tapping...what am I doing wrong this time?

P

paintfool

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Sep 7, 2004
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I'm trying to tap a 2-56 thread into 316ss rod, making a pivot.
I can only get so far in to it then it just seems like the tap won't go any further.
I'm using oil, I'm tapping as straight as I can. this is my 3rd try after 2 broken taps...this is going to be one expensive pivot :barf:
the pin is cut down to about 0.2" is that just too deep to tap?

I would use another pre-made pivot, but I'm trying to make something smaller in dia. than what I have.

TIA Steve.
 
don't feel bad i use at least 2 taps per hole when i use 2/56 :grumpy: they are just to dam small

david
 
All I can say is drill a bigger hole, the next size drill will help a bunch if your not already using it.

Good luck

Bill
 
what bill said

gettting it straight is the most important part


using tap free is the next.

make sure you have a sharp tap


getting it straight.........if you dont have a lathe or a fixture, its probably not straight
goto www.halperntitanium.com and buy some from them!!!! :eek:
 
I tried to use the next size up and the screw seemed to have too much play.

now I'm using a #51 which should give me 69% (I think?) but it's so friggin hard to tap it, at this rate it's going to take a couple more hours...

the tap I'm using is brand new, all 3 of them were, not meaning that they are that sharp but they should be...

I guess I'll just keep at it and see what happens.

Thanks, Steve
 
I'm thinking 316ss is going to be a pain anyway It will boogger up on you something like N/S

like Mike says
getting it straight is the most important part
if you don't the tap is going to try a follow the hole :eek: not good for a tap that won't bend a lot.
hand tapping you'll feel it start to bind,, at that point you may have gone just a tad to far and the chips will want to bind you up backing it out.
asumeing you have a drill press...
set your pin up in a vise then drill it using a center drill to start the hole
leave it in the vise then use your drill press to start the tap in the hole
just turn the spindle by hand ( don't turn the machine on :eek:)
Unless of course you are set up to use a tapping head,
 
Dan's right 316ss will be a pain, with a high nickel content it is not a free machining steel, get rid of it and get yourself some 410 or 416ss and you shouldn't break any more taps.
 
I had it almost finished, the tip was starting to show on the other side, then snap........grrrrrr......

I have to order more taps now, so I guess I will be getting something a little better to work with, like you guys suggest.

Thanks again, Steve.
 
Let me get in a couple cents worth here!

First of all, I hope you are tapping that small of a hole (in the end of a s/s rod, no less...) EVEN while it's being held in a lathe between centers. That small of a tap is going to get wobbly just from the rotation of the planet, even if you did stay sober last night (no really... I believe you... really...)! You are best to do it that way, but if you do have very strong, stable hands, it can be done freehand.

Secondly, take a look at the taps you are buying. What is the Pitch Diameter Limit? The pitch diameter is the spot on the tap where the width equals the width of the space between the teeth. The pitch diameter determines the tolerance of your thread fit, namely the Pitch Diameter Limit

The pitch diameter limit is designated on fractional taps by the letter "H", and the letter "D" on metric taps, and the tolerance is always in increments of +.0005. That's pretty tight! A designation of H1 is a tight tolerance tap, and they are rare to find in the lower sizes, unless you are making watches or nano-robots (grin). Chances are you have a H2 tap, and the tolerance on that would be +.0005 to +.0010. Still pretty tight, considering the rather Lilliputian threads you are forming. Try to find an H3 or even an H4, and you'll really see a big difference.

Tapping fluids: This may seem funky to you, but I use Lestoil on the small stuff with great success. Sometimes I put a drop or two of kerosene in it also. If you look at the ingredients of the regular tapping fluids, this is pretty much all it is anyway. :D
 
they are GH2(G?)
they are just the cheap doall brand, my father got them for me so I didn't have a say in what he got, not that I would know the difference anyway. :D
I hate to say it, but I gave up for now..:rolleyes:
the last tap broke when I was right near the end, and I wasn't hardly turning it, I guess it just had too much.
I'll get some better materials before I get more taps.

How much are you selling your tapping jig for when you get them on the go?

Steve
 
Mostly what everyone else said with a few exceptions.First 316ss is tough stuff so using the largest recommended tap drill size is in order.Tests have shown that anything over 60% thread is useless strength wise.That being said , a #51 drill (.067) gives a theoretical thread % of 82 but taking into consideration the probable oversize of .0017 you end up with a 74% theoretical thread (to tight IMHO for this small of tap).A #50 drill (.070) figuring all the same above info gives 63% thread.About correct for max. strength.But we are dealing with 316ss! A # 49 drill with all the above info gives 49% theo. thread.Probably strong enough for the screw size.But--are you hand drilling (means larger probable oversize) or machine drilling (mill,lathe etc.).My thread % might be less than some tap charts list but some dont consider the probable oversize hole you will get if you are not center drilling.indicating your drill bit perfectly and using an excellent drill chuck.Also scrap all 4 fluted taps for hand tapping,use a 2 or 3 fluted tap for all your tapping needs and your luck will improve.After starting your tap straight take it out,blow the hole out with air pressure,tap a few more degrees take the tap back out blow the hole out again and repeat until finished.MOST OF ALL,DONT BE IN A HURRY WITH MICRO TAPS!!Cut a little bit at a time.Thats my 2 cents,good luck.
 
Also after re-reading your post I didnt answer your .200 thread depth question.The recommended full thread depth for max. strength is 1 1/2 x the major thread dia. Off hand I cant honestly tell you what the major dia. is on a #2 thread but just guessing I would say that .150 - .187 full thread should be deep enough.So .200 deep is in the ball park.I hope all you guys have a really great day.Talk to you later.
 
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