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  1. #1
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    Hi everyone .. I have a thread that is part of a fine adjusting knob on my Benchrest rifle rest.
    The thread is different to me in that it
    has the with / pitch / crest of a acme thread that might be say 12 - 16 TPI , however, there is like a .2 inch distance between each thread peak ...
    How do you cut this on a lathe ?
    What kind of thread is this?

    Thanks
    Randy

  2. #2
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    Is this a speed screw?

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    Without a little more info, it's hard to guess what type of thread it may be. Does it have a sharp crest or is the crest flat? What is the angle? Can you post a pic? .2 translates to five TPI, not 12-16. If you have a lathe capable of cutting threads of the same pitch, should be no problem. You might have to grind a special tool to match the thread configuation.

  4. #4
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    Not sure if its a speed screw ..
    its on the base of a Bald Eagle rest
    I think Sinclair has them ..
    the crest is flat and it has an angle
    much like a 60 degree does ..
    just that the thread itself is small in width .. maybe its just because I'm not used to such a low TPI ... LOL ..

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    There are a lot of different speed screws around. Some have fairly fine threads and some aggresive. I made one from a drawing Randy Robinett sent me, and all it consists of is a normal 60* thread that isn't taken in all the way, hence the Acme look. Then the socket/knob is threaded to fit. Not a difficult project but fun. I installed mine on a Hart rest. However, I don't use it for the full rise on the target. I don't like the way the rest tilts during the full rise from sighter to record. I use the primary rise for the bulk of the adjustment, then fine tune with the screw. That all passed when I went to a Farley rest!

  6. #6
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    That sounds like it ...
    I agree on what you said about the rise..
    I noticed that too .. seems to tip the
    rest a bit more than one might want ..
    Ok .. I'll try it that way ..
    It looks to be like 5 TPI .. but I want it
    a little finer I think ... maybe 8 or 10 tpi
    .. But from what you are saying it sounds like a speed screw .. Thanks everyone

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    That sounds about right, 8 or 10 tpi. I turned the body from CRS, 3/8-16 to fit in the leg of the rest, then 3/4-8 or 10 for the speed. Made the knob from brass, knurled the outside, and used a piece of drill rod for the pin.

  8. #8
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    Sounds good .. thanks for the info ..
    I was thinking about brass ..
    Certainly easier to work with ..
    and I think it looks nicer..
    I replaced all my adjusting knobs
    with brass ones ..

    [This message has been edited by Lanmanb4 (edited 10-27-2003).]


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