You misunderstand. I had two hours into the piece when the tap broke (without warning) on the next to last hole. I threw the piece accross the shop!!!!! Not proud, but I was royally P-O'd.
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How to identify machine taps used for tapping head?
- Thread starter nnam
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I guess for me its a habit since I've always tapped by hand because I get more of a feel of the pressure on the tap, power tapping is not for me. No matter what style tap I will go 1/2 turn down add back then advance. I have the Telco tap tool but have never used it. Thanks for your reply.
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The spiral point taps should not be reversed when in the cut. I believe the have quite a bit of positive rake, so the cut easily, but they are prone to chipping (unless you are all the way through). Because they shoot the chips ahead, save them for use on through holes - like most things in life, one will get the best results when using things as they were intended (exceptions aside).
If I have a lot of holes to tap, I review the application with the tooling supplier - get the best tap available and use it per the instructions. One job was 270 pieces, with 2 tapped through holes 3mm screws, I set up the drill press VFD on a slow speed and electrical reverse. I held the tap in an ER16 solid collet (no slip) - after 540 small holes, job done pretty quick and the tap looked great. In this example, the tapping head would not have been better (probably just a pain to set up).
If I have a lot of holes to tap, I review the application with the tooling supplier - get the best tap available and use it per the instructions. One job was 270 pieces, with 2 tapped through holes 3mm screws, I set up the drill press VFD on a slow speed and electrical reverse. I held the tap in an ER16 solid collet (no slip) - after 540 small holes, job done pretty quick and the tap looked great. In this example, the tapping head would not have been better (probably just a pain to set up).
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Several years ago I had to tap many 3/4-10 holes through 1 1/2" of structural steel. I power tapped them without a tapping head and using what most call a hand tap. There were no problems with broken taps or chipped cutting edges. The machine I was using was an old Barnes geared head drill with a 5 Morse taper spindle and a 10 hp. motor.
Just like most things in this world, there's ALWAYS more to the story, caviats, exceptions, and alternatives, and things that you can't do, but you can get away with anyway if you've developed a good feel for it, but here's what I've boiled it down to.
Hand taps are the simplest to make, cheapest to buy, and most readily available. You must back them up to break the chip however. They are what they are.
Spiral POINT taps (Gun Taps) will "shoot" the chip ahead of the tap. This type of tap, in a three flute design, is the strongest you're going to buy. (Staying in the more common range, let's say #8 through half or five eights inch...). You can power these through a hole without stopping, or into a blind hole IF you leave room for the chips. You can hand tap with them, choosing to, or choosing not to back them up, depending on how the material feels when you're tapping. (The chips "flow" better under power than they do by hand where you have to stop to reset your grip on the tap wrench). I don't know if it's a universal fact or not, but I also feel like when hand tapping, they are in general (with exceptions) more "free cutting" than a hand tap.
Spiral FLUTE taps are for power tapping. You can hand tap with them, but they're not as strong, like for like. You can NOT back up with them to break a chip when hand tapping, as you need the chip to stay together, otherwise they jam. In other words, if you have to stop and back up, you have to back all the way out.
For my needs, I've all but given up on buying hand taps. For general purpose/keeping the cased set full, and the little boxes where I keep mulitple spares of very common/mission critical sizes, I buy spiral point. Maybe something with magic metallurgy and fancy expensive coatings if I use it a lot, or for something in particular, or maybe it's an oddball that I use once in a blue moon, I don't care if I have to replace it after not enough uses, I might get a cheap one. But for general use, spiral point (gun taps) with three flutes seems to be the best "ready for anything" tap out there. Hand taps are mostly (for me) best suited to purchase and grind myself and emergency bottom tap, which I hardly ever need, but when I do, I tend to need it right now. (And chasing rusty threads, which ruins ANY tap very quickly). They're cheap enough and quite adequate for that. Spiral flute taps, they're useable, but they're only good (in my experience, others may vary), for tapping under power, in materials that will produce a continuous chip. And they're great for that. So I only order them when I know I'm on a project where I'm going to be tapping a large number of holes in the drill press, and my go to (the gun tap) won't cut it. Which is honestly pretty rare. But they are great when it's exactly what you need.
Hand taps are the simplest to make, cheapest to buy, and most readily available. You must back them up to break the chip however. They are what they are.
Spiral POINT taps (Gun Taps) will "shoot" the chip ahead of the tap. This type of tap, in a three flute design, is the strongest you're going to buy. (Staying in the more common range, let's say #8 through half or five eights inch...). You can power these through a hole without stopping, or into a blind hole IF you leave room for the chips. You can hand tap with them, choosing to, or choosing not to back them up, depending on how the material feels when you're tapping. (The chips "flow" better under power than they do by hand where you have to stop to reset your grip on the tap wrench). I don't know if it's a universal fact or not, but I also feel like when hand tapping, they are in general (with exceptions) more "free cutting" than a hand tap.
Spiral FLUTE taps are for power tapping. You can hand tap with them, but they're not as strong, like for like. You can NOT back up with them to break a chip when hand tapping, as you need the chip to stay together, otherwise they jam. In other words, if you have to stop and back up, you have to back all the way out.
For my needs, I've all but given up on buying hand taps. For general purpose/keeping the cased set full, and the little boxes where I keep mulitple spares of very common/mission critical sizes, I buy spiral point. Maybe something with magic metallurgy and fancy expensive coatings if I use it a lot, or for something in particular, or maybe it's an oddball that I use once in a blue moon, I don't care if I have to replace it after not enough uses, I might get a cheap one. But for general use, spiral point (gun taps) with three flutes seems to be the best "ready for anything" tap out there. Hand taps are mostly (for me) best suited to purchase and grind myself and emergency bottom tap, which I hardly ever need, but when I do, I tend to need it right now. (And chasing rusty threads, which ruins ANY tap very quickly). They're cheap enough and quite adequate for that. Spiral flute taps, they're useable, but they're only good (in my experience, others may vary), for tapping under power, in materials that will produce a continuous chip. And they're great for that. So I only order them when I know I'm on a project where I'm going to be tapping a large number of holes in the drill press, and my go to (the gun tap) won't cut it. Which is honestly pretty rare. But they are great when it's exactly what you need.
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I broke a tap yesterday while backing it out. I was tapping cast iron for my lathe brake. I have never broken a tap in steel or aluminum. But I have broken taps in cast iron multiple times. This time I was lucky. The gun tap broke right where it transitions from shank to tapping flutes.
I didn't understand why on the way out it broke.. I had been blowing using a needle tip the dust from the tapped hole. Lots of particles exitting, so I thought the compaction would get removed.. It was a relatively new tap. ..
I didn't understand why on the way out it broke.. I had been blowing using a needle tip the dust from the tapped hole. Lots of particles exitting, so I thought the compaction would get removed.. It was a relatively new tap. ..
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- May 4, 2019
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Any side load on a tap can cause it to snap. Keeping balanced hand pressure on the tap wrench is important. With a T type tap wrench I keep the jaws a bit loose so if my hands wiggle a bit I'm less likely to break a tap. I am surprised Wodchucker's tap broke where it did. Taps with side load tend to break near the surface of the work. Maybe there was a defect in the tap.