View Full Version : Square burrs

17-06-2017, 10:22 AM

I'm about to step into learning how to set stones. I've got a basic idea, but in seeing what I've seen so far, it's got two questions bugging me : Is there such a thing as a square burr bit for cutting square holes ? And I'm concerned that I might burr too far through a ring when creating a hole for a stone, so is there a depth gauge I can attach to a hanging pendent drill ?

Thank you

17-06-2017, 10:32 AM
Strictly, there is a drill that will cut square holes based on a Reuleaux triangle (https://en.wikipedia.org/wiki/Reuleaux_triangle) but I've never used one. I'd go out on a limb and say no-one is using them in jewellery applications (happy to be proved wrong though!). For cutting square seats in a plate I'd drill through with the largest burr that'll fit, then pierce a taper bearing with a saw before tidying it up with scorpers. Same goes for other fancy shapes.

17-06-2017, 01:19 PM
For squre seats do as Peter suggests.

For small square holes to let light through from the back, drill right through and then convert the exit hole to square with a suitable tapering punch. You can easily grind one of these from tool steel, or a nail punch from an ironmonger.

Some small bench drills have a depth stop, but failing that just mark the drill with a fine waterproof pen and double check on a piece of waste first. Dennis.

17-06-2017, 01:19 PM
As Peter says, a triangular bit would produce a square..never seen or used one though!
You'll have to pierce or cut the corners by hand after round drilling.

Maybe not the easiest task to do as a beginner but then again you have to start practicing it to be able..
Is drilling through a problem?

Paul Kay
17-06-2017, 04:20 PM
[QUOTE=Skieferins;94978]...so is there a depth gauge I can attach to a hanging pendent drill ? /QUOTE]

There are these:


and these, which look like they'll need a few pages of instructions, but no doubt do amazing things if the picture is anything to go by:


17-06-2017, 06:36 PM
You can get tiny broaches to make square holes after drilling a round hole but I've never used them

18-06-2017, 04:54 PM
Broaches are rotated by hand to true up holes made with a twist drill, because twist drills leave them slightly oval. They will also slowly enlarge holes.

I have often used them for adjusting holes, starting slightly undersized, to get a good snug fit for a rivet. For example when making a hinge for a brooch, or fitting a wire to hinges. Dennis

18-06-2017, 06:25 PM
Some broaches are, but there's another class of broach that relies upon linear motion (e.g. mounted in an arbor press). Again, not generally used in jewellery. Quite handy though for many other things (including cutting hammer eyes in plastic mallets).

18-06-2017, 10:18 PM
Looks like I should have added the words: tapered square.

I guess linear broach for jewellers could be read as 'saw blade', or even these:

http://www.cooksongold.com/Jewellery-Tools/Anderson-3-Piece-Miniature-Saw-----Frame-Set-prcode-997-3310&query=tiny%20saw%20frame&channel=uk Dennis.