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AYS Leg Vise Chain Adjuster

For the past several months I have been discussing a parallel guide adjuster designed by Jim Ritter (who owns and runs the Anchora Yacht Service, AYS). My input has largely been devil's advocate while Jim sharpened up the design for production. I have no interest in this venture other than wanting to see a good product made available for others to use.

The leg vise parallel guide adjuster is an alternative to the St Peter's Cross, both of which enable a leg vise to function without the pin adjuster. No more stooping and setting the parallel guide for a specific width. Instead there is a single setting for all work pieces. In theory there should also be more pressure as the chop is more upright.

I completed assembling the pre-production kit, and here are a few pics with my impressions.

From the front you will not notice any change to my leg vise ..

Close up those who know too much may note that I have replaced the steel screws with brass .. 

From the side you will see a solid parallel guide and, above it, a chain ..

Solid parallel guide?!

Yeah .. in for a penny, in for a pound ... off came the parallel guide of my 6-month old leg vise on my 6-month old new bench !

.. and replaced with this new, hole-less version ..

What the Butler saw

This is the chain mechanism …

The kit …

consists of two rollers withing brackets, with a chain (which is larger than the standard bicycle chain), and attachments for each end.

Note that the rollers were part of the pre-production kit. They are to be replaced with sprockets in the production kit ..

Installing The Chain Mechanism

The chain runs from the chop, under the screw, through the leg, then down along the inside of the leg, and along to the end of the parallel guide.

The journey begins with the plug to which the chain is attached ..

The plug will be situated at this point below the screw ..

The first step is to drill the mortice for the plug (Note that the chain will run as close to the screw as possible. Just make sure that you allow space for the screw block) …

The chain is threaded through, and this is all that that remains on the front of the chop…

On the other side of the chop …

The next step is to drill the hole for the chain through the leg. As mentioned earlier, this will end up as close to the screw block as possible. I really pushed this to the limit. It is not necessary to get quite this close!

That is all the hard work that needs to be done. The chain is now threaded through the bracketed rollers that form part of the kit.

It is now necessary to remove the internal balance wheel, if you use one. It will no longer be required as the chain will do this job. The external wheel (under the chop) will remain.

The wheel is replaced with the lower bracket and roller/sprocket. The picture below was taken when I was adjusting its position.

And the chain terminated at the end bracket ..

The completed installation from the working side ..

In all, including building a new parallel guide (which I do not expect others to do), the installation took a day. 

How well does this all work

It grips ...

... and grips ...

.. and continues to grip ..

. no matter how little there is to grip ..

Fine tuning the chain

The only negative impact of the chain was a slightly stiffer rotation of the screw handle. I had set it up according to Jim’s instructions, which directed the chain to be quite tight. Playing with the chain adjuster I discovered that a looser, floppier set up restored the smoothness of the handle, and the lighter feeling I originally had with the screw.

The best way to examine what I described is to do so visually. So here are a bunch of pictures.

This is what I meant by a floppy chain ..

Here is the position of the chop - just slightly open. The chop looks fairly parallel, but admittedly it is not doing any work. Still, it opens parallel.

Now if I insert a thin board ...

... the chain tightens up ..

Here is a wider board. I am attempting to assess for parallel. The easiest way is to see if both the sides of the board are held evenly ..

This board is easier to see. I would say it is perfectly parallel (where it counts - at the chop) ..

Here is another example. With the chop closed down but not tightly, it is apparent that the top is toed in slightly. The chain is loose, indicating that there is no tension ..

Now I add a quarter turn on the screw. The chain tensions, and the chop pulls square ...

Throughout this process, the leg vise has been working very sweetly. 

It’s now about 5 weeks since the chain mechanism was installed. It is here to stay.

Jim may be contacted at:

Regards from Perth


August 2012