaped each end of the metal matching them to the sketch on the anvil.  Once they appeared balanced and even I cut the stock in half.


After cutting to length I punched a hole in the ends of each piece and test fitted them using a small nail.  I had to do a small bit of filing to remove some small burs and then I used the cut nail to permanently rivet the calipers together.


Outside Calipers

The process of creating the outside calipers was basically the same except that stock I started with was round.  I found this old S-hook left from a previous class at the shop.  I started by straightening it out for my purposes.


I again sketched my idea on the face of the anvil and went to work shaping 2 pieces to match the sketch.


 Once nearly done I made sure that both pieces were as much alike as I could manage and then proceeded to punch the hold for the rivet.


So far so good.  I again used a small nail to do the test fit.

Once satisfied with the fit I cut the nail off and made a small leather washer which I oiled and placed between the pieces.

Once riveted up I did a small amount of file work on the tips to ensure proper alignment.  I peened the rivet over just enough to be snug when in use but not too tight as to stick too much.