Fast spiral tap speeds

[Foster]

I've used the hand taps for years: lots of oil, take your time, put oil in the hole as you cut the threads, back the tap out to clear the tool after a few turns, remember to use oil, don't force the tap it will cut the threads and of course, oil is your friend.

Very successful on all the taps I've done. And with all the roboteers I've taught to tap holes.

I need to tap four 5/16" holes in 2" steel pipe (clearly not a robot project) and a friend gave me "fast spiral tap". These look like twist drills, but have the tap threads on the first 1/2 of the bit. So I drill my starter hole and then use the fast spiral tap to do the tap.

I'm looking for the speed I should set the drill to. In this current project, I'd love to be able to use a hand drill rather than trying to move the project to the shop and the drill press, so if you have hand drill tips that would be great.

I'm also good with "Hey, since you can use a hand tap, use that, just remember to use oil, it's only 4 holes."

[Cory]

It's going to be really hard to align that straight enough with a hand drill. I don't ever tap by hand with spiral flute taps because of that reason.

I would go as slow as possible until you know you're aligned and then you could bump it up to a couple hundred rpm

[JR0405]

I remembering seeing a guy on YouTube use a block of wood with a hole drilled in it to make sure he started straight. I'd recommend doing this.

[ChuckDickerson]

V-Tap guides are helpful for starting perpendicular taps:

https://www.amazon.com/V-Tap-Guide-S.../dp/B000ZN30U4

[Foster]

Originally Posted by Cory

It's going to be really hard to align that straight enough with a hand drill. I don't ever tap by hand with spiral flute taps because of that reason.

I would go as slow as possible until you know you're aligned and then you could bump it up to a couple hundred rpm

Ok, so I'll drill and just use my hand taps since I know that works.

Thanks to the others that posted, I agree that I've "over thunk" an easy job.

[Cory]

If you are looking to be able to tap through holes without stopping and reversing the tap to break off the chip, look into spiral point taps. They will drive the chip ahead of the tap and should tap any reasonably ductile material in one shot without reversing. They are also no harder to align than a standard hand tap.

[ratdude747]

Originally Posted by Cory

If you are looking to be able to tap through holes without stopping and reversing the tap to break off the chip, look into spiral point taps. They will drive the chip ahead of the tap and should tap any reasonably ductile material in one shot without reversing. They are also no harder to align than a standard hand tap.

Seconded. At my employer, this is they type that engineers (like myself,), fabricators, and maintenance workers use. They're great for both hand use and machine use (I've used them at "slow" speeds using cordless drill, drill press, and lathe with good results).

As for brands (at least the ones I've used), Hertel ones aren't too bad (I've grenaded a few but I was abusing them a bit) and the few Kennametal ones I've used at work were awesome (same abuse as the Hertels, didn't break). Irwin ones are pretty good as "retail" brands go (their tap handles not so much, the one I bought my father in law cracked on the first use). Craftsman ones are good as well. Harbor Freight ones (never used at work, personal work only) aren't so good but for aluminum and mild (unwelded) steel are OK if you're nice to them. Avoid the cheapest ones though, as they might as well be made of silly putty. The mid-grade and upper tier ones are worth the extra money.

Somewhat relevant trick of mine: if there is trouble clamping the part in the drill press vice, the tap is slipping in the drill chuck, or if you're tapping a blind hole, use a drill press/lathe to start the tap (to make sure it's straight), and once the tap has started, back out the tap and move the part to the bench vice and finish it by hand. I had a weird foot for a jig clamp I was fabricating for a work project last week that drilled fine on the drill press but wasn't agreeing with the tap (deep hole, M8 tap, Jacobs chuck was slipping) and this trick was how I salvaged the part.

TL,DR: Spiral point taps are awesome!

[DonRotolo]

Although the OP decided to solve the problem by using a different tool, the spiral point tap he was given appears to be the same as what Cory mentions.

Regardless of the RPM, it is critical that he have a way of reversing (or at least stopping) the tap before the tip hits anything solid. So if he doesn't have a Tapmatic head, slow is the answer. But a good tap can run at several hundred RPM, maybe 1200, depending on the details (a harder job needs slower speeds)

Tapping with a hand drill will break the tap with even the slightest movement. Don't even try.

[Foster]

They look more like a spiral drill bit with a tap at the middle rather than what Cory posted. Best picture I could find was this one



I found a site that had the speed calculations I was really after

For mild steel pipe and the 1/4" size hole/tap I needed to go ~30 RPM.

After I did the project with a hand tap, I did try the drill/tap just as a learning point for me. In a press, it was easy peasey to drill the hole and then tap right behind it at a slow speed. Needing to be able to reverse is a key thing.

Unlikely I would have been successful out in the yard doing this with a hand drill.

And if I could afford a Tapmatic head at $350, I'd be lots smarter than I am and would have done this before I sank the pipe into 350lbs of concrete.

Thanks again to all that replied.

[Cory]

Oh, that's just an integrated drill/tap. Totally different than what I thought you had.

I thought you had one of these:



The one you have should in theory not present any problem with following the hole since it's also making the hole (though it could easily end up with both being non-perpendicular to the surface). The one above is much more difficult to align perpendicular to the hole since it has almost no lead in and the flutes are more "aggressive" than a standard hand tap.

[mentorDon]

The drill/tap combo (DRAP) is best used on a CNC machine. The amount of material thickness must be less than the drill length of your tap of course. No blind holes! And for your case, the inside diameter of the pipe must be larger than the combined length of the cutting portion of the drap. The machine is programmed at a surface speed for drilling depending upon material and diameter. A feedrate is calculated to match material and speed. At a programmed 'z' depth after material brake through, the spindle speed is reduced and a new feed rate to match the rpm and pitch of the thread. After reaching the lower 'z' setpoint, the spindle is reversed and the tapping portion is fed out using the previous feedrate. Once the tool is clear, spindle direction is reset to clockwise, rpm increased, and moved to the next location. There are special tapping heads with springs to allow for inaccuracies of rpm and feedrates.

[Foster]

Thanks. After I did the tap the old way, I did some trial runs on some scrap tubing. Key thing is to be able to have slow speed for the tap and being able to reverse. Since the drill press I have had slow speeds I was able to get it down to the suggested 30 RPM.

On the plus side, they are much easier to use as a hand tap since the initial bit helps keep the tap straight in the hole.