How can I automatically tap 500 holes in 5/16-18 thread size using a hand drill or drill press?

You need a drill press and a small Tap-Matic, or drill the holes and use a hand tap. But why do you need to tap so many holes? Usually the point of T-slot is that you can use special "nuts" that slide or tilt into the slot.

Several years back I scrounged a Procunier #2 tapping head off of ebay. It fits into the Morse 2 socket on my drill press and will do what you want all day long.
When you pull down the lever on the drillpress, it drives the tap forward at a one speed. When you lift up on the lever, it reverses and unscrews the tap at a faster speed.
It is a joy to use and I set it up any time I need to tap more than three holes.
If you scrounge one used, make sure you get as many collets as you can. Definitely make sure it comes with the 5/16. Use spiral point taps and kerosene or wd40 for a lube.
Paul K. Dickman

There are special machines that look like hand drills, but they are specifically made for tapping (slow, high torque, torque limit, reversal).
i

thanks for the tips on the tapmatic tools. I love this forum already! While browsing Tapmatics site I noticed tools are often designated 30x, 70x, 90x, etc. What does this number mean? Also I'm wondering if I can get away with a tapmatic that has a max range of 0-1/4", when the tap I'm using is 5/16th? Probably not, but since the drill part is 17/64th that is really really close to 1/4".
It's true the Tslot features are nice, but I still have to tap many ends.

"There are special machines" Very cool, but what are they called so I can try to buy them?

If I bougth this procunier #2 tool off of ebay what is the best place to buy the 5/16th collette from? Also I remember when I assembled my drill press I fit the chuck on, but what's the best way to remove it now? Just use a crow bar?

============== More than likely you have a Morse taper shank. To remove these you need a wedge. If you have a large old file and small [#2 MT] you can some times use the shank. You can also break the file when you hit it.
for an example of the right tool click on are looking for "drill drifts and sets." Most mill supplies and mail order suppliers will have these in stock.

Take a look at think there are similar products from other vendors.
"Special features: Automatic reversing mechanism backs tap out of threaded hole at high speed"
As in "pull the trigger to tap the hole and don't let go until the tap has backed out completely."
I'm retired now, but when I was working, I saw one of our people using something like this at a job site. DANG if we didn't buy some nice toys!

Dewalt cordless drill. With reverse.
There are tapping machines out there, that look like an air drill on a swingarm, for production use.
A tapping head on a drill press, can be got cheap if you have time to shop ebay, or less cheap if needed immediately.
Cheers Trevor Jones

First off, I don't understand why you need the combo drill-taps. Aren't the holes already in the extrusion, ready to be tapped as required?
I've done a lots of tapping on Item extrusion (though fortunately never as many as 500 holes at one time) and have found spiral flute taps to work best by far. See McM p/n 2529A19. Use an aluminum tapping fluid (e.g., Alumtap), or wax stick lube (McM 1311K1) applied to the tap.
I do the short lengths held in a fixture with a quick acting clamp that mounts vertically to the front of a Bridgeport table. Anything longer than about 3-1/2 feet long would require a hole in the floor. As has been mentioned, a drill press and tapping head would also work, but you'd still run into the length limitation.
A *good* 1/2" reversing drill handles the long lengths. It's touchier and less convenient than tapping on a mill or drill press, but not bad once you get the hang of it, especially with the proper taps and lube.
Let me know if you'd like a photo of the locating fixture.

Hi Ned I'd love some pics. re AT rollandelliott.com is my email. You're right the aluminum extrusions are pre drilled so I just need to tap them and you are also right in recommending the flutted taps. I just never knew they exsisted!
I guess my dilemna now is whether I should some how rig up my drill press horizontally with a tapping unit or if I should get one of these fancy handheld drilling units. I've already busted $50 worth of taps so I'm a bit aprehensive about using a handheld tool that introduces wobble and busting more. should that be a concern?
The extrusions I have are 12feet, 8 feet and 4 feet long so if I go the drill press route I'll deffintely need to put the drill press on its side. I hope that won't mess up the tapping unit somehow?
Trevor, thanks for the cordless drill advice but Been there and done that and $50 bucks down the drain :(
Cecil, thanks for the link, at $360 or more I think I'll pass though. I did find a couple used for half that price though.
George, thanks for the link. I'd never be able to remove that chuck with out your knowledge. I guess you just take a hammer and bang on the end of it?
thanks everyone and happy new year!

The only reason sharp taps break in correctly drilled holes is because the tap is not square to the hole (or you bottom out the tap - silly mistake).
I've got a large 1/2" drill (corded - tons of torque) with two gear speeds, variable speed, etc (mine's a Metabo, but everyone makes them). I've tapped down to M4 reliably (in high gear) under power without the use of a square, and without breaking the tap with this thing (soft cast iron, mild steel, 4140).
You have to gain a feel for getting the tap in square. It could take several holes for you to get the feel, but.... You basically just gently rock the drill as you start to drive the tap in, and you'll feel it when the tap kinda *slides* in easily instead of getting a lot of reverse torque from the drill - this means you're square. If you don't get this feeling, you're not square and you need to reverse out and try again - do NOT just ram it in! If you're not confident, reverse and do it again. You have about four thread pitches from the tip of the tap to *get it* or else you have gone too far to make any further angular adjustment.
If the holes are quite deep and you're not too concerned about leaving chips inside the hole, use a spiral-point tap (most ideal). Spiral- flute, on the other hand, are good when you want the chips to come out of the hole (blind hole, or you don't want to dig them out) BUT they are weaker and typically more expensive than spiral-pointed taps (not a good situation when you don't have a lot of experience).
Buy a new tap for this job, and don't use it on steel until you're done (steel work will dull the tap much faster than aluminum). Always! use lube when tapping aluminum (and pretty much any other metal).
Remember, you can chuck these taps in a reversing drill press, or milling machine and do the work that way too. It inevitably takes long to do this type of work on a machine as opposed to by hand, but you don't have the issues with squareness.
Good luck. 5/16" taps are pretty strong. You shouldn't be breaking them in aluminum.
Regards,
Robin

Hey Robin,
Thanks for taking the time to write that detailed post. I've got a new sense of confidence now and I might try the hand drill tapping machine with your advice. mcmaster lists the following spiral point taps. I'm guessing 2 flutes is more ideal than 3 (more room for chips to leave). I'm guessing cheap $4.68 one will do fine unless someone tells me these coatings are worth twice the price?
Tap Material Surface Coating/Treatment Thread Length Overall" #Flutes Each High-Speed Steel Uncoated (Bright Finish) 1-1/8" 2-23/32" 2 2523A412 $4.68 High-Speed Steel TiN (Titanium Nitride)-Coated 1-1/8" 2-23/32" 2 2762A48 $6.41 High-Speed Steel TiCN (Titanium Carbonitride) 1-1/8" 2-23/32" 3 2568A43 $9.75 High-Speed Steel Oxide-Over-Nitride-Treated 1-1/8" 2-23/32" 3 8300A19 $7.83 Cobalt Steel Uncoated (Bright Finish) 1-1/8" 2-23/32" 2 8779A31 $10.65

That one is a little pricey for one without any collets. $75 is more reasonable.
Ebay collets go out at 8-15 bucks each. Retail on the collets from the usual suspects (msc, mcmaster carr, etc) is 25 or 26 bucks.
If you don't have a morse taper on your drill press, the procuniers also come with a 1/2 in straight shank that you just mount in the chuck. I changed mine to a morse taper because it was too long with the extra length of the chuck.
Paul K. Dickman

A few years back Ryobi offered a bench top, swivel head drill press. It wasn't very expensive 'cuz it wasn't a heavy industrial machine, but the swivel feature was kind'a sweet and it's sturdy enough for the work you describe . You might find one on ebay that would work well to horizontally tap those long lengths.
Cheers.

Well. Dunno what to suggest then.
Work up a set of callusses, maybe. :-)
At least, drill bigger pilot holes. Try to run about 60 percent of the diameter of the tap for the pilot. Most tap drill charts are at about 75 percent, and if you are drilling any smaller hole than 75 percent thread engagement, then slap yourself for making life harder than it has to be. The loss in strength is disproprtionately small, compared to the ease in tapping that you gain.
I've done a pile of holes, mostly 1/4 inch coarse and fine, and a right pile of 10-32 ones with a cordless drill.
Done a pile with a reversing Sioux Air drill too, that was even faster.
You twitchy when holding stuff that's supposed to be steady? If so, work out a way to support yourself for steadiness.
If the volume makes it worthwhile to spend the money, take a look online for tapping arms. Just ar eversing air motor, with an arm that keeps it pointed in the right direction. Pretty expensive, but usefull.
Gunpoint taps shoot the chip ahead of the tip, and are used for tapping through a hole. If you have the clearance behind the hole, use a starting tap and run it down in one shot, fairly fast. Use a lube. The Tapmatic Al. stuff works well, as does beeswax, or the cutting lube sticks.
Have fun!
Cheers Trevor Jones

The fixture in position for tapping. It mounts in the mill's t-slot with flat head socket caps: The 5/16 dowels fit in the extrusions t-slot and keep it aligned. The screw with collar on the right clamps in the extrusion's t-slot. The fixture in position on the mill table to cross drill for the fastening sets. The dowel pin locates the end of the extrusion to locate the cross drilled hole. A detail of the clamping screw. It's a socket set screw with a collar loctited in place. The allen wrench for tightening is visible in the first pic. See my response to your other post.

The only quibble I have with Robin's advice, based on my specific experience working with these extrusions, is regarding spiral point taps (gun taps) vs. spiral *flute* taps. I use gun taps for almost everything, but tapping these extrusions is one exception. A gun tap will work fine 98% of the time, but for some reason, 2% of the time something goes wrong and the tap buggers the hole. Since I started using the spiral flute taps I've had zero problems. I gave McMaster's p/n for a 5/16-18 spiral flute tap in an earlier reply.
I'll second Robin's endorsement of the Metabo drill. I bought one on his recommendation and love it. You should not need a special tapping tool to cut 5/16 threads in aluminum as long as you have a drill with good speed control and adequate torque.

your drill press probably came with a metal wedge, a stamped piece of steel that is vaguely triangular in shape (if it is a taiwan/china drill press) - you lower the spindle and find the slot and tap the wedge into the slot to dislodge the morse taper