Thread: Where to buy an 8-40 forming tap (or set)

Originally Posted by No good names left

I'd be cautious with forming taps, all the ones I've used produce quite a loose thread and a raised ridge around the hole. My preference is for cut taps but forming taps are stronger but do take a little more force to start.
I'll check my toolbox tomorrow but I'm not likely to have one.

If you're going to tap them in a machine try to avoid any taps with straight flutes (hand taps) as they block and break too easily, machine taps have spiral flutes that pull the swarf out the top of the hole or spiral point that push the swarf out the bottom of the hole (deep or thru holes only)

I will just be tapping by hand, carefully. I hadn't heard of forming taps until I was searching the net to try and find out which type of thread standard I should use. It did occur to me that the forming tap might create swelling.

I may have used machine screws in the past as self form tapping screws and had noticed this happening.