Simple guide shim for narrow rips

[dogutsukawu]

When ripping stock narrower than the width of the guide, the non-cut side of the guide tends to sag under the weight of the saw.  Hence the practice of putting stock of the same thickness under the guide to support it and prevent sagging.  In other words, we "shim" the guide.  Not a big deal, but often a nuisance to get a shim of the right thickness.

Here's one solution to the shim problem.

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I wedged a super magnet in the upper T-slot of the guide.  I cut a piece of PVC pipe to length, and epoxied a washer to the pipe.  This shim attaches to the underside of the guide and stays there, thanks to the magnet.

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Although the guide is shimmed only at its midpoint instead of its entire span, it's enough to essentially eliminate sagging.

You can make a set of shim of varying sizes matched to the stocks you use, and label each with the corresponding stock thickness.  They take very little space and you'll always have on hand a shim of the right size.

 

[jvsteenb]

Handy mod, but won't the rail bend? I can imagine the rail bending ( just a tiny bit ) under the weight of the saw next  to the shim, even offsetting the cut and/or the effectiveness of the splinterstrip.
I like to use a full length support, that's placed under the "other" non slip strip whenever possible. You may not always have a full length support handy, that's for sure.

Regards,

Job

 

[dogutsukawu]

To address the concern that the guide shimmed only at its midpoint would deflect too much, I did a test.  I supported the guide with my shim and with a small piece of wood under the cutting edge at its midpoint.  I set up a dial indicator to measure the deflection of the guide.  As I slid the saw weighted with a quart of varnish (to simulate the force of plunging), the maximum deflection I measured was about .3 mm.  This is about .01 (less than 1/64) inch.  This is good enough for me.

It's easy to why the deflection is so small.  The saw's sole plate, which is rigid, is about 30 cm long.  The guide rail between its end supports is 80 cm.  When the saw is a quarter of the distance along the guide, there is only 5 cm from the front support to the back of the sole, and 5 cm from the front of the sole the shim.  That doesn't give the guide much leeway to deflect when the saw is positioned for maximum deflection.