For the creation of specialized parts and plates, I've started using the
same vendor that produces my PC boards. No room for a machine shop here,
and honestly, I'm not much good beyond a drill press and jig saw.
The CAD software is called eMachineShop. So far, I've had them produce
plates with several rectangular holes for Molex connectors that use
retaining end tabs. One can control every aspect on the X, Y, and Z axis.
Last month, I used the software to re-create a small tapped block of brass
used to hold a switch assembly on a Bird PEP wattmeter board.
Since childhood, I've been creating plate cut-outs with a series of drilled
holes inside the outline perimeter, followed by a hand nibbler, then
finished off with a flat file for square holes; semi-round for circular
holes. Two tools I've depended on to get any kind of precision with manual
cutting methods: (1) a General brand precision metal ruler; and (2) a
high-quality caliper.
The big "negative" when using the CAD software is the cost. You can't
accomplish any project, no matter how simple, for less than about $150 for a
prototype. The high cost is mainly due to setup fees. It makes much more
sense to use these vendors when quantities are involved. By contrast, I
don't know what my projects would cost had I taken them to a commercial
machine shop -- but I suspect it would be similar.
Paul, W9AC
----- Original Message -----
From: "Bob Sullivan" <robert@isquare.com>
To: "Jim Garland" <4cx250b@miamioh.edu>
Cc: <amps@contesting.com>
Sent: Friday, September 13, 2013 8:54 AM
Subject: Re: [Amps] Workshop Danger
Jim,
I could not agree with you more! Fly cutters should be simply tossed away.
For large holes I pay the freight and take the panel to a local machine
shop. For a few dollars I get pretty large holes at no danger to myself.
:-)
73, Bob
WØYVA
http://www.isquare.com/personal_pages/ras-hardware.htm
On Sep 13, 2013, at 8:24 AM, Jim Garland wrote:
My least favorite part of homebrewing an amplifier is making the meter
cutouts and tube socket holes. Last evening I cut three 2.90 holes for
GU-74Bs and survived the experience. I have a set of hole saws, but not
metric ones for Russian tubes, and therefore had to use a fly-cutter.
IMHO,
fly-cutters are the most dangerous tool in a workshop. I hate the things.
I
securely clamped the sheet aluminum stockl to the bed of a large
(floor-mounted) drill press, set the drill press on its slowest speed, and
used aluminum cutting fluid. One has to advance the fly-cutter VERY slowly
to prevent the cutting tool from grabbing the aluminum. If that happens,
the
sheet aluminum is likely to go flying around in a big circle like a sythe.
The other danger is absent-mindedness, which can lead the drill press
operator to reach in with his fingers to remove a piece of aluminum
debris.
Fly-cutters should never be used with a hand drill, as I stupidly tried
once
as a teen-ager. They absolutely require a large floor-mounted drill press
with a sizeable bed.
73,
Jim Garland W8ZR
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