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What's your favourite technique tapping really small holes?

implmex

Diamond
Joined
Jun 23, 2002
Location
Vancouver BC Canada
Hi All:
I'm building a robotic hand right now, and I'm making finger joints.
This involves tapping dozens of M1.0 x 0.25 threads and I have had poor success just rigid tapping these tiny threads in the past.

So here's how I do it these days.
(This is just for prototyping...I have only one finger to do so far, and there are 41 tapped holes in total)
I write the code for drilling in the conventional way.
I drill all the holes.
I then make a copy of the code with everything stripped out except the X-Y coordinates.
I set up an end mill holder and a tapping chuck that's just a 1/4" rod with the tap set screwed into an accurate concentric bore at one end and a 1 inch diameter knurled button on it so I can turn it with excellent "feel".
The endmill holder allows the tap and its holder to float up and down.
I can then drop the head in Z so the tap is just above the workpiece.
I then single block through the locations and hand tap at each location, using the spindle to hold the tap in good vertical alignment.
It works well, but I have an old old Haas Minimill that has only the most primitive door interlock on it so I can defeat it with just a C clamp and run the code with the door open.

What do you guys with more modern machines that have sophisticated interlocks do?
Can you even run a program with the door open?

Can you trust rigid tapping with a 1 mm diameter tap with say something like a Brother or a Robodrill?
Do you threadmill tiny holes like these?
Do you try to form tap them?
Do you have another way you'd care to share?

My way is great for the prototyping phase, but it'd be a bloody PITA to try to run any kind of production volume this way, so I'm looking ahead and planning...:D

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
 
Just got finished with hundreds of m2 holes in nitronic 60 with a form tap and rigid tapping in a DNM5700 Doosan machining center. Broke 1 tap, but I think that may have been from chips left in the hole before tapping. Good tapping fluid (Rigid dark sulfer based threading oil ,moly D or something similar). I think we changed taps every 80 holes, just in case. We had the taps in stock and didn't want to risk it.Don't know if we really needed to or not. We have done 0-80 the same way, but not in any large quantity. Are you using form or cut taps?
 
I try to form tap whenever possible. What material will you be tapping? One of our clients uses Brother to form tap 100s of M1.2 x .25 in Titanium everyday. Another one of our clients asked me if he could use his brother to tap 0000-160, I said let's give it a try and it worked great. Tapping on Brother is excellent. They patented Synchronized tapping back in 1985. It's a step up from rigid tapping. Brother still has the edge in tapping.
 
I do it Marcus' way fairly often, but not for 41 holes. I have an old beater TG100 holder with a 1/4" dowel in it that pilots into the back of a T-handle tap wrench I made. When tapping with small taps, I leave off the T handle and just turn the knurled tap wrench nose with my fingers. I stick M0s in my g-code at each hole. I don't have rigid tapping, and a Bilz floating holder has too much force and uncertainty for tiny taps.

The tap wrench is a copy of an old Greenfied but with the back end extended and precision bored to fit a 1/4" dowel. It's way nicer than anything I've encountered commercially, and beats the heck out of using a spring-loaded tap guide and a normal tap wrench.
 








 
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