Hammer/Felder style table extensions

[ian maybury]

Just nearing readiness to start up my shop again after a long (much longer than expected!) fit out and re-layout.

Some Hammer/Felder/Aigner 'plank'/cantilever/diving board style table extensions would help with upcoming project, and it'd be nice to be able to afford a selection of the extruded alloy ones they do. I'm thinking however that in order to keep the cost under control it might make sense to make my own.

The machines are just about to be started up - the saw is a K3 Perform with an Incra positioner rip fence, the planer/thicknesser an A3 41 and there's an F3 shaper too. The band saw is an Agazzani B-24.

The K3 saw will need it's own arrangements off the Incra rails, but the thinking is that the same extensions should be usable on three sides of the band saw, and both ends of the planer and probably of the shaper's fixed table too.

One option is to fabricate 3 x 1000mm long (roughly) box section extensions from 19mm or 25mm birch ply - of a similar width to the Felder items. The vertical webs at both sides of the top and bottom (the box sides) would be about 75mm deep. Support would be by a single adjustable leg.

The harder question is how best to attach them to the machine tables. I can't easily inspect the Felder method, and it's not that clear from the pictures how they work. i.e. do they have a fine height and leveling adjustments?

One thought is to bolt a flat bar to the ends/sides of the tables (set out a little on spacers) - much like the roughly 8x50 bar used on the Agazzani to guide the fence. Then to screw a similar vertical strip screwed to the front face of the end of upper leaf of the extension (with a rebate behind it - see the sketch) drop down behind it. A couple of grub screws in threaded inserts would provide height adjustment, and a knob below would lock it down. This wouldn't be capable of being cantilevered in the way that the Felder items is.

Has anybody done anything like this? How does the Felder system work, and what sort of weight capacity does it have? Anything to watch out for? Or is there a better way???? :)

PS Here's the Aigner version: http://www.simantechinc.com/index.php?l=product_detail&p=35

Thanks

ian

192706

[Wes Grass]

Functionally, the Felder setup is like what you've drawn, plus leveling screws bearing (horizontally) near the bottom of the rail. That's all the shorter tables have. The longer one has them but I wouldn't attempt to bear any weight on it without the leg extended. There's a lot of leverage there.

I don't know what the dimensions of the Hammer rails are, but assuming they're the same or similar to the Felder F-rail, 10mm thick, 11mm down from the table, I'd think you'll need something more solid to attach your metal end cap to. Maybe forget it and just do the whole thing in plywood, stacked up a couple inches wide at each side of the table. Should be fine as long as you're always using a support leg.

[Jamie Buxton]

I have Hammer extensions that came with my A3-31 jointer-planer. They're about 18" long. I never use them. If I put much load on them, they flex at the connection to the main machine. What use is an extension that can't hold much weight? The problem, of course, is that they only have an inch or two of height to hold up a long lever arm with a heavy load on it. That isn't an easy problem to solve.

This is a long way of saying that you may use Hammer as a conceptual model, but you should invent a better version of it for your shop.