Sliding Dovetail Holder / Clamp

[Bill Adamsen]

My chisel mortiser works well, but the workpiece hold-down leaves something - actually just about everything - to be desired. It's the transitions between mortises that kill me. Current setup should work ok if the piece(s) is (are) exactly the same width the full length, and if I managed to get the hold-down perfectly parallel. So in other words ... it never works well.

The two solutions that come to mind are ...

1. a sloped pneumatic clamp ... I'd just need to build a sloped ramp for my existing cylinder and add a clamp pad of the same angle. Very doable. I've seen these on I think General mortisers(?) do they work?
2. an offset clamp lever (like on my Powermatic Chain mortiser) that could clamp down on the top of the piece and be adjusted/released quickly. It would slide in the existing hold-down dovetail way. (not sure where one would get something like this).

I'd be curious hearing about other idea alternatives, and also what might have worked for others including those ideas above. I have a screen window job and expect to be sliding in many rails (same width) and getting this fixed first would be great.

[Brian W Smith]

Color me slow Bill.......I read your post several times and am not quite understanding "exactly" what the problem is.Obviously there's something amiss with the hold-down.....but what exactly is happening?Is your clamp system just not strong enough?Is something flexing?Too slick of a clamp surface?

[Bill Adamsen]

The pneumatic holds the wood tight against the fence, but at the current angle (perpendicular) does not have the proper "force" to retain the stiles when the chisel is extracted. When extracting the chisel the wood "lifts." So the mortiser has a metal hold down welded onto the fence. It is very cumbersome to adjust, though it does successfully retain the wood when used. Often when looking to slide the stile out, in or just along the length, it requires loosening one or both of the two "brass colored" levers on the front of the table to lift the fence. Theoretically, were the piece being mortised exactly the same thickness, it could be "slid" from one mortise to the next. And sometimes this happens. But then it also sometimes doesn't.

Below is a photo (thanks to AWWM) which shows a manual bar type hold down on a chisel mortiser. This would likely be no improvement from what I have. The second photo shows a typical manual hold down we're all familiar with on manual mortisers, again likely no improvement (and it wouldn't fit).

What I seek is something that can fit into the dovetailed way of my current fence, and fast clamp either pneumatically, or with a lever, so that I can quickly process numerous stiles with mortises. I'm just looking for ideas on what works for others.




MortiserHoldDown.jpgManualHoldDown.jpg

[Brian W Smith]

Gotcha now......

The VERY first thing to pop into my pea brain and probably what we'd start with here(our shop,not necessarily anyone elses) is cam locks.Being that Destaco's taking up too much room....not,that they wouldn't work however.

Ever see those sheet metal brakes the siding guys use?I "think" there's two basic kinds of material locks.Look for images of the "older" style.They utilize a single handle that operates at least a cpl(maybe more?)of wedge clamps.This is another possibilty.

Next idea(and can do this all night) would be something that's spring loaded and only "holds down" when activated(when you need it).....the "trick" part being it could be foot operated.Edit to add here....another sheet metal hold down....look for old Pexto stomp sheer.....really look at how the hold down functions.

Next,would some "dead" weight,albeit with rollers help.It just rides on top of work....this one's kinda FF(Fred Flintstone) though.

There's always more pneumatic.

And,like you've said......put your existing closer on a wedge base.Good luck.