[NLRS] 4-40 tap

[Donn Baker]

Hi Jon,
Any good hardware store should have the common size taps, down to 4-40.  If
you don't find a set, you'll need a #43 drill for tapping steel or brass.
Like Jerry suggested, a larger drill works better for aluminum, say a #41
or #40.

Never cut a thread without lubricating the tap, especially in Al.  "Tap
Magic" is the best I've seen, but, again as Jerry said, kerosene works
well.  Oil does NOT (for Al).  Light oil is for steel or brass.

4-40 taps are quite breakable.  Quite frankly, I'd advise you to buy two
while you're at it.  Hub Hobby may have them, but Lowe's, or a hardware
store, is a better bet.  You really want "tool steel" for the tap.  A lot
of the ones you'll find (especially at Lowe's or hardware stores) will tend
to be "carbon steel."  May be marked that way, or a darker color.  Carbon
steel cuts well, but its a lot more brittle than tool steel, and will break
easier.

Oh.  If you're going to tap copper, work VERY slowly, use LOTS of fluid;
cut maybe 1/4-turn, back off, repeat.  Copper is sticky, and will break
taps very, VERY easily. (Experience speaking.  AND its a )*&(&() getting
the broken tap out of the hole !  Mostly, you don't.)

Lastly, make sure you don't flex the tap.  It needs to be perpendicular at
all times.  You can get away with being sloppy with 10-xx and 8-xx taps;
maybe w/6-xx, but not so much 4-xx.  Smaller than 4-40, I do tapping in the
drill press or mill (with out power, of course... just to keep alignment of
the parts).

73 Donn
WA2VOI/0

At 16:26 11-02-07 EST, W0ZQ at aol.com wrote:
>
>
>Anyone know of a good source for a 4-40 drill  and tap ?   I suppose Hub 
>Hobby ?   I looked at DigiKey and  did not see a listing for taps.
>
>73, Jon
>W0ZQ
>
>
>Thanks for  your participation in the 2007 MnQP !  
>
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