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: (Amazon.com product link shortened) 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
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On 23/07/18 15:34, Jim Wilkins wrote:

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.
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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.
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On 23/07/18 19:41, Jim Wilkins wrote:

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.
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The small taps I used for electronics are new and high quality. The >1/2" ones that I bought for repairs and home projects like my sawmill 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.
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On 24/07/18 02:39, Jim Wilkins wrote:

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?
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This shows the machine but I didn't find a photo of the center grinding attachment http://vintagemachinery.org/pubs/1141/1691.pdf
which looks like bench centers mounted on a swivel base. http://www.penntoolco.com/spi-heavy-duty-bench-centers/
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: http://www.shars.com/end-mill-grinding-fixture It sharpens only the ends so when roughing a slot I minimize side wear with plunge cuts. -jsw
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On Tue, 24 Jul 2018 16:46:23 -0400, "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.)
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wrote:

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
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On Thu, 26 Jul 2018 08:35:24 -0400, "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.
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wrote:

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
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On Mon, 30 Jul 2018 17:35:42 -0400, "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.
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wrote:

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. https://en.wikipedia.org/wiki/Traditional_engineering "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
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On Wed, 1 Aug 2018 08:47:03 -0400
<snip>

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." ;-)
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Grand Rapids MI
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wrote:

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.
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On Wed, 1 Aug 2018 14:07:01 -0400
<snip>

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.
https://patents.google.com/patent/US709014A/en
It looks like that patent was still being cited in the early 2000's...
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    [ ... ]
    Look for a four-volume book set of _Ingenious Mechanisms_ to see lots of ways to do things. :-)
    Enjoy,         DoN.
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Email: < snipped-for-privacy@d-and-d.com> | (KV4PH) Voice (all times): (703) 938-4564
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wrote:

The sort of problem I have difficulty with is for example how to splice 4" x 8' steel channel for a 16' gantry hoist track without the bolt holes weakening it or the heads or shanks interfering with the trolley wheels. Welding would make it too long to store under cover. Hand-fitting the bolt holes to minimize play is acceptable, tapered shank bolts aren't.
I have a design and the materials for the intended use where it's suspended from a roof beam at the center splice and tripods at both ends. The version without center support is a paper exercise though I might use a good solution.
C4 x 5.4 depth=4, width=1.584, web=0.184, area=1.59, Ixx=3.85, Iyy=0.319 I get a safe(?) working stress of 12.5 ksi with a 500 Lb centered load, or 1000 Lbs for the two 16' channels together.
-jsw
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On Wed, 1 Aug 2018 08:47:03 -0400, "Jim Wilkins"

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!

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.
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