019 THREADING ON THE LATHE, LATHE 101 MARC LECUYER

[@fredflintstone8048]

One of the best videos on youtube for explaining the single point threading process. As usual just like knowing the instant one needs to disengage the half nut, one must know when to stop your videos to avoid hearing that person screeching in the song.

[@TheDefeatest]

Great video. A little something I do for the 30 degree chamfer at the beginning of the part is I make it about equal to or slightly deeper than the thread clearance groove. So if the thread clearance groove is .55 in diameter then make the small diameter of your front chamfer at least .55 or a bit smaller. That way there is no guess work and you have a nice chamfer to start your nut on! Its easy to measure and a good rule of thumb. Also I guess you could take the depth of thread and double it and make it a bit smaller than that. Hope that's not confusing! :)

[@Ujeb08]

Great video Marc! I've watched many of your instructional videos - they're all good and accurate too. I will recommend your channel to my students to learn the right way to machine parts. The youngsters try to learn everything from the internet these days and we all know how dangerous that is with all the hacks out there pretending to be machinists! The problem is that the newbies don't know the difference. I've found about a half dozen machinist channels on youtube (out of hundreds) that are very competent including yours. Thank you! and please keep up the good work.

[@rodneycassidy6037]

thank you mark for you passion of teaching others and sharing the wealth of knowledge you have. I have always had an interest in general machining but never actually had the opportunity to learn in a school setting. your videos allow me a easy way to get accurate usefull info. very important not to learn the wrong way. thank you thank you thank you.

[@dannyb8955]

I know this vid is 3 years old, but THANKS...probably the simplest video I have seen on how to thread.

[@THATLAZYMACHINIST]

Thank you Danny, as you can see I am a little late with my responses but it's better late that never! Keep the compliments coming, Marc

[@daveknowshow]

I was struggling tonight trying to cut a thread. this will greatly help me. thank you so much!

[@markusclam]

Another excellent video Mark. I never realized how much there was to know about threading. Thank you

[@PrussianRedWhiteBlue]

By far the best screw cutting video I've found . . Inspirational! Thank you for showing us :) By the way per 29th edition the relevant table is actually table 3 page 1834 on my electronic copy of Machinery's Handbook.

[@PioneerSaturnDougie]

Excellent video, sir. I was shocked at the lack of 'likes' on this until I realized that I was watching the video + taking it in and I didn't pay any mind to anything else...I'd suspect 9/10's of your views here were simply too into the material to realize that there's a 'like' button, otherwise they would've clicked on it.

[@MrShobar]

Excellente démonstration et technique . Merci beaucoup , mes amis.

[@stumplifter]

Marc, A thousand thank you’re for doing this in ‘Standard’ measurement instead of Metric. I sincerely appreciate that.

[@AmateurRedneckWorkshop]

Once again a great video and just in time for me. I have a Lee bullet feeder that I have just received and the bottom opening is just about .0010" to .0020" too short and the cast bullets get hung up on the top when the fingers try to move them sideways. The easy way to fix the problem would be to just get a dremel grinder and cut the opening a little taller. That would stop me from playing with my lathe so I am going to duplicate this piece with the proper opening. And it gives me a chance to use the milling attachment on one end and thread the other end as well as drilling two diameters inside. The piece is a 5/8" hex shape with one end threaded 5/8 18 and the other end with a rectangular slot milled in it. The smallest inside diameter is about .370 (9mm bullets) and the largest one is .465" to allow inserting a plastic tube. I am lucky enough to have a preformed threading tool that I purchased with the lathe in the late 1960's. Please keep up the videos as I need all of the refresher training I can get.

[@jimmilne19]

Perfect. I got it. I is nice to understand something, now I'll go and do threading more accurately than ever before (well, I'll try). Thanks for yet another great video. Can one purchase a collection of all your videos on flash drive or DVD. I'm standing in line already.

[@THATLAZYMACHINIST]

Hi Jim, two years ago I tried to put my French videos on a flash drive. One full 32G drive later (not even half my videos) and several hours older, I decided that this was not the way to go. To help people find what they are looking for I got a web page from the (Green) racing car people and called it THATLAZYMACHINIST.COM my site is not pretty, mainly because I don't know how to make nice websites but it does have a MY VIDEOS page (in French and in English) that contains all my videos, grouped in a way that makes them easy to follow. I have over 100G of videos and plan many more in the months and years to come so I think the web page is the best way to go. If you do want a hard copy, I have no objection to you screen capturing the videos. I hope this helps, thanks for the kind words, Marc L'Ecuyer

[@oldman1505]

Very good videos, I have learned a lot from them. Thank you!

[@doriancharles608]

Mac you're the man!!! Thanks a lot it all my sense for beginners like me.

[@maintmech1245]

You are an excellent instructor

[@Skyrunner13]

Really informative and explained simply. I need simple.

[@MrShobar]

Marc: When I use PD wires, I usually support the three wires by inserting them in a gum eraser. My dexterity is good, but if one or more of the wires goes in the chip pan, it's a show stopper. Best Regards.

[@JRo250]

Excellent video. Wikipedia should link their "screw thread" page to this video. Happy new year!

[@libertarianlife3651]

The Trail Smoke Eaters, the Kimberly Dynamiters, Gordon Lightfoot, Randy Bachman, Burton Cummings, Kokanee beer, and now I can add you to my list of favorite Canadians. I'll have a half sack in your honor Sir.

[@louisalleva1381]

Merci pour l'info. La j'ai très bien compris. Merci pour l'explication, tu sait Marc, avec l'age des fois ont n'est pas vite....Merci et continue les bons video

[@JeffChoppah]

I always thought cutting threads was as easy as turning or as shown on KZbin until I got all my tools and lathe and no thread happened 😂 that's why am here... Great explanation great video let me go try again...

[@marlorup]

Happy New Year Marc. I really enjoy your videos. Thank you for taking the time to share your knowlege with all of us. Thanks again, Mark.

[@calvinjoziah8788]

instablaster

[@RelentlessHomesteading]

Appreciate it --- you explained the going back to 0 each time. Was watching some threading and couldn't see how the entrance of cut was synched with each pass - that explains it in relation to the thread chasing dial. You do a good job of explaining. I didn't see why the 29 degrees dialed in - presume it is that cut starts on one side of thread and not in the center (if from center then would be cutting same amount on each side of tool). Very interesting.

[@THATLAZYMACHINIST]

If you want more explanations about the 29° plunge angle you could watch my little quickie video on the subject. Her is a link to it kzbin.info/www/bejne/jaK3nZx7fNebgpY or you could find it in the green section of the third page of my website THATLAZYMACHINIST.COM Thanks for watching and be safe, Marc

[@RelentlessHomesteading]

Thanks so much Marc. Just watched the other video. Very well done. Things are sinking in. Appreciate your in depth teaching. So much to do to get my shop all set up, but trying to learn everything I can before getting to the building of the lathe and mill. It is so very fascinating, ...enjoy the metalworking even more than woodworking. All the Best to You!

[@RelentlessHomesteading]

I went and checked it out - thankyou very much.

[@CarlosContreras-gk9gp]

thank you for your teachings... I really like...all you do thank you a lot

[@zzanzak]

great video on threading , best i'v seen thank you

[@billshiff2060]

1:15 The actual tolerance of the angle of the thread itself is much greater. The 1/2 angle tolerance ranges from 40 minutes to 3 degrees depending on the TPI. With the finer threads getting the greatest tolerance. You can easily hand grind a tool within that specification using a fishtail gauge. But yes, for the 3 wire method you'd like it to be as accurate as possible simply for measurement purposes but the thread itself can be out and still be within specifications. For your 5/8-18 the permissible half angle error is 1:05:00

[@awlyons2]

Great video, however, pitch is actually the distance from one point on a thread to the same point on an adjacent thread. The distance a thread travels in one revolution is called the "lead". On single start thread they are the same but for multi start threads the pitch is multiplied. You have a very good teaching manner.

[@MrShobar]

Very nice explanation. I also liked the JFK reference at the end.

[@EVguru]

Not all top/compound-slides have their angles marked the same way. Unless they properly understand the reason for angling the slide (to cut mostly on the leading edge of the tool), it's quite common for beginners to have them set at just under 30 degrees to the spindle axis, rather than the cross slide. I've always advocated using simple radial infeed unless you're having a problem with the finish of your thread. Even then, I wouldn't angle the top-slide, just feed it 50% of the radial infeed each time. You didn't touch on calculating the thread depth, which is how most people do it I think. That's another reason I like radial infeed (where possible) as it gives a direct reading. Keith Fenner's trick of using a dial gauge against the tool post to measure radial feed when using flank feed is a good one though. Keep up the good work.

[@Abom79]

Good instructional video. Thanks for sharing. I'm afraid id be scrapping some parts if I had to use that lathe. It's set up completely different then what I've always used. I don't think I've ever seen the half nuts on the left side of the carriage.

[@THATLAZYMACHINIST]

I also sometimes use the cross slide sometimes, especially in soft materials. A good trick for people who don't want to go the three wire method is to cut close to finished using the depth of thread as a guide and finish with a die. Marc L'Ecuyer

[@madmadmickhog]

BRILLIANT EXPLANATION !!

[@hdoug5]

Happy new year to you and yours and ty for sharing your knowledge in these videos :)

[@caemaridwn]

Thank's Mark really well explained. Happy New Year to you and yours

[@billshiff2060]

9:16 The major diameter is only smaller on 2A and 1A threads only for clearance on lower quality threads, for 3A it is a max of nominal as your book showed .6250-.6163. It is permissible to have a 0 clearance fit in 3A-3B threads.

[@rsrobb63]

Ich denke, dass Sie eine große Unterrichtsstil haben, können Sie eine tolle Stimme und Verhalten haben. Ich genoss die Mathematik, wie ich 3-Leiter vor und Dur und Moll und nie wirklich verstanden haben. Danke !!

[@THATLAZYMACHINIST]

Thanks Robb for your kind words, Marc

[@rescobar8572]

Thank you amigo!!! Very informative and thought out.

[@waltermayer3425]

I was taught to set my compound to 29.5 degrees when chasing UNF threads but over the last 25 years havent noticed much difference in thread quality between 29.5 and 29 degree compound angle settings.

[@mrrice5274]

Very good video. Thank you.

[@meljazz]

Ever thought of making this video using a mini lathe, as most of us have and use a mini lathe, mine is a 7x 8 Sherline 4000.

[@darryldodge8383]

I do really like the Harrison ( VS 330 TR -? )Lathe in your videos. Can you tell me what year it was built ? Does it have a metric leadscrew ? What pitch ? Thank you very much. D. Dodge

[@thatoldbob7956]

Very precise, very enjoyable, thanks. Regarding the wire method all I can say: God should have given us a third hand.

[@julianjones7493]

Thank you Marc!

[@madhavak6684]

What a wonderful teaching video! Any lay man can easily digest by your explanation on threading. I got one question sir why compound rest to set 29 degree instead 30? Please explain. Thanks

[@cabletie8896]

I'm guessing that when the load comes on the tool it moves slightly.

[@THATLAZYMACHINIST]

Sorry for the late response (I get so many messages that some fall through the cracks). Here is a link to one of my videos that ex^plains the 29 degrees for threading. kzbin.info/www/bejne/jaK3nZx7fNebgpY Thanks for watching and be safe! Marc

[@danielpeters957]

good video!! thanks very much!

[@jimburnsjr.]

fn exceptional video....subscribed, and hit the bell, do wish you picked a name other than the veneration of lazy, do wish you would have given better illustration of positioning the wires, and do wish you never give an example of reading a mic off the part...but gn love your videos....thanks much for an honest contribution.

[@federicobolanos7146]

Thank you so much. Now I know what I was doing wrong.

[@dwightcarlson7136]

Do you ever do a final cut of a thousandth or two to clean up the right side of the thread by advancing just the cross feed? Also do you run a flat file across the thread as a clean up of the OD of the thread? Is there a way to calculate how far the compound feed should theoretically be advanced from it's initial/zero position?

[@billshiff2060]

(Pitch X .54126588) / 0.866025403784438 That can only be a close estimation because your tool nose depth will vary but it gives you a target to aim for to get close before you need to measure. More important to know is how deep to cut in each pass. Finishing the last thousandth is not needed if everything else is correct but it does allow you to cut directly the amount needed to get your pitch diameter without the compound angle.

[@mertonsilliker4858]

Thanks for the view

[@ffff1758]

nice video Marc, as usual. but, what if we do not have the thread chasing dial in our lathe? how do we know when to engage? would you please teach me? tks

[@THATLAZYMACHINIST]

carlos m. zaccaro Hi Carlos, you can cut a thread without the chasing dial as long as you do not disengage the lead screw. First! the biggest problem is stopping the tool at the end of the thread, so cut slowly! set up as you would normally do and engage for your fist cut, at the end of the cut turn off the machine. Retract the tool to clear the part and reverse the motors rotation (you have to reverse electrically, you must not change or disengage any gears!). This will bring the tool back to the start of the thread. Set up for the second cut (return to last depth plus new cut) and keep going. As long as you do not disengage the split nut from the lead screw or change any gears, you will return to the original groove. I hope this helps, Marc L'Ecuyer

[@ffff1758]

THATLAZYMACHINIST Thank you Very much Marc, what a soon reply!! I agree with you with the proposed method, which is the one I usually aply, but may be my question wasn´t propperly written: I´m concerned about the looseness of the gears and screw. It seems to me that the thread cut by this procedure (without the chasing dial) isn´t as perfect as the one in your video, is it?. Again, thank you for your answer and your videos. best regards carlos

[@נוחיחזקאל]

@@THATLAZYMACHINIST THIS THING IS THE MOST IMPORTANT FOR MOST VIEWERS. THESE USE UNIMATS, GRIZZLIES, TAIGS AND SO ON.

[@tintinfan007]

is it possible to cut threads using a threading insert on an automatic lathe ?

[@rdkitchens]

The formula you use to calculate the diameter over wires is not how I was taught to calculate. I'd appreciate your thoughts on this. I was taught to look up the max and min pitch diameters in the handbook, then look up the constant that correlates to the wires found on the chart that comes with the thread measuring wires. Add the constant to both max and min pitch diameters to get you measurements over wires. Is this just another way to get the same numbers or was I taught incorrectly?

[@THATLAZYMACHINIST]

Good insight, the formulas are all based on the thread angle and , since nothing is squared or cubed, are linear in nature. If your wires come with an indication of what wire to use for what pitch, you can dispense with the calculations from the handbook and do what you have been doing. The formulas shown can however be useful if no standard wires are available (bizarre or non standard pitches) and you wished to use drill blanks or whatever. As a general rule (charts do exist) you should not use a wire smaller than the BEST WIRE SIZE, but you can use a larger set as long as they do not contact the thread to close to the crest. All you need to do is calculate using the diameter of the wires you will be measuring with instead of the best wire size and all will be fine.

[@rdkitchens]

THATLAZYMACHINIST Thanks for the clarification.

[@chrisstephens6673]

THATLAZYMACHINIST Rather than use 3 wires, I find it much easier to use copper wire which is wrapped around the thread and then measured. Saves all the lost wires in the chip tray. It does help if you have rolls of enamel coated copper wire of all the usual sizes.

[@charleshendry5978]

Chris Stephens I told the Missis "I need a bottle of wine for the 'shop'" because I needed a cork to hold\stick my thread wires into. :)

[@azizmechergui9263]

pourquoi vous avez Monsieur de choisir l'angle d'inclinaison de la porte outil à 29°

[@shadowdog500]

Thanks for the great video! I see different people say anywhere from 29°, 29.5°, and 30° on the compound. Why the difference??? I always set mine to 29.5° because it is in the middle of the three numbers. But I'm still trying to figure out why people use three different numbers. Any guidance would be appreciated. Thanks!!!

[@THATLAZYMACHINIST]

Hi shadowdog500, There has always been confusion on this subject because there are several different answers, and many of them are good. If you use the compound rest to set your depth of cut (the method used in the video) you can set the compound rest anywhere from 0° (parallel to cross slide) to 30° (parallel to the trailing edge of the tool). When set to 0°, you are plunge cutting and producing an equal chip from both sides of the tool. This is the highest pressure situation since one chip pushes off the other. If you use 30°, you will form a chip only on the leading edge of the tool (less force required). So anywhere between 0° and 30°(inclusively) will produce a 60° thread if your tool is 60° and it is properly positioned in the tool holder. So why 29.5°? The answer is anticlimactic, you must absolutely not pass 30°, in order to ensure that you don't go to far it is recommended to undershoot. Placing the compound rest at 29° or 29.5° is a way to ensure that you stay below 30°. I hope this answer helps and thanks for watching. Marc L'Ecuyer

[@larryschweitzer4904]

@@THATLAZYMACHINIST I'm not a machinist, just hobby. It seems to me that if the compound isn't at a perfect 30 then both edges will be engaged in cutting but one will likely be more "rubbing" than cutting because there isn't enough depth of cut to start the cut. Result: heat and sideways force. On a larger diameter part not enough to matter. On 4-40? As to greater force coming into play when you plunge cut, is it enough to matter? For about a year now I've been plunge cutting with tool upside down and cutting away from the chuck. I can run at higher speeds, have no issues with having to stop the cut in a very short time and the entire process seems simpler. What am I missing? I started doing this after watching Joe Pieczynicki's video on thread cutting.

[@Max_Marz]

Don't seem very lazy at all :P Awesome video.

[@damojfowler]

MINUTES.

[@timmerchant5624]

Damo Floy

[@JDLuke]

Perhaps it's the pinot noir talking, but I enjoyed the heck out of this video

[@THATLAZYMACHINIST]

The last bottle of Pinot Noir that I opened was not very verbose, so I am guessing that you just fell victim to my charisma! :-) Thanks for watching and for taking the time to write, Marc THATLAZYMACHINIST.COM

[@6mxcman326]

Hey there! I am knew to machining and I just bought a 14 X 40 lathe. Would some one Please explain how to work out this formula? I have tried it and I come away with a different Number. Thank you!

[@gilbertestrella5166]

How did you get 29 degrees on the compound?

[@billshiff2060]

UNF does NOT stand for "unified national fine", it stands for "Unified fine". It is an INTERNATIONAL standard agreed on by USA CANADA UK. You are confusing the obsolete American National thread standard that was replaced by the UNIFIED standard.

[@pwave123]

THANKS!

[@drew7376]

Hi do you have a video of working out that formula?? I just cant seem to work it out! Yo mention in the formula .6603 but you have .86603 on the board, I may sound silly I am new but where did you come up with that magic number for 60 degree thread?

[@SoWe1]

sin(60°) = 0.86603 (rounded to 1/100,000) it's in there because you are projecting one line unto another and there's a 60° angle between them if that was unclear feel free to ask

[@marcliebeskind1496]

Hi Marc, I noticed that the threading dial stops turning when you engage the halfnut. Is that is what is supposed to happen? Thanks. Marc

[@THATLAZYMACHINIST]

Hi Marc! It is normal that it stops since when the split nut is engaged the apron and saddle (carriage) moves at the same speed that the lead screw is turning. So even if the screw keeps turning the thread chasing dial doesn't turn since it is part of the carriage and is also moving at the same speed as the helical groove (thread) of the screw. It's late and I am not sure that I was clear with my explanation. If required let me know and I will reformulate the explanation. Marc L'Ecuyer

[@marcliebeskind1496]

I think I understand. I have an old Craftsman 12" lathe, and I did not understand why the thread dial stopped when I engaged the half nut.

[@nonpropaganda7092]

finally I get wires.. thnx marc..

[@donmathias1705]

Your comments re indexing dial do not hold true if your lathe has a metric leadscrew and you cut 18 tpi. In that instance you can not disengage half nuts but must use forward reverse function of main spindle.

[@HAINGUYEN-id8gs]

Hello If I cut thread M20 x 2 x 2 or M20 x 2 x 3. I don't know DEPTH CUT = ? (mm) How to calculate depth cut in multi threaded screw metric? Can you help me?

[@crossthreadaeroindustries8554]

Fun with Geometry and Trigonometry. Watch More of Mr. L'Ecuyer's videos and study en.wikipedia.org/wiki/Screw_thread, get a copy of Machinery's Handbook - There is a pdf of the 29th edition posted on the internet somewhere.

[@kickinthegob]

Damn, Tom Lipton's long lost Canadian brother!

[@THATLAZYMACHINIST]

Yes but Tom is much more attractive!

[@stevebark4873]

I’m a retired master mechanic learning the machinery trade. I’m grateful to you for your clear & concise method of teaching. Threading has been a particular challenge to me because of the wear in my 1942 13” South Bend lathe. I am getting better though and am learning how to compensate for the wear.

[@marclecuyer9930]

That's great Steve. I am happy that you are improving and having fun. That's what it's all about. Marc

[@cyzam]

within 12 "minutes!" =D thanks for tips btw!

[@sergei509]

cool

[@louisalleva1381]

Salut la video des filets la formule me trouble j'explique M= E - 0.86603 et la le (P -ou+)et on fais quoi avec le + 3 W. et pourrais tu m'expliqué la formule en métrique. Merci super cette formation par video.

[@THATLAZYMACHINIST]

Salut Louis voici les variables, M est la mesure hors piges, E est le diamètre moyen de filet (pour un filet métrique tu utilise des millimètres), P est le pas du filet (le pas est la distance axial par tour de filet, pour un filet métrique utilise le pas métrique) et finalement le W est le diamètre des piges que nous utilisons. Le E, le P et le W sont disponibles dans les recueils technique tel le Machinery's Handbook. et la formule est M=E-(0.86603P)+(3W) Les filets métriques et impériaux ayant un V de 60° utilisent la même formules. Merci pour l'attention que tu portes a mes vidéos, Marc L'Ecuyer

[@richardmassey5005]

mmm thanks...I like it ...

[@darryldodge8383]

Anyone ever look at these comments / questions ?

[@THATLAZYMACHINIST]

Hi Darryl, I read all the questions and comments and try to answer as many as possible but I get 20 to 30 questions a day and it is impossible for me to answer all of them. However even the ones I don't answer help me find what needs more explanations and they often guide my little quickie videos. Thanks for watching, Marc L'Ecuyer

[@lunardust201]

What angle are most worms cut at, (for worm drives)?

[@lunardust201]

Hi Marc, thanks !!! Marc I want to tell you that you are the best teacher I've found on KZbin, seriously. You make things so easy to understand. I know one user pointed out how you tend to pause a lot while talking? I actually really like that. For some reason it seems to help get the idea through to me more effectively because of those pauses. It doesn't sound unscripted to me! Really appreciate the machining videos you make. I am not a machinist, I'm a software engineer, but I love knowing how to make things. I am glad you share this information with us - seems like anytime people talk about any trade, it kind of becomes an ego battle because of the whole apprentice/teacher thing, unions, etc. Knowledge tends to stay "guarded", and I always feel like if you think you know what you are doing then the old guys laugh at you. Maybe that's not really how those in the industry are, but just my impression. So thanks SO much for making these awesome instructional videos, especially I can see the amount of work you must put in when you are doing them in two languages. Please know I am one viewer that really appreciates your effort

[@breakingtoast2255]

1:17 that was a simpsons moment

[@THATLAZYMACHINIST]

Breaking good Hi, in the video I said seconds and didn't notice it until the very end of editing and reshooting wasn't an option so that is what you get when old machinist do video editing. It's all for fun, thanks for watching and be safe! Marc

[@breakingtoast2255]

THATLAZYMACHINIST I wish I had 1 / 10 th of the knowledge that you have in machining I love your tutorials and your great teaching skills thanks for the uploads mate

[@Harrzack]

Well - for a pro machinist the math is def important. But for the casual hobby turner it seems a bit over the top.

[@mashed-out]

square root of 3 then devide by 2! hmmmm... SOH CAH TOA 😨

[@zzanzak]

1:15 lol

[@panon5292]

Height, NOT heighth!!

[@Leartech81]

You seem, to, use, a lot of, commas in your, speaking.

[@THATLAZYMACHINIST]

+Bill Schlosser That is quite possible, what is a comma?

[@Leartech81]

+THATLAZYMACHINIST Pauses.

[@THATLAZYMACHINIST]

Yes I do, and the reason is lack of preparation. I do not script my videos just as I never scripted my classes. That means that I have a good idea of what subjects I want to cover in a lesson, but I am never quite sure how I am going to get to my objective. When I was a teacher, this approach permitted me to taylor my classes real time to the people sitting before me and that was quite appreciated by the students. It was dynamic and ever changing and quite stimulating. It means however that I have to think on my feet and the pauses are the result of that and also the fact that I am a French speaking Canadian and English is not as natural to me as French. I loved the question and thanks for watching, Marc (and I now know what a comma is)

[@Leartech81]

+THATLAZYMACHINIST I figured it was the French thing... wasn't a knock against you- it's a great video! I was thinking of picking up a small combo machine to do some metal work and wondered how threads were cut. Thanks!

[@NuttyforNissan]

Thanks very well presented, have a great 2014

[@fkgmail]

I look up this site. www.engineershandbook.com/Tables/threadlimits2.htm It shows the minor diameter is 0.5554. Which is correct?