Enlarging saw nut holes in sawplate


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    William Balmont

    Hi there,

    I have been restoring a 16″ unbranded hand saw and I received some nice brass nuts from Thomas Flinn. The only problem is that the current holes in the plate are about 4mm diameter and the bolts will need 5.5mm I believe.

    I have little experience with metal working so when I tried using a standard hss drill bit it started to work and then stopped. I later looked it up and found that I probably blunted the bit very quickly. So my question is how best to do this? I have an additional problem in that one of the holes is slightly elongated so when I tried to drill, the bit corkscrewed it’s way in without removing metal.

    I have read that a carbide tipped drill could work (note: I don’t have a pillar drill). Would a round diamond needle file do the job? Or is there an attachment I could use on a dremel? I’m guessing no drill bit will work on this elongated hole?.

    Thank you

    Chris Wood

    The steel plate on hand saws is typically too hard for a standard HSS drill bit. If the bit is of good quality, and many of them these days are not, and sharp then it should work provided it is fed at the correct speed. There are specialist bits which work on hardened steel. I would search out the best quality bit to do the work. Using a file may cause the holes to become out of round.

    William Balmont

    Thank you Chris,

    I will find the right hss drill bit then.

    Larry Geib

    The eccentricity you get when trying to enlarge a hole is often due to there being more than one flute on the bit. Try using a bit that has only one flute. I use a step bit.
    Unibit by Irwin is the original patent, but the patent expired so now there are some pretty inexpensive versions that will get you through at least a few saw plates.
    It will even correct oval holes. Use a small one. The larger step bits often have 2 or 3 flutes.
    And a drill press isn’t required, though a power hand drill will speed things up.

    William Balmont

    Thanks Larry. I’ve never seen this type of bit before. I can see that it could work well though so I’ll look for one.

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