[Amps] Metal work.

[Jim Thomson]

Earlier some one mentioned about building cabinets and metal parts for amps.
Some things do come easier for some than others. That's a given, but to 
build an amp and do all the metal work is difficult and time consuming 
unless you have the proper tools.
###  You fellow's are making  a mountain out of  a mole hill. Sure,amps  are 80%  metal work, 20%  wiring.   I make all my panels  from6061-T6  plate... 1/8" thick.   Front panel only, is a shinier  alloy. All the various plates are put togethervia  1" x 1"  x  1/8" thick   ANGLE  AL  [6061-T6]K7RDX does the same, or similar.  Each individual panel can be removed, andpunched/drilled, then re-installed.  Huge advantage over pre-fab chassis, done ina break press.  Screw something up?   Simply replace that one panel.  4 x platesmake the sidewalls of the chassis, then main surface is added, then the bottom cover plate.Everything joined  via 1"  x 1"  angle AL. Greenlee  now makes  a combo  drill AND tap.. [ mouser]that drills  and taps a hole, [ and deburs] all in one  swift motion.  The kit  comes with4-40  6-32  8-32  10-32  10-24  12-24  and  1/4-20/28 .  I also use a roper Whitney #5 jr  compound hand punch ,comes with punch's and mating dies  from 3/32"   up to  9/32" [ in 1/32" increments,7 x punch's + dies in all]  If you can punch AL... punch it, don't drill it! I also got a BIGGER ROPER Whitney bench punch, with a 25" armcam action, that will easily punch  3/8" holes in 3/8" thick  6061-T6 platePunched holes are always cleaner than drilled holesMy small drill press  was modified.. and mounted on upside down, 4" channel AL,with a 4" x 4"  block of wood below it.  Now the  19" wide sheetscan sit directly to the bench,  clamped down with special vice grips[threaded rod to below bench with quick rls lock rings. ] All u need is  'A-9'  green  cutting fluid  [for AL]   Lets take the tube mounting and pressurized compartment to start.
There are a lot of holes to put in the surfaces.  This takes a punch or 
a drill specifically sharpened to drill Aluminum without leaving a burr, 
or sharp edge. Edges that need to be "broke" need an even bevel or 
radius that doesn't look like it was done with a paring knife.## Nonsense. Any  Zirconium drill bit  will easily curt clean holes in AL plate.  Ditto with Greenlee  combo drill/taps.    Use the  10 ton hydraulic punch to whack the holes  for the socket and blower assy.    The holes for the tubes and sockets must not look like they were done with a hole 
saw. This can be done with either a fly cutter, or punch press.   Fly 
cutters are used on mills which cost more than the amp. They are also 
very dangerous. ##  fly cutter's are useless things.   You can buy a 10 ton hydraulic punchWITH  5 x large  dies and  from harbor freight  for  $89.00  A fraction of thecost of the eq  green lee product.  Cuts meter holes, tube socket holesblower holes in a matter of minutes, real fast.  Or  borrow one  from urfavorite electrician, they all have one in their trucks. A set  of  28 x TRANSFER punch's is  $10.00  from harbor freight tools,perfect to find the center of holes in vac cap flanges etc. IF you have to cut large diam holes, like for 120mm fans, etc,  I use a Bosch jig saw,  with steel cutting blades.. and SLOW the speed WAY down.Cuts like butter.  My Bosch looks like a long sausage, low to the table.I  also used the Bosch to cut  3  1/16"  diam holes in 3/8" AL plate,for my Rohn  TB-4  bearings, etc.  The holes  were  perfect, looked they had been donewith a hydraulic punch.   U can cut  3/4"  thick  AL  plate  with a bosch.    Punch presses take dies as well which are not cheap 
and not normally made at home. Even given the proper press and punch the 
hole, or holes needs to be made with out deforming the metal sheet. You 
don't just put it all together and punch a good looking hole in a sheet 
of Aluminum. It takes a bit of skill. ## wrong.  A  12 yr old girl can punch clean holes  within 5 x mins ofbeing shown how to use either a 10 ton hydraulic punch, OR any of the roper Whitney products.  It's that simple.     To top it off, there shouldn't be 
ANY scratches in the surface of the metal.##  The only place u really don't want scratch's, is the FRONT panel    Of course the dimensions must 
be proper and the material sturdy enough to make for a solid 
construction.##  I get all the al plates  sheared in huge press, at the local metal shop.Pay cash, and don't ask for a receipt.  I buy the 6061-T6 plate there too.  They usually have loads of NEW scrap ends etc.      Could I use the equipment to make the chassis and sub 
chassis using the drills and fly cutter? Yes I can, BUT I'm not so sure 
about the scratchless surface.  Any scratches and I'd throw it in the 
scrap bin and try again.
##  Most AL plate comes with a protective plastic sheet film on one side.Just leave it on, and drill /punch right through it. Remove, dead last.  Zero scratch's.  Could I build a high powered amp cheaper than purchasing one? ##  Moot point imo... since  emtron, alpha, etc  don't use vac tune and load caps on their amps.    Most  won't handle high power on bypass.[I string all my amps  nose to tail, and use a rotary switch to activate separate key lines for each amp.]The tank circuits in most of them are a joke, esp Ameritron.   The  3/16"  tubing in the alpha  is clearlyundersized for 20-10m. ##  Rolls of 1/4"  3/8"  and  1/2"  Cu tubing is dirt cheap at any home depot.I silver plate all mine with ..'cool-amp'   [ cool-amp.com]  Ditto  with all cu strap.  OTOH Cabinets are fairly easy to make, if you have a good metal brake 
and notcher for the inside corners along with some practice. It's those 
pesky holes that are the hard part.
##  Just rack mount the RF  deck into a surplus 19" / 24" rack cabinet...dittowith  B+  supply, etc.  The panel is probably the hardest part as it includes the difficult task 
of getting large and small holes in the proper position with clean 
edges. Then there is the lettering which can be silk screened, 
airbrushed with a template, or grooved and filled. Each takes a 
particular skill and no small amount of practice. Maybe the most 
difficult of all is just organizing the panel to make it look useful 
without being cluttered.  This is where most home brew projects really 
look like they are home brew.
##  what ??   There is minimal stuff on the front panel as is. While you are at it, buy some digital calipers from home depot, alongwith T square's etc.  Those german stadeler  marking pens [.5mm tip]come in loads of colours, and ,mark AL  easily.   When all holespunched/drilled, marking lines are removed.     There's a reason they don't have a 
row of meters all the way across the panel and only a part of it is to 
save money.  Rather than designing an amp around a tube or tubes, maybe 
it'd be better to keep in mind the size of the tubes while building the 
amp based on the front panel design.
##  well, I use  a row of 4 x  new meter's  across the front of my amps.plate V.. plate I  ... fil V    Grid I    I also meter  fil current, and also hr meter on thefil xfmr, and also meter line V, etc.   Misc meter's on lower portion of rack. Hydraulic punch, bam, done.   Then add turns counters  for the 2 x vac caps+  knobs, etc.   Powder coat, or spray paint the front panel, and it's a thing of beauty.When u fire it up, a smile comes across your face, knowing you just beat Henry radio,Alpha, Harris, and Emtron, etc.. hands down.   At least with HB amps... you can properlysize the  components. Jim   VE7RF   
73

Roger (K8RI)