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  • threading tool

    Here's a few pix of my nearly completed threading adapter. The board represents the direction of the lathe bed. In the first pic, the tool is shown in the forward position.



    In this pic, it's shown in the fully tilted back position.



    This is how it's oriented when mounted on the cross slide, from the operators perspective behind it.



    It tilts forward and backward at the 30 degree thread angle. The graduated wheel turns a threaded adjustment rod which limits how far forward it tilts. The hardware at the bottom is how it's clamped into the T-slots. The hold-down on the top is designed so I can pull it to the right, which takes up all the side play where the cutter sits in its groove. The tab nearest the operator is the reference point for the markings on the wheel. The wheel moves in and out as you rotate it, so I figured this would give a way to keep the zero line and the markings close together, regardless of the position of the wheel.

    I made one mistake- the threaded rod I used for the adjuster is 1/2-20. I wanted the wheel markings to be .001 per division, which would mean 50 markings. For some reason I scratched on 100 markings. So now each line represents 1/2 thou. If I want .003 of feed, I'll have to count 6 markings.

    It's fully functional as shown, just not cosmetically prettied up. I did a quick test and it seems to work fine, though I have only done a small thread. We'll see how well it works with a deeper thread when that kind of project comes up.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  • #2
    Looks good, glad to hear it passed the first test and made a thread.
    Would love to see a vid of it in action if possible.

    Originally posted by darryl View Post
    I made one mistake- the threaded rod I used for the adjuster is 1/2-20. I wanted the wheel markings to be .001 per division, which would mean 50 markings. For some reason I scratched on 100 markings. So now each line represents 1/2 thou. If I want .003 of feed, I'll have to count 6 markings.
    Could you not just toss the wheel on an arbor and knock out every other "high spot" and bring it back to 50 ?

    _
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    • #3
      Sure. I was thinking I might just scratch out every second groove to get rid of the black nail polish. Not something I'm really worried about.

      When I get to play with this more, I'll be trying to determine the best 'full forward' position, since that would correspond to the full depth of the thread. All parameters that need to be controlled in the shaping of the thread must come together at this point. I don't think that's a big deal anyway, but I will be checking to make sure any thread is correct at full depth.

      One parameter that will impact on the cutting action is how far out I place the tip of the cutting tool. So far I've had it just a little ahead of the pivot axis of the adapter, thinking that it might balance out the cutting forces so the tool doesn't push back when the tip engages the workpiece. It seems to work, but I haven't done anything beyond a small test piece. I'm going to try sticking the cutting tool out further, and clamping it back in further- hopefully I'll get a feel for where it likes to be. I'm sure that several factors will come into play in this regard- the relief angles, the sharpness of the edges, the nose radius, the particular material being threaded, etc.

      If it turns out that there's an overall tendency for the tool to push back, then I'll have to rig up a retraction mechanism using levers or whatever to maintain the forward position up against the adjustment rod. This might have to be a torque multiplication system so I don't end up pushing the cross slide ahead through its play. But part of the general operation of this adapter is that the cross slide gets dialled to the right point for the diameter of thread being cut, then locked there. Using this tool, there is no dialling in and out all the time, just a small adjustment of the wheel to allow the cutter in deeper for each pass.

      The angles are all set. As long as the cutter has the two 30 degree angles ground on it correctly, you just mount this adapter, make the initial cross slide setting, lock it, and you're ready to go.
      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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      • #4
        By the way, I've noticed one thing- although I carefully set up the threaded rod in the 4 jaw and dialled it in before turning the collar, there is a bit of an eccentric feel when you turn it. The four screws on the top, nearest the wheel, are to adjust the degree of friction and to remove all play from the adjustment rod. With some friction applied, there's an uneven binding as you turn the wheel. If the collar was perfectly concentric with the threads, this effect would not be there. I'll have to open up the hole that the collar rides in. All in all, a pretty minor glitch.
        I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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