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Tap drill for 3/8-28 tap

plastikdreams

Diamond
Joined
May 31, 2011
Location
upstate nj
I have to tap 2 holes 3/8-28. All the drill charts I've found do not have this size. Per the ghuring site it recommends .340 for the hole size at 75%, which is basically a letter R (.339) drill. Does this sound correct? This is for a sensor not load bearing.
 
I have to tap 2 holes 3/8-28. All the drill charts I've found do not have this size. Per the ghuring site it recommends .340 for the hole size at 75%, which is basically a letter R (.339) drill. Does this sound correct? This is for a sensor not load bearing.

For standard taps (75%). Your tap drill will be the major diameter (.375) minus the pitch (1/28)
.375-(1/28)
.375-.03571=.3393
Or, as close as you can come to than size.
 
I didn't see 28 in my mh v28. But looks like the numbers match up. Looks like they are going to use a nut to tighten up some threaded suction cups to hold vacuum. I guess npt wasn't good enough :nutter:
 
It can be a shitshow here one engineer from dept a specifies something being made for dept b but then an engineer from dept b says its supposed to be something else...then we can't get the 2 of them to qualify what is right because neither are sure...we've had to rework brand new molds because of this lol.
 
Bsp wasn't even remotely in the equation...I've never even threaded anything bsp. Funny thing is, they brought me 2 taps and a similar part that would thread into the block. The nut on the part threaded onto the 3/8-28 a little loose but wouldn't even start on the bsp tap. Tapped a hole using the 3/8 tap and the part was very tight threading in, tapped a hole bsp and the part was just a little lose and the nut could be used to tighten it up. Crazyness...
 
It can be a shitshow here one engineer from dept a specifies something being made for dept b but then an engineer from dept b says its supposed to be something else...then we can't get the 2 of them to qualify what is right because neither are sure...we've had to rework brand new molds because of this lol.

and to cap it all a machinist who can't figure out the right diameter drill for a tap........
 








 
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