Rigid Tapping Question

kentd · Jul 3, 2019

I'm going to start experimenting with rigid tapping on my Haas S-Mini Mill, and I've ordered the correct taps for aluminum, but in the mean time can I use standard taps that are used for manual hand tapping? ( In other words the style that most hardware stores sell )

I'm going to be tapping a 5/16 18 coarse thread 1" hole that has been predrilled to about 1.25" deep.

I would definitely use the peck feature to help extract out the chips ( especially until I get my tap that is designed for CNC )

Thanks for any thoughts or suggestions.

Kent

Booze Daily · Jul 3, 2019

I wouldn't use hardware store cutting tools, but if you have time to kill, extra parts and want to experiment, have at it.
I wouldn't expect good results though.

Brian · Jul 3, 2019

Hand taps, which is what you will find at hardware stores, don't work well being power tapped. They tend to load up with chips and need frequent backing off and clearing of the chips. You will want spiral point taps for thru holes and spiral flute taps for blind holes.

If you have any time invested in the parts you want to thread, snapping a tap off in the material is an expensive proposition. So it might be best to test on scrap material.

gkoenig · Jul 3, 2019

kentd said:
I would definitely use the peck feature to help extract out the chips ( especially until I get my tap that is designed for CNC )

If you are tapping aluminum, you didn't get the correct taps - unless you have a compelling reason not to, the aluminums should always be form tapped. No chips. That is a somewhat big hole, so you can futz with the pre-drill hole size to get the power requirements down (if necessary) with little/no impact on final thread strength.

metalmadness · Jul 3, 2019

you definitely dont "need" form taps. I use them for anything under 5-40...but I have never broken a spiral flute tap in 6061 larger than that, even in shallow blind holes. All you need is a good spiral flute with the right coating. Emuge and Kennametal are my go-to brands.

Also, I have custom ground many standard hand taps for use in 6061 blind holes and had no issues, as long and you drill deep enough and use peck tapping. Aluminum is easy. Assuming you have flood coolant or good chip evac.

G00 Proto · Jul 3, 2019

I must be feeling disagreeable this morning

Don't bother trying hardware store taps for rigid tapping. They are drastically inferior material and they have the wrong grind. For rigid tapping (or any power tapping for that matter), you need a spiral tip tap. It will break the chip and push it forward. A hand tap (hardware store) has no chip breaking characteristics because this is accomplished by both the start and stop of manually turning a tap and by periodically reversing the tap. You may be able to accomplish this by peck tapping, but I wouldn't bet much on your success ratio.

Common rule of thumb is that on blind holes in stringy material, you are better off with a spiral FLUTE tap. It will bring the chips back out of the hole. I must be marginally incompetent, because I find spiral FLUTE taps drastically more fragile and not worth the risk. For blind holes in most materials, I use a form tap.

If you have a through hole or one with plenty of clearance in the bottom, it is recommended to use a spiral TIP tap. It is designed to break the chip and push it forward (also called a gun tap). These are generally stronger than spiral FLUTE taps.

G00 Proto · Jul 3, 2019

Hand Tap/ Spiral Tip/ Spiral Flute

Wsurfer · Jul 3, 2019

I used hand taps with my new machine while waiting on tooling. They were 1/4-20. Worked fine, but i also ran low sfm. There is also a drastic difference in hardware store taps and quality taps. I would not try it with low grade hand taps. I once bought a crap 1/2-13 hand tap that was so dull new, even using a cheater bar it wouldn't tap aluminum worth a crap.

g-coder05 · Jul 3, 2019

Here's a really good vid from Haas on taps.
YouTube

Bobw · Jul 3, 2019

Wsurfer said:
I used hand taps with my new machine while waiting on tooling. They were 1/4-20. Worked fine, but i also ran low sfm. There is also a drastic difference in hardware store taps and quality taps. I would not try it with low grade hand taps. I once bought a crap 1/2-13 hand tap that was so dull new, even using a cheater bar it wouldn't tap aluminum worth a crap.

Larger straight flute (hand taps) are actually pretty easy to turn into a spiral point (gun tap). A dremel tool
and a cut off wheel, and you're off. It may not be perfect, but if its the difference between a $30 tap and a
$100 tap to punch 4 holes, I'll make the modification...

As for the hardware store stuff. Unless you have a VERY special hardware store, its all garbage.. And my local
hardware store even carries split point cobalts, and all their taps suck..

However.. On a Sunday, in a pinch, those Hanson POS's can be made servicable.. Especially in the larger sizes.
The biggest problem with them that I've found, is they finish grind them, and then heat treat, so all the edges that
NEED to be sharp get rounded over.. Dremel tool and a cut off wheel. Bring the inside of the flute back so that the
cutting edge is sharp, and they can get you through an emergency.

Wsurfer · Jul 3, 2019

Bobw said:
Larger straight flute (hand taps) are actually pretty easy to turn into a spiral point (gun tap). A dremel tool
and a cut off wheel, and you're off. It may not be perfect, but if its the difference between a $30 tap and a
$100 tap to punch 4 holes, I'll make the modification...

As for the hardware store stuff. Unless you have a VERY special hardware store, its all garbage.. And my local
hardware store even carries split point cobalts, and all their taps suck..

However.. On a Sunday, in a pinch, those Hanson POS's can be made servicable.. Especially in the larger sizes.
The biggest problem with them that I've found, is they finish grind them, and then heat treat, so all the edges that
NEED to be sharp get rounded over.. Dremel tool and a cut off wheel. Bring the inside of the flute back so that the
cutting edge is sharp, and they can get you through an emergency.

Good info, thanks.

eaglemike · Jul 4, 2019

Learn to use form taps in aluminum. Life will be far better. The Super Mini is decent at tapping. Don't try to go too slow, rpm-wise.
I can't remember how many, or how many different sizes I did when I had one, but it was a lot. I usually kept rpm between 750 and 1500.
Taps made for aluminum help. I did at least up to 10mm without issue, and smaller worked even easier.
On my Brother machines, I've form tapped up to 1/2-13 4" deep (because the customer wanted it that deep) without issue. Would have been more of a challenge to cut tap.

DMF_TomB · Jul 4, 2019

many times a part is machine tapped to 3 tap dia deep and then hand tapped to final depth to avoid breaking a tap in a part
.
so 5/16 tap x3 is 15/16" deep machine tapped. as part gets more complex and labor intensive you take more precautions to not scrap the part. that is 5 minutes hand tapping to final depth versus remaking part taking 4 to 40 hours.
.
even a 2% failure rate can often cause 10x the delays in time that you were trying to save. that is at end of year if remaking scrap parts takes 100 hours and you were trying to save 10 hours of time. it literally is taking 10x longer than the time you were trying to save by the end of the year.

Larry Dickman · Jul 4, 2019

just my $.02. If you're just experimenting and just trying to get comfortable with tapping cycles with shitty hardware store taps, I would drill the minor dia a little oversize. Makes tapping easier. For a 5/8 thread an inch deep, I wouldn't bother pecking. It's not that deep.

Kapster · Jul 4, 2019

I am using Emuge form taps more and more in aluminum and even mild steel. Saves so much heartburn in blind holes.

I would think a hand tap would be ok short term as long as you did pecks.

Sent from my moto g(6) using Tapatalk

NAST555 · Jul 5, 2019

Don't go the "hand tap" way because well... they are made for hand tapping.

g-coder actually linked the vid I was going to after reading your post.

I do loads of general rigid flange tapping from M8 to M20 all blind holes in Aluminium,Stainless and profile cut mild steel. Like G00 Proto wrote Spiral flute taps are definitely weaker but it is what I have to predominantly use because of the hole depth vs tapping depth requirements. The correct coolant concentration is pretty important on Aluminium. I sometimes ever grab a can of cutting paste on stainless and get the operators to coat the tap properly before each hole.

There are so many guys out there that make great taps that I don't mess around with crap stuff, honestly even YG have REALLY decent Aluminium specific taps that kick butt. So for your application I would go with an aluminium specific spiral flute tap and not even bother with pecking.

I am not disagreeing with the guys that said that form tapping is the way to go but if I only had a few parts to do I would grab any spiral flute Aluminium specific tap that I have and seriously hit it hard...

DMF_TomB · Jul 5, 2019

spiral tip and spiral flute taps are normally what is used for machine tapping.
.
be aware taps are often made for special materials. a slightly dull general purpose tap used on aluminum bronze can break 10x easier than a sharp or better yet a sharp tap made for aluminum bronze tap.
.
when you hand tap to final depth you can "feel" the cutting resistance. machine tapping you normally have no ideal how much stress is on the tap. some dull taps will squeal or make noise tapping but often the tap just breaks and was making no noise.
.
a "bilz" tap holder is a clutched and often floating extension compression spring holder. some have a clutch and a thin rupture disc. that is if too hard to tap clutch slips and as machine pushes on tap it goes into the holder. rupture disc is like a fuse, once broken you replaced it, its just a thin metal disc against end of tap.
..... without having a method to allow tap to go into tool holder on overload you often got only one second til tap breaks if its not turning its being squashed as machine travels forward

Bluejeep · Jul 6, 2019

really you should be able to get a proper tap in just a day or 2 why mess with crappy hand tap.

g-coder05 · Jul 6, 2019

Just when you think you are good at rigid tapping here comes Emuge to spice things up a bit. I would really like to see the code for running these.

YouTube

DMF_TomB · Jul 7, 2019

rigid tapping cnc can be amazing. if you ever hit the Z soft stroke limit tapping in a hole, machine will literally stop tapping tap still in hole. most times if tap holder holds tap with set screw you loosen setscrew and handle mode the tap holder out of the way and put hand tap holder on tap to finish tapping hole.
....Z soft stroke limit common on many cnc like horizontal cnc to keep machine column from crashing into pallet/table. new machines often leave more space like many inches between column and pallet where maybe later soft stroke limit is adjusted so safety clearance is much less
.
a machine that has trouble rigid tapping will continue spindle turning with Z not moving and tap will screw itself into part pulling out of tap holder. that is the tap in tap holder length can change if machine is having trouble rigid tapping. many machine when they sense being out of tolerance rigid tapping will stop with error message. usually high speed tapping in low gear can give problems with some machines

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