Monday, March 29, 2010

Hold-Downs- Assembly

I chucked up a 1/2" straight cutting bit in the router table, attached a fence and stop block, and cut slots for wear strips.

I put a stop on the mitre saw and set it for the width of the routered slot, tested with scrap.

I then made a sandwich of milled scrap, transfer tape, and brass shim stock.

A trimming cut was made, then parts were cut against the stop block.

A 1/2" circle is drawn on the end, and the disc sander roughs it out.

The curve is refined by handsanding.

I've used dowels for hold down shafts before, but it's not long before they are burnished smooth and no longer work. For this pair I'm using Lee Valley's short Hold-Down Posts. They are steel, machined with barbed grooves.

I drill a 3/4" hole 3/4" deep.

Then 3/4" deeper with an 11/16" bit.

I threaded the heads on, and the fit feels secure. If they become loose in the future I'll epoxy them, or cross drill and pin with a brass rod.

Leather is then glued to the pads, and clamped to dry.

To replace the fluted dowel, I hacksaw a 1/2" brass rod into two lengths, 1/8" longer than the clamp bodies are wide. The rod is chucked into the drill press, and lowered against sandpaper. 120 grit is used to remove the saw marks, then I went to 800 to polish. A sponge is used to back the sandpaper, which allows the ends to dome.

The leather is trimmed and the wear strips are epoxied into place.



I'm having a hard time not thinking of them as "bench bunnies".

Hold-Downs- The Cams

Two levered cams were laid out on a piece of 8/4 beech.

The cam applies pressure as the lever is pushed down. The lobe is 1/8" higher than the tounge at rest, and 1/8" lower when engaged. The peak of the lobe is forward of centre, so when closed it wants to stay closed. The curve behind the lobe is an 8" radius, to match the kerf of the dado stack.

A rip blade was installed and the tall cheek cuts were made.

Then the blade was lowered and the shoulders were cut. Pressure was applied to the stock to prevent it falling into the blade when the supporting waste was severed.

They were then seperated on the mitre saw.

The pattern I drew on the now removed cheek was bandsawn out.

A 1/2" dowel gets chucked into the drill press and spun against a piece of sandpaper.

This skinny dowel makes it easy to test fit my template.

I used the edge sander until I was pleased with the action, then I transferred the outline to my stock.

I used the removed cheek, transfer tape, and a 1/8" shim to make a stable platform so I could bandsaw to the line.

The lobe was refined with hand tools and sandpaper. The body was then shaped on the edge sander to allow the lever to raise.

The edge sander does quick work of shaping the body and lever. The roundover at the back of the body and the handle make a natural gripping point.

Hold-Downs- The Body

Today I made myself a couple of cam action bench hold downs.

I started with a piece of 8/4 beech, and drilled a 1/2" and a 1/4" through hole.

The gap was laid out.

The dado head was raised to the right height, and a stop was clamped to the fence.

The bandsaw made the kerf.

A stop was clamped to the mitre gauge and two heels were defined.

The block was then moved and the other two were cut out.

The waste in the middle was then removed.

The bodies were then parted in two on the mitre saw.

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I'm a woodworker on the Canadian prairie.