Even the experts give bad advice...

  Continued work on the cross pieces for the clock.  Just shaped them and sized them nicely.  There is still a bit of cleanup but that will be done with files and one or two holes will need to be punched to complete them but I am much happier than before.  This shows the pieces on the clock.  Once again, the clock is not actually fastened together that is what the rope is for.  Also, the clock won't be perfectly square until I actually pein the tenons.  Here is the pic.  The two pieces I just laid on the frame to give an idea of what it will look like.



  I am anxious to get the frame done.  I will try to remember to scan a photo I have of the original clock's frame to show what all I need to do.  The next part that I decided to work on are 4 small tenons that will be added to the horizontal end pieces.  Those 4 end pieces essentially do the same thing as the two crosspieces that I am working on.  They will hold vertical uprights that in turn will hold the clock axles.

  Anyway, these pieces are about 1" by 2" with a slit on one end of it.  This slit is to hold a wedge that will hold the vertical uprights in place.  I decided to make a drift open up this slit.  After some experimental tries, I decided that for what I was trying to do, a punch was a better choice.  I pulled out some car spring to make the punch.

  In getting ready to do this, I noticed that one of my main chisels was a bit soft and deformed.  So I filed it back to shape and went to reharden it.  When I quenched it, I introduced a stress fracture that caused the chisel to fail when I went to cut a piece off the car spring.

  How did the stress fracture get there?  I quenched the chisel in water instead of oil.  Usually when quenching tool steel, you either quench in oil or just let it cool in the air.  This introduces the hardness needed.  However, I started water quenching some of my tools because of a tip I got on a blacksmithing video.  The video stated that for the most part, water quenching could be used instead of oil quenching for a lot of the common tools.  This seemed a bit odd to me but I followed the advice.  Since then, I have lost 3 or 4 tools due to stress failures.  Proof that even the experts sometimes give bad advice.

  Now for a quick lesson on heat treating to explain the problem.  Heat treating is essentially a 3 step process.

1) Annealing: Bring the metal up to a critical heat (steel turns non-magnetic) and cool it very slowly.  I usually put the piece in wood ash to do this.  This process helps to relieve stress that was introduced in the forging process or that may have existed before forging.

2) Hardening: Bring the metal up to a critical heat then rapidly cool it.  This is usually done either in water, oil or air.  This causes the metal to become very hard, but also very brittle.  A good comparison is glass.  Glass is very hard but also easy to break.

3) Tempering: Bring the metal up to a temperature range around 450-750 depending on the tools intended purpose.  This softens the metal some and makes it less brittle.  Too little heat and the tool will be too brittle, too much and the tool will be too soft.

  So, what was I doing wrong?  In step two, I was quenching in water instead of oil.  Water cools the metal much faster than oil.  This can cause the metal to crack under the stress of cooling.  Once again, this is similar to glass.  If you take a glass still hot from an automatic washer and fill it with ice water, it can break from the temperature shift.

  The main reason that I was using water was because of the tip from the video and because water is just more convenient than oil, especially at demos.  Well, I won't do it any more.  I've lost too many tools.  So, one of my next projects is to build a container for oil that I can use at home and at demos.  I'm thinking of making a wooden box for this.  I'm trying to go for a more period look at events so I want to avoid any modern metal container.  I'm not too worried about fire as the oil is easy to extinguish if it catches fire by simply closing a lid or removing the hot metal from the oil.  (mental note: check that fire extinguisher is filled...)