The humble screwchuck has changed dramatically over recent years, and is more often now seen as just one component in a complete chucking system of some sort, Picture 1. I have been turning long enough to remember the days before these multi-chucks were so widely available, times when the screwchuck was possibly the only means of holding the work. Consequently I am something of a fan of this most simple of holding devices, but it does need careful use if you are to get it to work really well.
However, there are a few basic hints and tips which will solve most of the problems commonly faced by new users to the screwchuck, I hope this brief guide will help you overcome some of them. I do not really count the big heavy machine screw type as ‘proper’ screwchucks. These are really a quick method of ‘first fixing’ big chunky workpieces whilst you turn the chucking recess or whatever. This article is concerned with the conventional chucks that take an actual woodscrew, Picture 2, and which are mostly used for holding small workpieces. The first thing to remember is that screwchucks are often used to hold end grain work, and the grip is obviously not as secure here as when you are holding into side grain. It is therefore vital that you do everything possible to maximise the holding power of the single screw. Don’t try and hold anything too long otherwise the leverage

becomes too great and the wood soon tears off. I would not hold a workpiece anything longer than about 5” in end grain on a single screw, Picture 3. Note that the pilot hole for the screw must be the right size, there is a common misconception that if you drill a smaller hole the grip will be tighter. Nothing could actually be further from the truth, a small pilot hole will just cause the screwthread in the wood to strip and the grip will be nil, so drill it the right size!
Make sure that the surface of the wood that mates up against the chuck is dead flat. The screwchuck will never work if there is the slightest bit of play in the wood when it is screwed up against the chuck face. This is the most common source of problems, and whenever I hear someone say that they cannot get a screwchuck to grip properly I know that they are not getting a secure enough initial hold. A tiny bit of movement at the chuck end is a large amount of waggle at the other end of the wood, particularly if it is quite long.
So how do you get this seating rock solid? There are a couple of tips here which should help. Firstly remember that whenever you screw the chuck into the wood it inevitably throws up a small burr around the screw, Picture 4, and no matter how flat you cut the face this burr will become trapped between the wood and chuck, acting as a pivot point.

There are several ways of overcoming this; perhaps the simplest is in the choice of your actual chuck. I prefer the type where the woodscrew is set in from the front, Picture 5, as with these you can usually set the screwholder back in below the main face of the chuck. This obviously leaves a shallow recess, which accommodates any burr or other irregularity and provides much more positive seating. This little recess does make all the difference, it has solved all the screwchuck problems of dozens of beginners I have helped, it is the difference between a close fit and a total fit, and there is a difference.
If you already have a chuck without this facility, and with a totally flat face, Picture 6, don’t panic. Take the screw out of the chuck, mount it on the lathe, and with a countersink bit or a large twist drill in the tailstock, just form a shallow recess around the screwhole, Picture 7, it doesn’t need much. Now try the difference, you will be amazed!
If you are using longer workpieces there are a couple of other dodges. To be absolutely sure you have a secure seating, turn the work between centres initially and slightly dish the end you want to hold, Picture 8.

Now take it off the lathe, drill the pilot hole, remove anything that remains of the ‘pip’ with a chisel, and this will now seat all around the rim of the screwchuck for maximum stability. If you are into really long pieces, or the end grain grip is a bit weak, try drilling a hole through the end of the work at right angles to the screw, Picture 9.

Then hammer in a dowel of some other wood, and mount this on the chuck. You are now gripping into side grain rather than end grain, Picture 10, so the hold is that much stronger; you just part off clear of this as the last operation. This is a good tip not often seen these days, but was standard practice in the past when you wanted to be sure the work was secure.
Another important point with screwchucks is to make sure the actual screw is in good condition. They wear quite quickly, and soon lose their ‘bite’, so be prepared to replace them regularly, Picture 11. You will need short fat screws, at least size 14’s, and these are often a bit tricky to locate, being what is technically called a non-preferred size. Try the original supplier of your screwchuck if you have any problems. Don’t just shove in a thinner gauge screw, it will be loose in the holder and will have no gripping power at all. As usual the only way is the right way.
So that’s all there is to using the screwchuck, used properly it is a vital part of the woodturners chucking armoury, but even minor departures from the proper set up will render it pretty well useless.

I regularly demonstrate eggcup turning on a screwchuck, using blanks 5” long, held on the single centre screw, Picture 12. This involves deep hollowing on the end grain, Picture 13, and then parting off as the last operation, Picture 14, and every demo always attracts at least one person who comes up afterwards and says, “I can never do that on my screwchuck”. Now I hope you can!

Picture 12.