Help With a Screw Chuck

[Don Z.]

Well, I tried using a screw chuck for the first time on Sunday. My "project", in this case was an oval handle made from osage orange for a screwdriver. The first one came out a little lopsided, but I think I can do that a little better next time.

The problem I had, however, related to the screw chuck. My tools were sharp (fresh from the Tormek), but every now and then, if I was a bit too aggressive instead of cutting the wood, the blank would "tighten" on the screw. It got to the point where it was pulling off the live center (probably why I'm a bit lopsided in some areas).

What can I do to limit this (other than re-sharpening my tools, which I'm working on this week). From what I can tell, either I drilled the pilot hole a bit oversized, allowing not much torque to "spin" the blank on to the screw, or I should use a left handed thread instead of a right handed thread.

I have Ernie Conover's book, but other than suggesting "with a right hand screw, the work self tightens on the chuck", I really can't tell where I'm going wrong. I mean, there's self tightening (good) and there's "tightening so much the stock stops turning and the screw begins to strip", and thats where I'm at.

Suggestions?

[flairwoodworks]

I think the problem is neither your tools, sharpness, live center, nor technique. You said that you were turning a screwdriver, and I'm guessing that means you drove the screw into end grain. Perhaps the tool caught, or dug in, and when that happened, the screw chuck continued to turn while the workpiece did not and stripped the hole. Try mounting something like a bowl blank with face grain towards the screw chuck. I don't think screw chucks are intended (or suitable) for spindle work (defined by the direction of the grain being parallel to the lathe's axis. I've never spindle turned with a screw chuck, but I've used one to turn many bowls without the use of a tailstock.

[Roger T]

Don,

You dont say if you are bottoming the shoulder/bottom of the handle out on the screw chuck. If not, and you have space on the screw end, you can use a nut and washer to bring a stop to the handle, rather than screwing the handle on deeper to get to the shoulder of the chuck. (Did that make sense?) In other words, the end of the handle needs to butt up against something to keep it from advancing.

What I have taken to doing, is after drilling the mounting hole, take thin CA glue and put some into the hole, covering all the inside walls of the hole, and give it a shot of excelerator. Then take and using a machine tap, tap the hole to the thread pattern of the chuck. Take the handle back off and give it another dose of CA glue/excelerator.

Hopefully this helps, and if you still have questions, please post back, possibly with pictures to help us help you.

Roger

[dalboy]

If you need to use the screw chuck into end grain try and have the blank at least 2" longer drill a hole across the blank the same size as a piece of dowel insert dowel and cut off. The screw into the end of stock and throught the dowel which is across the grain. much better than just into end grain

[Lawrence Brown]

Don't know if you have one or if you can afford it, but if you can, you would probably be better off just using a standard 4-jaw chuck. You'll get much better grip and no slippage. You will also have the advantage of being able to work without the tailstock for such operations as boring the center hole for the driver.

[Don Z.]

Thanks... I thought about using the four jaw chuck, but the problem with that is I'm using offset centers to turn oval handles. The four jaw chuck would make that very difficult.

Also, I don't mind boring for the screw, as that's the same hole the screwdriver shaft uses.

What I have learned is that I have less problems if I eight side the blank first. Also, I need to be more aware of where the tool rest is, and on the thinner sections make sure the rest is closer to the workpiece.

The good news is that I'm learning. The bad news is that I'm blowing through my limited supply of osage orange. Time to practice more with beech.

[Roger T]

Thanks... I thought about using the four jaw chuck, but the problem with that is I'm using offset centers to turn oval handles. The four jaw chuck would make that very difficult.

Also, I don't mind boring for the screw, as that's the same hole the screwdriver shaft uses.

What I have learned is that I have less problems if I eight side the blank first. Also, I need to be more aware of where the tool rest is, and on the thinner sections make sure the rest is closer to the workpiece.

The good news is that I'm learning. The bad news is that I'm blowing through my limited supply of osage orange. Time to practice more with beech.

Don,

This post clarified some info for me. When I have done off center turning, I only use either a 4 prong, or 2 prong drive center in the head stock. After you have done your layouts for the centers, just punch them with an awl for the center point to locate in. I would think doing off center turning with a screw chuck would in itself be problematic.

Roger

[Whitebeam]

You can hang quite a long piece of stock on a screw into the end grain, if you properly prepare the stock first. Also, bare in mind that a purpose made parallel shank screw with a deep thread works far better than any standard woodscrew or bolt. There are a few stand-alone screw chucks on the market and there are also a number of parallel shank screws available to fit many of the four jaw chucks and collet chucks on the market.

To prepare the stock, mount it between centers, rough it down to a cylinder, and then slightly dish or undercut one end. It is usually best to undercut the tailstock end because you tend to have better access and can cut in closer to the middle. The purpose of this is to ensure that the stock then rests on the outside edge when fully tight on the screw. This will prevent it from rocking and slipping on the screw.

The same method can be used for square stock, its just a case of missing out the roughing down stage. This method will enable multi-center turning, you just need to drill several holes for the screw, and because the end is undercut even if the screw mount is off center it will still tighten down on the outside edge.

Hope that helps and is clear.

Ben