Gang-Saw:  Buzz-cutting your head.                                                                            January 2006

I’ve made a number of special heads for my model airplane engines over the years.  Cutting cooling fins has  never  been  the  most  fun  part;  tiny  endmills turning as fast as an old Bridgeport will go is a pain at  best.     With  a  VFD,  I  could  spin  a  little  0.062” cutter  at  double  speed,  but  it  is  still  a  slow  and repetitive process at best.  It is also too easy to ruin a head with one tiny false move.

Faced with the prospect of making a dozen engines with  some  significant  performance  improvements, amongst them making a  dozen  special heads,  was something short of a romantic notion.

Another  means  to  do  the  head  cooling  fins  is,  of course,  the  use  of  an  appropriately  sized  jeweler’s saw in the mill.   Again, old man Murphy can wreak havoc.   Often, it will ruin that head on the last cut, or  with  some  luck,  it  can  be  ruined  earlier  in  the process,  at  least  making  the  grief  come  sooner. Clearly,  a  better  and  simpler  way  had  to  happen.

Using   a   ‘gang’   of   saws   of   the   appropriate thickness,  and  spaced  appropriately  seemed like  a  good  way to  go.   Once  set  up  properly, things should progress smoothly, quickly, more accurately, and with better results.

So, the Gang Saw was born for this little project. This  mandrel  can  be  loaded  with  thicker  or thinner  saw blades,  thicker  or  thinner  spacers, and more or fewer cutting blades giving a pretty universal tool once completed.

Just  a  general  overview  here: The  mandrel itself  is  from  AISI  1144,  commonly  known  as

“Stressproof”.  It          has  made    some great crankshafts for me in engines turning in excess of  30,000  RPM,  so  I  figured  it  would  be  good enough for this.   Also, I happened to have it on hand.   Another nice feature of the 8 foot bar of 1144 that I have is that it’s SO close to 1 inch, that  the  3”  saws  with  1”  ID  must  be  very carefully pushed into place.  There just isn’t any slop; it gives an excellent fit.

This link goes to  an excellent and complete description of ‘StressProof’ steel:

http://www.niagaralasalle.com/products/stressproof.html

For the spacers, I used 6061-T6 aluminum 1½” OD ¼” wall stock I had on hand.   I trimmed the ID to leave them about two thou oversized so as to slip into place easily.  The   nose-cap is made such that it   can accommodate  another  half-inch  stack  height, and  a  narrower  stack  at  any  size  would  be easily accommodated with an appropriate spacer.

There are a few photos below to show  the  general arrangement.   Detailed plans and more photos will  be  published  in  Home  Shop  Machinist  or Machinist’s  Workshop   sometime   later  in  the year.   For that article, some minor changes will be suggested and shown on the drawings.   For a one-off for me, this is filling the bill just fine.

For a more detailed look at the saw, see http://public.fotki.com/TheAeroSmith/gang_saw_for_cuttin/

I’m very pleased with the initial results.  This tool will be a very useful addition to the arsenal.  Any questions, feel free to ask me:

Bob@TheAeroSmith.com