Tapping methods without rigid tapping

[Brian]

Fadal made a special bracket that you bolt up to a Tapmatic head that clocks it in and out of the tool changer. That's your fastest way to tap. Second is the tension and compression unit with Bilz style quick change holders, if you use the clutch versions, you can tap to the bottom of a blind hole and not worry about breaking the tap if it hits the bottom. Thread milling on anything over about a 1/4" hole is good, but if you use a single form thread mill you have to circle a lot of times to get to thread depth. If you use multi tooth cutters they are pitch specific, so a 16 pitch will only do 16 pitch threads and so on.

 

[sinha]

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.

Rigid tapping can be almost 2x faster, because up to 20x retraction speed is possible.

 

[EmGo]

Rigid tapping can be almost 2x faster, because up to 20x retraction speed is possible.

On an elderly Fadal, maybe not so much ...

 

[dandrummerman21]

I would suggest that a tap in a floating holder can also retract at 20x speed too (yes assuming the machine is capable).


If the machine is capable of running a rigid tap cycle, you can put a floating holder but code it as rigid. Makes no difference unless you have a tight depth tolerance.

All of my programs have rigid tapping programmed (except for when they get moved to the 1 mill in the shop not capable), but I would say I use floating holders 50% of the time due to having so many of them and depth usually isn't a concern.



I assume some machines may under/overfeed at various RPM, while others don't start and stop the spindle at the same time as movement occurs. The machine that I run without rigid tapping seems to follow along just fine. But firstly when it starts, the spindle turns on, maybe 1/4 second later it starts feeding. When it gets to the bottom of the hole, the feed stops, but the spindle takes 1/4 second to stop. Then when it reverses, same thing, the spindle gets to speed BEFORE the z starts moving back up. I'm fairly confident with running a floating holder that can only extend and not compress with this machine. Because when at the bottom of the hole, the amount it stretches when stopping the spindle is equal to the amount it contracts when it reverses. Can't say the same for all machines, though.

 

[EmGo]

I would suggest that a tap in a floating holder can also retract at 20x speed too (yes assuming the machine is capable).

I think the bilz'es are the bee's knees, so easy to switch out taps and they hold length and the things work so slick but if Fadal made a special bracket for a tapmatic, the spindle doesn't have to reverse for those and if'n I had a 'dal, might be a good choice ... specially if starting from zero.

Not that I'm dissing on Fadals but can't hurt to cut them a little slack in the wear and tear category ...

 

[DouglasJRizzo]

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 ...

Agreed. I do a lot of 1" to 2" diameter threads and thread milling is the way to go.
Under about 3/4" - a toss up, I think. But I still like it better than tapping if I can get away with it.

Good point about the helical interpolation. I know it was optional on a lot of machines up thru the 90s.

 

[kenton]

I've just started to play with thread mills on the Prototrak machines at work, but I have found I have to make the CAM software output any complicated 3D motion as straight line moves or else the control will randomly throw continuity errors.

That might be an option for a machine without helical interpolation, if you have enough memory.

 

[Maverick302]

For the Bilz/reversing style - does the quick change collet outweigh the fact that I could have 3 or 4 comp/tension style holders loaded for the price of one reversing head? ie is it quick and easy enough to just swap taps in an optional stop in the machine and then continue the program, vs preloading 4 different taps?

 

[sinha]

I would suggest that a tap in a floating holder can also retract at 20x speed too

It is not possible without rigid tapping feature.
If rigid tapping is available, there is no need to use floating holders.

 

[dandrummerman21]

For the Bilz/reversing style - does the quick change collet outweigh the fact that I could have 3 or 4 comp/tension style holders loaded for the price of one reversing head? ie is it quick and easy enough to just swap taps in an optional stop in the machine and then continue the program, vs preloading 4 different taps?

Which tension/compression holders are you talking about? Are you talking about those with a regular kind of collet?

All the lyndex t/c tap holders I've got have bilz style quick change tap "collets". Bilz are great.

I've never used one of those tapmatic reversible heads but there's a drawer with a few of them from a long time ago. Almost set a drill press up with one but went another direction.

It is not possible without rigid tapping feature.
If rigid tapping is available, there is no need to use floating holders.

uhhh

G1Z-1.F10.S100M3
M5
G1Z1.F200.S2000M4
M5

I wouldn't personally do that... but you ~could~

I will tell you that on the newer mills (still ~20 years old) that retract taps at 2x the rpm, I use floating holders in them all the time.

I would never buy a new floating holder for a rigid machine. But I've got the toolholders already, may as well utilize them!

 

[bigjon61]

I use floating tap holders whenever I can on our lathes. Our older Okuma lathes don't have the option, but on some of the newer machines it works well. Some of the other setup guys poke fun at me, but I tap to depth in one shot and rarely break a tap, and they are snapping off 10-24 taps by the bushel basket full while peck tapping. Who is the clown?

 

[sinha]

G1Z-1.F10.S100M3
M5
G1Z1.F200.S2000M4
M5

Why just 20x!
Even 200x is possible!!

 

[Maverick302]

Which tension/compression holders are you talking about? Are you talking about those with a regular kind of collet?

All the lyndex t/c tap holders I've got have bilz style quick change tap "collets". Bilz are great.

I've never used one of those tapmatic reversible heads but there's a drawer with a few of them from a long time ago. Almost set a drill press up with one but went another direction.

Yeah, a regular collet style tension/compression holder vs the more expensive options. The Bilz style is basically the same functionality except the taps stay in the quick change portion of the collet and they click in and out? Then there's the reversing style with torque limiting devices. Either of those would be more expensive and thus I have to weigh out my options starting from scratch. Might be worth it to spring for one of the better ones and get another (or more) if I feel it's needed.

 

[CarbideBob]

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, .....

What???

 

[EmGo]

For the Bilz/reversing style - does the quick change collet outweigh the fact that I could have 3 or 4 comp/tension style holders loaded for the price of one reversing head? ie is it quick and easy enough to just swap taps in an optional stop in the machine and then continue the program, vs preloading 4 different taps?

You have to make that decision, and whatever you choose later on you will think it's wrong Changing a tap is instant tho. Just push the ring, out pops the tap, in goes the new one. They are nice. I never regretted using them.

Maybe on fleabay ?

Since someone mentioned it, on a fadal I might be tempted to go the tapmatic route, only because there's no spindle reverse. It's got to be a bit bulkier but maybe that doesn't matter for your work.

No perfect solution here in machine-land ...

^ Me and 5 axes are kind of on the same side here Bob, but probably depends on the type of work you do ... tension-compression always worked great for me but I wasn't tapping 2500 10-24 holes in aluminum, either.

 

[Orange Vise]

Compression/tension heads - I get how these could work in through holes, but aren't blind holes a problem?

Blind holes shouldn't be an issue.

The "risk" of T/C holders is that if there's a delay in the tap grabbing the material, the holder compresses and the net result is a shallower-than-expected thread depth.

The opposite is virtually impossible. The tap cannot grab early as it's not in contact with the material. Therefore the tap can't go deeper than your programmed Z-depth unless the spindle for some reason doesn't want to stop.

 

[Maverick302]

Blind holes shouldn't be an issue.

The "risk" of T/C holders is that if there's a delay in the tap grabbing the material, the holder compresses and the net result is a shallower-than-expected thread depth.

The opposite is virtually impossible. The tap cannot grab early as it's not in contact with the material. Therefore the tap can't go deeper than your programmed Z-depth unless the spindle for some reason doesn't want to stop.

Isn't it possible for some error in spindle rotation to over-rotate the tap and bottom out?

 

[EmGo]

Isn't it possible for some error in spindle rotation to over-rotate the tap and bottom out?

It's not really error, the spindle has mass so it doesn't stop on a dime, that's why the extension feature. You can't program to the bottom z level (or you can but then offset it a little for safety), but at least for me the reversal was repeatable, so once you got it set you were safe. I didn't do too many blind holes right to the bottom tho, otherwise I'd probably like rigid tapping more. Just give it a little extra z offset on the first part, then go in with a hand tap and see how much farther, that's chickenshit hokey but it works

I'm thinking the tension-compression is going to be safer for blinds than the tapmatic tho - at least they have that compression feature, blow it on a tapmatic and kerplow goes the tap.

 

[angelw]

Fadal made a special bracket that you bolt up to a Tapmatic head that clocks it in and out of the tool changer. That's your fastest way to tap. Second is the tension and compression unit with Bilz style quick change holders, if you use the clutch versions, you can tap to the bottom of a blind hole and not worry about breaking the tap if it hits the bottom. Thread milling on anything over about a 1/4" hole is good, but if you use a single form thread mill you have to circle a lot of times to get to thread depth. If you use multi tooth cutters they are pitch specific, so a 16 pitch will only do 16 pitch threads and so on.

Hello Brian,
Extension, Compression tapping tools are available that have a Freewheeling zone. Typically and in its simplest form, its an axial slot in the bore that the tapping tool runs in, with a drive pin engaged in the slot. The Freewheel feature is an Annular groove that the axial slot crosses. To operate:
1. the Z axis is stopped short of the full depth to be tapped and a dwell programmed. During this dwell the tap continues to feed towards the bottom of the hole until the drive pin finds the annular groove. In this position, the spindle can rotate but the tap won't be rotating and therefore, no further feed of the tap occurs.

2. the spindle rotation direction is reversed and the Z axis starts to feed back towards the Z Start Point for the tapping operation. As the Z axis moves, the drive pin engages in the axial slot on the opposite side of the annular groove and starts to feed out of the tapped hole.

With this type of Tapping Tool, very accurate tapping depths can be achieved and tapping close to the bottom of a blind hole is consistently achievable.

Regards,

Bill

 

[Maverick302]

It's not really error, the spindle has mass so it doesn't stop on a dime, that's why the extension feature. You can't program to the bottom z level (or you can but then offset it a little for safety), but at least for me the reversal was repeatable, so once you got it set you were safe. I didn't do too many blind holes right to the bottom tho, otherwise I'd probably like rigid tapping more. Just give it a little extra z offset on the first part, then go in with a hand tap and see how much farther, that's chickenshit hokey but it works

I'm thinking the tension-compression is going to be safer for blinds than the tapmatic tho - at least they have that compression feature, blow it on a tapmatic and kerplow goes the tap.

Got it. I really appreciate the information I'm getting from you all. I'm leaning towards a bilz-style t/c head or three...