Help tapping small threads, please

[olympic]

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.

Great idea! Advice on removing broken small taps (say, 4-50 down to 0-80) would be really welcome (not that I personally have ever broken one)).

 

[almega]

Since the material I need to tap is only 1/8" thick and will be through tapped, what about using self tapping screws to create the threads? Those are much less costly than the taps and though they might only be good for one or two threads, they might be more cost effective in this case. Thoughts?

 

[goldstar31]

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?

sharpening taps:-
Are there many home built machines which are capable of such a thing?

broken taps:-
I've got a broken off 2.5mm screw in an insert type milling cutter. Too far in to drop a spot of weld from a Mig welder. Maybe I should try wearing the broken stud away with a Dremel and diamond grit and once out fill with weld, drill and re-tap. All this stuff about reversing a drill and hoping for miracles- in that size have proved hopeless.

Then I re-read Prof Chaddock on his Quorn and he could make 1/10th diameter milling cutter-- but couldn't re-sharpen them. He also had problems.

One thought that came to me was drill or D bit the exposed threads away and knock the offending it out and Mig weld new metal in , drill and re-tap.

Maybe someone will comment.

Norman

 

[Ken I]

Since the material I need to tap is only 1/8" thick and will be through tapped. Thoughts?

Here's a piece of advice - the problem with tapping is we generally turn the taps way too slowly (for good reason) but that increases the torque.

So I use my cordless drill and blast through (add one drop of HP lube) on small through (not blind) holes. (Set the clutch to the bare minimum + hope.)

Get it wrong and the tap will break - I tapped 200 consecutive M2 holes through 2.5mm thick 316 stainless without breaking a single (spiral point HSS) tap.

Not for the faint hearted or inexperienced.

A reversible tapping attachment c/w slipping clutch that won't snap the tap and can be instantly reversed in and out as required is the answer - but I haven't yet found one for really small taps - does anyone out there know of such a beast or better yet a design ?

Regards, Ken

 

[larryg]

I have at times when drilling and tapping small holes on the mill released the drill chuck, held in a 1/2" collet, and chucked up the tap and turned the chuck that is guided by the collet.

lg
no neat sig line

 

[Naiveambition]

For broken taps, solid carbide will drill right through. After this there a plethora of options, but you can chip it away , they break away rather easily, and if you can take out the center with drilling u can pick out just the threads, or maybe get enough bite for a screw extractor. I have even drilled out the whole tap and made a plug to suit, then Re tap.
Here are the ones I have. They were bought to drill thru hardened steel and are straight flute.

 

[savarin]

I threw together a very simple edm for my broken tap removal using Derek Lynas's circuit that used to be on this website but I cant find it here now.
I can post the circuit if wanted.
This version is a better version
http://mikesworkshop.weebly.com/a-spark-erosion-apparatus.html
Mine is not a build to be proud of as it really was just thrown together and would NOT pass the safety audits of today.
I drive it from an old stick welder transformer.
I has been a god send rescuing me from my own clumsiness breaking taps and also making tabbed washers in stainless steel.
It is not fast and can overheat the coil so 5 mins on, 10 mins cool down.
I usd a thin tig electrode the last time I used it to burn out a 6mm tap, straight down through the centre web and the three flutes just fell out.

 

[mfrick]

When serving my apprenticeship I had a job taping several hundred 4-40 and 5-40 holes in mild steel plate 3/16" thick we kept the taps in cutting oil on a hot plate to keep them warm and limber which cut down on the breakage. So still today 50yrs latter I still warm up small taps prior to using them.

Mike

 

[goldstar31]

For broken taps, solid carbide will drill right through. After this there a plethora of options, but you can chip it away , they break away rather easily, and if you can take out the center with drilling u can pick out just the threads, or maybe get enough bite for a screw extractor. I have even drilled out the whole tap and made a plug to suit, then Re tap.
Here are the ones I have. They were bought to drill thru hardened steel and are straight flute.
View attachment 106363

I'm talking about 2.5mm which means that one has to drill out the core which is less than 2mm diameter.
Again, what sort of rig will keep the drill central-- without it breaking as well??

Freehand is not an option for me, I'm partially blind and a wee bit over the hill or such things.

I've seen miniature welding sets with turret heads which might work but they are dental things and cost hen's teeth.

Really, I'm just plain mean and should buy yet another replacement segmented cutter-- and live a little.

Meantime, off for Christmas amongst people who push stents into arteries and others who weld with these miniature things

N

 

[abby]

I have to agree with Goldstar , break a very small tap and you will be unlikely to drill it out .
Best solution is to be very careful , I tap hundreds of holes from 10BA down to 12BA , admittedly these are all in brass or gun-metal.
I have found that the best method is by hand with the tap held between the finger and thumb in a pin chuck , squared visually.
This is a skill that has to be learned and I did break one or two taps before getting the "feel".
Practice is the key , try tapping some holes in a piece of scrap , never use more force than can be applied by twisting between thumb and forefinger.
Dan

 

[Jhawk]

I have seen a post (don’t remember where) about using brass tube the size of the inside diameter of the the threads. Glue diamond grit on the bottom of the tube, chuck up in your mill/drill press and grind the tap out. Supposedly you grind the threads off the tap, that’s why a tube is used. Haven’t tried it but think about experimenting with it ever now and then.

 

[BP_1]

Wouldn’t call this advise, but maybe a conversation starter...I have a 2-56 tap broken in an Al casting flange. My best remediation plan so far is to burn the broken tap out with an EDM. Thoughts?

 

[colby15642]

Buy an inexpensive "sliding machine-mount" tap wrench like this one for $16.00: https://www.mcmaster.com/tap-wrenches

McMaster-Carr part #2550A64

First drill should be a spotting or center drill for precise hole location in relation to spindle center-line. Drill and tap with one set-up so that the drill-press or milling machine spindle remains perfectly aligned with the hole. Use a new commercial-quality USA-made tap. Save your Chi-Com and hardware-store-grade and well-used taps for cleaning threads in rusty manure spreader parts.

 

[john_reese]

If using spiral point or spiral flute taps DO NOT reverse the tap every revolution. It is not necessary or desirable to break the chips with these taps.

 

[MachineTom]

Small broken taps are usually the most difficult to remove. If the is any material above the base workpiece this has worked for me. First photo shows a countersunk hole, which fits over the broken tap. Fill the hole with weld then unscrew the tap, as in photo two. Thats a 4-40 tap.

 

[Ken I]

Broken taps in brass or aluminium can be removed by boiling in Alum (Aluminium Sulphate) - same stuff used as flocculant in swimming pools.

Slow simmer in a saturated solution does the trick - it disolves steel but not brass or aluminium. 3 hours - its slow but effective.

 

[Richard Carlstedt]

for very small delicate taps like 1mm (.039") I tap upside down.
I'd post a picture but do not know how.
invert your work and bring the tap up from the bottom , having a normal T handle tap wrench works as gravity holds it straight down like a pendulum and the "feel" is excellent, you only feel the chip load, no wrench weight or trying to stay vertical is taken care of by gravity and the bonus is chips fall out of the hole. Works really well

having tapped thousands of holes , and breaking a tap in a part with 50-60 hours in it is a most unpleasant thing. So I built a home made EDM unit designed by Ben Fleming
see:
http://www.liming.org/edm/index.html
https://groups.yahoo.com/neo/groups/EDMHomeBuilders/info
https://www.homebuiltedmmachines.com/

I was the first guy to build Bens first design and did it for $100 but had a lot of junk on hand
here is a picture of the inside of the "brain"and his book is written for dummy's like me

https://groups.yahoo.com/neo/groups...&sortOrder=desc&photoFilter=ALL#zax/365981007

Rich

 

[petertha]

Just do a search for 'broken tap' here on the forum & you will have lots of reading, including by yours truly.

For small tap sizes up to 6-32 or about M4 I made simple holders from drill rod (tool steel, but unhardened). I feel there are several advantages. Inexpensive & simple to make. Nice close fit on more area of the tap shanks for improved alignment. The OD slides inside a corresponding mill/drill collet or (my go-to method) ever so slightly loosened drill chuck jaws. This gives you a very sensitive feel for tap progression & keep the tap axis in perfect alignment from start to finish. The 2 set screws are all you need resting on the tap flats to resist torque. The tommy bar gives you nice feel or you can remove it if you want to run in for a ways under power. They are nice & short so you don't have to open up a wide gap to accommodate a typical ratchet tap handle & centering do-dad that consumes 6" of headroom. Its kind of part specific but I feel the best time to do the tapping is immediately after pilot drilling the hole since you are never going to be any more concentric to the hole which is another reason for bad threads or broken taps. Good luck!

 

[Naiveambition]

The Carbide drill in my pic is 2.5 mm so they are rather small. I've used them a couple few times and have had no problem snapping. They actually went thru rather easily. I broke it down to the level surface then lightly applied pressure progressively. Also worked on a countersink bit that broke the tip off on the work.
I did do some research buying them, and was worried about the flex and so forth, and I don't have great machines, but no problems yet. I agree 080 is gonna be tough as I can barely see the threads anyways. their is most likely better options and I am not a machinist by any sort, but this has worked well for me so far.

 

[twombo]

‘I’m on the verge of drilling and tapping the 50-some holes in my steam loco cylinder blocks. All 10-32. All are blind holes, but plenty of depth is available. good info here for the task. I am considering a tapping head for my mini mill. The reverse switch was plug and play. I have had good service from the better line of taps from McMaster. I like the TiN coated HSS best. 65% thread depth is fine for my needs. Sharp, fresh, HSS taps and carefulprocedure should carry me through. F ortunately, these castings have been really nice and consistent. As an aside, My machine shop instructor taught me that the body to clearance ratio of the 6-32 is the worst out there. 6-40 is much superior strength!! Funny how I proved he as right before the lesson! For a variety of reasons in confluence. A busted 10-32 tap set me back years. The failed extraction created such an eyesore that I scrapped my frame bars!!! Yikes! We live, and Yearn!!!