Taps (not for the bugle)

[George F.]

For the machinists out there, can you enlighten us as the different types. I know there's taper, plug, bottom taps. What is the difference between 2,3,& 4 flute taps, other than the obvious number?  What about spiral taps? what are they used for? Also, the material they are made of? I know there's HSS and HC, are their other materials they are made from? What's a good lubricant to use?  What about straight body taps, and reduced body taps? How do you know when a tap is dull and needs to be replaced? I've seen tap removal tools in Brownells, do they work? If holes are drilled on a drill press, and the tap is started by hand, is there a chance the tap will not cut threads straight, or wonder off some? Is there a prefered method of starting taps? If I missed a few, please add it for us non- machinists. Thank you  ...Geo.

[oldiemkr]

Good Question!  I used to have to teach some "student shop" courses at a university. I've possibly seen every way NOT to do it.

If you are going to have just a few taps around for lock work and rifle building probably 2 flute spiral tip HSS taps are easier to work with {others might disagree}. These are usually for tapping through holes or holes where you drill deep enough to hold some chips, not for blind holes where threads go to the bottom. I almost never use HC taps.

The most common tapping problem {if the hole is drilled correctly} is not breaking the chip or backing the tap to clear the chip. Just pushing the chip along is adding pressure to the tap. Thats more of a problem in tougher metals but its an issue.

HSS taps are High Speed Steel usually M2 and they have some other stuff in there to reduce wear etc. HC taps are high carbon steel. There may be some good HC taps around but usually the ones you find lately are Chinese or similar quality. Not real good to start with and HC taps won't last near as long. They might break easier too.

Exotic lubes are not too important on mild steel or brass usually what you find in rifle making. Motor oil,3 in one oil, various spray lubes, wax sticks or even paste wax will work. An 0-80 tap hole in 304 stainless or a 2-56 in monel is a complete different story.

An easy way to start a tap straight is to drill the hole in the part {with the part clamped down} then remove the tap drill and put the tap in the chuck and start the tap by hand, Even if you just get the tapered part of the tap into tne material it has started straight. Sometimes you might be able to tap it through other times you can remove it from the drill prss and finish it by hand.

The only tap removal tool that works every time is an EDM machine. HSS taps are !@*%&@ hard. determining a dull tap is mostly by feel and possibly looking at the sharp edges to determine wear. Trying a used tap vs a new tap in a scrap piece may help.

[flehto]

I drill the hole and whether the part is clamped or not, the tap is lubricated, the drill press is turned on and then off and while the spindle is "coasting" , the tap is brought down into the hole and stops after a few turns. The tap is then unchucked and a tap wrench is used to complete the threading either at the drill press or on the bench. The RPM of the drill press has to be judged so a suitable "coasting" speed is used when entering the hole.....Fred

[famouseagle]

I have a Sears variable speed drill press.  Speed is changed by repositioning the belts.  

After drilling the hole with the tap drill, I put the tap in the chuck and remove the drive belt.  I turn the chuck by hand with a little downward pressure until the thread starts to form.  I turn the chuck back and forth to break the chip until the tap is through or to the desired depth.  Has worked well for me.

[Ken G]

I do it by hand also.  Turn the drill press off and turn it by hand.  Power anything has resulted in grief and agony for me.  SOmething I do not want to experience when installing a ventliner. 
Ken

[Benedict]

I do it by hand also.  Turn the drill press off and turn it by hand.  Power anything has resulted in grief and agony for me.  SOmething I do not want to experience when installing a ventliner. 
Ken

I used to put the tap in the chuck too and it worked fine.  But since I have gotten the kind of tap wrench that fits in the drill press chuck I have had much better success and think it is easier.

Bruce

[Stophel]

I avoid HSS taps at all costs.  If you break one, you ain't gettin' it out easy.  If a good plain high carbon tap breaks, you can use a punch and bust it out, and usually, you don't even damage the threads you have already cut.  Sometimes, though, HSS is all you can find.  Use them and be careful.  I tried the Brownell's tap extractors years ago (the little finger deal).  Not worth fooling with.  If a tap is broken, it's probably because it's stuck (usually because it was dull), and them little fingers ain't gonna turn it out.

I like Hanson taps.  I hate Vermont American taps.  They suck badly.

You know that it's time to replace a dull tap when it just don't cut well anymore.  A dull tap is dangerous, and an invitation to breakage.  It will get tight, feel "squeaky", no matter how well lubricated, and they're easy to snap off when they get like this.

I often tap just by hand.  Yes, you can get it cocked.  The longer/deeper the hole I guess the straighter you could get the threads going by hand.  I have a pretty good eye, and don't have too much problem getting crooked threads, though on more critical screws like bridle, sear, frizzen screws, etc. I use the drill press gizmo, which is made to go into the drill press and holds the tap vertical, and I use that to tap, or at least start tapping (It's not driven by the drill, it's just held in place and you turn it with your hands). After I get it going, I will usually finish by hand, as I can keep it straight and I can feel what it's doing.  You gotta be able to feel it.

Although people will scream, I just use motor oil to lubricate.  It works fine.  Do about a turn or so, then back up a bit to knock the chips out.  Turn again and back up.  Turn again and back up.  Blow the chips out every now and then, and if necessary, just take the tap out and clean it out and then put it back in to finish.

Unless you drill blind holes, you'll never need a plug or bottoming tap.  Sometimes you need to drill blind holes, though.  I will often take a broken tap or a store-bought bottoming tap and carefully grind the tip down to make a truly bottoming tap for doing that last little bit.

[northmn]

I have used a hand tapping wrench for all of my builds.  My worst problems have occured when I try to fudge and use a drill bit that is "close" to the right size.  As to breakage, I have had brand new taps snap off like glass and some that have gotten a little rusted cut through like butter.  Sometimes I can use a small punch and reverse them out or break them enough to get them out.  Mostly I have used small taps for building ML's.  10-32 about as big as needed for most things except vents and drums which can go up to 3/8. Its the small sizes from 8 on down that seem to cause problems.  I blind tap half stock ribs and use a bottoming tap and spend some time trying to get the screws to bottom and yet hold the rib firmly.  Surprisingly a lube I have had the best luck with is the Crisco that I use for patch lube.  If the correct bit is used with the tap, getting a straight enough thread is usually OK with hand held tap wrenches.  Even a slight countersink will help.

DP

[Dphariss]

Describing all the types. Oh boy.
Bottoming taps cut threads close to the bottom of the hole.
Taper have a long taper to start easy but will not cut full threads with in about 6 threads of the point.
I use HSS almost exclusively and detest carbon steel. Yes easier to remove but easier to break too.
Use a GOOD tapping fluid, something with Moly or such in it.

The IMPORTANT thing is tolerance. "H" number. H1 is tight H3 looser, quite a bit. H1 = .001 H3 = .003. .003 is about the norm for off the shelf stuff. But in small taps .003 is a lot.
If tapping for drums, breeches or vent liners I use H1. In fact I like them for everything. Gives less slop and better thread engagement. I like to make these parts with an adjustable die or on the lathe to reduce the tolerace a well.

Dan

[George F.]

Now the Tolerance factor is something that I didn't know about, interesting. I now know why I've had a hard and cautious time taping holes lately... my taps are dull. I posted this question to speed up others knowledge about the basics in the little machinist's skills we require. Although this was very informational to me personally...Thanks to you all...Geo.

[billd]

In our machine shop business H3 is the standard tap. Each "H" =.0005. Starting with H1 and getting bigger as the numeral gets bigger.  We use all HHS, never had a carbon steel tap in the shop.  Rieff & Nestor "was" the standard to go by, but lately I'm leaning towards USG and Cleveland.  The unusual thing about the number system is it's the opposite for the gauges. A class 1 thread is very sloppy, class 2 is standard, class 3 is a very close fit.

Don't confuse the "H" with the "G" used for metric taps. It's a completely different system.  I believe 6G is a standard and they get bigger as the number gets smaller.
 
Then there's roll or form taps, a whole different animal. I don't see any use for them in gun building, but for stainless and other gummy material they can be a the best thing since sliced bread. Roll taps don't cut metal. They displace the metal and form a thread. It's a much stronger thread than a cut thread but the hole has to be very precise. They cannot be used by hand, they must be power driven.

And for home use, WD40 is an excellent tap lube.


Bill

[famouseagle]

Good info!

[FL-Flintlock]

There's a lot of info on this site:
http://www.newmantools.com/taps/taptech.htm

I agree with Stophel, Hanson is very good quality without the high price, I have three of their micro-spline hex head screw extractor sets and several taps & dies, no complaints on anything.  According to a contact I have in the tool industry, Hanson makes the same products sold under other brand names that sell for 2-5 times as much.

Some other good brands are:  Tapco, Chicago-Latrobe & Greenfield

[Michigan Flinter]

Some of you folks use the drillpress with the spindle still moving to start your tap. I beleive that you have been very lucky in not breaking or screwing up your tapped hole .If there is any resistanc to the travel of the quill the tap will chew up the threads. Also a SAFTEY item , it is not a good idea to turn the spindle ,with your hands ,while the drill press is still pluged into an outlet. I've seen enough safety movies with mangled hands from people wearing rings , loose clothing ,stock not clamped down and people grabbing onto the spindle ,always be very cautious around machines.  Eric D. Lau Riverdale Mi.

[Dphariss]

Yeah I goofed the tolerance thing. Should have looked.
I have used almost anything for tap lube. But if you are tapping castings made of 4140 or some the other alloys you better use something with some slickum in it. Slick 50 with Teflon is even useful. Shiloh used to retap the tumblers after hardening to clean the threads. This stuff, one of the employees  brought in the dregs from a bottle, kept the taps from binding when everything else was failing (?). I tap SS making cleaning rods and have used Castrol with Moly with good results though sometimes they will bind up even when using taps ground for stainless. Suspect its inclusions in the alloy.
I break a tap now and then and start them in the mill as a guide but never with power, by hand. Once in a few threads I take the tap out of the chuck in the mill and finish by hand.

Dan

[FL-Flintlock]

On the starting/centering thing, I use a centering point in the drillpress chuck that engages the matching dimple on the end of the tap handle; the DP quill is only used to as a guide for the tap handle.

As for cutting fluids, Rigid brand high sulphur dark cutting oil will work very well even on hardened steel and most stainless steel.  I've tried many other "dark cutting oils" and only a couple are anywhere near as good as Rigid brand and most cost a lot more too. 

For most brass, bronze Rapid Tap or Tap Free are both very good, also on lower grade steel, stainless steel and softer aluminum alloys.

Renton A-9 is one of the best I found for all aluminum alloys including the very hard ones - also works well on the non-free-cutting non-ferrous alloys including pot metal and the low-grade cast brass that tends to be brittle or sticky.

For stainless alloys of 310 and above, Rigid dark mixed 50/50 with Amsoil 20W50 synthetic engine oil works very well.    BTW, the Amsoil by itself works quite well for most anything too.

[Stophel]

I have never heard of the H numbers before.  I just order an 8-32 tap, and I get an 8-32 tap.  I'd kind of like to be able to tap them tighter.  Sometimes the screws that I have end up looser than I'd like, and I make new ones, using the set screw on the die to open it up as far as I can to make the screw tighter.

[billd]

If you don't specify a H number you'll probably end up getting a H3.

[Acer Saccharum]

I like the HSS gun taps made by Greenfield(actually made in Japan) Two flute, black surface treated, with a necked down section between the cutting section and the main body of the tap. made for tapping stainless. These taps cut forever, and are TOUGH. I

When a tap starts to feel like it's cutting hard, that is the time to inspect the leading edge. If the teeth are chipped, it will fail sometime in the near future.

Lube is essential for tough steels. I use Rapid tap, which doesn't work as well as the old carcinogenic formula, but still pretty good stuff for tough steels like 0-1 or stainless steels.

Tom