Question concerning a tap problem?

C Craft

C Craft

Well-Known Member
I have this same thread on another forum so some of you will recognize it from there. I sure could use some advice.

I am in the process of building a 2x72 clone for grinding blades. I decided to tap the 1/2"thick side plates that make up the tube for the tooling arm for 10-24 flat head machine screws. In retrospect maybe I should have went to a larger diameter.

I am sure I am using the right size drill bit as I originally bought the titanium nitrate coated bit and tap combinations from Lowes, to work with. I think I am have broken number 4 of them and 2 plain high carbon steel 10-24 taps from Irwin. They were all what is called a plug tap.

I am doing a deep tap of approx 3/4" depth in what is suppose to be 1018. I am using plenty of oil and keeping a straight pressure on the tap. I am only turning a 1/3 to 1/2 turn on the tap before backing up to clear the burrs and reoiling and then another 1/3 to 1/2 turn, and repeat.

The funny part of this is the first side I did I only broke one tap and I think I let that one get a sideways pressure causing it to break. I ordered this metal from a company and it cut to length to speed up the construction of my grinder. They supply flat bar in 1018 and A-36. I suspect that this may be a piece of A-36 that was sent by accident or deliberately to finish out an order. I am getting maybe 1/4” + or – into the metal before I usually snap a tap.

Ok now you have all the same info that I have on this subject I am looking for suggestions here!! I am determined to finish this project as I originally started it. I only have about 8 more holes to tap! If I don’t go broke buying taps that is!!!!

Am I using the wrong style of tap for deep treading?

Is a titanium tap superior to the plain steel tap?

What do I do to minimize breaking the taps that I not already doing?

Any suggestions or help would be greatly appreciated, maybe some of the machinists we have on this site would care to comment!!!!!!!!!!!!!!!!!
 
Oh you may ask one of the reps from Balax what size drill bit they recommend for a thread forming tap. It usually calls for a size bigger than what the books may tell you or that kit from Lowes you bought. For example my 2-56 thread forming tap works great with a #47 drill size or a 5/64 either one but the books call for a size 50 and when threading titanium if you try that with a number 50 it just breaks taps all day long.
The Balax rep told me to use 47 and thats what I've used ever since. Maybe plug taps require a bigger drill size than the one you think it is too??
STR
 
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Are the holes, a thru hole? If so a plug tap would be fine to use. If the are blind holes I would use a spiral tap so the clips would curl upward instead of packin the hole. Also for a 10-24 nc-2b it is calls out for a #25 Drill (.1495 dia.) I would try using a #24 Drill (.152 dia.) for the deep hole. That's about a 65 percent thread, which should be good for what you are doing.

High speed taps vs. ti plated taps shouldn't matter, but I would only use a 2 flute tap vs. a 3 or 4 flute.

Tapping fluid is better than oil, and theres two types, one for steel and one for aluminum. Be sure to use the correct one.

Hope I help a little.
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Brad
 
A 10/24 thread is a long haul in 1/2" steel. :eek:
Your tap is probably still cloged even though you back it out 1/3-1/2 turn. Try tapping 1/3 of the depth and removing and cleaning the tap and hole before starting again. You actually need a spiral flute tap to clear the swath quickly. I tap a fair number of holes and I don't use anything but spiral flute taps anymore unless it's real thin stock. Even though I have a couple tappers for the drill press I still do a few by hand and have not broke a tap since I went to spiral flute taps. In 1/2" steel, I'd go with 1/4-20 at minimum...3/8-16 would be better. Good luck, hope this helps.

Rudy
 
Thanks everyone for the info. I have found out the problem is most likely the tap. I just talked to a machinist and he recommended to use a taper tap that had helical flutes.
I would like to finish what I started as I have already tape 24 holes like that. This grinder when finished will have a rest like this one in this thread.
http://www.bladeforums.com/forums/showthread.php?t=466024
 
what is the "H" size of the tap? if it is an H3 or 4 you may have to drill the hole a little larger. also I think that a 10 size tap is too small for the size of steel that you are using.
 
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