[Argofanatic]

Hi, several years ago I discovered just how magnificent spiral fluted taps were for small holes in aluminum. Since then that's all I use.
Now I need to tap a bunch of 12mm (1/2 inch) holes. Is there much of a difference between spiral fluted and regular taps for larger hole sizes ?
I haven't purchased that size tap yet.

Thanks,
Marc.

[dertsap]

spiral flt should work no problem , i wouldn t recommend using spiral point on blind holes on alum.
what about trying roll taps ? i ve had much success with them

[ajl6549]

Rolled thrds. tend to be stronger, esp. in aluminium.

[jackson]

Rolled thrds. tend to be stronger, esp. in aluminium.

yeah i have had the same expireanc the roll tap or form tap do very well but the spiral should work

[ajl6549]

Oh it'll definitely work, and well.

[RICHARD ZASTROW]

I vote for the rolled threads (form taps). Like I said in another thread, I live about 1 mile from Balax's plant.

[Argofanatic]

Thanks for the info. I'll buy a forming tap.

I should have mentioned earlier that my experience was with small holes 4-40 and I kept snapping taps, that's when I discovered spiral flutes.

Cheers.
Marc.

[dertsap]

Thanks for the info. I'll buy a forming tap.

I should have mentioned earlier that my experience was with small holes 4-40 and I kept snapping taps, that's when I discovered spiral flutes.

Cheers.
Marc.

even better time to use roll taps , the small sizes work great , i've done many parts with lots of 2-56 , 4-40 tapped holes in them and rarely one breaks ,
roll taps also work pretty good on larger tapped holes (1/4" + ) in stainless and such where other spiral point and spiral flt fail , didn t beleave it till i tryed it

[ajl6549]

4-40 wow thats small what s + f are you using?

[dertsap]

on a decent machine ,anywhere between 250 to1500 rpm on aluminum

[phantomcow2]

Forming taps are great for aluminum, we use them almost exclusively for all rigid tapping operations. We routinely tap 2-56 with almost no breakage using forming taps.

[kentavv]

Are the same size holes drilled for forming taps as for fluted taps? Do forming taps work fine for hand tapping and in a benchtop tapping tool?

[holbieone]

Are the same size holes drilled for forming taps as for fluted taps? Do forming taps work fine for hand tapping and in a benchtop tapping tool?

they use a special size drill

a forming tap requires a steady continuous motion

it would be very difficult to hand tap with a form tap

[dertsap]

you could easily start the first couple threads with a cutting tap to align the thread then finish with a roll tap

[phantomcow2]

As far as drill size goes, they take slightly oversized drill's compared to your typical flute tap. For example, a 1/4"-20 takes a .201 for a normal. A forming tap I believe takes a .221
There should be charts available online

[Argofanatic]

they use a special size drill

a forming tap requires a steady continuous motion

it would be very difficult to hand tap with a form tap

BUMMER !!!
I just bought several forming taps, I didn't know it would be a challenge to hand tap with these puppies. I have a mini-mill, any suggestions out there.

[holbieone]

a tapping head in a slow spinning drill press should work

[dertsap]

if you pay attention a reversable cordless drill that has different torque settings works great

[kentavv]

http://www.precisiontwistdrill.com/t...rill_sizes.asp

There should be charts available online

[WILLwork4money]

Here is a link to Drill/Tap sizes for "Roll Formed" Metric Threads

*** Make sure you check with your Customer, I've had Customers not wanting Rolled Formed Threads because of the Larger Ø Hole required for these type of threads, even after I explained to them that it is a stronger thread, they have said "NO"

http://www.tapmatic.com/pdfs/02_metricrollformchart.pdf

:cheers: