unusual threading die adjustment

I filled out the less common sizes in my tap and die collection from
the bin in a second-hand store, without regard to the OD of the dies,
since I'd probably only turn them by hand to repair existing threads.
Recently I got out the 1/4-18 NPT die to clean up rusty threads and
noticed that it was missing the adjusting screw that holds the die
open against the pressure of the diestock clamp screws.
The die is 1.5" round and the adjusting screw enters radially into the
slot, not perpendicular to the slot on a chord like normal split dies.
I made a 32TPI screw which fit when turned to 0.295" OD, not much more
than 0.281" or 9/32" which is a standardized thread:
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The die manufacturer is Card, USA.
The female adjusting screw thread in the die is noticeably tapered.
Since this is a pipe thread die the exact cutting size doesn't matter
and the die OD is under 1.500" with the home made screw fully
inserted, but I have other similar dies for straight threads and
adjusting then to cut the right size without a gauge would be tedious
if my custom setscrew is out of spec..
Does anyone have this type of die to measure or know whether or not
9/32-32 is the proper thread size for this adjusting screw?
Thanks
-jsw
Reply to
Jim Wilkins
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I can't help with your specific query as none of my pipe threading dies are split they just have a notch or notches to prevent rotation and are of a thickness to suit to intended thread size length. I presume they are all accurately made so that when run onto the pipe to cut the thread when the die is flush at the end of the pipe the gauge size of the
threading dies to suit the Rotostock machine.
Reply to
David Billington
I thought dies were split so they could be tightened back to size after grinding inside the holes to resharpening them. I resharpen old taps by running a cylindrical stone in the flutes.
Anyway, rather than leaving the lathe set up I made some 9/32"-32 setscrews which seem to fit well. The Schrader valve and 5C collet show that thread diameters can't be assumed.
Reply to
Jim Wilkins
Quite possibly although the pipe thread dies I have would require quite a bit of dressing back to significantly effect the pipe thread size cut. IIRC both NPT and BSP pipe threads are 1:16 taper on diameter so I think would be fairly tolerant to dressing and still give usable thread engagement but I've never had to dress a die yet.
I do use the adjustment feature with split dies with straight threads and one application for threading M10 x 1 on stainless tubing I made a double ended die holder with one die set for a roughing cut and the other die set for a finish cut, works very well. The die holder locates on a mandrel which fits in the tubing for alignment. That and using decent high pressure lubricant when cutting threads I haven't had to replace a die yet.
Most of my taps are small enough that if blunted for some reason it's easier to replace but I'll bear in mind the sharpening for some larger ones that are losing their edge from cutting threads in some poor quality steel.
Reply to
David Billington
The small taps I used for electronics are new and high quality. The
came from a second hand store and were often dull from production use. The largest is 2" NPT for which I paid less than 10% of its retail price. I have a surface grinder with a cylindrical/tapered tool grinding attachment and make sure the used taps I buy have center holes in the ends.
Reply to
Jim Wilkins
The tool grinding attachment sounds like another thing I'll have to make when I get my surface grinder up and running soon, any images of yours or similar available?
Reply to
David Billington
This shows the machine but I didn't find a photo of the center grinding attachment
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which looks like bench centers mounted on a swivel base.
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Notice that Chadwick copied the design of the head for the Quorn about 30 years later, except for the separate elevating screw.
This is the type of sharpening attachment I use the most:
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It sharpens only the ends so when roughing a slot I minimize side wear with plunge cuts. -jsw
Reply to
Jim Wilkins
Chaddock. The work holder was copied from the Deckel.
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Reply to
Jim Wilkins
Why are both guys on the Specs page cutting diagonals? They both have a hand on the X and Y axis handles. (Marketing never learns.)
Reply to
Larry Jaques
I do that too. The design gives up some rigidity for versatility, like a Shopsmith, and tends to develop a visible vibration pattern which slight zig-zag motion breaks up. The manual suggests that 25 microinches is the best finish you can expect.
I use it as a mill for hardened steel and to grind lathe bits to precise angles for threading and gear cutting. It's no match for the Brown & Sharpe suface grinder I learned on, but I couldn't have carried one of them into my basement.
Like the rest of my 50's/60's machinery it's better for a small shop making experimental and prototype one-offs than a high production environment. I'm far too inefficient to be a job shop. I tend to redesign the part as I make it. -jsw
Reply to
Jim Wilkins
So you rest the other hand on the handle to stabilize it? Aren't the gibs lockable?
That's often a good thing when you work for yourself, but not for others.
Reply to
Larry Jaques
The zig-zag consists of a slow continuous feed in or outward with the left hand's leadscrew while moving the table back and forth with the right hand's fast rack and pinion feed. It isn't the best way to grind to a precise dimension but it breaks up the wheel's vibration resonance and I normally just use the machine to grind below the dings and rust pits on a block of sheared or flame-cut scrap steel and make two sides parallel or all of them square enough to clamp before milling it. The mill vise needs two flat and parallel sides to hold work securely, the grinder needs only one to start and can grind the others square or parallel.
The better way is to feed in almost the width of the grinding wheel between passes, to equalize wear across it. I do that for a while after dressing the wheel until some narrow workpiece job like sharpening end mills wears it unevenly.
Designing and prototyping the packaging was an extra service I could offer to electrical engineers with minimal mechanical training or experience. Packaging is very important for microwave circuits. That largely means sealing your signals in and other signals out.
When I worked for others they had the proper shop. I've run CNC and manual Bridgeports and 15" lathes etc and designed sheetmetal to be fabricated on 10' vertical press brakes and Strippits. I just don't have the space or need at home for larger machines. -jsw
Reply to
Jim Wilkins
Grok that. Thanks.
Yes, I see the wisdom in that. Thanks for the Grinders 101. I've obviously never used one.
I'll bet that paid well, in addition to being interesting and fun for you.
Understandable.
Reply to
Larry Jaques
When I started in industry I quickly found that I couldn't reasonably design a part to perform a task without knowing something of how to make it, though not every newly minted engineer felt that way.
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"Traditional engineering is also known as over the wall engineering as each stage blindly throws the development to the next stage over the wall."
So I learned to operate some machine tools and observed how others worked, in terms of the geometries they could or couldn't create and the accuracy they could reasonably deliver. I didn't use the more dangerous equipment until taking adult-ed night classes in machining and welding at local high schools.
In small non-union startups that built custom equipment on order it was easy to learn machine tool operation without threatening the operators that I wanted their job since I clearly had a good job of my own, building and testing the electronics. I tended to become the liaison between engineering and production and had to learn new operations myself so I could explain them, or convince the designer to make a change..
Eventually when I bought a house I knew enough to assemble a small machine shop that was adequate to make the devices I'd thought up. I've never created anything patentable because I ultimately reduce problems to very simple solutions, like using a sink spray as a water-saving shower head. -jsw
Reply to
Jim Wilkins
Poking around, studying old patents is very enlightening and humbling. In the mechanical area there's not a lot someone hasn't already come up with. They can be deceiving too. I have a pretty much standard looking laminated padlock with a pin tumbler I found somewhere. It has a relatively new patent number on it. Seemed kind of odd to me, nothing special about the lock I haven't seen a zillion times before. So I looked up the patent. It was for the locking pawls and a novel way of manufacture. Yet they are still shimable and the core can be picked with a just a stern look. Looks good for sales though. "Hey look, this one must be better, it has a patent." ;-)
Reply to
Leon Fisk
I have an old Jacobs drill chuck, normal-looking except that the sleeve is diamond knurled, with the patent date "SEP 16 1902" stamped on it.
Reply to
Jim Wilkins
That's an older one for sure. From what I can suss out it looks to be the beginnings of what we consider to be a standard keyed chuck nowadays.
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It looks like that patent was still being cited in the early 2000's...
Reply to
Leon Fisk
I love that def. Isn't the vast majority of engineers that way? Most teachers are instructors rather than educators in the same light.
I think innate curiosity drives much of that, of people wanting to do more than they are, and wanting to find out how things work.
Cool. You were lucky to have worked at small non-union businesses, or your endeavor would have been quashed instantly. I'm sure that you had good relationships there, and then got plenty of good referrals in between those jobs.
Nice!
Whatever works, eh? I wouldn't be a bit surprised if someone tried to patent that, too, though, nowadays. Biological and genetic patents are really starting to bother me. I wonder how the Trump administration will affect all that.
Reply to
Larry Jaques
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I've heard that specifically about the auto industry, but the engineers I dealt with there were new hires brought in as vehicular electronics mushroomed. That business is secretive and no one talked shop. At Segway engineering was very hands-on and aware of production concerns. Other places varied among the individuals.
The teachers I had in various night schools were "night and day" different from the ones in college, since they worked at a real job for a living. In Mitre-subsidized night school I aced the Differential Equations course I had barely passed in college, because he explained it for people who use math as a tool rather than worship it as a gift from Vishnu. In Analytical Geometry all the problems used 30, 45 or 60 degree triangles so the answers included the square roots of 2 or 3, we just had to know where. We learned to do trig and logarithms in our heads without a calculator. Problems at work such as decibel gain or loss and phase shift modulation merely had different numbers in the familiar places. -jsw
Reply to
Jim Wilkins
Yeah, Segway was probably abruptly different from most settings for engineers. My new neighbor was an engineer at Boeing in TX. A white collar engineer/manager, which I found hard to wrap my head around. I'm pretty sure he was a computer/paper/meeting engineer, a different strip than most I've met.
VBG.
Cool.
Reply to
Larry Jaques

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