Considerations when making my own threaded dowel for a vise

Question

After looking at the answers for this question I was inspired to make a Moxon vise for easy table top use. This will buy me time until I make my actual woodworking bench. The one I have in mind is similar to this one:

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Some of the simpler designs involve a threaded wooden dowel, which is something I want to try out. The tool to use would be one just like this (but not necessarily this one):

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If I am going to make threaded dowel for a vise what do I need to consider? I can think of two things:

• Wood Something like a maple; at least a hardwood minimum
• Diameter Surely it needs to be of a fair size. Would 1 inch be sufficient? If it is too large, would there be a concern?

Answer 1

If I am going to make threaded dowel for a vise what do I need to consider. I can think of two things.

Wood Something like a maple; at least a hardwood minimum

I think you'll find that a lot of larger threaded screws made of wood (in the USA, at least) were/are made of hard maple. This is what Lake Erie Toolworks uses for their vise screws.

Hard maple is a good choice since it has tight, closed grain and is not generally subject to chipping. The side-grain forces on a screw require that it be resistant to chipping. Oak would probably be a poor choice for that reason.

Otherwise, if you look at a lot of older wooden plow planes with wooden armatures, they were generally made of boxwood or beech.

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Boxwood is very close-grained and tough as nails. Beech is also tough and pretty close-grained (not to mention cheap at the time). I imagine that lignum vitae would make a good screw as well since it machines so well.

The most important part to remember for any wooden screw is that it must be very straight grained and free of defects. Grain runout will weaken the shaft of the screw. Any little knots in the piece will cause extra wear in your screw mechanism and be that much harder to cut out when making the threads.

Diameter Surely it needs to be of a fair size. Would 1 inch be sufficient? If it is too large, would there be a concern?

You will likely find that large vise screws are much larger than 1". The Lake Erie leg vise, for example, uses 2-1/4" diameter dowels for their screws.

However, for a smaller vise like your Moxon vise, this is overkill. A 1" diameter screw is most likely fine. If the screw is larger, there is no real concern - to a point. If you have too large a thread pitch, the piece you thread into needs to be sufficiently thick that the threads have something to bite into. Example: if you have a 1" thread pitch screwing into a 1/2"-thick board, you don't have anywhere near enough thread wall in your nut to resist the screwing forces.

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If you want to take a crack at making the dowel yourself (without a fancy threading jig), have a look at L'art du menuisier, by André Jacob Roubo. I forget exactly where he discusses it, but I know it's in there. Lost Art Press has an English translation of it for sale, as well as the big book of Roubo's plates that accompany the volumes. You can also find scans of the original French text online.

Answer 2

Excellent answer already from grfrazee, just wanted to add some practical options.

The tool to use would be one just like this (but not necessarily this one):

I see in the Comments that you say this isn't terribly expensive but I'd like to offer a cheaper alternative to anyone for whom $50 or so, for a seldom-used tool, might be a bit much. Behold:

Yes, those are just a common nut and bolt. But using the same method outlined in this Answer the bolt can easily be turned into a tap, and a very good one at that.

For the nut you do the same basic thing, you file a groove (or more than one) in the threads to make cutting edges and provide clearance:

As important or more than when using a commercial tool-steel tap and die, lubricating the threads with oil when doing the cutting is highly beneficial. A range of oils have been used for this in the past but mineral oil/liquid paraffin is probably the most common choice these days. Also as with a commercial tap and die it's important to reverse direction periodically to clear swarf.

A slightly more involved method is shown step by step in this article on WK Fine Tools. A basic wooden holder for the filed nut as shown in this (taken from Le Menuisier Ébéniste by Roubo) could be advisable, but is not absolutely essential.

More general information and some useful details on tapping and threading wood in this piece from Christopher Schwarz, Tapping Threads Without Tapping Out.

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And a ## Heading ##bonus for those inclined towards cheap solutions...

Make your own dowels

Dowels can quite easily be made using various homemade and commercial tools and setups. Other than the potential cost savings it allows you to make your threaded rods from species which aren't offered commercially as dowels.

One basic technique is an old method, and involves bashing square wood through round holes:

Photos showing the method in use:

Note: shop-made plate in the top image, commercial plate below.

On the same basic lines but with a modern twist (pardon the pun) this method demonstrated on Lumberjocks by user stefang, using holes drilled at 45° through a mild-steel plate and a drill to spin the workpiece.

Dowels can also be spun through a jig/tool that cuts them round:

More reading on the pencil sharpener method, on Woodgears. And these two entries on Lumberjocks, one and two.

There are also various router-based methods that are worth investigating for those who own a router.