Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Default Protecting Finish in Mill Vise?

Gunner Asch fired this volley in
:

Its not the 60s anymore. In fact..its almost 50 yrs later.


And a lot of the young machinists who learned their trades back then are
still around, Gunner.

It's a pity you don't know more of them.

BTW, I never disagreed that the shops in YOUR AREA don't use the term.
You started by presuming it was a local term, and moved on to building a
case that nobody but esoteric and electrical users ever used it.

Such is not the case. Most of the machinists over age 60 whom I know
still use the term. It's not used as much in drawings for the reasons I
stated, but it's used by the older guys verbally and on quick sketches
all the time.

LLoyd
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"Gunner Asch" wrote in message
...
On Fri, 16 May 2014 19:45:51 -0500, Robert Nichols
wrote:

On 05/16/2014 06:36 AM, Gunner Asch wrote:
All the
prints/plans Ive been involved with use Gauge for wiring size as
does
the California building codes.


You've been working with the small stuff. ;-)


True enough. Biggest distro panel Ive installed was 1800 amps and
the
power company brought that in to the master disconnect.


That beats mine. The biggest I've built for was 1000A for a locomotive
controller tester and 800A for a Telco 48V battery tester. The company
bought welding cable which made our wiring work easier, but when the
DC one was powered up everyone in the factory jumped as the flexible
cables very loudly bitch-slapped the sheet-metal walls from the
magnetic force.

The Telco spec included a 1V drop to simulate something in their
system. I had the bright idea of asking a meter shunt company to quote
the custom resistor, and got a reasonable price. I allocated space
about the size of a hotplate for it. When it arrived I found that P =
E * I was too complicated for them, it was physically sized for 0.1V
at 80A.

This is what they look like:
http://www.amazon.com/AMMETER-SHUNT-.../dp/B005BHPG6K

jsw


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Default Protecting Finish in Mill Vise?

On Saturday, May 17, 2014 8:23:08 AM UTC-4, Lloyd E. Sponenburgh wrote:

BTW, I never disagreed that the shops in YOUR AREA don't use the term.
You started by presuming it was a local term, and moved on to building a
case that nobody but esoteric and electrical users ever used it.


It's a common term around here, and has been at least since I started working in the very early 70s. That the shops Gunner is familiar with don't use industry standard language may well explain why the vast majority of Gunner's business for the past several years has been closing these shops down and steal^H^H^H^H^H helping them dispose of their equipment.
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Default Protecting Finish in Mill Vise?

On Thursday, May 15, 2014 7:19:15 AM UTC-4, Doug White wrote:
I have a small part I need to modify slightly. It is steel, but with a

polished finish, and I don't want to scratch it up. It's difficult to

tell, but it may have a very thin epoxy or some other protective coating.

It's hard (RC ~ 52), and I will be using a sharp carbide end mill and light

cuts. I only need to remove 5 to 10 mils in one area.



I don't want it to slip in the vise, and I'm wondering what's the best way

to hang onto it while protecting the finish. I could use tape, but Scotch

tape is a bit slippery, and the adhesive on masking tape is thick enough

I'm concerened it might creep. I could ue thin cardboard shims, or maybe

even aluminum, but that might mar the finish.



Comments? Recommendations?



Thanks!



Doug White


Before this turned into a pleasant "pick on Gunner" session, you were asking about how to grip your shiny part in a vice. Assuming that it has flat sides to bear against the vice jaws, I might try some contact cement, applied very sparingly, Perhaps to only one surface - not to glue the part to the vice. You could use something like 3M 77 spray mount adhesive. Holds like the Dickens, but is very thin. It'll clean up easily with solvent.

You might also try rolling paper. It's incredibly thin but still pretty tough. You might try gluing that to either the vice jaw or the workpiece.

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Default Protecting Finish in Mill Vise?

On Saturday, May 17, 2014 3:05:32 AM UTC-4, Gunner Asch wrote:



It is kind of like saying " tenths " when referring to 1/10000 of an inch. You won't find mil on mechanical drawings , but you will find it on electronic drawings.



Dan




And electrical drawings are commonly found as part of the

parts/assembly bidding in machine shops? IE..they are used as whats

required to know before machining 10,000 widgets, Mark 1, ver 3.1.8.90

traveler #134767-2L?


Sorry, I was not talking about electrical drawings. I was referring to Electronic drawings. Here is an example:

http://semiconwell.quantumlabs.co/packages/dip300.htm

Dan






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Default Protecting Finish in Mill Vise?

On Sat, 17 May 2014 08:23:50 -0400, "Jim Wilkins"
wrote:

"Gunner Asch" wrote in message
.. .
On Fri, 16 May 2014 19:45:51 -0500, Robert Nichols
wrote:

On 05/16/2014 06:36 AM, Gunner Asch wrote:
All the
prints/plans Ive been involved with use Gauge for wiring size as
does
the California building codes.

You've been working with the small stuff. ;-)


True enough. Biggest distro panel Ive installed was 1800 amps and
the
power company brought that in to the master disconnect.


That beats mine. The biggest I've built for was 1000A for a locomotive
controller tester and 800A for a Telco 48V battery tester. The company
bought welding cable which made our wiring work easier, but when the
DC one was powered up everyone in the factory jumped as the flexible
cables very loudly bitch-slapped the sheet-metal walls from the
magnetic force.

The Telco spec included a 1V drop to simulate something in their
system. I had the bright idea of asking a meter shunt company to quote
the custom resistor, and got a reasonable price. I allocated space
about the size of a hotplate for it. When it arrived I found that P =
E * I was too complicated for them, it was physically sized for 0.1V
at 80A.

This is what they look like:
http://www.amazon.com/AMMETER-SHUNT-.../dp/B005BHPG6K

jsw

Biggest I've messed with, thrown the breaker, did NOT build, was an
experimental electrolytic cell for producing magnesium. 15kv feeds,
fuji rectiformer, either dc or 10Hz (low because of inductive losses).
The cell ran at 200vdc, 18000 amps. Main circuit was "wired" with two
slabs of 2"x24" aluminum, about 20 or so 500mcm jumpers to the
electrodes either end.

Pete Keillor
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Default Protecting Finish in Mill Vise?


When it arrived I found that P =
E * I was too complicated for them, it was physically sized for 0.1V
at 80A.


Heh! A lot of the old RTL and DTL mainframe computers had prodigious
low-voltage supplies, rated in the hundreds of amps, and with multiple
tens of Farads of filtering. I scrapped an SEL-840 from The Cape that had
two four-foot-long 5/8" x 2" solid copper bus-bars for the logic supply
rails in each of the six chassis cabinets.

Invariably in those old computers, you'll find at least one spot on one
bar where someone has accidentally gotten a wrench or driver across the
bar to ground. THAT must be exciting!

LLoyd
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Default Protecting Finish in Mill Vise?

"Pete Keillor" wrote in message
...
On Sat, 17 May 2014 08:23:50 -0400, "Jim Wilkins"
wrote:


Biggest I've messed with, thrown the breaker, did NOT build, was an
experimental electrolytic cell for producing magnesium. 15kv feeds,
fuji rectiformer, either dc or 10Hz (low because of inductive
losses).
The cell ran at 200vdc, 18000 amps. Main circuit was "wired" with
two
slabs of 2"x24" aluminum, about 20 or so 500mcm jumpers to the
electrodes either end.

Pete Keillor


Diesel-electric sub controls are pretty impressive, to the limited
extent they are exposed to view:
http://www.portsmouthnh.com/harbourtrail/albacore.cfm

AFAICT the complex switching isn't fully interlocked and depends on
crew training and -complete- focus to not short out 5000A batteries.

The power job I liked least was testing a 300V electric vehicle
battery that had to be fully energized to find its numerous controller
miswiring problems. The engineer was very skilled at design, less so
at documentation.

-jsw


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Default Protecting Finish in Mill Vise?

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 3.70...

When it arrived I found that P =
E * I was too complicated for them, it was physically sized for
0.1V
at 80A.


Heh! A lot of the old RTL and DTL mainframe computers had
prodigious
low-voltage supplies, rated in the hundreds of amps, and with
multiple
tens of Farads of filtering. I scrapped an SEL-840 from The Cape
that had
two four-foot-long 5/8" x 2" solid copper bus-bars for the logic
supply
rails in each of the six chassis cabinets.

Invariably in those old computers, you'll find at least one spot on
one
bar where someone has accidentally gotten a wrench or driver across
the
bar to ground. THAT must be exciting!

LLoyd


I worked on the development of 1980's computerized semiconductor test
stations with 100A of 5V power, largely for the power-hungry static
memory. Each board had its own 5V linear regulator card and the power
supply card cage was as large as the main one. The design engineer
filtered all that power so well that I could measure microVolts and
picoAmps on the device-under-test without interference from it.

At the last ham flea market I found some old 78000uF 40V computer caps
for the 20A variable power supply I'm building. After slowly and
cautiously reforming them until the leakage fell below 1 mA I checked
them by timing the charge to 20V at 20mA, which takes about a minute
and a half at 1 Second per 1000uF.

That's a lot of charge until you consider than one AA NiCad equals
around 1000 Farads.

-jsw


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Default Protecting Finish in Mill Vise?

Pete Keillor wrote in
:

On Thu, 15 May 2014 11:19:15 GMT, Doug White
wrote:

I have a small part I need to modify slightly. It is steel, but with
a polished finish, and I don't want to scratch it up. It's difficult
to tell, but it may have a very thin epoxy or some other protective
coating. It's hard (RC ~ 52), and I will be using a sharp carbide end
mill and light cuts. I only need to remove 5 to 10 mils in one area.

I don't want it to slip in the vise, and I'm wondering what's the best
way to hang onto it while protecting the finish. I could use tape,
but Scotch tape is a bit slippery, and the adhesive on masking tape is
thick enough I'm concerened it might creep. I could ue thin cardboard
shims, or maybe even aluminum, but that might mar the finish.

Comments? Recommendations?

Thanks!

Doug White


I've heard plain paper to prevent slipping. Might protect the polish
as well. I haven't tried it. Good luck.


I used this approach. It gave me a good grip, and didn't scratch the
part. That's the good news. Either the part is a lot harder than they
claimed, my carbide is softer, or (more likely), my little Clausing mill
isn't rigid enough to make small cuts in hardened material.

I haven't figured out what was flexing or slipping (the end mill in the
collet is another possibility), but the end mil barely scratched the
surface. I finally ended up grinding it down freehand with a Dremel.
It isn't as pretty as I would like, but it worked.

Sorry about the firestorm about "mills". The spare "l" was a typo on my
part. I have worked in the aerospace electronics arena since the early
70's, and was taught machining by a friend's father with a similar
background.

"Mil" is a VERY common term in microwave circuit work, electronics, and
printed circuit design. All the machinists I've talked to (in & out of
that field) in the Boston area recognize it. I also worked at HP in
silicon valley in the early 80's, and no one there had any issues with
it, so I don't think it's regional. It may be that if you do metalwork
for the electronics industry, it's a common term. I can see where large
manufacturing outfits that generally deal with bigger dimensions might
not use it as much. I just find it easier to say & type than "thou".
Verbally, "thou" works well, but when typed, I start wondering when
"thee" is going to join the fray.

Doug White


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"Doug White" wrote in message
...

I used this approach. It gave me a good grip, and didn't scratch
the
part. That's the good news. Either the part is a lot harder than
they
claimed, my carbide is softer, or (more likely), my little Clausing
mill
isn't rigid enough to make small cuts in hardened material.


I just raised the table of my Clausing with a chucked rod bearing down
on a load cell in the vise. Between the two the deflection rate is
almost 0.005" per hundred pounds. The load cell compresses ~0.005" per
thousand Lbs in the milling vise, so most of the flex is in the mill.
The measurements started at a 200 Lb preload to remove zero errors.

Both the knee dial and load cell returned to zero simultaneously,
showing that the collet held the rod without slipping. 1200 Lbs of
clamping force requires a little less than the max vise handle
pressure I apply.

jsw


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On 2014-05-18, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:

When it arrived I found that P =
E * I was too complicated for them, it was physically sized for 0.1V
at 80A.


Heh! A lot of the old RTL and DTL mainframe computers had prodigious
low-voltage supplies, rated in the hundreds of amps, and with multiple
tens of Farads of filtering. I scrapped an SEL-840 from The Cape that had
two four-foot-long 5/8" x 2" solid copper bus-bars for the logic supply
rails in each of the six chassis cabinets.

Invariably in those old computers, you'll find at least one spot on one
bar where someone has accidentally gotten a wrench or driver across the
bar to ground. THAT must be exciting!


Not as exciting as some other things.

A friend once worked for AT&T Long Lines, and on the next floor
up or down was the main exchange (which, as always, was powered by a
bank of really big lead-acid cells, and *trickle* charged at something
like 300A). Two banks of the cells, one on charge while the other
handles the load of the exchange. Most common voltage is 48V, but there
were higher and lower ones as well.

Anyway -- a new employee was given the job of opening each of a
number of *big* knife switches ganged together, greasing the contact
surfaces, and re-closing them.

Well ... he was not a hefty type at all, and was having
difficulty opening some of them, so he got a big pry-bar and started
using it on the insulating crossbar to pry the switch open.

Well ... one let go rather suddenly, and he fell back. The bar
touched one of the high-current blades at one end, and the other the
metal doors of the relay rack row behind him.

It cut through the sheet metal like a soldiering iron through
butter. He spent some time in the hospital from the burns, and then
when he got back was never trusted with anything more dangerous than a
broom -- until he quit.

So -- yes it *can* get more exiting. :-)

Enjoy,
DoN.

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"Lloyd E. Sponenburgh" wrote:

When it arrived I found that P =
E * I was too complicated for them, it was physically sized for 0.1V
at 80A.


Heh! A lot of the old RTL and DTL mainframe computers had prodigious
low-voltage supplies, rated in the hundreds of amps, and with multiple
tens of Farads of filtering. I scrapped an SEL-840 from The Cape that had
two four-foot-long 5/8" x 2" solid copper bus-bars for the logic supply
rails in each of the six chassis cabinets.

Invariably in those old computers, you'll find at least one spot on one
bar where someone has accidentally gotten a wrench or driver across the
bar to ground. THAT must be exciting!



The Vital Industries SqueezeZoom NTSC Video Effects System had a
linear 1000A 5V supply for all the TTL logic & RAM.


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