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Thread: How to rectify a wrong center punch

  1. #1
    Supporting Member garage nut's Avatar
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    How to rectify a wrong center punch

    Still waiting for my magnifying glass to arrive for my plastic block center punch tool , but in the mean time I am using my cell phone. (found a great app with added function to manually switch on flash light) Problem is you need 3 hands or a stand for the cell phone. No time for a stand now so took a chance only to be juuuust slightly too high. How to fix as the punch keeps jumping back into its initial/wrong hole?

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    Last edited by garage nut; 01-14-2018 at 02:04 AM.

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    Supporting Member Frank S's Avatar
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    It can be aggravating to miss punch an intended location even when going off of scribe lines. that is why when I have a somewhat critical location to center punch I usually use a prick punch first which will have a much steeper point angle. then use the center punch. However there are times when it seems no matter how careful you are a punch mark is just wrong. Maybe the inital scribe lines were slightly off or there was some surface imperfection or the punch just slipped a little the reason doesn't matter it happened and now I want to move my mark. What I usually do is try to eradicate the punch mark before re punching by flattening out the surface as best as possible usually I can get by with a simple light tap or to with the ball head of a ball peen hammer. Sometimes just angling the punch in the direction I wnat to moce the mark tapping lightly until the desired results are achieved will do the trick. Good luck
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    Supporting Member Toolmaker51's Avatar
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    Frank S is absolutely correct. Peening out miss-markings is likely most common correct modern use of a ball peen hammer. Light taps are all that is needed to 'erase', actually move metal back where it was. Another good reason to get older ones when opportunity arrives, they were more hemispherical in the past, where cold metal shaping was common. Now they present more of a tapered configuration. Easier to hit [tap] small locations, maybe not so desirable for radiused forming...

    I've got a light sense of touch. Center punching, I can feel the fine point descend into one scribed line, and move it into where axis cross. There are 3 such punches; prick which is nearly needle sharp, about 30 degrees included angle. That's too delicate for a real mark to hold a drill point or compass. There are two larger, about 60 and 90 degrees you can follow up with when needed. I use 60 for center drills, 90 for hand drilling.
    Sincerely,
    Toolmaker51
    ...we'll learn more by wandering than searching...

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  7. #4

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    From "How to Run a Lathe, 42nd edition" published by South Bend Lathe Works,
    Changing the Location of Center Holes
    "...the position of the center punch mark can be changed by placing the center punch at an angle...and driving the center over. The shaft should be securely clamped in a vise while this is done."

  8. #5
    Supporting Member ncollar's Avatar
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    Spot punch marks for drilling should always be light, when confirmed to be spot on then use a larger punch to set the mark to get the hole where you intend to. If a prick punch is off just lean the prick punch and tap sideways until you are over you spot and set the correct position. Drilling off is just from being in a hurry and rushing. If it is worth doing do it right.
    Happy boring
    Nelson


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