On Tue, 09 May 2006 17:31:34 -0700, Eric R Snow
wrote:

So, after looking at the SP 125 Plus welder wiring diagram and
corresponding with folks here I have come up with most of the parts
necessary to build my own timing option. Using a kit from Velleman
(PMK 111) will provide the timing. It has two adjustments: Pause and
Pulse. The kit comes with pots that allow for a .5 to 5 second Pulse
and a .5 to 60 second Pause. The Pause time pot is a 10 megohm and the
Pulse is a 50k ohm device. Since the Pause pot has so much more
resistance it is very hard to finely adjust. I will be replacing it
with a 50k pot. In fact, I am going to replace both pots because the
ones in the kit are trimmer pots and I want the adjustment knobs on
the front of the welder. Whenever the the timer is powered up it
pulses first so I'm going to wire the timer power to the trigger
switch. The timer power comes from a 12 volt 200 ma wall wart. By
using a double pole/double throw switch the timer can be totally
isolated from the welder even though the trigger in the handle will be
the on switch for it. So the welder will have a switch on the front
that can be set to either CONTINUOUS or STITCH. Manually stitch
welding a few minutes ago I discovered that the Pause time should be
independent of the Pulse time. What I can't tell easily is how long
either should be and what would be the minimum and maximum times. The
timer should be made such that it has enough range without having too
much so that it is easiest to adjust. I think the Spot timer is for
plug welding. By Plug welding I mean that one piece of metal has a
hole in it. This piece of metal is clamped onto another piece of metal
such that the hole is blocked at one end. Then the hole is filled by
welding. I hope I'm using the correct nomenclature. Please feel free
to correct me. Since the Velleman timer uses higher resistance to
increase the Pause time, and since it resets every time the power is
removed, a switch which disconnects the pause pot will allow it to
weld for a set time and then turn off until the power is toggled.
Anyway, here are the questions:
1) What is the minimum Pulse time.
2) What is the maximum Pulse time.
3) What is the minimum Pause time.
4) What is the minimum Pause time.
5) What exactly is the Spot timer meant to be used for when the timer
is the one provided by Lincoln. I called Central Welding, where I buy
most of my welding supplies, and they hadn't even heard of the
Spot/Stitch timer kit for the SP125, or the SP135. So they couldn't
tell me what the Spot setting was for. And Lincoln doesn't sell it
anymore. There must be someone there who knows the answer but that
someone wasn't at the Lynnwood store today.

If anybody wants me to I can post a parts list and wiring diagram when
I'm done and it's working correctly.

Thanks for reading and responding,
Eric R Snow

Another name for "plug" or "spot" welding is rosette welding.

Ya don't need any electronic stuff to do this, said the congenital
EE. The timer in your trigger finger works just fine.

I've done a fair amount of both stitch and rosette welding with an
SP125+. For body work (rust work, not competition-class
restoration) I used a pneumatic punch 'n flange tool (50 bux HF) that
flanges one part and punches the other so they assemble to present a
flat surface. Stick the repair panel in place with kleeco's or
sheetmetal screws, fill the holes with MIG weld. It only takes a
couple of seconds. With a bit of practice you don't even need a mask:
just aim the gun, shut your eyes and fill the hole. One hole per
inch, takes about 5 minutes to stick in a rear fender skirt. Another
two minutes with the angle grinder to grind the weld flat, then about
a plum-sized gob of Bondo to fill the crease and it's ready for
sanding and primer. It's only a 10-year repair, but rust work isn't
often done with expectation of another decade of service.

Ya do need a mask to stitch, but the trigger finger works just fine to
accomplish the timing. A key part of the art and skill of welding
is in managing the puddle regardless of what process makes the puddle.
Gadgets work well in automated setups, but they need to be set up
right for a particular job. OK in production, but operator skill
works better in one-off or to make just a few welds in a given sit --
and the same operator skill would be required to get the production
setup working right.

Gadgets don't make good welds unless set up by a weldor, and weldors
don't need gadgets to make a few good welds.

I make no pretence of being a journeyman-class weldor, I'm an EE and
research puke by trade and training, but I weld well enough to do
what I wanna do most days.