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Help tapping small threads, please

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almega

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As a relative newcomer, I am seeking help with the best way to tap for small sized machine screws. I am looking at a need to tap a few holes for 4-40 in hot rolled steel and when I look at the size of the tap I am thinking that it could snap right off and be a real pain to remove from the hole. Are there special lubes that I should consider and will I need to build a tapping stand?
 

stevehuckss396

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Use a good quality tap. Don't use an asian tap. When you rotate the tap it should feel crisp like its cutting and not smearing the metal. When you back the tap off it should be free to rotate and not tight in the hole.

Consider a lower percentage of thread enguagement. Most tap charts have drill sizes spec'd out for a 65% - 75% thread with a #43 drill. Fine for aluminum, brass, Etc. You could drill bigger with a 42 or 41 even and still have a good strong thread @ 50%

Use lube like tap magic or some of the wax based lubes.

That's all i got!
 

almega

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I have Vermont American, made in USA taps. Will those work or should I be getting something else? They come in sets with #43 drill but you think a #42 or #41 might be better for the hot rolled steel. From the size charts it appears a 3/32" would work too. I will give it a try. Thanks.
 

RM-MN

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I have Vermont American, made in USA taps. Will those work or should I be getting something else? They come in sets with #43 drill but you think a #42 or #41 might be better for the hot rolled steel. From the size charts it appears a 3/32" would work too. I will give it a try. Thanks.
I bought a couple of those Vermont American tap and drill sets for 10-24 threads. Broke every tap. Bought a better taps on Ebay and learned to throw away that included drill from Vermont American and use a slightly bigger drill bit and the breakage was over. For most applications the slightly lower thread depth will have plenty of strength.
 

almega

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Thanks, good to know. I will use the larger drill and maybe save the #43 for aluminum or brass. Would I use the same tapping fluid for aluminum and brass as I use for steel or iron?
 

BaronJ

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Hi Almega,

If you haven’t got a tapping stand, then use your drill press ! Remove the belt so you can feel the tap. The larger drill will also help.

FWIW, I'm about to tap a couple of M1.20 X 63 tpi, in 1 mm diameter holes, fortunately in hard aluminium bar. The threads are so fine I can barely see them without magnification. I'll be using kerosene as a tapping fluid.
 

mgb

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I made a variation of this.
http://www.clickspringprojects.com/tap-and-drill-extenders.html

Drill out the holder, and fix the tap in with superglue. A short length of silver steel in the chuck, with the holder a sliding fit allows you to have a a great feel of the tap working. If you over do it, the glue bond usually breaks first.
Ideally, drill the hole first, and with the table locked off proceed to tap the hole with the same settings.

Worked for me on 2mm and 7BA taps.
 

ShopShoe

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Everybody so far has said the best advice, but I want to add that you need to reverse the tap more frequently than you think to clear chips. In steel, you may also want to completely remove the tap from the hole, clean the hole and clean the tap, then re-lube and continue. With good feel, you should be able to tell when the "going is tougher."

My unfortunate experience has sometimes been to start to feel more resistance, then say to myself: "The hole is deep and it should be harder. Just a quarter-turn more..." and SNAP. Patience takes longer but ends on a happier note.

__ShopShoe
 

olympic

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My unfortunate experience has sometimes been to start to feel more resistance, then say to myself: "The hole is deep and it should be harder. Just a quarter-turn more..." and SNAP. Patience takes longer but ends on a happier note.
How apropos! This is exactly what I did yesterday with a 6-32 tap in a piece of aluminum (very sticky material). Fortunately, I had room elsewhere on the piece, and the broken tap hole will be hidden when things are assembled. I did, though, have to go to a 4-40 tap to accommodate the bolt head.

Just remember, tapping stand or drill press, plenty of lube, light touch, frequent backing out to clear, and PATIENCE (which in my case I have not got)....
 

almega

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I think my next project before I move on and tap the holes for the current project had better be to build a tapping stand. Thanks for all the good advise. It is very nice to have a resource such as this, especially for those of us who are new at it.
 

Aerostar55

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As a relative newcomer, I am seeking help with the best way to tap for small sized machine screws. I am looking at a need to tap a few holes for 4-40 in hot rolled steel and when I look at the size of the tap I am thinking that it could snap right off and be a real pain to remove from the hole. Are there special lubes that I should consider and will I need to build a tapping stand?
I use a tapping s
As a relative newcomer, I am seeking help with the best way to tap for small sized machine screws. I am looking at a need to tap a few holes for 4-40 in hot rolled steel and when I look at the size of the tap I am thinking that it could snap right off and be a real pain to remove from the hole. Are there special lubes that I should consider and will I need to build a tapping stand?
tand from Harbor Freight @80 bucks it was a good investment. Also use Tap Magic fluid. Before starting to tap I blow out any chips in the hole wit compressed air. I keep the air gun close and blow out the hole and the tap frequently, adding fluid after cleaning the hole each time the tap is backed out.
 

happy hooligan

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If at all possible, I use the drill press to tap holes. I have used Vermont America taps almost exclusively simply they're available locally and I haven't really had any problems. I think the key to tapping with small taps is to keep the tap straight and backing it out frequently to clear it.
 

tornitore45

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Remove the belt so you can feel the tap.
Good advise, however once you get the feeling mastered, turning the chuck get old fast. By leaving the belt and pulling on it one makes quick work.
Building a tapping stand is a waste of time. If you have a drill press there are better ways:
1) For medium taps #8 t0 3/8
Put the tap in the hole and turn backward 3/4 turns. That centers the hole under the tap.
Clamp the part in position so it does not turn
One hand on the lever and one on the belt to turn the tap
Easy to go forward and backward.
2) For smaller taps
Make a tap holder 3/8 or 1/2 diameter about 2"-3" long, knurled 1/2 way. 2 radial set screw to drive the tap, do not need to be tight, just snug
Insert holder into chuck but do not tighten, free to rotate and move up and down
Set table height or column lock so that the tap and holder stay in the chuck without falling out.
One hand hold the part, free to autocenter. Other hand rotate the tap-holde/driver on the knurled section, with two fingers.
The driver being so small in diameter limits the torque and the finger have great sensitivity and feeling.
I used to break taps until I learned what broke them and stopped doing it.
 

kuhncw

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You might also look into thread forming taps such as those made by Balax or others. They work great in aluminum, brass, and soft steel. Forming taps do not have flutes like taps that cut the thread, so they are less likely to break. You do have to follow the manufacturer's recommendation for tap drill size as the forming taps require a slightly larger hole. Forming taps do not generate chips which is another plus, in my opinion.

Chuck
 

almega

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2) For smaller taps
Make a tap holder 3/8 or 1/2 diameter about 2"-3" long, knurled 1/2 way. 2 radial set screw to drive the tap, do not need to be tight, just snug
Insert holder into chuck but do not tighten, free to rotate and move up and down
Set table height or column lock so that the tap and holder stay in the chuck without falling out.
One hand hold the part, free to autocenter. Other hand rotate the tap-holde/driver on the knurled section, with two fingers.
The driver being so small in diameter limits the torque and the finger have great sensitivity and feeling.
Tornitore45 do you have any photos of what you are describing. It would be good to use the drill press instead of having to build another tool, especially if it will do the job.
 

MachineTom

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A Tapping stand is great, but for a #4 screw to much torque. I use tapping blocks, for that size tap. a 3/8 block in a mill or DP, drill a Body size hole, a tap size hole, and a 4-40 tapped hole. Now you can get a hole started straight, then position the tap in the block over the hole and thread as normal, as the tap is not that long you will need to remove the block an finish to depth. You can drill a hole the body size of the tap itself, half the depth of your block then a tap size hole the rest of the way, now the tap should have enough to do the hole.

I like a spiral FLUTED tap, expensive but much less torque needed to tap in tough material. A spiral [point tap work great on thru holes, the chips are pushed out ahead of the tap. Both of these are HSS, not crappy Carbon steel.
 

Cogsy

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Just for completeness I'm going to put down what (so far) works for me. My drill press gets very little work and I've never used it for tapping. I drill my hole using my mill, then without disturbing the setup I change to a tap in the chuck. I rotate the chuck by hand, with manual downfeed, until I have the tap engaged for a few threads and it will stay aligned. Then I undo the chuck and use either a tapping handle (above about 3mm tap size) or a simple handwheel for the smaller sizes. Using this method, with appropriate lubricants, I've tapped down to 0-80 in drill rod, brass, bronze, aluminium and steel. I also back the tap off a LOT - like every 1/2 turn at the most for small taps. The majority of my taps are cheap Asian stuff and all of my tiny taps came out of a $40 Chinese 'watchmaker' set. I probably shouldn't say this out loud, but I have not yet broken a tap since I got into the hobby in 2012. Your mileage may vary.
 

mnay

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If you can get them, two flute taps are stronger and harder to break
 

blanik

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As a relative newcomer, I am seeking help with the best way to tap for small sized machine screws. I am looking at a need to tap a few holes for 4-40 in hot rolled steel and when I look at the size of the tap I am thinking that it could snap right off and be a real pain to remove from the hole. Are there special lubes that I should consider and will I need to build a tapping stand?
Look for High Speed Steel Taps - not the cheaper High Carbon Steel taps. With small size taps, it is very important to use exactly the right size drill - just a tiny bit too small a hole will be disastrous, and just a tiny bit too large a hole, and the thread will be weak. Look up the right sized tapping drill size and then buy the exact size specified. Don't just grab the nearest size that you have on hand.

I do a lot of tapping of small size threads (typically from 1mm threads up to 2.5mm). The easiest way to break a small tap is to bend the tap. The next easiest way to break a small tap is to fail to back the tap out of the hole every turn. In one turn and back a half turn to break the chip works well.

What I do to make sure that I don't bend the tap and break it, is to use a purpose make Tapping Jig. If you only use small taps occasionally, use the chuck in your drill press (or small mill, or small lathe), to hold the tap, and to keep the tap in line with the hole. Use your finger tips to turn the chuck with a very loose grip so that you can feel what the tap is doing. When I use my drill press, I remove the belt, so that the spindle rotates very easily.
 

DJP

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No one has offered advice on how to remove a broken tap which is sure to happen. All it takes is one dull tap. It should be part of this topic, in my opinion. Perhaps we should expand the topic to sharpening taps. It should be possible to grind a bigger slot. I have made thread cleaning taps out of bolts with slots that I ground by hand. It worked well enough for my needs.

Any thoughts?
 
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