Threading minor dia question

[MILLRUNNER]

I have asked several different people about this, and nobody seems to know the answer. I am trying to make a 14 x 1.25mm left hand thread bolt to match the threads in a bicycle crank arm. I have my bolt set up in a bridgeport easypath lathe and I am fixing to cut threads. Problem is, I don't have a nut. Usually, when I am creating threads for something I have the nut or part that has internal threads so that I can match it. In this case, I don't have it.

 

I think my x dials in diametrical. If I have a threading tool set up and I touch the surface of the bolt (which would be 14mm or.551") how deep do I need to cut these threads (to what X number) before I know I have created the correct depth?

 

Thanks

[crazy^millman]

Sorry, but does anyone own a machinist handbook anymore? It is all in there, just look up the thread table and you should be able to determine everything. You should have something you are making this too. If not go to a bike shop and get the cheap pair of peddles and use them to check the thread. I never make threads without some kind of a standard or other item to check my work. You can try to make it by cutting to a certain depths, but I would not do it without something to check fit to. Just my opinion on it.

[Tony35]

handbook online

 

My link

[MILLRUNNER]

Sorry, but does anyone own a machinist handbook anymore? It is all in there, just look up the thread table and you should be able to determine everything. You should have something you are making this too. If not go to a bike shop and get the cheap pair of peddles and use them to check the thread. I never make threads without some kind of a standard or other item to check my work. You can try to make it by cutting to a certain depths, but I would not do it without something to check fit to. Just my opinion on it.

 

I have the handbook, I was just hoping somebody could verify. I am the exact same thinking as you aabout needing a standard. Problem is, I need a nut or crank arm, not the bolt. We cannot find this particular tap, and we are going to make one to fix a goofed up thread in a crank arm we have. I can cut it to what the book says, but I will never know if it is right. It's a dilemma..

[iowajim62]

If you have thread wires to check the pitch dia. you can go by the #'s in the Machinery Handbook and you will be good to go.

[Tony35]

If you have thread wires to check the pitch dia. you can go by the #'s in the Machinery Handbook and you will be good to go.

 

+1

[MILLRUNNER]

I do not have the wires.

 

Thanks.

[iowajim62]

.527-.528 should be your minor dia.

so .551-.527=.024

.024/2=.012 for your x value

[MILLRUNNER]

.527-.528 should be your minor dia.

so .551-.527=.024

.024/2=.012 for your x value

 

Thanks.

 

I have been looking in the handbook, 27th edition but all I see is 14 x 1.5 and 14 x 2.. Am I missing something??

[crazy^millman]

Sometimes you have to look in the pitch chart and use it to come up with the size for ones not listed.

[iowajim62]

go here and then save it for future ref

 

http://itstool.com/tapdrillchart/tapdrillchart.html

[MILLRUNNER]

go here and then save it for future ref

 

http://itstool.com/tapdrillchart/tapdrillchart.html

 

Thank you.

 

My thread looked about halfway when I dialed in .024, so I am assuming it is radial? Or diametrical? I can't remember the differnce between the two. I turned my max (OD) to .449 (.002" under .551"). I then went in .048" (.024" x 2) with my threading tool, which should have gotten me a min dia of .501". I then dialed in another .002" for extra and made a final pass.

 

It looks correct, but you never can tell without the nut / inside thread to check it with.

 

We will try this. If it doesn't work I'll spin another one down. Didn't take but 10 minutes to make it.

 

I really appreciate the help guys.

[darko herak]

why not use formula? minor is 12.64, that is theoretical

[MILLRUNNER]

Just tried the bolt in a bicycle crank arm and it worked.

 

Thanks again for the help.

[iowajim62]

Right on and your welcome

 

BTW I was thinkin bout that a bit more and that is the same thread as spark plugs