considerations for thread forming taps

[1ctoolfool]

need to tap 1.5" deep M8 1.25 blind hole in al 6061. first .5" is clearance with no thread. Thinking of thread forming tap for the reason of no chips, single pass,
anything i need to consider and is this a good application for this type of tool?
thanks
joev

[dertsap]

thats a good application for a form tap, just remember the tap drill size is different than what you would use for a cutting tap , it maybe worth looking at the tapdrill dia tolerance for that depth of hole , it would be safer tapping if you drill near the top end of the tolerance

[AMCTony]

Run your coolant very rich or use a tapping fluid like tap magic. Both of these methods have given me good results.

[PBMW]

I tap about 3500 5/16-18 1 1/4 deep holes a day .
Form taps rock.

[Vern Smith]

Do you do this in one shot or with a peck or two?

[PBMW]

One shot.
I'd have to go look to be sure, but I think we're using an"M" drill. 1500 rpm. Balax taps

[the thrill]

Originally Posted by PBMW I tap about 3500 5/16-18 1 1/4 deep holes a day . Form taps rock.

indeed they do. i love form taps

[JMFabrications]

I run the OSG form taps in 6061 all day, I agree with everyone else.....they rock! I run my 8mmx1.25mm taps a little on the safe side at 50 SFM, that comes out to about 30 IPM and 606 RPM. I use a 7.4 mm drill which gives you about 70% thread.

[bremenrules]

OSG and Greenfield both work great. Big fan of form taps for our own projects. Unfortunately, they tend to leave a little bit of a lip at the top of the hole which can easily be cross threaded by careless customers and shop owners.

[the thrill]

a lip? are you making a large enough chamfer at the top of the hole? maybe you need to change the angle of your spot drill. are you using a 60 degree center drill or an NC spot drill?

[bremenrules]

I'm using a 120-140 degree NC spot and doing a 90 degree chamfer before tapping. It's not like a huge amount of metal's bumping up over the top of the part, but there seems to be a bit of thread before the start of the hole which can be easily bungered up. At least that's my observation with finer/smaller threads like 6-32 and 4-40. Just enough metal's being squeezed up over the top to cause issues. It's a shame, because I'm a huge fan of form taps. Thousands of parts from a single tool and not an ounce of chips to deal with....

[duenow]

Originally Posted by bremenrules I'm using a 120-140 degree NC spot and doing a 90 degree chamfer before tapping. It's not like a huge amount of metal's bumping up over the top of the part, but there seems to be a bit of thread before the start of the hole which can be easily bungered up. At least that's my observation with finer/smaller threads like 6-32 and 4-40. Just enough metal's being squeezed up over the top to cause issues. It's a shame, because I'm a huge fan of form taps. Thousands of parts from a single tool and not an ounce of chips to deal with....

Tap it then spot with 90 degree, with a sharp spot. I do that all the time.