tapered PIPE tap

[bchee]

 

[Travis E.]

A pipe (NPT) tap will be harder than a straight tap. A course thread tap will be "harder" to tap than a fine thread because you are removing less material with a fine thread. If you are going to tap a hole for a 1/4-28 bolt you would use a No, 3 drill bit which is .2130 where a 1/4-20 would be drilled with a #7 drill bit .2010
Brass should be fairly easy to tap when using a good quality cutting fluid.

 

[bchee]

 

[Travis E.]

If it is more than 1 thread in I would probably leave it depending on how crooked it is. You may be able to countersink the hole a bit to get rid of what you started, but being a course thread like that it is probably in pretty good for it to be crooked.

 

[Frank The Plumber]

Brass is very tricky because it likes to chip out and gum, In most cases you do not just go forward in a hand tapping situation. You go forward and then reverse and clear. It can be challenging.

 

[flatheadguy]

1. Lots of grease of some kind on the tap before you start.
2. One turn in, followed by 1/2 turn out. Repeat and repeat. This clears chips from the tap. Go slow. Plumb, straight, is always best. (smiling)
With a PIPE TAP, check fit after six or seven full turns. Go too far and you have a problem. Continue tapping until it is at least halfway into the tapped threads.
3/4 into the threads is best. You do not want the fitting to "sink" it all the way into the tapped threads. Be sure to clean out the "hole" to remove all the chips.
I'm sure an expert will chime in.

 

[Heavy Metal Doctor]

Brass is very tricky because it likes to chip out and gum, In most cases you do not just go forward in a hand tapping situation. You go forward and then reverse and clear. It can be challenging.

x2

 

[mdbeck1]

Watch a few of these and become well.... not an expert but maybe knowledgable????

 

[larry_g]

If your crooked then you going to be removing a lot more material from the hole than you should so the tap will get very hard to turn. If your to crooked then the root of the tap will bottom out on the clearance hole and your screwed as you are now having to displace material, not cut it away. They have reamers to taper the hole that your tapping into so that you do not ever try to cut 100% thread depth with the tap.

Good luck

lg
no neat sig line

 

[regguy1]

I wouldn't use grease, you want a cutting oil like "Tap Majic" that comes in a can.

I also wouldn't go a full turn before backing out. I go 1/4 to 1/3 turn, then back out a bit and then go again...don't rush it.

Tap Majic cutting fluid:
http://www.grainger.com/Grainger/TA...cm_sp=IO-_-IDP-_-RR_VTV70300505&cm_vc=IDPRRZ1

 

[bchee]

If your crooked then you going to be removing a lot more material from the hole than you should so the tap will get very hard to turn.

With a PIPE TAP, check fit after six or seven full turns. Go too far and you have a problem. Continue tapping until it is at least halfway into the tapped threads.
3/4 into the threads is best. You do not want the fitting to "sink" it all the way into the tapped threads.

 

[Kevin54]

If I understand this correctly, I don't want the bolt or fastener to sink in all the way? My understanding of pipe thread is that it is tapered, and this taper helps to seal the thread. So I don't want the tap to go all the way through the hole?

The tap has an obvious taper, in addition to the taper that a standard tap has.

If you run a tapered tap (NPT) all the way through the hole, you're screwed. You defeated what the intent is. You only want to go partial on the tap (1/2 to 3/4 depth of the tap), then check fit your plug If you go all the way through your hole with the tap, then you are at major diameter and lose your sealing capabilities. A standard tap will have a slight lead on it but is completely different than a tapered pipe tap.

 

[bchee]

 

[Morrisman]

You normally tap brass dry, no lube, no grease. The brass breaks into tiny chips as it cuts and often falls away before clogging your tap, so adding oil or tapping paste just causes it to clog.

 

[bchee]

 

[Frank The Plumber]

I thread my own copper ******* and brass ******* from pipe sections, it saves a lot of money. I use a titanium nitride bit and the green fluid that ridgid sells for the machine, I use a minor air flow to flush the tap out. I think it depends a lot on the copper content or quality of the brass, mine seems not to chip that much.

 

[Morrisman]

..... I think it depends a lot on the copper content or quality of the brass, mine seems not to chip that much.

You might be using what is known as 'spinning brass' in the UK. It is made softer and less brittle specifically for turning.

The swarf that flies of normal brass when turning is horrible, hot and sharp, and it get everywhere. You need to use cutting tools with negative rake ideally.