Subject: Wire-Drawing: how to keep ends tapered

From: [email-masked] (Boris Beizer)
Date: Mon, 20 May 1996 10:06:17

>To:	[email-masked] asks: 

>During drawing wire (silver, gold or Cu-Ni alloys) one end (which
>should be put through the drawplate) should be kept tapered to allow
>entering into the drawplate. Each few holes I file it off to keep it
>tapered, but when it's smaller than 1.0 mm (I am not familiar with
>gauges) diameter it is *very hard*and refiling is necessary after
>*each* hole.
>
>Can somebody help me with other ideas to keep it tapered ?

Here are prescriptions in decreasing probability order. 

1. Sounds like you're not annealing it after every few holes. 
  Usually, you can't go more than three or four holes (depends on the
  alloy) without reannealing the wire.  Depends on the alloy.  For
  white gold (e.g. Cu-Ni alloy), you might have to anneal every two
  holes or so.  The finer you get, the more often you have
  to anneal.  Also depends on the step size of your draw plate.  
  With silver you can usually go five or six holes; yellow gold is
  between.  Check the wire after every draw. If it has any springyness
  to it, time to > anneal.  

2. Are you lubricating the wire?  The typical (traditional)
  lubricant is beeswax.  After you anneal the wire (before you start
  the first draw) when it is still hot but not so hot you can't hold
  it, pull it through a beeswax cake (jewelry supply).
  Relubricate after every draw; the wire is usually hot enough
  after a fast draw to melt the beeswax. Also stuff a little beeswax
  plug into each hole from the wide end before you draw.    

3. Do not make your taper circular--keep it square.  The trick is
  to use a triangular file to make a tapered groove in your bench pin.
  You lay the wire in the groove (it acts as a cheap tapered v-block)
  and file a flat.  Turn it over, file flat, etc. Two flats are all you
  need.  Keep the taper square because your pliers have flat faces.
  When you try to draw a  circular cross-section your plier will just
  squeeze it flat anyhow and  harden it in the process.  Use a very
  fine file.  You want a smooth finish on the point.  

4. You may be trying to jerk it through the drawplate.  It takes a
  smooth pull.  This is difficult to do because the starting friction
  is much higher than the running friction.  When you get below 1mm or
  so, things **do** get dicey and indeed you may have to file a new
  point every two or so draws--especially if your draw plate
  is dull.  Make sure you have enough room behind you to complete
  the entire draw without ever stopping.  NEVER STOP, NEVER STOP.  Once
  you start drawing, go all the way in one smooth motion.  

5. Are you pulling straight on?  Your pull must be directly on to
  the axis of the hole.  Any slight upward, downward, sideway, off
  axis will drastically increase the force needed to draw and create
  big pressures on the point.  Keep your draw as perfectly aligned
  with the axis of the hole as you can.  Also see (8) below
  as a possible cause of tilt.   

6. Your drawplate could be worn out.  No repair possible.  Buy a
   new one. If it was rusty when you got it (at a flea market) it's
   totally worn and you'll have to live with reannealing and refiling
   the point frequently. 

7. What kind of pliers are you using?  The best is a special
   drawplate plier. It has a hook on the end that allows you to lock
   it with a piece of rope. Jaws are about 1 to 1.5" long and 1/2" to
   3/4" wide.  Handle is about 12-18".  That is best.  In any case, you
   should always use a flat-jaw, smooth-jaw (no serrations) plier. 
   Jaws are **soft*** steel.  Hard copper jaws are also good; some
   come with brass or bronze jaws (I like bronze jaws best for this
   job). 

8. Is your vice solid?   You need a big, solid, vice to hold the
   drawplate.  A small vice will tilt (even microscopically) and it
   means that you're not pulling directly in line with the hole.  I
   recommend nothing less than 50 pound vice with four inch or bigger
   jaws tied to a very, very solid workbench.

9. I assumed that you are pulling circular cross-section wire.  If
   square cross-section, it will be twice as difficult (possibly
   annealing after every hole for white gold), or if triangular,
   even worse.  
 
10. The drawplate numbering could be any of the following (most
    likely order)

   a. arbitrary "hole number" labeled from smallest to largest or
      the other way around.     
   b. douzieme gauge
   c. US standard wire gauge
   d. metric
   e. Any of a dozen obsolete American and/or European "wire gauges"
      not excluding some that go back to the 18th century.  

   Only sure thing is to draw wire of the same hardness (e.g., brass) 
through the holes, mike it up, and calibrate the plate.  You have to 
do that anyhow because the size of the wire after the draw will not be
the same as the hole size. For example, silver may be several thousands
under, gold over, etc.  The finished thickness of the wire can never
be judged by putting a drill blank, say, into the hole and miking that
up.  The finished thickness can be either under the hole size and more
important, ***over*** the hole size.  The finished thickness depends
on (among other things): the alloy, annealing state, speed of the draw 
(the faster the thinner), hole step size (bigger step, more under).
The point is that for soft wire you are not only drawing it through
the plate but stretching it as well (hence under).  The **over** is
caused by the metal bouncing back out after it's through the plate--
which is why you can never, never, never, pull a wire through the 
plate in the wrong direction.  

Boris

Boris Beizer

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