Full Chisel Blog

May 26, 2008

Gimlet Bits

Filed under: Drilling,Uncategorized — Stephen Shepherd @ 8:04 pm

Or Gimblet bits are a special type of bit for a brace and should not be confused with the T-handled gimblets used to make holes for screws.  These bits are usually quite small and that is their intended purpose.  However people think that the brace gimblet is for the same purpose.  And of course if most people think that, then I have a reason to explore other possibilities.

The photograph shows my collection of brace gimlet bits.  The number markings stamped on them differ from other bits as they are marked in 32nds, hence a 5 would indicate 5/32″.  And this marking continues until it gets to my largest which is actually marked 5/16 in fraction form.  The smallest is 3/32″ and all up to the largest are marked in this manner.

Gimblet bits

If you look at the bit on the left and the one 4th from the left have both been ‘untwisted’ or deformed during use abuse and this can happen to these bits.  I have not bothered to twist them back as they still drill holes of the proper size in their present condition.

There are also some sources that say that these bits can’t be sharpened, maybe they couldn’t sharpen them, but I have found it possible to sharpen any and all of these bits.  It takes some fine round needle files on the insides, but it is possible, the outside flattened with a flat file.  Care must be exercised an the flat on the outside should be lightly dressed so as not to reduce the effective diameter of the drill.

Now here is where my views vary from others.  While the smaller bits can be used to make screw holes, these bits are tauted as being for screw holes and the diminutive bits perform that function just fine.  However they probably weren’t used for that purpose as a brad awl (I will get to these soon as they make fine holes) is a preferred choice for making holes for screws as no wood is removed in making the hole.  One must remember that screws were blunt prior to 1846 and only AFTER that date are wood screws pointed.

So you don’t need a pointed hole for a blunt screw and while it is a good idea to make a pilot hole, drilling is not the best option (Brad Awl), for making an entry hole.

Gimlet bits make a fairly good entry hole, there may be some splitting, but it usually isn’t bad and because no one ever uses them to drill holes through the wood, no one apparently has mentioned that they make a great exit hole without any backing as required by other bits.  Gimblet bits pierce the opposite side with a small hole then continues making it larger as it advances, but it pulls the chips back through the hole leaving a clean exit hole.  No backing required.  Got a gimblet bit?  Try drilling a through hole, you will be amazed.

When I first got gimblet bits, no one told me they were just for screws as I may have never tried them for through holes, but they work wonderfully.  And besides I don’t have any 3/8″ diameter screws for my largest gimblet bit a 5/16″ and I haven’t seen too many old examples that would require a special bit of that size.

The association of gimlet bits and screw holes I think is because of the shape of the bit to the shape of the screw.  But screws that big are rare and there are much better ways of making holes for screws.  I don’t think they were originally intended for screws, I could be wrong, but somehow I don’t think I am.

I use these bits all of the time as they are handy and work well, but I hardly ever use them for pilot holes for screws, but I have been known to do so.  Most of the time it is to drill a smallish hole through thinner boards because of the swell of the shank and tang, they can not drill holes very deep.



  1. Stephen,
    Great info on these bits. I recently picked up a handful of orphan ones on ebay thinking they were spoon bits as the listing described them. The pics were not good enough to really tell what they were. I thought they might be gimlets but all of the T handle gimlets I had seen had lead screws. I posted some pictures of them on a couple woodworking forums and was advised by some very knowledgeable folks that they were, in fact, gimlets. Only a couple of mine have numbers on them to indicate size, but several are stamped “JMHoff & Lange” and “Germany”. The only reference I’ve found to that manufacturer was from an old unusual hacksaw at MJD Tools. After cleaning them up a bit, I was playing around with them and found that they are very good at drilling holes at angles and, like you said, make excellent exit holes. Anyway, thanks for the info on sizing.

    Jerry Palmer

    Comment by Jerry Palmer — July 19, 2008 @ 10:15 am

  2. Jerry,

    Thanks for your comment, and you will enjoy these bits, I use mine all the time. People really need to try them for through holes as they never think about that. The bit makes a small exit hole then enlarges it by pulling the shavings back through the hole, making a clean exit hole.

    Thanks again for your comments.


    Comment by Stephen Shepherd — July 19, 2008 @ 9:50 pm

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