Tapping methods without rigid tapping

[Maverick302]

First off, I apologize if this topic has been beaten to death, but I have done a fair amount of searching and haven't landed on a lot of concrete information. I have a Fadal 3016 without rigid tapping. In the future I plan to add it, but for now, what are my best options? I do low quantity work so versatility is key. It seems the main methods I could use are:

• Compression/tension heads - I get how these could work in through holes, but aren't blind holes a problem?
• Thread milling - How small of a thread size is realistic? Does cost of tooling really add up relying on this method? Any other caveats?
• Manual tapping on drill press with self-reversing clutched head - this is an option, but I would imagine tapping in the machine is better if possible

 

[Philabuster]

Threadmilling works awesome (especially on shitty material) as long as the thread depth is within the tool's reach. I would go that route way before hand tapping. I have threadmilled 4-40 threads in 718 Inconel .250" deep without any issues.

 

[EmGo]

I have a Fadal 3016 without rigid tapping. In the future I plan to add it, but for now, what are my best options?

Tension-compression worked fine for me ... on the first hole go way shallow, then run it in by hand and count the turns, then adjust. Leave yourself a little room, they aren't too easy to second-guess but they repeat well, so once you have the first one figured, you're set.

I wouldn't try running right up to the bottom of a blind hole tho.

Unless you are doing a lot of tapping, they aren't half-bad. I never felt deprived.

 

[gustafson]

On a slower machine with slower spindle tapping heads seem to work well, I imagine there is a learning curve, but since you can accurately tap on a drill press with a stop it really cannot be that hard

 

[EmGo]

On a slower machine with slower spindle tapping heads seem to work well,

These aren't the tapping heads you are thinking of, those would not work in the tool changer for poop. These are more like a collet with a square drive that are spring-loaded in both directions. Think of it like rigid tapping that's really sloppy. It works the same way, you just have to give it more room for the spindle to change direction. The springs give you that leeway.

The ones I had were nice, Erickson maybe ? The tap collets clicked in and out, could change a tap in seconds.

 

[DouglasJRizzo]

I've really come to like thread milling quite a bit.
Accurate, fast, and the quality of thread is pretty good.

 

[EmGo]

I've really come to like thread milling quite a bit.
Accurate, fast, and the quality of thread is pretty good.

Maybe for bigger or nicer threads but tapping is gonna kick its ass both speed and cost and ease for average threads.

Do early fadals without rigid have helical interpolation, btw ? Seems like they should but them groovy sooprizes can bite one's ass ...

 

[Maverick302]

Tension-compression worked fine for me ... on the first hole go way shallow, then run it in by hand and count the turns, then adjust. Leave yourself a little room, they aren't too easy to second-guess but they repeat well, so once you have the first one figured, you're set.

I wouldn't try running right up to the bottom of a blind hole tho.

Unless you are doing a lot of tapping, they aren't half-bad. I never felt deprived.

I assume it gets programmed as a rigid tap cycle?

 

[rklopp]

I assume it gets programmed as a rigid tap cycle?

Yes, but I always under-feed at about 90-95% of the rate given by pitch x RPM. This lets the spring in the holder pull out.

 

[EmGo]

I assume it gets programmed as a rigid tap cycle?

On K&T and Sundstrand it was a cycle, G83 maybe ? Just set your start point, finish point, and lead and the cycle did the rest.

 

[gustafson]

These aren't the tapping heads you are thinking of, those would not work in the tool changer for poop. These are more like a collet with a square drive that are spring-loaded in both directions. Think of it like rigid tapping that's really sloppy. It works the same way, you just have to give it more room for the spindle to change direction. The springs give you that leeway.

The ones I had were nice, Erickson maybe ? The tap collets clicked in and out, could change a tap in seconds.

They make tapping heads just for this. I own one, but never used it
Smaller than a face mill

 

[Booze Daily]

The ones EG is referring to are Bilz tap holders.

Bilz USA

 

[RCS Machine]

I've been using a Flex Arm pneumatic tapper for decades now. Most of my stuff is long hour, one-off stuff where I can't afford to have any tapping mishaps/broken taps. Do thread milling also but on larger holes and stuff I can afford to F-up if something goes south.

 

[EmGo]

The ones EG is referring to are Bilz tap holders.

Bilz USA

Exactly ! you've probably still got a memory and everything !

They are nice and they work super and I never felt deprived from not having rigid tapping. Basically it's the same, except more like dirt track than asphalt ...

Was G84

G84 TAPPING CYCLE {MODALI Functional Description:

When programmed with X,Y,Z,R and F-word information recognizes a clearance plane and feeds to Z depth at programmed feedrate. When Z depth is satisfied, the spindle is reversed and a delay is forced which is sufficient to allow the spindle to achieve 80% of the programmed RPM. The Z axis then feeds back to the clearance plane. When the clearance plane is reached, the spindle reverses direction in anticipation of the next coordinate. This cycle can be initiated in either the clockwise direction (M03) or the counterclockwise direction (M04). While G84 is in effect, the feed.rate and spindle speed are forced to 100% of their programmed value during actual cutting regardless of the setting of the override switches. Feed.rate and spindle speed override are re-established during motion to new hole locations.



You may already have something similar, cycles like these were common before rigid tapping came along.

 

[Mud]

There are Tapmatic tapping heads for CNCs, nice for lots of holes. Program the same as a boring cycle. I have a few I no longer need.

 

[memphisjed]

There are Tapmatic tapping heads for CNCs, nice for lots of holes. Program the same as a boring cycle. I have a few I no longer need.

Are they shelf holders or going into the for sale section soon?

 

[Mud]

Are they shelf holders or going into the for sale section soon?

I'll have to dig them out first before I can put them up. The last dozen things I put up got no interest so I cooled off on putting in the effort.

 

[dandrummerman21]

Here's a consideration that you might sometimes face when your machine doesn't have rigid tapping.

I was FORM TAPPING some holes on a mill without rigid tap (the only one in the shop without it), and the tension/compression holder that I was using (lyndex) could float in both directions, up and down. (Some varieties can only "pull out" and not "push in")


Anyway, it was an M8 form tap in stainless, and sometimes the tap would not start right away until it had bottomed out on pushing, then the thread would start.

Also the thread had to go to pretty close to the bottom of the hole, maybe 3/4 deep.

So what I started doing was program it to tap the hole twice to full depth. If the form tap didn't start immediately when tapping the first time, it would have just a few threads started, and the 2nd pass would follow the first right to the bottom of the hole.



I wouldn't do this on a cut tap, as a cut tap might not want to follow previously cut threads. But then again, cut taps rarely have any issue getting started in a hole unlike some form taps.


I doubt that will help anyone. but it worked in a pinch.

 

[sinha]

Yes, but I always under-feed at about 90-95% of the rate given by pitch x RPM. This lets the spring in the holder pull out.

I heard about this suggestion earlier also.
Since floating holders work better when in slight tension, in-feed can typically be 0.95 x F, and out-feed be 1.05 x F.

 

[5 axis Fidia guy]

You really don't need rigid tapping unless your tapping hardened material or peck tapping for whatever reason. Get yourself a good floating tap holder, use spiral point taps and drill the hole slightly deeper, tap to depth and be done with it. It kills me when I see guys power tap short and finish by hand. If you break a tap every once and a while mill it out, not a big deal.