Is a "plug tap" the same thing as a bottom tap? (i.e. for tapping a blind hole)

From pictures it doesn't look like you could get very close to the bottom of the hole...

No a plug has more taper than a bottom tap.

And I will add a bottom tap is for finishing a bottom tapped hole after a standard or spiral tap ....not for tapping a blind hole complete

Thank for confirming that. How are plug and taper taps different then?

Montea

A taper tap has a generous taper ground on it to help the tap start in the center of the hole.

A plug tap is tapered but not near as much as the former.

A bottom tap has only a minimum amount of taper so you can thread to the bottom of a hole.

Of course you would use them in that order.

Would I need to use all three of them in that order? For instance could I use a taper tap and then go straight to a bottom tap, even on a shallow hole, say 3/16" deep?

If you go from a taper tap directly to a bottom tap in a blind hole you increase the risk of over stressing and breaking off the tap. You might get away eith it but it is not recommended.

Here is the rule of thumb with taps.

A Taper tap has a chamfer of 7-10 threads.

A Plug tap has a chamfer 3-5 threads.

A modified Bottoming tap has a chamfer of 2-2.5 threads.

A Bottoming tap has a chamfer of 1-2 threads.

On a shallow hole I would use a modified bottoming or a bottoming tap.

On blind holes, especially front sights on thin barrels, if I have to tap, I mill the holes to get a flat bottom and use a Bottoming tap that I modify to reduce the tapered leade. This allows me to get up to two more complete threads compared to a drilled hole of the same depth. I start the threads with a plug tap since a Taper tap's chamfer is most often longer than the depth of the hole. You can of course modify the tap to reduce the length of the tip.

Montea
Sounds like your kinda new to this.
Do not buy carbon steel taps like
they sell in a general hardware
store.
Buy high speed steel taps.
I haven't used or bought a taper
tap in 20 years.

Right; you don't need a taper tap for anything and I never buy bottoming taps either; I have enough used plug taps to break off the end and make bottoming taps. One use for carbon steel taps is that , if, you break one in a blind hole, you can break up the remains with a punch and pick the pieces out. A HSS tap; you can't break up (you can break them in two though). So practically impossible to remove. Lesson, be careful and do not break one. Good carbon steel taps are sharper too, but I use mostly HSS ones. NOT the ones from local hardware stores.

Since this has turned to broken taps here is a trick that can save your ass. If you have a mill or have access to one try this. Take a solid carbide endmill (does not have to be new or sharp) and turn it at 2500-3500 rpm. Using a rigid set up, line it up with the broken tap and using moderate pressure bring it down. It will burn through any tap unless its carbide. With a little practice you can even feel when it reaches the bottom of the hole. This will destroy the end of the endmill most of the time. I just grind a spade point on it and use it again. After you have burnt through the tap, run your drill back into the hole to clear out any remaining chunks and retap the hole.
Since I do all of my drilling and tapping on my mill this is an easy way to remove a broken tap in a hurry.

And if you don't tap in a milling machine(I love my little Chinese miller for this!), you can grind out the broken tap with some of those cheapo Dremel diamond bits that Harbor Freight sells. Just takes a steady hand and time....

I burn them out with one of our EDM sinkers but haven't broke a tap in years

I and most of us I presume, don't have EDM machines but I forgot about the cheap little diamond bits for Dremels. I have used them, but usually just be careful and don't break taps. Only when they get dull and I try to squeak one more hole out of them.

Most small shops dont have a use for edm

Im an injection mold maker so I cant live without them.


The size of your tap handle is the key to not breaking taps

I use Starrett handles and always use the smallest one the tap will fit in

Also dropping down to 60 to 65% on 2-56

Union Butterfield is the best tapping fluid I have found in 26 years

Same tap handle for size 5 to 3/8ths. I have a big one for over that. For new tappers; you do have to be careful with the small taps and that especially includes size 6s normally found in scope mounts.

I'm glad to own 7 sizes

14" downt to 2"

A very good tapping block is also a fine addition to any tool maker's Kennedy

Tapping fluid that contained 1,1,1, trichloroethane
was the best that ever was or will be. After it was
found to cause snail darters to become cross eyed
It was taken off the market maybe about 15 years ago.
I now think Castrol's Moly-Dee is the best

Tapping fluid with 1,1,1, Tri was the only fluid
that you could tap nine chrome-one moly with.
Now nine chrome-one moly is un tapable.

1.1.1 Tri is awesome stuff. I still have 5 gallons, and I don't give a hoot about snail darters! I have heard that White Lead was really good as well but that predates me. Have any of you ever used it?

quote:

Originally posted by ted thorn:

A very good tapping block is also a fine addition to any tool maker's Kennedy

Kennedy?? Most people here have the really good stuff. Mastercraft or Rubbermaid!!

I've used white lead on dead centers. I was taught
by an old timer that was to cheap to buy a live center.
I'm wanting to say I was taught with Rex 95, but I think
it more likely said China than Rex 95.
Never tapped with white lead. I think he used rancid lard.
Wish I had bought Kennedy. Got on a Snap On kick a few years
ago. Pretty sure I put the Snap On mans daughter thru
Harvard.

Brad,
I have used lard on geometric die chasers with good results. I have heard that the white lead was mixed with linseed oil when used for tapping. I have used never seize for tapping difficult materials like Inconel. But the best thing is to buy the right tap for the job.
Snap on makes a good tool box, but if you are a machinist or Tool and Die maker there are only two choices. Kennedy or Gerstner. Or at least that was how it was when I started. I take a lot of pride in my tools and tool box.

Dirk
Lot of good info in your post there.
Yea, Never Seize is handy as pockets on a
shirt.
Yes, picking the right tap can decrease the
pucker factor tremendously. I'm partial to
Greenfield EMSS and Emuge. We have a huge advantage
from just a few years ago on tap selection.
I own a shop and most hires have no tools at all.
So I have half a dozen boxes filled with tools. Hell,
I would be happy if a new hire could read a scale, much less
own one.
I'm more of a blacksmith. I have a 16 lb. in my hands as
much as a micrometer.
I have tremendous respect for you smiths.
Some of the work I see takes my breath away. I guess
the reason is that I can look at that work and know
what it takes to do that.

Brad,
I like Emuge and OSG. The OSG powdered metal taps blow my mind. I have tapped 10-32 threads in hardened steel that rockwelled 64! I was very skeptical when they told me that I could do it. But it cut exactly as they told me it would.
Do not sell yourself short. I lease my shop from a guy that uses a 16lb hammer a lot. I have the utmost respect for his skills! He can look at something and have a simple solution in minutes. I look at it and figure out the most complex solution possible. He is an excellent machinist as well, just not happy with tight tolerances.
I was fortunate to serve an apprenticeship to a German tool and die maker. He was also a firearms mfg. I was lucky to learn from him. It combined two things I love, machining and firearms.