Machining threads

[kb426]

Those of you that like machining might enjoy this clip. This is from Harvey Tool who makes tooling that the mini engine builders use.

https://instagram.com/p/BxhqtZulfyg

[39deluxe]

Isn't that slick?

Tom

[chimp koose]

Pretty neat . Climb milling . It truly is amazing what can be done with a CNC machine . Back in the early 80's when we were feeding punch tapes into the cnc they told us that one day we would be able to 'send' the machine a program from a computer .    thought that was funny back then , just a bunch of dreamers !    Now you could probably send a program from your phone while flying somewhere! Nice thing about threading with CNC is being able to adjust by .0001". We had a demo piece (remember this was 80's we had to sell the abilities of the machine) Double start LH acme thread and matching machined nut , that we would set on a table and let gravity spin the nut on after getting it started.

[Ohio Blue Tip]

Still have to do it the old way on the lathe!

[chimp koose]

I teach the 29 degree offset compound method of threading to my students . Yes it is faster to plunge cut but it does not always give as nice a finish . For the really good ones I'll show them how to do 3 wire measurement .  

[kb426]

Explain the 29 degree method, please.

[chimp koose]

Offset compound to 29 degrees . Feed in for threading using the compound , this has most of the cutting done by the front edge of the cutter , reducing tool chatter . withdraw and return  the tool using the cross slide and only use the compound to set the tool deeper . Just as the thread is beginning to fit , start plunge cutting .001 per pass until nut goes on .    .75/#TPI =compound infeed.   . I have the kids start with larger cuts .005" and work down to .001" per pass by the last few cuts . When setting up the cutter I get it close to the work with the cross slide but make sure the handle is at a 5o'clock position and zero the cross slide , then I bring the cutter to touch the work with the compound and zero it . This way if the operator ever engages the half nut in the wrong place all you have to do is pull up on the cross feed handle and it will retract the tool eliminating the need to figure out which way to turn the handle in a panic . I have seen similar explanations on youtube but I have never seen anyone do the 5o'clock crossfeed handle setting nor have i seen the .75/#TPI  formula used  there . When my classes were shut down for covid in march I looked for a video on threading and could not find one doing those things . Many at 29 degreed but none with the other details.

[kb426]

^^^
Thank you. I'm self taught. That means I don't know much.

[chimp koose]

I have seen your work , self taught , you had a good teacher ! You are from a generation of people who had to figure things out on your own and as such , have an ability that our younger generation is missing out on .While youtube is convenient for us , for the young kids it is too easy to skip past the thought process and leave that skill un developed . I have a difference of opinion with a colleague who teaches the same subject in a different school . While he makes up worksheets to guide the student through every step of the project , I give them the blueprint and a few pointers and make them THINK their way through . I am always available to help and instead of giving direct answers I will ask a series of questions to get the student to reason their way out to a solution . I try to get them to UNDERSTAND the process so they can apply the knowledge in similar situations . All of my projects for the class are a progression of complexity in the job plan with each one having more likelihood of 'painting yourself into a corner' if you do not come up with a job plan at the start. If a kid works consistently in my class , there is a good chance that they will finish all of the projects with a few weeks to spare . That is when I take them over to the hot rod/harley/mini chopper and ask them if they would like to make something for one of these or do they have something else they would like to make ? This allows the kid to now get into designing something , not just following a blueprint . If they have trouble with that I will show them how I go about designing a part and all the things to take into consideration . In the end I think my kids end up learning more than just how to operate a machine .

[jaybee]

I know now I would have found it very rewarding to have been a machinist. I had a different way in mind, and I was too stubborn to see and consider some paths which would have been very good for me.