1940ís 9A Threading Stop Hole Depth
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  1. #1
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    Default 1940ís 9A Threading Stop Hole Depth

    Iíve been restoring a 9A for the past couple of months. Everything has been going pretty well so far, but Iíve had to deal with an issue of removing a broken tap from the blind hole in the cross slide used to attach the threading stop. It came that way when I bought it, and a previous owner had even drilled and tapped another hole next to it (which I will fill in before painting).

    To remove the tap, I started with a carbide burr in a die grinder. That got a little hard to control though, so I moved to my radial arm drill press and used an angle plate to position the cross slide under the chuck. I then pecked away at the tap with much better success. I believe I removed all of the tap, but I would like to confirm the depth of the hole. As it is right now, the hole is ~7/8Ē deep. Does anyone out there know if this is how deep they came from the factory?

    I would also like to confirm that the thread should be 5/16-18. Most of the threads were removed during the grinding, so I plan to install a helicoil this week once I know the correct thread type.

    Thanks, I appreciate the help!
    -Keith




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    I have a 10K that uses a similar cross slide stop. The hole for the threading stop is 1/4-20 and probably not more than 5/8' deep. If you really need an accurate depth, I can measure mine.

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    Quote Originally Posted by Illinoyance View Post
    The hole for the threading stop is 1/4-20 and probably not more than 5/8' deep.
    Thanks! Iím 99% sure that the tap I just ground out was a 5/16-18, so the previous owner must have been trying to change the thread size from what was original. Since the threads are supposed to be 1/4-20, I think I may fill the current hole with JB Weld and then either drill and tap directly into that, or install a thin-walled insert. The threads wouldnít see much force if using a threading stop correctly, so I wouldnít think the JB weld would be an issue. Iím open to any and all opinions though.

    Thanks again!
    -Keith



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    Quote Originally Posted by USNmechanic View Post
    Since the threads are supposed to be 1/4-20, I think I may fill the current hole with JB Weld and then either drill and tap directly into that, or install a thin-walled insert.
    The holeís been filled and Iíve got the 1/4-20 insert. I plan on installing this tonight so I can get to painting.

    Would anyone be able to verify the center height of the hole from the bottom of the cross slide? Thanks! -Keith


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    I ended up just assuming the previous owner had kept centered with the original hole, and did my best to match it. I scribed as close to center height as I could tell, and then scribed a line the same distance from each side of the cross slide to find the horizontal center. I punched and then center drilled, followed by a 21/64 drill. I went up 1/64 from the usual 5/16 for a 3/8-16 thread, but Iíve found that the keyserts sometimes have a hard time threading in. I only had one keysert and the working load on this hole should be pretty light if it ever gets used, so I donít think it will be an issue. Everything turned out great, and it will be ready to paint this week! Only a couple more weeks and I should be done painting, then on to the bench.



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    Looks good!

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    A couple ďbeforeĒ shots. Iím not sure what the hole next to the one I repaired was for, but it got filled in.





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    Your repair looks good. If nobody recognizes that other hole then it was drilled for some reason over the last 75 years. You filled it but it's still there if you find out you need it.

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    Quote Originally Posted by mllud22 View Post
    Your repair looks good.
    Quote Originally Posted by iwananew10K View Post
    Looks good!
    Thanks! Iím glad I didnít decide to just fill them both in after my first attempts at getting the tap out didnít go so well. I donít know if Iíll ever use a threading stop, but at least now I have the option



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