[NLRS] 4-40 tap

[Dr. Gerald N. Johnson]

On Mon, 2007-02-12 at 01:12 +0000, Donn Baker wrote:
> 
> 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

One other thing. Use the smallest tap wrench and take the cross handle
out. Often its held by a ball and spring. To get it out will need a
slope cut on the outer end of a groove in that handle. You don't need
the torque that handle gives or the inertia it supplies when using a
4-40 tap. Twirl the tap with thumb and forefinger on the outside of the
chuck. That's all the torque the tap will safely handle.

Soap is interesting. Which soap. Ivory, or any deodorant soap?

73, Jerry, K0CQ