FORMING TAP

[mirek1017]

Hello Guys ,I start use forming taps on my job .On first part  we run slow ,tap only -.35 deep and retap by hand .My operator complaint ,when he want to retap the tap going very hard .I check a couple  webside with drill size ,I have good size drills ( i thing so) for example for M6 *1  = .2165 drill .My question is ,what is the tolerance for forming tap ???

 

THANKS 

[Leon82]

You have a lot less tolerance with a form tap on the hole diameter.

you should not be hand tapping with a form tap either ,it is going to be very hard you can peck tap if you want

what kind of material

[mirek1017]

on print is ISM 1125  I think this is 1125 steel ???I have 30 taps holes M6  M5 AND M4  .After 6 hols I broke tap .We start tap only start and retap but these taps going very hard .I can make bigger hole ,but haw bigger ???this costumer is very exacting ,they check all taps holes .

[Leon82]

What was the minor diameter of the holes after they were tapped. If its small use a bigger drill. .0005 will make a difference in the formed minor

[Leon82]

If your using a 213 drill its probably too tight. Buy a 5.5 mm drill. 

[mirek1017]

ok,thanks .I will try tomorrow 

[nickbe10]

What are you hand tapping with? Form taps often work harden the surface which makes re-tapping difficult. If re-tapping with a cut tap your customer will probably spot it and reject the parts as they give a different thread form.....especially if they are  picky about their threads.

They might be specifying form taps for the higher strength they provide , especially in small holes.

you should be able to find form tap drill sizes from various sources (Machinists Handbook). They are always bigger than cut tap sizes because you are displacing material, not cutting material away.

[mirek1017]

OMG  ,then I will change this for standard .I will think the way will be fester ,but is more problems for my .The was my first contact with forming taps 

 

thanks one more time