Tapping 300 M6 holes in Mild Steel - HELP

Long story but like the title says I have to tap approximately 300 M6-1.00 holes in 0.75" thick mild steel. Most are through holes but about 75 are blind holes. I have a drill press, hand drill and tap wrench. Whats my best option? Any suggestions on tap brands / composition / coatings? Spiral flutes, straight flutes, thread forming??

Help please.

Maybe time to invest in a small tapping head? Spiral tip for the through holes; spiral flute for the blind. OSG is a good brand, but there are many.

You "might" get away with power taping held such that if it jambs the tap slips in the drill chuck, but...

If you insist on doing them by hand, guide the hand tap wrench from the drill press chuck. Several types enable that.

You won't need to back-off with either of the above types - just go...with cutting oil.

Lakeside53 said:

Maybe time to invest in a small tapping head? Spiral tip for the through holes; spiral flute for the blind. OSG is a good brand, but there are many.

You "might" get away with power taping held such that if it jambs the tap slips in the drill chuck, but...

If you insist on doing them by hand, guide the hand tap wrench from the drill press chuck. Several types enable that.

You won't need to back-off with either of the above types - just go...with cutting oil.

Click to expand...

I would use my taping head, each hole will take a few seconds and you will do all 300 without breaking any taps. You need to get one, looks to me like you would pay for it on this job.

I will be #3 for a tapping head. I would prefer a thread forming tap due to the robustness of the tap. However, if your drill press and chuck aren't up to snuff you may have a difficult getting the proper tap drill hole size for the forming tap. The forming tap will require a larger hole with less tolerance on the diameter than a cut tap. With a forming tap the forces are higher, so your tapping head should be rated for at least 5/16 holes.

Best option is to find somebody with a tapping head and promise them first dibs on your sister if they lend it to you for a few hours.

If you're an only child you're pretty much SOL for a tapping head.

In the latter case I'd go buy a spiral flute M6 and a cheap drill stand. Mount the drill in the stand, set it to screwdriver mode and play with the clutch to find the right setting for the tapping drill size you finished up using. M6 is big enough to take a reasonable amount of torque. 0.75" is thick enough that you'll want that tap going straight, so going with the tap in the drill handheld (aka Pete bodge mode) probably isn't going to be a good idea.

Promise to buy yourself a tapping head with all the money you make from this job before taking on another one like it.

20 minute job with a sensithreader and no tapping head to buy.