I need to know what is the strongest most reliable tap for threading 6-32 into stainless steel. I used like 3 cheap steel taps and they all broke. Any advice is greatly appreciated.
I will try to mount the tap in the drill press rather than doing it by hand in that case.Cheap taps are commonly made from Carbon Steel. More reliable, harder taps are made from High Speed Steel.
HS is almost certainly “High Speed”, the steel goes without saying.
G H3 is probably the finish and oversize. H3 may mean 1.0 to 1.5 thou oversize.
Find some way to support the tap in line with the hole. Experiment with cutting fluid, oil or soap. That will almost certainly reduce breakage. Some taps in some materials produce the best finish by cutting continuously. Others require a slight advance, then a reverse to break off the cuttings. You will need to experiment to find the best technique.
Corrosion is usually the most important parameter, but if possible select a grade of stainless that is free machining.
I tried it both ways without the drill press and it broke regardless. Funny thing though I just screwed it in in the drill press and it worked even without turning it back.Sorry if you know this but... Are you just trying to screw the tap in or are you doing the normal half turn in and a quarter turn out?
Could you explain the material hardening? I still don't fully understand it. The stainless type is 420Different stainless steels work harden differently. If you “work” the tap you may harden the material, then break the tap when it hits the previously hardened wall. If you continuously turn the tap the chips will be hardened but the material being cut will be fresh and normal hardness. The speed of cutting is important because the hardening process is a chemical phase change. In some materials, if you back off torque momentarily you may hit a hardening wall.
Avoid machining old, salvaged or unidentified stainless steel. You will probably need carbide tooling.
There are different flute profile taps, spiral flute taps are designed to cut continuously while straight flute are designed to be reversed to break the chips. Don' be mislead by “spiral point”, in hard materials they are often as bad or worse than straight flute because they clog with chips, especially in blind holes. The spiral path of the flute decides the curl of the chip and the quality of the thread finish.
There are many different stainless steels. What grade material are you threading ?
How long or deep is the thread you are cutting? Blind or through hole?
Is your material new or aged? Has the material been subjected to cold temperatures? for what periods?
Any time you are tapping a hole you are creating friction and friction creates heat, that tends to change the crystalline structure of the metal. That being said I highly doubt that will happen when hand tapping a hole in stainless steel. I used to thread pipe with a ridged pipe machine and that creates a lot of heat and I've never seen it (harden the steel). to harden any kind of steel you basically have to get it cherry red then cool it rapidly. Stainless steel tends to be a bit harder then mild steel anyway. Most of the trouble with taping steel comes from the hole itself, if you don't (size) the hole correctly for instance if the hole an tap are different sizes or if the hole is slightly (wallowed) it can grab the tap and put it in a bind. I have seen aluminum break taps, its so soft it grips the tap and the metal chips get hung up and the tap just breaks. It happens, you just have to work with it.Could you explain the material hardening? I still don't fully understand it. The stainless type is 420
Yeah the harder tungsten carbide taps will shatter like glass if you shock them. I have actually seen taps break simply from dropping them on concrete floors (probably cracked from use already). Most of the hardened tooling has a fracture point. I got a carbon steel piece hung up on a piranha "punch" and thought I could just hit it with a hammer and knock it off, the piranha punch broke off in the hole.True, also I found a very easy way to get small broken taps out is by hole punching it about 20 times. It just flies right out.
You are being pessimistic. It is not a black art, it is a science.I have seen aluminum break taps, its so soft it grips the tap and the metal chips get hung up and the tap just breaks. It happens, you just have to work with it.
Thanks guys I think this sort of knowledge is very good to know, and you will mess up at some point when first learning it. As long as you learn something from it that's what's important.You are being defeatist. It is not a black art, it is a science.
There is an optimum way to perform any operation. If you are breaking tools then you do not know what you are doing. If you use a spiral flute tap made of the right material, with the correct cutting lubricant and the correct technique, then it will not break the tap.