[modeleng] Tiny screws
- From: "Shep" <shep.28@xxxxxxxxxxxx>
- To: "Modeleng" <modeleng@xxxxxxxxxxxxx>
- Date: Sun, 2 Dec 2007 11:12:12 -0000
Some years ago, I made a half-sized copy of a Stuart V10 stationary engine.
I reduced the Stuart plans to 50% and made the entire thing out of solid brass.
The spoked flywheel and the minute sliding valve were quite fun to make -
particularly when I dropped the valve and took two hours to find it again!
This size model needed quantities of 12 BA screws and numerous tapped holes.
The 12 BA taps are very easy to break - but I had no such problems. I drilled
the tapping hole in the milling machine, and did the tapping without moving any
of the slides. I held the tap in an Eclipse pin vice, which has a hollow
handle. I fitted a rod, as a sliding fit, into the hollow handle, and held
the rod in the drill chuck. This made tapping easy and accurate.
CUTTING such small screws to length is always a problem. I have a Dremel
mini-grinder, which fits into a little drill press, which has a vertically
adjustable table to alter the height of cut. I attached a Jacobs chuck
vertically on this table to act as a vice. I placed a collar above and below
the drillpress head, thus immobilising it vertically, but allowing a free
horizontal swing. When fitted with a tiny cut-off disc, with the screw held
in the chuck, and the length determined by the position of the table; one swing
of the cut-off disc neatly severed the screw, giving a square cut, with an
undamaged thread.
What about some favourite hints from you chaps?
Cheers! Hubert
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