Machining Non-Standard Threads

This video provides some general mechanics and information on how to create a non standard, custom or proprietary thread, that is not in the book. Take A Look !!
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[@thebeaver6596]

I read an article on the cnc cookbook where he talked about “thinking like a machinist” and you are THE guy to reference when someone says think like a machinist.

[@joepie221]

I was flattered to be the guy picked for that.

[@worthdoss8043]

Happy Birthday Joe.

[@joepie221]

Thanks Worth. I'm flattered you remembered.

[@erikbroberg9785]

Just want to say Joe, thanks for these videos. You’re content is a machinery handbook in video form. Extremely helpful.

[@David-hm9ic]

Thanks for this one, Joe! Working on the Battleship Texas restoration we run into threads that only an engineer in 1910 could come up with. Recently we ran across a 1"-40 tpi and 3"-10 tpi threads while working on secondary (3" and 5") Naval guns. Sometimes we have to make new parts with threads that are not in the books.

[@bruceanderson9461]

I watch your videos to learn new techniques and best practices and you never disappoint. As a former teacher I appreciate your teaching ability. I knew I had made it as a good teacher when my name showed up scrawled on the bathroom stalls AND my section had the most A grades as evaluated by others. Keep it up as it is appreciated by your subscriber base. For those who complain there are lots of lesser KZbin videos to watch!

[@ddaxe]

Great videos Sir, Your attention to the finer details of machining has made my home shop fiddling that much better and precise. 👏🏻👏🏻👏🏻

[@joepie221]

Glad to help

[@BrianBrowder-e1w]

I have never done any threading. One reason was I didn't have a good understanding and the other was I have always had the choice of delegating it to someone that works for me. I now have a very good understanding and feel confident I can. You took away what seemed to be black magic. I surely learn a lot from your videos.

[@joepie221]

Thats very rewarding to hear. congrats on the new found confidence. BTW, I do have considerable material on threading and measuring threads for your reference. Enjoy and thans.

[@joepie221]

Pasted Comment... Bob Warfield • 2 hours ago Hi, Bob Warfield from CNCCookbook. I just took a look at the math in G-Wizard's thread calculator to see whether the bore formula will work for all threads. The math is based on the actual (many boring pages!) thread standards. Joe's shortcut works--it'll fall with the acceptable min/max range for all UN and ISO 60 degree threads.

[@royarmstrong6613]

You do a great job. I've been a machinist for 40 years and over the last few months have been watching your and many other machining video sites to get a different perspective on how to do things. In this trade you can never stop learning. There is one trick to threading I was shown by an old timer many many years ago but have not seen anyone mention it in a video. If the TPI of the thread you want to chase is divisible by the TPI of your lead screw you can engage the half nut at any time what so ever and the cutter will be in time with your part. I didn't believe it either until I tried it. Give it a shot. Throw a piece of scrap in the lathe and a rag over the timing dial and chase some threads. No specific size, all your testing is the timing

[@enginebill]

Another great video. I had to make four non standard cap screws for a 150 year old German engine that were not imperial or metric standards and I had a sample to copy. The OD was .520" or 13.2 mm, the threads were 11.94 TPI or 2.127 mm pitch. The OD was simple but for the odd TPI, I 3D printed custom change gears for my lathe to get the 11.94 TPI. The only way to get the pitch was to use a 67 tooth prime number gear on the stud and a 200 tooth gear on the screw with a 4 TPI lead screw. Stock gears for the lathe were 10 DP and I made 18 DP gears with a new idler so they would fit the lathe.

[@williams4645]

Always amazed at your knowledge and your willingness to share it!

[@ArcFlashWarning]

Greetings Joe, I've spent a lot of time looking at the handbook and the wires and end up sneeking up on everything as i dont trust my calculated targets. this was very informative.

[@joepie221]

Its a good practice. I sneak up on everything.

[@jamesferguson1054]

I really love the way you present the information. I hope the young guys that watch your videos pay close attention because you sure know what your doing, especially when you mention any safety issues. I owned my shop for 37 years and never had an employee injury. Kudos on these videos.

[@matthewhelton1725]

Most of the time a "Unicorn" Thread is used is for a specific application or a use case. Threads used in Compressed Gas applications purposefully use uncommon Diameters, Pitches and/or Thread Directions and mating surfaces. Another place unusual pitches are used is in optical instruments for precision graduated adjustment wheels (sometimes with Optical Instruments, threads are cut diametrically).

[@ArcFlashWarning]

And surprisingly table lamp nipples are 3/8 27...or something odd. why I do not know.

[@matthewhelton1725]

@@ArcFlashWarning #14 - 20 (*NOT* 1/4" x 20 UNC) used to be very common for carriage hardware, furniture, and interior and exterior household hardware (doors, locks, hinges, rollers, hasps, etc...); You hardly ever see that size anymore. Regarding Electric Light fixtures, there were specific sizes to use codified by the ASME: paxtonhardware.com/blogs/news/lamp-thread-sizes

[@michaelschnackenberg4769]

Great video, it helps a lot, machinerys handbook is a must, I have a PDF copy and print the applicable parts and make notes and calculations on it. The wire chart is brilliant, and works well. I have not done an internal thread before, as I usually purchase the nut from a bearing shop, so, I was waiting for the clever way to measure the thread depth, it would be more practical and make more sense to make a go no guage tho. Again, thanks mate Michael from AUS

[@ponga782]

This is a great video! Thank you Joe! From Gonzales, Tx.

[@joepie221]

Glad it was helpful!

[@captcarlos]

Hi Joe. Great video as usual, thanks. Though you still haven't convinced me to get left hand threading tooling...yet. One of the non standard thread challenges I've encountered, which does happen regularly enough in the hydrolics game, is the repair of the threaded end and making a new piston to fit that thread and cylinder. There are many variations but... You have to use the original pitch of the rod but cut it deeper until you have a clean thread, 'discover' the new nominal thread size, best while 'sharp', turn the 'flats' to 1/4 hight, debur and polish. Then make the close tolleranced tread in the newly minted piston. It would be easier to test a finished piston on an evolving rod end, but, if you made the piston tread first, you would have to guess the size of the rod threads finished size ..or, over estimate and make the rod weaker than absolutely necessary . Another wrinkle is you have to remove the piston from the lathe to check the fit on the rod... And set it up, again, each, time... Question, is there a way to measure the effective diameter of the nuts threads to be sure of the correct size before removing it from the chuck? Oh, and contrary to the quoted drill size for tapping, ie nom minus pitch, which breaks less taps but is a lot less thread flank engagement, weaker but more fit tolerant.. The theoretical correct bore for a nut ( 60° threads) with 1/4 hight flats is: Bore diameter = Nom diam - 1.299 X pitch, (I go 1.3 x pitch, easy to remember) do the math. 2mm pitch, hight (radius) = The square root of 2 squared -1 squared = 1.732mm Less the hight of the flat, 1/4 H, 0.433mm on radius Equals 1.299mm on radius, Or 2.598 on diameter smaller than Nominal diameter . So, say you end up with a nominal M57 x 2mm the nut bore for the flats would be: 57 - 2.598 = 54.402mm (54.40 say). In a perfect theoretical nut to bolt thread there is only 50% contact, losing more on 'critical' fits seams unwanted.. I will step down from that rather wobbly soap box. Commence firing..

[@jimlock3514]

Hi Joe, the tip about de-burring clockwise AND anticlockwise solved a mystery that had me stumped for a few months and caused me to nearly write a part off.......now I know it will never happen again. Thanks!

[@joepie221]

Those fibers can be better than loctite.

[@charlienewman9824]

Man thats a great video ! I enjoy your instruction ! Please keep it up

[@sakosti7990]

This video has answered so many of my questions. Just starting out with an old South Bend 9 playing around in my basement. Great video!

[@joepie221]

Glad to help!

[@johndevries8759]

Great video Joe, you always manage to show me something new, either in your approach or your technique. Thanks for that.

[@joepie221]

Glad you enjoyed it

[@TomokosEnterprize]

One of the best investments I ever made was the wires and the mic for them. I don't often use them but when needed they are never wrong.I often had to send pieces to the bush that I had no nut for. All I had to go by was from the service manuals. When machine downtime is over a thousand $ per hour and often more parts just can't be going back and forth a day at a time both ways. My old Czechoslovakian lathe had no split nut. It had a pedal that would fast feed the apron for returning to the start in either direction. It took a bit to get used to but I swear by it now. I am sure we all ruined a thread by not getting the nut fully engaged. That is some slick threading there my friend.

[@samrodian919]

Brilliant video Joe! So helpful for those of us in other parts of the world (UK) who haven't got a Machinery's Handbook lol. You make it look so easy, and to you it obviously is but those of us lesser mortals it leaves us scratching our heads! Thank you for posting this valuable video. You and your family stay safe and well mate.

[@greatdane3343]

Love your work Joe. Thanks for sharing.

[@joepie221]

Thanks for watching!

[@patlaird4188]

Joe. I just wanted to thank you. A while back you explained and used a tooling ball. I decided to buy one. It came in handy on a job at work on the lathe. I was running a thin wall taper with a guage point 1" in. My senior said do you have a ball bearing. I said no but I have a tooling ball. So I was able to confirm my ID. Thanks and keep up what you're doing. Making some of our lives easier. 🤙

[@joepie221]

thanks. I am truly glad to hear that.

[@jackheath8184]

i learn something every video. very interesting. thanks Joe

[@johnjenkins2315]

Thanks Joe for a most enthralling video. At my age I’ll never need to do anything like that ( l hope) but in saying that I do throughly enjoy watching. Heads up from NZ.👍

[@ianpendlebury3704]

One of your best, Joe. Thanks for continuing to make these instructional videos. Much appreciated.

[@ChrisORiley]

Great video, as always! I find myself doing custom threads often enough that I wrote a small program to calculate the diameters. I enter threads per Inch, a thread contact percent and any one of the external or internal major or minor diameters, and the program calculates the other 3 and the thread height. It only works for 60 degree threads, but that's all I do, so it works for my needs. It was written years ago in Adobe Air/Flash. I should really try to re-write it in something more common these days so I could share it more easily.

[@Stefan_Boerjesson]

Thanks a lot for the Master lesson! Being a bit new in mechanics threading is thrilling, every time.

[@jonvassella1076]

Best on web! Thanks Joe from this absolute beginner

[@flyingshards595]

I really like your style of thread cutting! Makes so much sense!

[@bcbloc02]

Making non standard threads is a great way to keep people from copying your stuff. :-)

[@imysteryman]

I have run into this issue a couple of times, one I can remember when I was threading a backing plate to mount a chuck on an LW Dividing Head, it turned out great and I can't even remember how I determined what size to bore it before threading, Now it is going to be a walk in the park. Thanks for sharing

[@joedrouin6957]

Awesome video Joe !! thanks ! I'd like to hear you expand on making a thread plug gauge for internal threads ....

[@joepie221]

I actually covered that in another video. Just be sure to use the internal PD as the PD for the external gage, and be sure the gage OD is spot on size. All should end well.

[@johntenhave1]

That was a most enlightening demonstration, with a stunning result. I need to go watch your first threading video - clearly! There is an electronic copy of the machinery handbook somewhere online. I remember seeing it many years ago. It is gold. Thanks again for my continuing education, Joe and thanks for the gift of your knowledge. It is appreciated.

[@joepie221]

Glad it was helpful!

[@1957StrokerPan]

Another great video Joe. Oh you so remind me of a good machinist instructor when I was in school 30 years ago.

[@glenncpw]

Another pearl of wisdom. Thanks Joe

[@HobbiesHobo]

If I ever see a "Joe Pie" endorsed tap & die set for sale you can bet it will end up in my tool box, Thanks for all the interesting vids. Mike (Not a Machinist)

[@mr8ballme4]

I worked in a big machine shop years ago that made control valves and did a lot of threading. I have always plunged threaded and never used the compound. We did a lot of this style fitting. The company had about 5 to 600 machines and we had thread Gauges (go & no go). Even though we did measure everything with wires the QC relied mostly on the gauges. Great video. Always love watching them.

[@brandons9138]

Gages will tell you if you are in spec or not, but they can't really where you are within the tolerance. On small threads, or threads with tight tolerances, wires can tell you where you fall within the tolerance. This is handy knowledge if the parts have plating called out on the print. That build up has to be accounted for.

[@SuperAWaC]

@@brandons9138 measuring small threads with wires is awful. if you have to measure threads often you should just buy a 0-1 thread pitch micrometer

[@brandons9138]

@@SuperAWaC I absolutely agree. Thread mic all day if available. At my last shop we did quite a few large diameter(80.0mm dia and larger) X .5mm pitch threads for lens barrels. All of the parts were either black nickel plated or black anodized. We had to get the pitch diameter exactly right to account for plating build up. We had no choice but to use wires as the total tolerance was about .004 from "go'' to "no-go".

[@matspatpc]

Very well explained. I have explained a few times how you figure out what size hole you need for a X TPI thread.

[@joemiller5110]

Thanks again Joe

[@markcohen8061]

Thanks for your time, Joe.

[@Bristoll170]

Always a great watch Jo. Not sure what point Mr Pearson is actually trying to make, but if you are new to the industry then the bag of experience is quite empty. Learning the correct methods for a start is very important. After your bag of experience fills up a bit, then you can be in a position to make a call on how precise the job at hand needs to be. That call can be made AFTER you have the grounding with correct, tried and proven methods. Stay safe and looking forward as always to the next clip. Cheers Pete'.

[@tunafish3216]

Great video on threads. I used to use rubber bands to hold the two thread wires together, easier to hold onto.

Great video Joe. Happy Birthday. Take the rest of the day off.

[@MattysWorkshop]

Thanks Joe, I found this very interesting as I do with all you videos, so much to learn, very much appreciated, thank you, take care mate, Cheers Matty

[@joepie221]

Thanks for watching Matty.

[@russelldold4827]

Concise and complete, as usual! Happy birthday, Joe - belated because of the time zone difference (2 hours earlier than GMT).

[@joepie221]

Thank you!

[@brandontscheschlog]

I believe I requested this and you have provided! Thank you Joe! I restore Schrader Navy diving helmets and all of the threads are non standard (uncommon fractional sizes and pitches). I have been successful threading but your video has just cut out a huge amount of time fitting the male to the female thread. This will be especially helpful with specific start and stop locations of the thread for the neck rings.

[@joepie221]

I hope you found it helpful.

[@davemason6273]

Spooky! I did this exact thing earlier today, even the threading away from the chuck & the de-burring process. Think I must have picked up more from Joe than I thought lol. Thanks Joe, & Happy birthday.

[@joepie221]

Thank you.

[@christurley391]

Nice demo. Thanks for the video Joe.

[@markharris6078]

For those in the uk thread wire sets are available from Acreurotrade.

[@krazziee2000]

great lesson and demonstration, thanks

[@CraigLYoung]

Thanks for sharing and Happy Birthday!

[@joepie221]

Thank you!

[@raymondhorvatin1050]

Thanks again for the excellent instruction Inhaven't single pointed many threads but am planning to

[@robertblaze5549]

Good stuff thanks for all the information you share with everyone.

[@richardcranium5839]

you're braver than i am with the fingers. i'll use someting i can replace easily. but good stuff once again thanx joe

[@CH-pt8fz]

Great video Joe, thanks for sharing.

[@angelramos-2005]

Certainly appreciated.Thank you

[@parlinate7314]

Please keep the great content coming....

[@ls2005019227]

Great video/info! Thanks Joe!

[@fredgenius]

Not often I *need* that level of precision, but I like to strive for perfection. Yes, we in the metric world have difficulty getting hold of metric thread wires - either unobtainable or crazy expensive. My solution is piano wire or guitar strings, and CAD. I can model pretty much any thread, a bit of basic geometry and I get a measurement right off the screen. Doesn't matter what diameter the wires are, as long as they contact the walls of the threads and sit with the top of the wire above the top of the threads. I even made a tool to assist with the micrometer bit.

[@infoanorexic]

nice to know I'm not the only one that 'cheats' with a cad program! especially while working with tapers, or figuring out if I'm understanding the machinist handbook correctly.

[@fredgenius]

@@infoanorexic Don't forget the triangles!

[@tallbrian100]

Years ago worked at a grinding job stop one of the things done there was thread grinding. Making threads to plastic injection molds. The dia and pitch had to be adjusted for the shrink of the plastic so there was no standard threads made.

[@glacierfinancial]

Thank you Joe, great info

[@brianrvd]

I was expecting a crankshaft video.

[@ramongonzalo5076]

Can you make your own style threads........absolutely. Yep, when I worked at Babcock and Wilcox Nuclear in Barberton Ohio, we used to cut modified buttress threads (we would alter the sharp corners with radii) in single, double and quad start. Fun stuff.

[@joepie221]

Isn't that a 'J' thread profile?

[@Smallathe]

Awesome demo. Thank you!!!

[@therealstubot]

All my threads start out standard, and end up non-standard.

[@joepie221]

Been there, done that.

[@wlogue]

Thanks again Joe!

[@outsidescrewball]

Great lessons...thank you

[@joepie221]

Hi Chuck, Thanks for stopping by. I hope you and your family are well.

[@TheTacktishion]

2455 views and (1) thumbs down.... What's with that guy....? Good Job....! Keeping it simple....

[@johncarey9400]

Ok thank you I have to make some Odd size Acme Nuts, taps are not available. (5/8"-12 Acme)

[@georgewocosky]

Now . . . if you bore out the 'plug' end , you'll have a SECRET hiding place for the wolf spider fangs ! * would make a beautiful 'anodized' treasure box with the outside turned ! Great methodology Joe ! "V"

[@joepie221]

Good idea!

[@rtkville]

Thanks Joe.

[@lescotta7427]

Pat your a""" on the back man, that was excellent as usual great demo !!!

[@DJ-yp4kc]

Great Info..Thanks A+

[@prodoverjeff2876]

I've been told the old time blacksmiths used to make their own threads. Standardization only came about to satisy the needs of those who built weapons in large volume.

[@kmitchl1]

Wish I had seen this a few days ago. I was making a headstock spyder for a 12x36 lathe. The headstock threads are internal so finding the PD with three wires is not possible. Since the lathe is Chinese I suspected the threads were metric, however then checked at 16 tpi with a thread gauge. I could measure the internal diameter. With the internal diameter and the thread pitch I believe I could have backed into the starting OD for the male thread. The real pain comes in test fitting as I don't have an adjustable chuck. Every time the part was removed I had to dial it in again.

[@garywalters4286]

Great video, the focus seemed to have a little trouble catching up with you,all around nice job.

[@Steelcrafted]

There a great app that i use called UN Threads that gives all kinds of thread data for basically any thread out there....you can even specify custom wire sizes and it will calculate over wires dimensions for you....I had to make a 1/4-24 bolt one time for a friend and I didn't have the mating part, and didn't have thread wires , so .030" mig wire stood in and worked great...

[@mosfet500]

Nice Job!

[@joepie221]

Thanks!

[@deemstyle]

Joe- other than the fact that you can cut your own relief (or "starting track" as you called it) and the fact that you can run at a much higher speed without fear of crashing the lathe- is there a reason to run with the tool inverted? Sorry, if you mentioned it I didn't catch it. Thanks! [EDIT]- I see the link to the video in the description now. Looks like I'm not the only one to ask! Thanks Joe- you rock!

[@colebrown77]

Joe, I am task with making a internal and external 40mm x7 metric acme thread. Any information you have will be appreciated. So far my research shows a metric acme thread is 30 degrees as opposed to the standard 29 degree Acme. I read also they make a metric acme 30 degree tool gauge but I can't seem to find one. Thanks for a great channel. I tell all my apprentices to watch every single video you have made.

[@mikeb1520]

This is 4 months later, so you probably already figured it out, but for anyone else that comes across this problem, search for DIN 103 thread inserts, that specification is for the trapezoidal thread form used for metric Acme, and the inserts are usually labeled that way. All of the major insert manufacturers would probably have them. I can’t help you with the gage, but that would probably be available from European suppliers, many of which ship to the States.

[@wayneacaron8744]

expertly done. but why was i thinking you would put a crank machining vid up?? lol roflao poppy

[@leeklemetti1887]

It's simple, we are all CRANKS!

[@SuperAWaC]

I think it is a bit more useful to know (or at least have written down somewhere) the actual formulas for doing wire measurements on threads, so you can actually understand what it is that you're doing instead of being one of those "machinists" who can only follow charts. There's two ways to do it: Measurement Over Wires = Pitch Diameter + (3*Wire Size) - .86603 / TPI Measurement Over Wires = Pitch Diameter + (3*Wire Size) - .86603 * Pitch .86603 is your constant. There is a theoretically optimal wire size for a given pitch, and again, there's two ways to obtain that: Best Wire Size = .57735 / TPI Best Wire Size = .57735 * Pitch Rounding to the nearest thousandth of an inch, will easily be close enough, though you'll notice with many wire sets that the wire it tells you to use is a few thou off and still good enough.

[@johnnybarbar7435]

Joe, Is there any disadvantages to using the triangle type guages instead of the wire type?

[@joepie221]

If you remember to use the correct side and have a good feel for them, they are fine. I know guys that swear by them. I've never warmed up to them personally.

[@tobydulanski3000]

Joe, do you have any experience with Buttress Threads, Application Hydraulics or Tooth Paste Caps?

[@barryking8966]

Double entry threads are fun to cut.

[@bwyseymail]

I don't know why but when I saw "fun to cut" the phrase "peaceful protest" popped into my head.

[@peteengard9966]

Doing some old tractor and machinery rebuilding you can run into some odd threads. I remember trying to find left hand 11/16 x 18 tpi nuts once. I ended up having a machine shop make them. Very expensive for 10 nuts. One side crowned the other had a washer face. Old Ford tractors had a proprietary 1/4 and 5/16 inch fasteners. Neither USS or SAE. As a joke we called them left handed Dodge bolts because of the old saying Flipped Over Regurgitated Dodge. Feel free to exchange Flipped to your favorite four letter word.

[@timothyprochilo4840]

I wish I could hold those wires and measure with 2 hands🤪🤣. . . .I use 2 o-rings just under the major diameter to hold the wires.......thanks for the vid Joe.😎

[@joepie221]

You actually only need one.

[@glennwright9747]

Great tutorial. I am relatively new at this. How do you measure and cut tapered pipe threads? I had a chinese knock off 1/ 2 inch pipe die that the casting broke. The dies are ok. I am attempting to make my own holder for the dies...but measuring the resulting pipe thread is proving problematic for me.

[@RambozoClown]

Cut with a lathe taper attachment, measure with a gauge. Just don't measure Chinese pipe threads. They are all over the place, a mix of British and Imperial and whatever.

[@glennwright9747]

​@@RambozoClown Lets assume we are doing single point turning - if I have thread wires and not a special pipe gauge ... ( I don't count fittings from Home Depot as a gauge).. and I want to verify how much more to take off...what is the procedure? Home Depot fittings may be OK as a gross check, but far from precision. They are not well finished, and if they were made in China the day after a binge night they could be suspect.

[@RambozoClown]

@@glennwright9747 You can measure with thread wires and a sine bar setup. Pratt & Whitney made a device for doing that, and others I'm sure, but the cost makes it only practical for a shop that makes gauges. Best is to just buy a GO / NO-GO gauge for the size you need. For most things, testing with a quality fitting should be good enough for pipe work. Since you are looking for a binding thread, fitting to the actual parts would be the ideal anyway. For example you can get pipe plugs that are over or under spec, so they work in worn threads or fit below flush to a surface.

[@curtisvonepp4335]

Trashed all my thread gage wires i use now GO NOGO GAGES and adjustable gages for + or minus DONE .😄

[@robertlark7751]

I have an older South Bend lathe with a screw mounted chuck. Would love to use your threading technique. Any ideas on how I can secure the chuck to the spindle?

[@dimtt2]

Hello Joe. It wasn't quite clear to me what the depth of cut should be on the internal thread to obtain the desired fit for the non standard thread you chose. Can you please explain this?

[@RambozoClown]

When you said oddball thread, I was expecting something like a 1.710"Ǿ, three start, 3-1/3 TPI lead 70° thread.

[@joepie221]

Thats normal around here.

[@dwightcarlson7136]

Excellent video and with many excellent tips re deburring, etc. Just for clarification, is the OD to which you refer, the value that you measure with a micrometer across the male thread? i.e. if the the thread is a 'standard' thread, then I believe the OD of the male part will less than the designated definition of the major diameter of the thread. eg. for a 3/4-16 thread, the major diameter is 0.750" but I believe the size measured by the micrometer would be a bit less than 0.750" ????

[@joepie221]

Ideally, the major is the absolute max mic reading.

[@johncarey9400]

Hi Joe, thanks for sharing! Are the calculations and relationships the same for Acme vs Unified?

[@joepie221]

To be honest, I'd have to dig deeper into that, but I almost doubt it.

[@therealme613]

Hey!! you have a Playland sticker … that’s in my neighborhood…

[@joepie221]

That was given to me by the maintenance machinist there. I made him a boring head adapter.

[@Jmastffp]

I really appreciate you taking the time. I fumbled through this myself to make a fire hose thread (1.25"-9) cap for some our nozzles at work. Can you please reply with a little more explanation on the math. I was curious why you used 1.000" to do your bore size math as opposed to the actual major diameter of your thread (1.710??). Is that because 1.000" is the root diameter of the thread? Thanks again

[@joepie221]

Sure......1" is the length standard by which the pitch value is divided into. This gives you the crest to crest, or the root to root distance and becomes the constant to subtract from the major diameter of what ever thread you are making, to drill the hole. example 2 1/4-10 thread 1" divided by 10 = .100 2 1/4 - .100 = 2.150 That would be a reliable bore size. You could probably go smaller as the material and application dictates, but this will get you in the mid class ball park.

[@Jmastffp]

I see. So that 1” constant would work across the board then. Say for a 0.75”-10 thread I could use 1” as my constant there as well. Thank you sir

[@joepie221]

@@Jmastffp Correct. But somewhere in my vast collection of things I once saw, isn't a fire-hose thread a different thread profile than a standard 60 degree 'V' style?

[@Jmastffp]

@@joepie221 I honestly have no idea. I do know that it’s an NST thread and that it’s a 9 TPI. I made two caps (thread protectors) that were 60 degree V thread. The fit very well. I spent about a week researching thread specs and the best I could come up with was they were 60 degree. If I’m wrong please let me know as I intend to make more of those thread protector caps.