Notes from the technical team
David L O Smith
Guild Technical Committee

deburr /diːˈbəː/ to neaten and smooth the rough edges or ridges of an object.

WE ARE ALL FAMILIAR with this process, even if we may just call it cleaning up the ragged or fuzzy edges. For cleaning up the edges of cut plastic card, it is popular to use a scalpel blade dragged sideways at right angles to the rough cut and, for cleaning up the edges of cut metal sheet, a file is drawn along the edge.

For small round holes, I find that gently twiddling a larger worn drill removes the rough corner; using a worn drill is preferable as it will not ‘dig in’ and try to cut a larger hole, as might a sharp drill. It is but a small job to mount worn drills in a handle such as a piece of dowel, so that you may easily identify them and pick them up. Fig 1 Worn drills in dowel handles

For larger holes, say larger than ⅛in/3mm, I find that a hand-held countersink is easier to use and, with its multiple cutting faces, it is most unlikely to dig in.

Fig 2 Hand-held countersink

There are situations, such as large holes (say, greater than ½in/13mm), shallow holes and the machined edge of bored holes, where the use of a typical hand-held countersink is not feasible. There are many inexpensive hand-held deburring tools available online these days for such cases but, years ago, I made a triangular scraper from a broken centre drill (any tool steel would do) and I have always used that, along with a larger example that I bought at a tool shop.

Fig 3 Commercial deburring tool

I have saved until last one of my favourite rather nifty finds: a cup concave cutter. Like many I am sure, I found that deburring the ends of wire that were projecting out of buffer planks to represent the heads of rivets was really rather trying, chasing the fuzzy bits around with a needle file, and the end result was an unprototypical flat end, at best. No, what I needed was some sort of cutter that would debur on the outside (just as a drill deburs on the inside) and I found one in a cup concave cutter. As for the worn drills, it is a simple matter to mount them in a dowel handle to twiddle over the projecting wire to chamfer off the edge – a rather simple, neat and inexpensive solution to a common and troublesome problem.

Fig 4 Triangular scraper

Cup concave cuttters, and many other useful tools, are available from suppliers to the jewellery and clockmaking trade, for example. I would thoroughly recommend searching out sources on the internet rather than relying on the limited selections on offer at model railway exhibitions. Cup concave cutters are available from Cousins (www.cousinsuk.com/product/cup-concave-cutter-maillefer-s) and others; the smaller sizes (0.8 – 2.3mm) are less than £2 each.

Fig 5 Cup concave cutters mounted in handles, detail (right)