tap drill's

balibalistic

balibalistic

Joined
Jul 14, 2004
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What size drill do you guys use for tapping 2-56 screws? i've been tapping stainless and TI up to 1/8" using #50 drill's,it's damn tight and i'm on the edge of my seat most of the time,but i've yet to break a tap..,until this week!! and i've broken all three trying to tap .160 Titanium.What size drill would you's recommend i use for this,i need something slightly bigger,#49 maybe?
 
A larger hole may work, but the thread will not be as strong. One thing that I have found when tapping hard materials SS, tool steel, etc -- use the tap only a couple of times. Dull taps break frequently.

If you have been using the same three taps for a while, this may be the cause of the breaks.
 
my chart calls for #50 for 2-56, but if we are tapping stainless or other tough materal we always go up a few thousands.
 
spikedog said:
A larger hole may work, but the thread will not be as strong. One thing that I have found when tapping hard materials SS, tool steel, etc -- use the tap only a couple of times. Dull taps break frequently.

If you have been using the same three taps for a while, this may be the cause of the breaks.
Click to expand...

The first tap i broke is the only one i've used for quite some time,with great result's! the other two broke on the first use.
 
With a 2-56 in Ti, you can go as large as a #48 in 1/8" material, and a #49 in 1/16".
My experimentation has shown that @ those diameters, the stainless screw will break before the thread strips.
Doesn't need to be any stronger than that does it?
Haven't experimented with stainless yet since all my small tapping is in Ti.

Experiment yourself, and see.
Drill a series of holes in increasingly larger sizes, tap them, and then torque a screw in them until something fails.
 
When testing by screwing, put a washer with a larger ID than the thread OD of the bolt, between the bolt head and the testpiece. Otherwise your results will be skewed by threads being bulled directly against the face of the bolthead. It will give you a higher 'safety' factor.

Lang
 
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