Hi, This is my first visit to this forum. I need to tap about (60) 4-40 threads in alum, 6061. I bought a thread forming tap, but have no experience with forming taps. I have regular cutting taps, but I thought a forming tap might go faster. The only thing I know is the tap drill size is larger, #38.
How do I use this type of tap?
Can I drive it with a cordless drill or just hand tap it?
Do I need to back it out every 1/2 turn like with cutting taps?
Do I need to use a lubricant?
Thread forming taps
I'm no expert (never used forming taps), but the reason for backing out a regular tap is to clear the chips. Forming taps have no chips, so no need to back out.
I've heard lubricants are necessary, and it sounds like that makes sense, given the rubbing forces involved. Not sure what you use, but it might not be a cutting fluid, as you are not cutting .
It may be better with a drill press, as you can be sure that the tap is going in straight, although the hand drill with one of those tap aligner devices might work.
Steve
I've heard lubricants are necessary, and it sounds like that makes sense, given the rubbing forces involved. Not sure what you use, but it might not be a cutting fluid, as you are not cutting .
It may be better with a drill press, as you can be sure that the tap is going in straight, although the hand drill with one of those tap aligner devices might work.
Steve
There is no need to back the tap up periodically.
You definitely need a lubricant, but not a cutting oil. I've found that way lube works quite well. So does 75W-90 synthetic hypoid gear lube. I imagine most any heavy oil designed for high pressure applications will work. I've also had success with a moly-graphite grease but it was a pain to clean out of the threads afterward.
I haven't tried power tapping with them but I always start taps in the mill, lathe or drill press with the drive belts disengaged (cranking by hand) to get good alignment. If I need to tap fairly deep, I finish with a tap wrench because it's less awkward. A good quality, properly lubed forming tap actually takes less torque than a hand tap so you probably can tap with a cordless drill but don't try to go too fast because it generates a bit more heat than a cutting tap.
Check the tap after every hole because it will pick up any chips left from drilling which can end up friction welded to the tap. If you catch them early, they are easy to remove (I scrape them off with the back edge of a utility knife blade). If you don't remove them early, they will scrape more material off each following hole and form a big chunk which will mess up the threads and make the tap more difficult to clean. In a 4-40 hole, that doesn't take much.
You definitely need a lubricant, but not a cutting oil. I've found that way lube works quite well. So does 75W-90 synthetic hypoid gear lube. I imagine most any heavy oil designed for high pressure applications will work. I've also had success with a moly-graphite grease but it was a pain to clean out of the threads afterward.
I haven't tried power tapping with them but I always start taps in the mill, lathe or drill press with the drive belts disengaged (cranking by hand) to get good alignment. If I need to tap fairly deep, I finish with a tap wrench because it's less awkward. A good quality, properly lubed forming tap actually takes less torque than a hand tap so you probably can tap with a cordless drill but don't try to go too fast because it generates a bit more heat than a cutting tap.
Check the tap after every hole because it will pick up any chips left from drilling which can end up friction welded to the tap. If you catch them early, they are easy to remove (I scrape them off with the back edge of a utility knife blade). If you don't remove them early, they will scrape more material off each following hole and form a big chunk which will mess up the threads and make the tap more difficult to clean. In a 4-40 hole, that doesn't take much.
Thank you for your response. It all makes sense. I will give it a try and report the results laterjutz wrote:There is no need to back the tap up periodically.
You definitely need a lubricant, but not a cutting oil. I've found that way lube works quite well. So does 75W-90 synthetic hypoid gear lube. I imagine most any heavy oil designed for high pressure applications will work. I've also had success with a moly-graphite grease but it was a pain to clean out of the threads afterward.
I haven't tried power tapping with them but I always start taps in the mill, lathe or drill press with the drive belts disengaged (cranking by hand) to get good alignment. If I need to tap fairly deep, I finish with a tap wrench because it's less awkward. A good quality, properly lubed forming tap actually takes less torque than a hand tap so you probably can tap with a cordless drill but don't try to go too fast because it generates a bit more heat than a cutting tap.
Check the tap after every hole because it will pick up any chips left from drilling which can end up friction welded to the tap. If you catch them early, they are easy to remove (I scrape them off with the back edge of a utility knife blade). If you don't remove them early, they will scrape more material off each following hole and form a big chunk which will mess up the threads and make the tap more difficult to clean. In a 4-40 hole, that doesn't take much.
Maybe STP? Those of you old enough might remember the commercial where someone (Andy Granatelli?) dips the screwdriver blade in STP and the guy can't hold on to it.jutz wrote:You definitely need a lubricant, but not a cutting oil. I've found that way lube works quite well. So does 75W-90 synthetic hypoid gear lube. I imagine most any heavy oil designed for high pressure applications will work.
Steve