Tap drill size for 1/2 -10 Acme

[DavidR8]

Where did you get the tap? I think I bought mine from McMaster-Carr or MSC.

I bought it from MPI tools.

 

[devils4ever]

I looked and I got mine from McMaster-Carr. Not cheap, but quality stuff.

 

[sdelivery]

The tap arrived today.
I drill a hole in the mild steel stock using a Z letter drill.
The tap wouldn’t even begin to bite no matter how much pressure I put on it.
So either the tap is junk or it needs a bigger clearance hole.

It will take alot of force to get this tap started, it doesn't have the pull of a regular tap.
If using a lathe set up the feed to help you push it.
If you are going to rough in the threads by single pointing then you might as well just finish them that way.
Don't fear your equipment, respect it and think the process through, beware of the what ifs but dont drown in them.

 

[SLK001]

The tap wouldn’t even begin to bite no matter how much pressure I put on it.

These taps require a LOT of force to start. Another reason to "start" the tapping with a single point tool on the lathe.

 

[WCraig]

The tap arrived today.
...

Can we see a picture or two?

Craig

 

[MrWhoopee]

The tap arrived today.
I drill a hole in the mild steel stock using a Z letter drill.
The tap wouldn’t even begin to bite no matter how much pressure I put on it.
So either the tap is junk or it needs a bigger clearance hole.

You are beginning to understand why I just bought a nut, turned a shoulder on it and pressed it in.

 

[Papa Charlie]

If you make the part a little longer than you need and create a tappered beginning to get the tap to start, that would help. You can see how much force it will take to drive the tap. I would be concerned that I might apply a little too much side force accidentally and snap the tap if I was using a vice and free handing it. I would recommend leaving the part in the lathe and do your tapping there after you bore and taper the entrance, where you can turn the part using the chuck key and have the rigidity of the lathe to use to your advantage.

 

[DavidR8]

Thanks so much for all of the excellent advice. I'll have another go at this tonight I hope.

 

[DavidR8]

Can we see a picture or two?

Craig

Here's the tap.

 

[ErichKeane]

Woah, that is such an interesting profile! It looks like a normal 60 degree tap until the 1/2 way point with squared-off tops, then 'squares' up the holes in the 2nd half.