Tapping Threads Into Aluminum

I need to tap some new holes (#10-32) in a 3" Max Q aluminum fin can. I bought a #10-32 tap from McMaster (part #2522A759) and looks like most recommend a "tap wrench" for these and doing it by hand.

Who's to say I can't chuck this thing up on the drill press and tap away?

AlnessW said:

I need to tap some new holes (#10-32) in a 3" Max Q aluminum fin can. I bought a #10-32 tap from McMaster (part #2522A759) and looks like most recommend a "tap wrench" for these and doing it by hand.

Who's to say I can't chuck this thing up on the drill press and tap away?

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You can, but you still have to turn the tap by hand. There is actually a tapping jig for use with a drill press.

No problem. Do it manually, keep pressure and go slowly. You are only going 1/16". You could also use a variable speed hand drill.

Usually tapping requires a tool that handles the removal of the chips. With the tap wrench I use, I have to turn it clockwise and then counter clockwise part way to get it to back the chips out. For the thickness you are looking at and since it is a through hole, it might be fine. I already have the wrench though so I would use it. Hopefully someone with more direct experience will weigh in.

The other thing a drill press for tapping does is stop and reverse... The tap has to instantly stop and reverse back out of the hole, or you'll just bottom the tap in and strip out your new threads.

Adrian

I've done it with a Hitachi power screwdriver and a Dewalt hand drill with clutches. You can do it on the drill press too. Put it on the lowest speed, put light pressure on the quill handle and turn it off a few threads before the tap bottoms out. You can also use a rod in the chuck as a guide to keep the tap straight while you get the threads started.

I do so much tapping that I bought a tapping head, but even used they are a couple hundred dollars.

Use a cordless drill and some wax. Plow through it if it is thin (1/8" or thinner) you can use oil instead of wax but it is messy. 1/16" you may not need anything. Don't be shy

I build with a lot of aluminum. We only use the Tap-a-Matic when doing bottom taps in letters

Thanks all for the advice - and yes, the material I am tapping is only ~1/16" thick or so.

I guess I'm wondering how this is usually done on a lathe (for example - threads on a forward closure) to avoid the "stopping and reversing" procedure others have mentioned? Or is that still just a part of the process?

AlnessW said:

Thanks all for the advice - and yes, the material I am tapping is only ~1/16" thick or so.

I guess I'm wondering how this is usually done on a lathe (for example - threads on a forward closure) to avoid the "stopping and reversing" procedure others have mentioned? Or is that still just a part of the process?

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Unless you have a tapping head, odds are you do the "stop and reverse." I know I do and it's one of the most arduous portions of making bulkheads.

Once you start cutting threads, 1/2 turn forward, 1/4 turn backwards.
You can deform, chip and stress crack the threads.
And it can damage the tap.

I wouldn't do it under power. It would grab quickly and either strip your hole or spin your workpiece.

Use your hand to turn the chuck. If you have a tap holder then it typically has a small recessed divot in the top. It's used to press a live or dead center into it to apply pressure when turning the tap holder. You can do the same thing in your drill press by using any sort of centering drill bit that you might have. You simply pull down on the drill press handle while manually turning the tap clockwise, then let the spring release the pressure from the tap when you back it out to relieve the chips.

I do the exact same thing with my lathe except that everything is set up in a horizontal orientation rather than vertical. The only practical way to do it under power is with an expensive tapping head that as a built in clutch and allows for automatic reverse as soon as the take the pressure off it.

Also, a 10-32 pitch requires a #21 drill bit.

I tend to agree to not do them under power. If it were 1/4", sure, but 1/16"? I had to tap some thin aluminum recently, I found a scrap piece to practice on before the real deal.

Here, I made a video.

[video=youtube;BiW0Nrbb8-4]https://www.youtube.com/watch?v=BiW0Nrbb8-4[/video]

Good video. That was easy! I've only ever done it with hand tools. Even in high school, we did it that way. External threads we cut on a lathe a few times but that was only the large ones.
Good to know thin stuff can be tapped with a bit of power assistance.

Lard or Crisco makes tapping aluminum very nice.

For tapping on a lathe under power I use interrupted thread taps. I've tapped 1/4 NPT with these. It is also critical to get the NPT tap reamer and run that first.

Edward

Hand taps are for use by Hand. There are Power taps intended to be used in either Lathe or Drill Press with an attached Clutch-Chuck to prevent the tap from stripping out the threads and/or breaking the tap when it hangs up (something that happens often). Both Hand & Power taps are also intended to be reversed out of the tapped finished hole(s).
Putting a hand tap in a drill is the quickest way to creating a new 3/16" threadless Hole LOL!

Get a T-Handle for you hand tap and use it to tap your 1/16" Aluminum Fin Can. It will only take a minute without the need for any other power then turning our wrist (expecially in 1/16" thick aluminum). Pat b is correct you also need a #21 Drill bit for tapping 10-32 pitch threads.

Micromeister said:

Hand taps are for use by Hand. There are Power taps intended to be used in either Lathe or Drill Press with an attached Clutch-Chuck to prevent the tap from stripping out the threads and/or breaking the tap when it hangs up (something that happens often). Both Hand & Power taps are also intended to be reversed out of the tapped finished hole(s).
Putting a hand tap in a drill is the quickest way to creating a new 3/16" threadless Hole LOL!

Get a T-Handle for you hand tap and use it to tap your 1/16" Aluminum Fin Can. It will only take a minute without the need for any other power then turning our wrist (expecially in 1/16" thick aluminum). Pat b is correct you also need a #21 Drill bit for tapping 10-32 pitch threads.

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+1.

Micromeister said:

Hand taps are for use by Hand. There are Power taps intended to be used in either Lathe or Drill Press with an attached Clutch-Chuck to prevent the tap from stripping out the threads and/or breaking the tap when it hangs up (something that happens often). Both Hand & Power taps are also intended to be reversed out of the tapped finished hole(s).
Putting a hand tap in a drill is the quickest way to creating a new 3/16" threadless Hole LOL!

Get a T-Handle for you hand tap and use it to tap your 1/16" Aluminum Fin Can. It will only take a minute without the need for any other power then turning our wrist (expecially in 1/16" thick aluminum). Pat b is correct you also need a #21 Drill bit for tapping 10-32 pitch threads.

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That is true and not true at the same time. When you are working with thin aluminum which is 1/8" thick or thinner and using 8-32 or 10-24/32 it just does not make any difference. Actually, it won't won't make much difference up to about 1/4" thick aluminum. The thicker material is more difficult to tap using a drill because you need a bit of a touch to go all the through and when to back up. A new tap with a proper lube will go all the way through in one shot provided you don't wobble the drill and break the tap.

The Tapmatic self reversing tapping heads are nice and I use those for blind tapping into Corian or acrylic using a bottom tap. (done on a drill press). These are expensive and usually not worth it for a few holes. Unless, you have to have every gadget.

The only time I use a T handle is when I am using a larger tap. I will use the drill up to 1/4" tap.

Keep in mind I am referring only to aluminum. You can do the same with steel but it takes a bit more care. I would be saying something different if this was about tapping steel plate or precision tapping.

I am not saying that hand tapping this small thin stuff is wrong. I work in an industry where we tap thousands of holes a year pretty much as demonstrated in my video. I have tapped thousands of holes using this method. It is not hard to learn and we use ordinary hand taps you buy at ACE Hardware. You can foul up by hand tapping as well and ruin your hole.

If you don't have a number 21 bit use a 5/32". A #21 bit is .159" and 5/32" is .1562"

Now, go tap some holes.

That's why I tried some practice parts, on pieces actually thinner than what I needed. What worked best for me was drilling 1 number bit undersized.

I don't know the term for it, but drilling undersized, left a bit of a mushroom out the bottom side, which -may- have allowed me an extra thread. Ymmv

I hand tapped it with more of a screwdriver handle than a T-handle, I found I could keep it more straight and square while applying pressure.

Ok, fine, it was a Crescent wrench

mkadams001 said:

That is true and not true at the same time. When you are working with thin aluminum which is 1/8" thick or thinner and using 8-32 or 10-24/32 it just does not make any difference. Actually, it won't won't make much difference up to about 1/4" thick aluminum. The thicker material is more difficult to tap using a drill because you need a bit of a touch to go all the through and when to back up. A new tap with a proper lube will go all the way through in one shot provided you don't wobble the drill and break the tap.

The Tapmatic self reversing tapping heads are nice and I use those for blind tapping into Corian or acrylic using a bottom tap. (done on a drill press). These are expensive and usually not worth it for a few holes. Unless, you have to have every gadget.

The only time I use a T handle is when I am using a larger tap. I will use the drill up to 1/4" tap.

Keep in mind I am referring only to aluminum. You can do the same with steel but it takes a bit more care. I would be saying something different if this was about tapping steel plate or precision tapping.

I am not saying that hand tapping this small thin stuff is wrong. I work in an industry where we tap thousands of holes a year pretty much as demonstrated in my video. I have tapped thousands of holes using this method. It is not hard to learn and we use ordinary hand taps you buy at ACE Hardware. You can foul up by hand tapping as well and ruin your hole.

If you don't have a number 21 bit use a 5/32". A #21 bit is .159" and 5/32" is .1562"

Now, go tap some holes.

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I also worked in industry where we drill and tap thousands of holes from 4-40 to 1-8 for 45 years.

What is TRUE is Always TRUE not both ways. I say again: Hand taps are for HAND tapping, Sure if you have a good amount of experience and a steady hand it's possible to use these Hand Taps in your 1/4" hand dirll. But for those who do not have that experience and Have I single or couple holes to tap it is MADNESS to suggest doing it with a power drill.

If tapping a couple holes is all that is required; USE the proper tools for the job. That is a standard 10-24" or 10-32" Taper Hand tap with the proper drill bit which will give the maximum Thread pitch and depth in this case #21, Coat the tap with either Cutting oil or good old WD-40 or some lubricant , secured in a T-Handle where consistant down pressure and vertical alignment can more easily be maintained. Working with deliberate,concentrated attention will be rewareded with will tapped holes with well formed threads in these fairly thin aluminum materials.

If at some point you have a bunch and I mean a bunch of holes to tap, then if you have gained enough experience to feel comfortable using a variable speed drill or drill press then go right ahead.

Actually, you are correct, a hand tap is a hand tap. I just use a drill held in my hand.

Micromeister said:

I also worked in industry where we drill and tap thousands of holes from 4-40 to 1-8 for 45 years.

What is TRUE is Always TRUE not both ways. I say again: Hand taps are for HAND tapping, Sure if you have a good amount of experience and a steady hand it's possible to use these Hand Taps in your 1/4" hand dirll. But for those who do not have that experience and Have I single or couple holes to tap it is MADNESS to suggest doing it with a power drill.

If tapping a couple holes is all that is required; USE the proper tools for the job. That is a standard 10-24" or 10-32" Taper Hand tap with the proper drill bit which will give the maximum Thread pitch and depth in this case #21, Coat the tap with either Cutting oil or good old WD-40 or some lubricant , secured in a T-Handle where consistant down pressure and vertical alignment can more easily be maintained. Working with deliberate,concentrated attention will be rewareded with will tapped holes with well formed threads in these fairly thin aluminum materials.

If at some point you have a bunch and I mean a bunch of holes to tap, then if you have gained enough experience to feel comfortable using a variable speed drill or drill press then go right ahead.

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+1.

I was at Balls one year, walking down the flight line. Saw a couple of guys holding a 54mm case with a plugged fwd closure, and they were driving a tap into it with a hand drill. I said "You need a tap handle and some oil." One of them rsponded with a remark I'm not allowed to type here, so I just took two steps back, and watched. 15 seconds later, I heard that tell-tale "tink!" Then I said "Yeah. 30 years in a machine shop, and I don't know what I'm talking about." And walked away.

Yes, a drill press can be used as a tapping fixture without an expensive tapping head. Unplug the drill first, turn the chuck only by hand. In one turn, out one half turn, and repeat. Helps keep the tapped hole square to the work piece. Be careful. Break that tap, and the price of a good broken tap removal tool will make you cry.

Wilson, best bet is to buy yourself a tap handle. Cost is less than a G motor. Turn the tap in one turn, then back out a half turn. In a turn, out a half. Tapping 1/8" Al won't need cutting oil. But if you have a job that would require it, for lack of anything else, plain old kerosene works great for cutting aluminum.

View attachment 280679

cherokeej said:

+1.

I was at Balls one year, walking down the flight line. Saw a couple of guys holding a 54mm case with a plugged fwd closure, and they were driving a tap into it with a hand drill. I said "You need a tap handle and some oil." One of them rsponded with a remark I'm not allowed to type here, so I just took two steps back, and watched. 15 seconds later, I heard that tell-tale "tink!" Then I said "Yeah. 30 years in a machine shop, and I don't know what I'm talking about." And walked away.

Yes, a drill press can be used as a tapping fixture without an expensive tapping head. Unplug the drill first, turn the chuck only by hand. In one turn, out one half turn, and repeat. Helps keep the tapped hole square to the work piece. Be careful. Break that tap, and the price of a good broken tap removal tool will make you cry.

Wilson, best bet is to buy yourself a tap handle. Cost is less than a G motor. Turn the tap in one turn, then back out a half turn. In a turn, out a half. Tapping 1/8" Al won't need cutting oil. But if you have a job that would require it, for lack of anything else, plain old kerosene works great for cutting aluminum.

View attachment 280679

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Everything he said, spot on, I, too, have tapped a lot of aluminum while fabricating parts over the years. I found a small can of Tapmatic at a supply house, the formula they have for AL. It is convenient and you can keep it for years on the shop shelf.
When you get tired of calling and running around stores trying to find parts for rocket building, McMaster-Carr has everything from the smallest screw to t-slot launch rail. I order by noon and it comes the next day! (depending how far you are from a distribution center.
When you want large quantities of nuts, bolts, washers, Boltdepot.com has great prices on quantities and assortment sets.

AlphaHybrids said:

Lard or Crisco makes tapping aluminum very nice.

For tapping on a lathe under power I use interrupted thread taps. I've tapped 1/4 NPT with these. It is also critical to get the NPT tap reamer and run that first.

Edward

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... or break the tap. Ask me how I know...

Gerald

I far prefer straight tap wrenches such as the top few Starrett ones here: https://www.use-enco.com/1/3/starrett-tap-wrenches (got mine used in very good condition on ebay years ago, for much less).

This sort of tap wrench leaves the rear of the tap free. Now many taps have either a hole in the backside, or are tapered to a point. These are designed so they can be used with a spring loaded tap guide. One chucks the tap guide in a mill or lathe or drillpress chuck. The spring pin on the guide has either a point or a conical hole. This rests on or in the back of the tap and provides centering and pressure. Then, one just turns the handle.

Taps - come in many different types. For through holes, there are ones designed for continuous feed which push the chips out the bottom of the hole. For those, one does not back up the tap to break the chips up. There are different taps (and tap coatings) for different materials, and different tap specifications for how much oversize to make the thread. Using the right tap for the job makes a huge difference in the quality of the result. But, for most jobs that extra quality probably does not matter. Please note though that the taps one typically picks up at a hardware store are junk compared to what is available. The Chinese made FMT taps from Fastenal are better. Also, for a hole which does not pass through, one typically uses two taps. One gets most of the threads, and then a bottoming tap to thread near the bottom of the hole.

For lubing for tapping aluminum, well, I've done most of my tapping on my Bridgeport. Now Brigeports leak spindle oil... I just dip the tap in a puddle of spindle oil before tapping each hole. I find the spindle oil works very well for aluminum. I prefer Moly-D (however it's spelled) for steel. Different lubes for different materials...

Gerald

As Gerald stated, using a GOOD tap is critical. I used to cringe every time I had to tap a hole. I was using taps I bought at the hardware store ("General" brand) or at the hobby shop. I broke a few and scrapped a couple projects. When I got serious about machining I started buying taps and the matching numbered drills at the local machine tool store. They are usually OSG brand and they are SHARP. I have a couple General brand tap handles and they will definitely make your tapping easier. A drop of any type of oil, even WD40 will make the tap cut through that thin aluminum like butter.

Generally the reason taps break is that they get loaded with chips. Use the correct type of tap and they will get the chips out of the way. I use spiral point taps(aka gun taps) for through holes. They push the chips ahead of the tap and out the bottom of the hole. I use spiral flute taps for blind holes. They pull the chips up the flutes and out the top of the hole. Since I started using these taps I haven't broken a single one. Hardware store taps generally have straight flutes with square corners on them. They usually aren't very sharp either. With these taps you HAVE to back out of the hole every turn or two to clear the chips. They are horrible.

Sheesh, I turn my head away for a little while, and now look where this has gone...
Anyways, thanks all for the feedback.

OK, so it sounds like trying to tap on a drill press is out. The whole idea behind that was to avoid having to turn the tap by hand. In watching some other instructional videos on YouTube, in general there seems to be much greater "finesse" with this kind of thing than I originally thought. Since I'm only tapping 6 x #10-32 holes in 1/16" thick material, I can't imagine that would be a particularly arduous task to do by hand... And yes, not breaking taps is always a smart thing to do!

I'm still waiting on an airframe to arrive, so I'll report back once tapping is complete.

I guess I'm still wondering how machinists can do this kind of thing so easily? Is it never that easy? Or is it just another matter of spending hundreds (or thousands) on "the right tool for the right job?"

I would say, if you can, try some -practice- pieces by hand. You can watch and feel when it's grabbing and starting to make threads. Slow , steady , but firm pressure.

I practiced on material that was actually thinner than I was going to be using, and was much thinner than 1/16.

I used a 'cheap' tap I got from Ace Hardware. For what you are doing, and the amount of holes, IMO you don't need a fancy expensive tap.

AlnessW said:

Sheesh, I turn my head away for a little while, and now look where this has gone...
Anyways, thanks all for the feedback.
And yes, not breaking taps is always a smart thing to do!

I guess I'm still wondering how machinists can do this kind of thing so easily? Is it never that easy? Or is it just another matter of spending hundreds (or thousands) on "the right tool for the right job?"

Click to expand...

While it NEVER gets easy it does sometime go a bit faster when we have a bunch of holes (100's or Thousands) to thread there are specialty spirial "Power Taps" that are made for use in special clutch attachments in very low speed drill presses set-ups or clutch driven lathes. These taps are very expensive regardless of size and are still subject to snapping if mis-used by the machinest.
At home I do 00-90 to 1/2-13 holes in all kinds of materials Brass, Aluminum, Steel, 304 & 316 Stainless Steel, Plastics and Phenolics, All with the same "decent quality" Bottom and Taper Hand Taps. These are Generally mounted in T-handle or Ratchet T-handle manual holders. One or 100 holes are NOT all the taxing to do by hand. Time consuming...well yes a little but not all the vexing to the master hand
Do yourself a Big favor. As Jeff mentioned a couple posts ago PRACTICE a few hole in scrap material so you become fimilar with the "feel" of the tap as it loads with chips. Two or Three turns in, then back out and remove chip load, return adding another two or three turns, back out to unload chips. and so on until the hole is complete. Once the hole is complete you may want to run the tap through a second or even third time to ensure you have cut as deep a thread us your tap and material will accept. Can't stress enough to use some form of cutting oil or lubricant before and during tapping aluminum. There are lots of Cutting oils on the market but plain old 3-in-1 Oil , WD-40, CSC-56, or 30wt Motor Oil will work and prevent your tap from freezing in a clip clogged hole. My personal preference is "Drill Chill" but there are as many cutting oils are there are companies manufacturing it