Tapping threads into metal

[Loren Gameros]

Hi Gerald and Everyone,

I am about to start tapping holes and I was wondering if you guys are tapping by hand (cordless drill) or using a press? I see that some blind holes are required for the racks and I am not sure the best or most appropiate way to go about this? Trying to get them perfectly straight is a real pain. I had considered a tapping head, (Tapmatic Tapping Head) is this a bad idea for blind holes?

Thanks Loren

[J.R. Hatcher]

Last week I spent a few hours installing a reversing switch on my drill press. It was well worth the trouble, but first hole (6mm) I tapped, I broke the tap (how? don't ask, operator error). The next 30+ went smooth as silk. The few holes I need to tap in blind holes I'll start the tap using the drill press by hand. Get a short rod that fits the hole that the chuck key fits to help turn by hand (unplug the press), use a press vice, you will need to put a little down pressure to overcome the up spring of the press. Happy tapping J.R.

[Gerald D]

There are only 8 blind holes to be tapped. 2 of those holes on the one y-axis rail will probably never be used. They can be the learner holes.

A tapmatic would be a total overkill for this small quantity.

Those blind holes have a lot more thread turns (depth of hole) than required by the diameter of the screw - therefore you can easily afford to drill the pilot hole bigger than what the tables tell you. My drills are every 0.5mm, so I just drill 0.5mm bigger. That makes the hand-tapping a LOT easier.

For the drill-tapping, I have always wanted to have one of these levels on the back of the cordless for vertical tapping:.........

50


.......but normally I call someone over to stand to my side and tell me if I am going vertical.

In general, I judge the length of thread against the thickness of the nut that would normally be used on a particular screw to decide if I can drill the pilot hole a bit bigger.

[J.R. Hatcher]

Gerald I didn't know where to post this:confused:, so please move as needed. I have a suggestion, on the motor mounts in place of the + for the tapped motor mount holes why not let the laser cut 5mm holes and be done with it. The most someone would have to do is chase the hole with the drill bit. From what I've seen the laser is so accurate that wouldn't even be necessary. I didn't have a problem but I can see the potential. Drilling from scratch if the bit walked a little there sure would be one. Just a thought what do you think? J.R.
ps I did have to weld up a few holes, just not in the motor mounts:D

[Gerald D]

JR, the laser guys around here don't like piercing holes where the diameter is smaller than the plate thickness - they will do it, but the quality suffers. Also, the lasering sometimes leaves a hard crust that the taps don't like. A drill particulary does not like to take out only the laser crust - the drill wants a bigger bite. For general purpose drawings, to be used by any old laser cutter, and to be drilled and tapped by any quality drills or taps, I didn't want to take that chance. But yes, the laser accuracy, versatility and cost is pretty impressive - realise that you are going to be doing the same to wood! :)

[GregA]

I am from the school of hard knocks. I have broken taps twice. I am not certain ~how~ I broke them. Other than that, I have dozens of successful taps. What am I doing wrong when I break them?

Sorry for the newb question.

[smreish]

...here in sunny florida I do it this way,
- purchase high speed, automated tap (they look like a drill point on the point and standard tap up the shaft, 4 flutes and tapered.
- chuck them up in my cordless dewalt with the clutch setting really low. Advance, back up , advance, back up.
- drill the hole the proper diameter
- run the tap with tapmagic cutting solution on the tap
- tap all day long.

Standard holes in my shop are mostly 1/2-13 UNC or 1/2-20 UNC. Fine threads have a tendency to strip out and hand tapping is recommended.

(this only really works for thru taps...bottom hole still should be done by hand.

Sean

[Doug_Ford]

GregA,

I was taught by my machine shop instructor to reverse the direction of the tap every half turn or so to break off the burr created during the tapping process. Are you doing that? You don't have to do that for the first few revolutions. If you do, you'll never get it started correctly. I just go by the feel of the resistance to turning. I usually break taps when I have cutting oil on my fingers and my hand slips off the handle pushing it sideways. They're pretty brittle compared to the steel they're cutting. Are you using the correct drill bit for the tap? The correct size is usually written on the tap.

Doug

[GregA]

Everyone with Advice thanks...

I am not breaking them all the time. I pretty much worked out the technique you described.

I was referencing one broken tap I had recently. It was a jacketed tank that I had custom built so there was a lot of time and money in it already. I was putting a thread in for an electric heater, and the tap was going along fine... Then it was like the tool slipped out of the thread... then the next turn it broke free... Next day was plasma cutter + chisel and ball-peen hammer. I was able to still use it after all that but... That day sucked...

Im guessing I should practice with the drill technique before I use it on anything I want to keep. Thanks for advise.

[Doug_Ford]

It seems like the more time you've invested in a workpiece the greater your chances of breaking a tap in it.:)

[Gerald D]

I have broken taps twice. . . . . . . . What am I doing wrong when I break them?. . . .

- Wrong "number" tap. In a set of 3, you must start with the most tapered, the number 1 tap.
- Blunt tap. A rusty tap is a blunt tap - the sharp tips are the first to rust off.
- No lubrication. Fat/lard/tallow/butter all work fairly well - no excuses for not having tapping oil.
- Pilot hole too small. If the hole is deeper than the thread diameter then you can increase the pilot hole size a little. . . .
- Not reversing often enough to break the swarf. Rather go half turn forward, quarter turn back in the beginning - "negotiate" the tap into the metal. Give & take....
- And then the biggest tap breaker.....trying to do it with only one hand. Use both hands on both handles of the tap wrench to make sure you apply an even torque to the tap. No bending load must be applied to the tap. With one hand you twist AND bend the tap - never bend the tap.

[driller]

My biggest problems have been too small a hole (wrong size drill)
followed by no cutting fluid.

When I tap, I put fluid one every hole to let it drip down into the hole, then also on the tap itself.

a can of tappin fluid is less than one tap. no excuse !

There is one thing missing on your list. That is on blind holes.
Cleaning out the chips ! on blind holes, you must withdraw the tap, use a blower and remove all the chips. get a thick sewing needle and make sure there are none stuck (compressed) in the hole.

I have long since, switched to gun taps so I can tap with my drill press or hand drill.

If you plan on tapping lots of holes, the cost of a tapping head is worth the price. It talks far longer to drill holes than to tap them with a tapping head.

Dave

[Gerald D]

For hand tapping I prefer a paste to a oil. The tap is pushed into the tub of paste before use. The lumps of paste stuck to the tap melt and give a good flow of lubricant. Traditional, and excellent, tapping paste is tallow (fat or lard), but butter also does a good job.

[GregA]

Ive found a number of power tapping tools in the McMaster catalog, It also looks like I need to switch to a "gun" tap for power tapping.

Can anybody suggest a link for a product that doesn't carry the McMaster premium?

[Gerald D]

The "gun" taps, or what Sean called the "high speed, automated tap (they look like a drill point on the point and standard tap up the shaft, 4 flutes and tapered.)", are great for hand tapping as well. Our other name for "gun" taps is "spiral point" (not spiral flute - that is something else) taps.

If I had to buy from McMaster, I would be buying 2671A74 and 2671A75, as well as a "set" 8305A37 & 8305A57 for the blind holes at the rack ends. For holding the taps, I would go no further than a 2550A65 and 25605A75. For lube; 1398K13. I could happily do all the holes without any power tools, or attachments for power tools - THAT is when the inexperienced really break taps!

[Gerald D]

Another tip is to countersink the pilot hole before starting to tap. After tapping, the holes should be de-burred again. I would want a 3285A36 90 degree so that it could be used for the other serious countersinking as well.

[GregA]

Gerald D,

Best answer ever. Thanks;)

So since that has been so decisively answered, mind if I ask another question that is not entirely mech mate oriented? When drilling whole with a small bit... say 3mm how do I get the drill bit to stay in the impression I made with the punch? If I press to hard with the drill, the bit tends to bend.

[Gerald D]

Center punch with a 1kg [2lb] hammer, and

Concentrate on not bending the drill - push down in line with the bit. Again, two hands are much better than one - same as for tapping.

[Gerald D]

If you are drilling and you don't immediately see swarf/chips coming off the drill tip, then STOP! Either your drill is blunt or you are not pushing hard enough. If you continue "drilling" while no swarf/chips are produced, you are only making lots of heat and changing the metallurgy of the drill bit and the work piece.

Woodworkers' drills (and drill presses) are mostly too fast for metalwork.

I don't bother with cobalt drills. You can manage without a drill-press - in fact, drilling the X-rail mounting beds cannot be done with the typical drill-press.

[jehayes]

Moved from elsewhere:

For those of us who are new to metal working, can someone tell me the proper sequence for tapping holes. I am working on the holes for the locking bars in the gantry (part 10 20 235). In the set of taps I have there are three variants of each size tap: a pointy one, a less pointy one and a blunt one. Am I supposed to use them in succession? Or are there places where one is appropriate rather than another? BTW - These are through holes. Thanks

[Gerald D]

For through holes, the "pointy one" can do the whole job. Just tap through till it turns freely.

[Jan de Ruyter]

Hi Joe, the set is sometimes numbered 1,2 & 3, For a blind hole, use #1 first, then #2 and lastly #3. This sequence is used when tapping blind holes. With through holes, only Tap #1 is threaded right through, which is usually sufficient.

Use tapping oil, which improves the cut and prolongs the life of the tap. Normal automotive oil is better than nothing but is not entirely the right thing to use.

You can use a suitable battery powered drill to do the tapping, saves a lot of time. Go at low revs and make sure you hold the drill perpendicular, else the tap can break, which is an entirely new chapter of fun.

[jehayes]

Thanks to both for such a quick response. I have tapped the first hole! A milestone for me.

Joe

[Gerald D]

After tapping a thread, it is good practice to lightly de-burr the entry/exit with a countersink cutter.

[jehayes]

will do. thnx

[jehayes]

After good advice on tapping from Gerald and others, I realized my skill levels wasn't up to straight hand tapping and I decided to invest a little in a hand tapping machine from Grizzly. It is not expensive and it makes great taps with ease (no, I don't shill for Grizzly, but I do like their stuff). So far I have used it to tap all the holes in the clamp strip for the gantry and in the spider plate with no problems. Figuring how to use it to tap the X-beams will be interesting.

Unfortunately, the machine only comes with inch collets, not metric.

You can see the machine here: http://grizzly.com/products/Hand-Tapping-Machine/G8748

[sailfl]

Joe,

Taping is not that difficult. I would suggest you try on some scrape pieces before you try on what you want to tap. Keep the tap 90 degrees and you will be fine. Some oil to make things work better.

Good luck. Remember to reverse to remove metal on a regular basis.

[Robert M]

Copied from another thread:

One question / option that been bothering me and I’m still not certain about ?

As for the screwing in place the rails on the main table beams, original design are to be hold down by screws & tap holes in the main beams.
Anything not right by no taping holes and going instesd w-drill through holes to then use screws, nuts and those bevel washers ?!?

Reasons I’m looking at this second option, I tend to imagine it would be faster & easier to do ( and as good) vs the drilling and tedious task of making those threads in the beams !?
Thanks, Robert;)

[smreish]

Robert, I have done both.

The bolt option works, it's just a bit of a pain to align the washer on each and every one as you move along. I would make sure NOT to over drill the beam hole and keep that is close to tolerance as the bolt size to minimize movement of the fastener/rail during machine vibrations.

Tapping those 5/16" holes with my screw gun only took about 20 mins for all of them.

Use the right lubricant and get tapping with a spiral point tap.

[Robert M]

Yep, thanks Sean…I’ll kick my butt and tap with a little more patience :o

I’m usually a very patient guy on elaborate & tedious work, but I’ll be honest …. I’m getting really anxious to get this project moving a bit faster and hate the thought of hand taping so many holes…a repetitive boring task :(
Till you told me you did yours with a drill, I was a little intimidated using my battery screw gun to tap, as I had a few time ( not on this project although) broken taps in the hole while in hand / manual mode…I would just hate to see this happen on this project this time :mad:

Bear in mind, loving this steel making experience with this project, but it’s neither my field expertise nor hobby to play making stuff with steel.
When no experience, I tend to move slower and more intimidated, afraid to screw up what I fell can happen…. Thinking of a Murphy’s law…. (doesn’t he say something like…When thing are going alright, something wrong is bound to happen…. Close to that !!)

What lube do you use?

I’ve use drilling & tapping oil for all my drilling ( a darn there is a lot of holes in my bolt on project !! ) and seems fine, but did not try it for tapping…YET !!

Well…Thanks again Sean…needed that push.. :D
Amicalement, Robert ;)

[Robert M]

Nothing like a simple test :rolleyes:

Well, broke my barrier…Did it with my drill / screw gun…

6951

Twice taped in C-3 as a test and all went super fine & easy with some treading / tapping oil.
Did this a few time in alu before, but was afraid to even think trying this drill thing in steel….May be I over lubed it, but rather a little more oil than a broken tap !!
Goes to say….give it a try, you may be surprised !!
Thanks again….Later, Robert ;)

[Gerald D]

Tapping some test holes is always a good idea.

Because we are tapping into relatively thick metal, you can increase the pilot hole size, which makes the tapping a LOT easier with the power drill. Again, experiment with pilot hole size to see when an over-tightened screw risks stripping out.

[Regnar]

I often tapped by hand and by a battery power drill for a long time until I read a tip on CNCcookbook.com

He uses a impact wrench and tap sockets. I also use a tap guide to get it straight in. But I have to say I can tap very quick now and with just one hand. I build a dolly out of 3/8 thick square tube and tapped 16 holes for the casters in under 5 minutes with no breakage. I bought the Butterfly Impact from Harbor Freight for 15.00 the tap sockets from use-enco for 20 and made my own tap guide for a few dollars in scrap aluminum. You will need a air compressor. I use to dread tapping any hole but now I just chuck it up and blast away.

Link to the article http://cnccookbook.com/CCBlogJul2009.htm

Information is about 3/4 down the page.

[riesvantwisk]

I often tapped by hand and by a battery power drill for a long time until I read a tip on CNCcookbook.com

He uses a impact wrench and tap sockets. I also use a tap guide to get it straight in. But I have to say I can tap very quick now and with just one hand. I build a dolly out of 3/8 thick square tube and tapped 16 holes for the casters in under 5 minutes with no breakage.

Where you in a tapping contexts?? That's a stunning 18Sec per hole!

Thanks for the link...

Personally I look at it from the top, and two side, then slowly I start tapping. Then I rotate, and re-check the sides and repeat this until the top goes through and take my time...

Ries

[Gerald D]

18 sec per hole is relatively slow - Russel was not exaggerating when he said under 5 minutes :)

[J.R. Hatcher]

Thanks Russell that info will come in handy. Show us a tap socket??

[domino11]

Here is one JR.
Tap Adapter (http://cnccookbook.com/img/Tooling/TapAdapters.jpg)

[J.R. Hatcher]

Thanks Heath

[Regnar]

18 sec per hole is relatively slow - Russel was not exaggerating when he said under 5 minutes

I guess I should have mentioned I took my time, Insured the tap was straight and clamped down the tap guide.

When I throw caution to the wind I can tap 1/4 1018 steel in 3 seconds and can tap 1.25 inches into 6061 in 15 - 16 seconds :D

[Regnar]

Thanks Russell that info will come in handy. Show us a tap socket??

I will do you one better JR. Here is a HD video of me tapping 6 holes. 3 in steel and 3 in aluminum. http://www.youtube.com/watch?v=_XLGCt5UQGM

Here is the links to the items I used.
Socket Adapter.
http://www.use-enco.com/CGI/INLMK32?PARTPG=INSRAR2
Butterfly Impact Wrench
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93100

[J.R. Hatcher]

Thanks Russell very helpful.

[Robert M]

Thanks too Russell….Now cause of you I feel like I’m from an inefficient dinosaur area with my screw gun, oil dip & tooth brush removing shaving after EACH tap :o
No wonder it took me 25+ minutes to tap what…. 30 holes !!
Progress + man and his toys = efficient, fun work :D
Seriously, thanks for this & the links.
BTW ( Half dinosaur, my screw gun has the impact option witch I did use !!!)
Amicalement, Robert ;)

[Greg J]

Russell,

Great video. I learned something :)

Thanks,
Greg

[jehayes]

Thanks, very instructive and good production value.

Joe

[Gerald D]

Maybe we do have to sound some caution here . . . . . . If we push the limits, we do increase the chances of breaking the tap. And it is no fun to remove a broken tap - sometimes (most times?) you won't get it out.

Maybe this is a good time to start discussing on the methods of removing a broken tap . . . .

[domino11]

Yes, I would like to know how to remove a broken tap. :( I had a crappy one I broke once and was able to drill it out. Believe it or not. :)

[Gerald D]

Here is a nice article from the web:

http://www.metalartspress.com/PDFs/Removing_Frozen_or_Broken_Taps_and_Fasteners.pdf

[Regnar]

Thanks guys for the comments.

Gerald is right though, Caution does need to take place. Although this method is extremely easy it just makes it that much easier and faster for you to screw up.

Industrial environments use a similar method but they are called tapping arms and go for thousands. One day I will build one but for now I just use my hand. You can see what I am talking about over at the CNCcookbook Bob just did a article on my video which explains some of the problems and solutions to my video.

Here is a video of some tapping arms. http://www.youtube.com/watch?v=FZLU-F9wcS0&feature=related

[Castone]

We have one of the flex arms it works great .

[KenC]

Pilot hole size is vital to make a good tap hole. Hole too small the tap will become hard to turn or even break frequently, too large the there will be too little thread left.

I hope this table will be helpful

M3 x 0.5 Hole dia. 2.5
M4 x 0.7 Hole dia. 3.3
M5 x 0.8 Hole dia. 4.2
M6 x 1.0 Hole dia. 5.0
M8 x 1.25 Hole dia. 6.8
M10 Hole dia. 8.5
M12 Hole Dia. 10.2

small variant from it is ok.

[Gerald D]

With standard metric threads, the hole size is simply the diameter minus the pitch. No need for a table like above. :)

[normand blais]

left hand drill bits could be use ,sometime it is all you need if you are lucky:)

www.nastyz28.com/forum/showthread.php?t=107063

[KenC]

With standard metric threads, the hole size is simply the diameter minus the pitch. No need for a table like above. :)

Another valueble lesson learnt. :D

[smreish]

...another reason to love the metric system.

[J.R. Hatcher]

Russell I took your recommendations and bought the stuff you suggested ..... can't believe how good it works. I tapped about a dozen 1/4" holes just for fun ...... man it's fast. Thanks J.R.

[Regnar]

J.R.

Im glad it worked out for you. I cannot tell how many non-believing emails I got from that Youtube video. As long as it helped out one person. Let me know if you want my plans for the tapping arm.

[domino11]

JR,
Was the stuff expensive? And do you have more info on what you got like part numbers and such?

[J.R. Hatcher]

Heath I bought the tap adapters like the ones you and Russell pointed me to, and the 3/8 butterfly impact wrench Russell showed me at Harbor freight. Everything cost about $45.00 us. I'll save that much in less aggravation in one day :D

[domino11]

JR,
Thanks. Did you have to throttle that butterfly adapter down for the threading at all or just run it at full pressure? I was worried about breaking a tap. :)

[J.R. Hatcher]

When you put the tap in contact with metal, you give it full throttle @ 80 psi and it immediately starts in the impact mode ..... it's a beautiful thing to see it tap. It will tap 1/4 20 tpi in .25" mild steel in 3 seconds flat........ that's smoking :). With the taps below you can also debur at the same time. I made an adapter so I could use these with the impact wrench. Oh one last thing, I don't use these to drill the hole.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=95529

[KenC]

I experimented with all the method suggested, cordless power drill, the pneumatic wrench, even auto tapping machine. But like Gerald, my favorite goes to hand tap using spiral point bits... After a few slanted tap holes & a broken bit, like cycling, everything just went on without a glitch. The monotonous back & for turning action with timely squeeze of WD40 is calming to the mental health. Also its easy on me ears & no need to dough flying chips. :D

Tap all the holes on the main beam takes less then an hour,,, not too slow in my opinion. Just grap a stool & its really comfortable.;)

[Regnar]

Ken, Sorry you didnt enjoy the Pnuematic Wrench. Almost everyone I have shown enjoys tapping that way. I will agree that it gets kinda loud but I just throw on my Ipod and some ear muffs.

[KenC]

Russel,
don't get me wrong, your wrench method is fast. It will be my 1st choice if mass production is involve. Just that I do work late into the night, so hand tap helps to keep complain down :D

PS,
I have a boom box in the shop, I don't like to expose to the danger of loose ear phone wire entangle with anything while working, it can be dangerous at times. Moreover, I feel secure when I can hear whatever that is happening around me... Just some of my hard habits...

[Gerald D]

like Gerald, my favorite goes to hand tap .....

Okay Ken, I think we have another misunderstanding; My favourite is NOT handtapping. (I go cordless drill just because they are normally lying around)

[KenC]

Ooops, another blunder, sorry Gerald.

[PEU]

After tapping a thread, it is good practice to lightly de-burr the entry/exit with a countersink cutter.

Depending on the thread pitch I do this operation before tapping.

[Red_boards]

Is it an idea to pass the tapping head through a block of wood to help keep it vertical?

[KenC]

That can work.

[MetalHead]

I have seen that done before. Here are some cool ideas.

http://www.rockler.com/blog/index.cfm?mode=entry&entry=7F491F43-1372-6771-F6E0FA7D26277FE0

[tjstamp]

if you have a standard tap start with that and finish with a bottoming tap. to keep it straight by hand is just practice. it isn't to hard if you take it slow.