Drill size for 4-40 screws

Nathan House · Nov 24, 2003

I am unclear on the drill size for a 4-40 cap head screws
is It a number #43 drill?
Also were is a good place to buy taps for the 4-40 screw.
Thanks for any input.
Nathan

Jeremy Evans · Nov 25, 2003

http://www.grainger.com/Grainger/wwg/homepage.jsp

jhiggins · Nov 25, 2003

Tap size - pitch size = hole size

~or~

Tap sizes should be in decimals. Pitch size for machine screws and fractional taps is determined by dividing 1 by the number of threads per inch (TPI).

~so~

4-40 Tap size - (1/40)Pitch size = Hole size
That is: .890 Tap size-.025=.865 Hole size

.865 is very close to a #44 drill, which is .860. Chances are since drills actually cut slightly larger than their diameter, you'll achieve 75% thread depth or better using a #44.

Nathan House · Nov 25, 2003

Thanks Jeff
That is some great info.
Nathan

Bruz · Nov 25, 2003

4-40 Tap size - (1/40)Pitch size = Hole size
That is: .890 Tap size-.025=.865 Hole size
.865 is very close to a #44 drill, which is .860. Chances are since drills actually cut slightly larger than their diameter, you'll achieve 75% thread depth or better using a #44.

Uhh yea, jhiggins beat me to it.

Dan Gray · Nov 25, 2003

http://www.knivesby.com/drill-tap-chart.html

Nathan as long as we've known each other,

I'm surprised you don't use this
it's on every one of my posts?
http://www.knivesby.com/knifemaking.html
it's in the Technical section

Nathan House · Nov 25, 2003

Dan
I really have never taken the time out to look it over
Maybe I should slow down some,I may be missing some important
info.
I printed out the chart you have,problem solved,I see a folder coming in the furture

Thanks Dan
Nathan

Dan Gray · Dec 1, 2003

sorry I just found this deep in my vast e-mail list
man I can't keep up with it

your quite welcome Nathan
just don't let it happen again:grumpy:

just kidding buddy

you send me a picture of that folder when done...

Droppoints · Dec 1, 2003

>4-40 Tap size - (1/40)Pitch size = Hole size
That is: .890 Tap size-.025=.865 Hole size

.865 is very close to a #44 drill, which is .860. Chances are since drills actually cut slightly larger than their diameter, you'll achieve 75% thread depth or better using a #44.<

In the interest of accuracy, a #44 drill is .0860", not .860". I think you will get a rather loose fit if you drill the holes .860.

Dan Gray · Dec 1, 2003

hey that looks purtty close to 7/8" don't it now..

arn't typO's fun.

Nathan House · Dec 1, 2003

Dan
I have somthing I am doing that is a little differnt
I am green when it come to taps size,I can use them but
I am dumb about the sizes.
This has been some good info
Thanks Nathan