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Antique tapered tap ID, please.

neilho

Titanium
Joined
Mar 23, 2006
Location
Vershire, Vermont
A friend dropped off a box of antique taps. He's downsizing and finally giving up the goods:).

Amongst oddities like adjustable taps and long taps with 1/2" square drive were these tang driven tapered taps: Most are 26 tpi, some 28, some 17, most of the small ones are 32. No maker's mark visible. Anyone know what they were used for? I'm also curious about the drive tangs and the tool used to drive them.

tapered taps.jpg
 
The tapered taps are likely 'boiler taps'. Tapered threads were tapped into boilers and tanks for studbolts to mount various fittings and steam dome covers. The tapered threads were used as they were self-sealing. In addition, the tapered taps were used to cut threads for 'patch bolts' used on temporary boiler repairs. Firetube boilers as used on steam locomotives, stationary and marine boilers, as well as traction engines, steam rollers, donkey engines, cranes, and plenty more were built in the days of riveted boiler construction. In order to mount various boiler fittings, pads were often riveted to the boiler and drilled thru for the connection to the fitting. Holes were then drilled and tapped in these pads for 'companion flanges' to connect the fittings. Other devices and equipment was mounted on studbolts tapped into the boiler 'sheets' (any piece of plate made into a part of a boiler is referred to as a 'sheet', even if it is not flat). Using a tapered thread on tappings on boilers made the threads self-sealing without having to rely on a nut/gasket on the inside of the boiler (next to impossible to get a seal on a curved sheet0. It also eliminated the need for gaskets under the nuts on the outside of the boiler. Thread pitches sound like commonly used boiler threads.
 
They are not boiler taps per se, but are just early style general taps. They are not intended to produce a tapered threaded hole but are intended to be run all the way through the hole where the finished diameter is at the top of the tap.

The form originated at a time when all that was done to provide a "cutting" edge was to file flats on the sides of the tap. That did not provide a very good cutting action so they more or less were forming taps and needed the taper to overcome the large turning forces.

Later grooves were ground in to provide cutting edges but the taper threads remained which cut gradually along the length of the tap. Later the threads became parallel to the bore and just a tapered end was ground to provide the cutting edges.

The wrench is just a standard tap wrench.

This book from 1864 gives the description starting on page 420.

 
Thanks for that reference. Also given to me were some taps with a conical square drive, as in figure 444, similar to woodworking bits for use in a brace, but not the same size.

These things are older than I thought....
 
The tapered taps are likely 'boiler taps'. Tapered threads were tapped into boilers and tanks for studbolts to mount various fittings and steam dome covers. The tapered threads were used as they were self-sealing. In addition, the tapered taps were used to cut threads for 'patch bolts' used on temporary boiler repairs. Firetube boilers as used on steam locomotives, stationary and marine boilers, as well as traction engines, steam rollers, donkey engines, cranes, and plenty more were built in the days of riveted boiler construction. In order to mount various boiler fittings, pads were often riveted to the boiler and drilled thru for the connection to the fitting. Holes were then drilled and tapped in these pads for 'companion flanges' to connect the fittings. Other devices and equipment was mounted on studbolts tapped into the boiler 'sheets' (any piece of plate made into a part of a boiler is referred to as a 'sheet', even if it is not flat). Using a tapered thread on tappings on boilers made the threads self-sealing without having to rely on a nut/gasket on the inside of the boiler (next to impossible to get a seal on a curved sheet0. It also eliminated the need for gaskets under the nuts on the outside of the boiler. Thread pitches sound like commonly used boiler threads.

Every boiler I've worked on or helped work on is 12 tpi for mounting studs and staybolts. Common pitch no matter the diameter or who the builder was. I believe it was customary to tap the hole straight and drive in tapered studs. Staybolt holes are tapped straight through. These have all been traction, portable or stationary boilers, locomotives may be different.
 
Peerless Repair:

You are correct about staybolt taps being straight threaded. 12 thds/inch is pretty much standard for staybolt threads. The last two steam locomotive boiler engineering jobs I've been working on used welded staybolts for all the rigid stays. One boiler (Chinese locomotive blt about 1986) got welded stays from the original build. The other locomotive boiler dates to 1920. With partial side sheet and inner door sheet replacement, the staybolts were changed to welded stays. Staybolt taps always intrigue me. As you know, these are long enough to cut threads thru the inner and outer sheets on a boiler's 'mud leg' (the water space surrounding the firebox).
The tap has to maintain the same 'lead' for the thread over quite some length, and there is a tapered leader to start the tap. Staybolt taps always seemed to me to be the longest taps I'd run across.

Engine Bill:

I stand corrected. I recall getting a box of stuff from a fellow whose father had been a blacksmith. The blacksmith had died in about 1952 and this was about 1987 or 88. The fellow was cleaning out his house prior to moving, and called me to come get some of his father's blacksmith tools and odds and ends. There was a wooden box which had held toe calks, and in it were a mess of tapered taps similar to what the OP has shown. I had no use for the taps, so kept the wood box and gave the taps to a working blacksmith who did some repairs/restorations to wagons. He was happy to get the taps.
 
John Oder:

Thank you for posting the catalog pages with the P & W locomotive taper reamers. On steam locomotives, in addition to tapered thread boiler studs, fitted taper-shank bolts were used on the frame and elsewhere. Various connections made to the frame or of frame members on steam locomotives had to be as rigid as possible. Tapered shank bolts with what amounted to a body-bound fit were used. Holes in mating parts were drilled undersized. On the erecting floor, parts were assembled for the frame and, eventually, the valve motion. Fitup was done using undersized bolts. Once final alignment was made, holes were line reamed through with the tapered reamers. Tapered bolts were then driven into the holes. Having had to remove some of these tapered shank bolts from old steam locomotive smokebox saddles, I can attest to the fact that they were in there in a death grip. Using a rivet buster (large air gun) and blunt steel did not drive them out. We finally burned them off flush and cored them with a cutting torch. Prior to the arrival of one-piece cast-steel locomotive frames, locomotive frames were built up from parts. The side frames were one set of steel castings, finished on planers and slotters. The cross ties were another set of castings. The side frames and cross ties were joined using tapered shank bolts. Even with the best of these efforts, the working of the pistons and side rods often took the frames out of square. When a steam locomotive underwent a major 'shopping', the original bolts were driven out, frames re-squared, and holes re-reamed for oversized taper shank bolts. I believe P & W also offered a line of staybolt taps used on the boilers. Nowadays, to lay one's hands on a bucket of tapered reamers and staybolt taps forgotten in some pile of dusty junk is akin to finding a small treasure. Not too many of us know what these tools are, let alone have any use for them. P & W along with Niles made not only the cutting tools but the specialized machine tools for steam locomotive building and repair.
 
Larry:

Thanks for validating my initial opinion as to what the tapered taps the OP inquired about were. 12 thds/inch is pretty much a standard 'boiler thread' in the USA. Still, it's hard to imagine how coarse a thread 1/4" -12 would be. In the days before welded repairs and cutting torches, boilermakers would put on a 'soft patch' on the outside of a boiler or tank. The soft patch was a piece of plate formed to seat against the shell of the boiler or tank. The boilermakers sometimes dished the middle area of this patch to allow the edge areas to seat on the curved areas of a boiler or tank. Patch bolt holes were drilled with an "old man' (ratchet drill and post, the foot of the post being chained around the boiler shell). After the patch was bolted onto the boiler, the edges had to be calked with a hammer and calking chisel (if the repair predated air tools).

The other application for the tapered boiler taps was to tap holes for mounting fittings and support brackets on the boiler shell. The backhead of locomotive boilers comes to mind with small diameter tapped holes for support brackets to hang various accessories.

As this thread evolves, I find myself thinking what a great advance SMAW (stick welding), oxyacetylene torches (and rosebuds to heat and allow hot forming on the spot) angle grinders & electric drills & mag base drills are. Nowadays, if we want to put a tapping for mounting something on a boiler shell, we weld a tapped pad to the boiler shell, and the pad has radius'd corners to reduce stress concentrations and spread out the loads. I've seen enough old boilers to marvel at the work the boilermakers did with what they had available at the time.
 
There were still some of those old boilermakers around in the 1950s, when I was a kid.

As I recall, all of them were very deaf. A boiler factory or repair shop was extremely loud, and PPE was not as it is now..
 
A lot of the old boilermakers were also 'punchy', similar to boxers who took a few too many punches. I've seen older boilermakers, who aside from being deaf (or nearly so), had a variety of tics and twitches like some boxers. Some of the oldtime boilermakers would have crooked noses or cauliflowered ears. This was from actually boxing. Boilermakers in the riveted boiler days tended to be a hardy and strong bunch. When times were hard or if they needed a few extra bucks, some boilermakers would get in the ring, boxing 'smokers' or similar local bouts. This accounted for the crooked noses and cauliflowered ears and the tics and twitches - if handling riveting guns and rivet busters didn't. Another thing I recall seeing old railroad boilermakers do was to wear "bicycle clips' around their pants cuffs. Bicycle clips were light spring steel clips which cinched the bottoms of pants legs around the shins, just above the ankles. Original purpose was to keep loose pants leg fabric from gettin g caught in the sprocket on a bicycle. The boilermakers used the bicycle clips to keep hot slag, grinder sparks and similar from going up their pants legs when they were working in locomotive fireboxes or furnaces and combustion chambers on Scotch Marine boilers. The building and repairs of firetube boilers in riveted days meant a lot of time spent using air riveting guns and air motors to run tube rollers and to ream staybolt holes. Lots of noise and vibration along with heavy work. The oldtime boilermakers worked without PPE, and it was the era when asbestos was freely used to insulate boilers and steam lines. They ate weld smoke, grinding dust, asbestos fibres and plenty more. I think there were two groups of boilermakers: those who died relatively young from the effects of what they were exposed to in the workplace; and, those who lived to very ripe old ages. This latter group probably had genetics on their side, and may have been in the minority of the boilermaker population.

BTW: I've got a very significant hearing loss, particularly in the higher frequency ranges. For many years, I resisted getting hearing aids. My wife prevailed on me and with insurance covering the cost, I caved in. Wearing hearing aids is something I do only on occasions when I might be at a meeting or presentation or in the car with my wife. Otherwise, I tell her most of what's out there is not worth hearing. I like being in my own world, figuring and designing in my mind to pass time rather than in idle BS. When I do wear the hearing aids, I have to be careful as the 'ear domes' sometimes detach and are left in my ear canal. This means a trip to an ENT physician to get the ear dome snaked out. Too many years around powerplant machinery, machine shops, fabrication shops and heavy equipment.
 
Looks like you nailed it, Mr. Lang.

Prob the reason my taps are odd pitches is they were leftover hardware store stock, sold at auction. Apparently my friend's neighbor spent the last few years of his life going to auctions.
 
Thanks Joe!
Anyone have any idea how these were driven?

Either by a wrench or a die holder (as shown in the picture below).
I have a die holder like this. It has a set (2) of blank dies.
You remove the dies and put in the blank ones and clamp the tap between them.
You might look on the side of the tang for a makers mark.

Rob
 

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They are not boiler taps per se, but are just early style general taps. They are not intended to produce a tapered threaded hole but are intended to be run all the way through the hole where the finished diameter is at the top of the tap.

The form originated at a time when all that was done to provide a "cutting" edge was to file flats on the sides of the tap. That did not provide a very good cutting action so they more or less were forming taps and needed the taper to overcome the large turning forces.

Later grooves were ground in to provide cutting edges but the taper threads remained which cut gradually along the length of the tap. Later the threads became parallel to the bore and just a tapered end was ground to provide the cutting edges.

The wrench is just a standard tap wrench.

This book from 1864 gives the description starting on page 420.

Take a closer look. The flat driving tang is larger than the major diameter. You ain't running them all the way through.
 
Hmmm. First time I've seen a die holder like that. A multi purpose tool.

There are the brand names "Merrill" and "M King" on two taps that have a tapered square drive, but I can find none on the blacksmith taps. There is the designation L on about a 1/3 of them, before or after the thread pitch number, for example the 1st tap on the left in the pic in the 1st post. No idea what that means.

tdmidget: There is a short section of tap between the thread cutting part of the tap and the tang whose OD is smaller than the minor diameter. It is pretty short - 1/4" long max on the largest taps. S'pose it could work if the metal were thin, but yeah, mostly not.
 








 
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