On 2008-01-21, Ned Simmons wrote:
On Sat, 19 Jan 2008 22:24:39 -0800 (PST), John Martin
wrote:


Plus a couple of what might not be cutoff blades at all. *These have a
cross sectional shape very much like a Lufkin No.902 (I dunno what THAT
is, either, but I have a pair of 'em in their original box. Any info?)
* *1 pc. is .192 wide x 0.739 high x 4.31 long
* *1 pc. is .223 wide x 1.100 high x 5.50 long
Both are square on one end and have 20 deg. "clearance" on the other.



I don't have a Lufkin catalog handy, but I'm guessing that what you
have may be shaper hold downs. Used also with milling or grinding
machines, to hold down thin parts.


Nice catch, John. Now tell us how the heck they work.

I'm not John, but I have a set of these and use them from time
to time. Lets try some ASCII graphics (view with Courier or some other
fixed pitch font to avoid distortion):

--+ -- vise jaw
|______ +-----------
|\ \___________________ |
| \ ___________________ | Workpiece
| \___/ |
| ^ |
| +-- hold-down |
--+ +-----------
----------------------------------------------------------------------

There is a second one of these on the other side of the workpiece. The
force against the edge of the angled back first causes the sharp edge to
bite into the workpiece, and then to apply a downward force. (Normally,
the wider area will be resting on the vise bottom and the workpiece will
be thinner, but I drew it as I did for ease of drawing.

Usually, the thinner area is angled down somewhat too, so it is
touching the bottom of the vise at the same time as the thicker back
edge. It is very nice for clamping a thin workpiece to the bottom of
the vise while it is worked by the shaper tool. Putting a thin
workpiece on a pair of parallels would risk it bowing and thus having
variable thickness across its width.

Enjoy,
DoN.

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