Monday 9 July 2018
Each new job that comes in presents a challenge in one way or another. The first thing to think about is how the work should be held on the lathe, and one of the simplest ways of doing this is on a screw chuck.
A wide range of jobs can be held this way, the only proviso being that it will leave a small hole in the base or end of the job.
Screw chucks are often associated with the initial mounting of bowl blanks and because of this, shop bought screw chucks usually have a rather large screw fitted.
Making your own allows you the freedom to use a more suitably sized screw to suit the job in hand. I regularly use a screw chuck for finials, fruit, drawer pulls and walking canes, and as long as a suitable size pilot hole is drilled, they will hold fast every single time. This article aims to show you how they are made and gives you some tips to help you get the most out of your homemade screw chucks.
Select a piece of hardwood â€“ in this case beech (Fagus sylvatica) â€“ a suitable size to suit your chuck jaws. Mine grip onto a 56mm spigot so the blank was around 65mm square and around 30-40mm long. Mount it between centres and turn it round with a spigot on one end, cut around 2mm larger than the perfect size for your jaws, in this case 58mm. All will become clear in a moment
You now need to mount the blank in your chuck jaws and true up the face. At this point you can also trim the timber down to the final size you require. I have selected a 50mm x 6mm Coach screw for this screw chuck, as I find it to be a very versatile size, being small enough for most jobs but also strong enough as well. Trim the blank to around 25mm which will allow a good half of the screw to show, once it is driven home
Next, you need to mount your drill chuck in the tailstock of your lathe with a suitable size drill bit and, with the lathe running at around 700rpm to ensure neither the drill bit or the wood overheat, carefully drill a central pilot hole, all the way through the blank for the screw to fit in. For my 6mm Coach screw I use a 4mm pilot hole, which will provide the nice tight and secure fit that you are looking for
The next step is to remove the drilled blank from the chuck and fit your chosen screw. Before driving it home you need to add some two-part epoxy resin to the shaft of the screw to make it secure. I find epoxy to be the best glue for wood to metal applications. I then leave it overnight to cure properly and thoroughly. The photo opposite shows just some of the sizes of screw you could potentially use to make your screw chuck. Your screw chuck is almost complete
Fit it in the chuck and test it but don't be surprised when it runs out of true. No matter how carefully you drill that hole it will almost always wobble. To correct, fit your drill chuck to the headstock of the lathe, lightly grip the screw thread, then with light cuts, true up the spigot. Now you see why it was cut oversized. Your new screw chuck is ready for use