I use a Lapmaster to lap titanium "pucks" flat from 0.4000" (machined
height) to no less than 0.3970". The process which uses these pucks is
optimum when the pucks are 0.3970" - 0.3980". Currently we analyzed
the time to lap these things and have it dialed accordingly, but
sometimes we get something under the limit (0.3970").

Any ideas on devising something that will signal an alert when the
accept thickness "window" as been reached? The fixtures used to hold
the pucks (and provide weight) are cylindrical and freely spin as the
puck is riding on the lapping plate.

Thanks to all responses.
Marcel

wrote in message
...
I use a Lapmaster to lap titanium "pucks" flat from 0.4000" (machined
height) to no less than 0.3970". The process which uses these pucks is
optimum when the pucks are 0.3970" - 0.3980". Currently we analyzed
the time to lap these things and have it dialed accordingly, but
sometimes we get something under the limit (0.3970").

Any ideas on devising something that will signal an alert when the
accept thickness "window" as been reached? The fixtures used to hold
the pucks (and provide weight) are cylindrical and freely spin as the
puck is riding on the lapping plate.

Thanks to all responses.
Marcel

Lapmaster sells two fixtures that essentially do just that. They prevent the
workpiece from becoming too thin.
http://www.lapmaster.com/accessories...g/default.html

In the first, the back of the workpiece is mounted to a plate. The outside
of the plate has three diamond-tipped adjustable screws that determine the
stop distance. The second has an outer metal ring that replaces one of the 3
conditioning rings. Inside is a vacuum chuck on a spring loaded piston with
an end-stop setting. I am not sure what they cost new, I got mine (the
second type) used. They would not be too hard to duplicate if you were
inclined. Both can accomodate indicators to set the thickness. In theory
they could monitor progress too, but I do not think I would want to keep
indicators there with abrasive dripping around.

I am not sure, but the diamond-tipped screw fixture might not work so well
on a lap with grooves. Pressure is momentarily relieved on one screw at a
time as it passes over the groove.

On Fri, 9 Oct 2009 11:38:22 -0700 (PDT), "
wrote:

I use a Lapmaster to lap titanium "pucks" flat from 0.4000" (machined
height) to no less than 0.3970". The process which uses these pucks is
optimum when the pucks are 0.3970" - 0.3980". Currently we analyzed
the time to lap these things and have it dialed accordingly, but
sometimes we get something under the limit (0.3970").


Can they not be surface ground?

You would need a fixture to hold them, but a 0.001" tolerance band is hardly
precision. It should be very quick work.


Mark Rand
RTFM

Mark Rand wrote:
On Fri, 9 Oct 2009 11:38:22 -0700 (PDT), "
wrote:

I use a Lapmaster to lap titanium "pucks" flat from 0.4000" (machined
height) to no less than 0.3970". The process which uses these pucks
is optimum when the pucks are 0.3970" - 0.3980". Currently we
analyzed the time to lap these things and have it dialed
accordingly, but sometimes we get something under the limit
(0.3970").


Can they not be surface ground?

You would need a fixture to hold them, but a 0.001" tolerance band is
hardly precision. It should be very quick work.

Not flat enough Mark.


--
John R. Carroll

On Fri, 9 Oct 2009 11:38:22 -0700 (PDT), "
wrote:

I use a Lapmaster to lap titanium "pucks" flat from 0.4000" (machined
height) to no less than 0.3970". The process which uses these pucks is
optimum when the pucks are 0.3970" - 0.3980". Currently we analyzed
the time to lap these things and have it dialed accordingly, but
sometimes we get something under the limit (0.3970").

Any ideas on devising something that will signal an alert when the
accept thickness "window" as been reached? The fixtures used to hold
the pucks (and provide weight) are cylindrical and freely spin as the
puck is riding on the lapping plate.

Thanks to all responses.
Marcel

Depending on the surfaces and edges that are accessible, an optical
sensor could work.

This type of sensor will detect the position of an edge quite
accurately.
http://www.bannerengineering.com/en-...Dot-PD-Series/

Some of the measurement sensors on this page may be appropriate.
http://www.bannerengineering.com/en-.../Laser-Sensors

Omron and Keyence also make this sort of thing.

--
Ned Simmons