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Thread: How much power is really needed for threading? (or, speed controller OK?)

  1. #21
    Boolit Master

    Join Date
    Mar 2013
    Northwest Ohio
    Some also used lawn mower / garden tractor transmissions for converting the old flat belt machines to electric motors. Another option is a variable drive pulley system from motor to jack shaft. The first shop I worked in had several lathes and a drill press with the transmisions on them this also gave them reverse when needed.

  2. #22
    Boolit Master
    Join Date
    Mar 2005
    I agree with you on this. All the guys need to do is round up some scrap and thread 25 to 50 pieces. By the time you go through that many repetitions your hand to eye coordination starts to be close to automatic like shooting skeet or hitting a baseball.
    I hear the stories about so many gunsmiths taking a half a day to a day to thread and fit a rifle barrel and laugh.
    Assuming you do not have to rework or blue print an action threading a barrel takes very little time. After you have cut a lot of threads you can judge how deep the thread is by how sharp the crests of the thread are.

    I will admit to one thing though. I learned to thread on an old 1920s Pratt and Whitney tool room lathe with bronze headstock bearings. It was old and worn and I could not take heavy cuts so I had to make lots of shallow passes. This lathe was designed for lots of threading because it had a threading cross slide built into the normal cross slide. This smaller cross slide had a sleeve around the cross slide screw that had a helical slot that pulled the tool back about 1" for 1/2 turn of the cross slide knob. Each of the 2 cross slides could be locked independently.
    To cut threads I locked the normal cross slide and unlocked the thread cutting cross slide. When I pulled the tool out at the end of a cut the tool came out about 50 times faster than a normal cross slide.

    I started running a lathe in a shop too cheap to buy much carbide so I also learned to grind my own tool bits. I think that is a lost art now.
    I have to pass on one other observation. While working my way through college I worked one summer in a half baked shop that made some tools for JC Whitney. The equipment in that shop was a collection of junkers and clunkers that had been sold off from other businesses. One of the machines was a Brown and Sharp single spindle automatic screw machine.
    Since a turning machine is a turning machine I was put on the Brown and Sharp to run a lot of acme thread nuts for a front end coil spring compressor. Once set up the machine would run unattended for a long period of time.

    Somewhere that machine had the original motor and controls replaced.
    There was a common frame size electric motor connected to a 1950s Chevrolet 3 speed standard transmission on top of the headstock. The output shaft from the transmission drove the machine. My first old Chevy had the same exact transmission so I knew how to shift it using the 2 side levers without being shown how.

    Quote Originally Posted by W.R.Buchanan View Post
    Not only that but the finish you get on those threads if the speed fluctuates would be pretty bad. You need to thread fast enough to get a good finish and to have the spindle speed remain constant thruout the cut.

    I see way too many guys here being so afraid of their machines and wanting to do threading by turning the spindle by hand it blows me away. You don't have to have 30-40 years in the trade to be able to thread right.

    One thing you can do is,,, Thread from the inside out in reverse. IE: you don't have to sweat the pullout.

    When Single Point Threading you typically will put a "Thread Relief "at the end of the thread. This is normally where you would disengage the half nut and stop the carriage. You can also start the thread at the thread relief in reverse and thread out . This way you don't have to worry about not disengaging at the right time.

    Virtually all of the older machines that you's guys have are able to make threads as designed. They were all made early on and things like speed controls were fiction. You changed speeds with the pulleys on the machine and worked with what you had available. Lots of work got done like that,,, and you can do it too.

    Sometimes you need some instruction,,, Sometimes you just need to practice a little more.

    What you really need to do is get some instruction from a real person and then practice a little. Threading just ain't that hard to do, and inventing workarounds for your fears is not productive at all. It doesn't advance your skills one bit. Nobody was born knowing how to do this stuff. It was learned and you can too!

    Part of the draw towards being a machinist for me was learning how to do new things that enhanced my abilities to build more stuff. The more you know the more you can produce. "Production,,, is the basis of Moral!" Learning new stuff makes you feel good! For lots of us, "Feeling good" is in short supply. This is a way to make more of it happen.

    What you could to do is visit an Oil Field Machine shop and watch a guy threading 6" Drill Pipe with tapered threads up to a shoulder at 300 rpms,,, on a big manual Engine Lathe. That will convince you that it can be done. The guy who's doing it wasn't born with the knowledge and he probably didn't get it off the internet. He probably got showed how to do it, and then practiced until he was good.

    Believe me any of you can thread on a lathe just like it was intended to be used. You just have to try a little harder.

    Last edited by EDG; 08-06-2017 at 11:37 PM.

  3. #23
    Boolit Master
    W.R.Buchanan's Avatar
    Join Date
    Mar 2011
    Ojai CA
    I had a B&S 00 Screw machine a while back and I can say that having that machine made me a lot better machinist.

    Everything on each part made on a B&S must be done in one revolution of the cam shaft.

    That can vary between 3 seconds and 1 minute.

    A simple Oil lite bushing takes 3 seconds to make from start to finish.

    Feed to stop, center drill, drill, chamfer OD and cutoff. do another one, 20 parts a minute spindle at 6000 rpms and You couldn't hear yourself think when it was running!!!!!

    I made thousands of them for this one outfit and made good money doing it. I even bought a counting scale to weigh the parts to count them.

    Different times now. But there are still shops that run them back east, and one that got this job out from under me had hundreds of screw machines running 24 hrs a day. they made big money with those machines.

    "It's not how well you do what you know how to do,,,It's how well you do what you DON'T know how to do!"

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