CNC retrofit- how to tap lots of 1/4-20

[nate]

whats the best way to tap a bunch of 1/4-20 holes in aluminum with a 3 axis BP conversion? some blind, some through.

can a tapping head be used with my Z axis? is their a tapping head that will allow me to just program Z down, go to depth and then z up for the retraction? will the movement in the z not allow the tap head to "pull" the tap into the metal as it is designed to do?

I dont have manual control of my Z anymore, so I need to fnd a way to use a tapping head in an automated manner.

Any thoughts?

[Sparky_NY]

What are you using for a control? I use mach3 and many people do semi rigid tapping with it on a regular basis. You will need a semi rigid tapping head for this purpose.

[Torsten]

You do not want a ridgid Tapping head if your machine dose not support ridgit tapping.
Use a Floating Tap head and just use a G84 Tapping cycle.

[nate]

I retrofitted with Mach3 and Gecko 203v's.

So i need a floating type / semi rigid? head? can you guys recommend one? seems their are a few hundred different kinds...

I dont think Mach3 suports G84. Am I wrong?

[gus]

a procunier tapping head is just a friction clutch drive you need a stop arm or maybe they make a housing for the quill.

should allow you to do what you want

[Sparky_NY]

Originally Posted by nate I retrofitted with Mach3 and Gecko 203v's. So i need a floating type / semi rigid? head? can you guys recommend one? seems their are a few hundred different kinds... I dont think Mach3 suports G84. Am I wrong?

You may be right, I am not positive but I do know many people do semi rigid tapping with mach, often called SRT. They write a custom M command for the purpose. There are examples and pre-wrote code in the mach forum. All reports say it works extremely well. I have a floating head and researched the subject because I will be doing it in the very near future. I just finished up a retrofit.

I have a hardinge TT tap holder. They come in 2 sizes the only difference is the shank size.

[Sparky_NY]

Little late but I verified tonight the G84 tapping cycle does indeed work in the current release of Mach 3. I am using a Hardinge TT semi rigid tapping head. Did my first row of holes without much effort. Its pretty easy.

[jmelson]

Originally Posted by nate whats the best way to tap a bunch of 1/4-20 holes in aluminum with a 3 axis BP conversion? some blind, some through. can a tapping head be used with my Z axis? is their a tapping head that will allow me to just program Z down, go to depth and then z up for the retraction? will the movement in the z not allow the tap head to "pull" the tap into the metal as it is designed to do? I dont have manual control of my Z anymore, so I need to fnd a way to use a tapping head in an automated manner. Any thoughts?

I used a Procunier 15000 CNC tapping head for this type of work. (I think maybe the 1/4" and up needs the 16000 model.) It is a pressure-operated forward/reverse clutch. When you push the tap forward, it engages the forward clutch, when you pull back, it engages a 2:1 reverse clutch. So, you calculate the correct feed at whatever spindle speed you select, feed Z to required depth, then retract at twice the forward feedrate. If the feed is a little lower that the exact number, the clutch will slip a little to allow the Z feed to catch up. (If the feed is too fast, ouch, it mashes the tap!)

The only problem with this is the thing is so LONG, the tap is about 8" from the spindle nose.

I used this with spiral flute taps, and it worked quite well, I could tap holes all day long. I made some fixture plates with 144 10-32 holes in less than an hour, spotting, drilling and then tapping the holes. You can also run combined drill-taps with it, although the lack of stiffness may make hole position a bit loose.

Jon