# Reasons to be careful

Page 3 of 4
• posted on February 28, 2016, 7:03 pm
On 02/28/2016 9:41 AM, dpb wrote: ....

Woops, dropped back into psi, not "Hg...
... barometric pressure is ... about 30" Hg, _not_ 0!!!
--

<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on February 28, 2016, 8:02 pm

And not a vacuum either. ;)
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on February 28, 2016, 7:38 pm

is not there. However,...
LOL, There is a negative board foot and no doubt you have seen it many times. Ever pick up a piece of wood to use only to find out it is a 1/2 " too short, or 6" to short?
Barometric pressure is relative, and a far different usage. It is also useful for altitude measurement.
Then here you now go into Temperature? There are a couple scales alright, degF and degC then there is a scale from absolute 0 wherein there is no molecular movement. But what is the point?
1 atmosphere equals 29.92 " hg positive pressure, not a vacuum.
.000024583 atmosphere equals .010 "hg positive pressure, not a vacuum.
As I have been saying, a vacuum is relative. There is in reality no such thing as less than O PSI absolute.

You can never achieve 30" HG barometric pressure unless you use a cheap gauge 29.92 is the best you can do, and it is not a vacuum.
but it was nice of you to explain why and how a vacuum is relative in your next to last paragraph. So can we consider this subtopic closed?
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on February 28, 2016, 9:27 pm
On 02/28/2016 1:38 PM, OFWW wrote: ...

Precisely, what I've been saying all along. Thank you.
--

<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on February 28, 2016, 11:25 pm

As I under stood you to say it was a vacuum. You said the formula, for sure, but that 29.92" was positive pressure.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on February 27, 2016, 3:10 pm

No, you've got absolute and relative pressure measurements mixed together. 0" Hg (absolute) is a vacuum. 0" Hg relative to 1ATM is, well, 1ATM.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on February 27, 2016, 7:19 pm

No, 0 psi is absolute. Vacuum is always relevant.
Atmosphere
Unit
The standard atmosphere (symbol: atm) is a unit of pressure defined as 101325 Pa (1.01325 bar). It is sometimes used as a reference or standard pressure. In 1954 the 10th Conférence Générale des Poids et Mesures (CGPM) adopted standard atmosphere for general use and affirmed its definition of being precisely equal to 1,013,250 dynes per square centimetre (101325 Pa).
Therefore 1 atm is equal to 14.69595 psi
There is no such thing as a vacuum, per se' it is always a relative measurement.
At 250,000 feet above sea level it is 0 PSI Absolute. Imperial measurements.
Using a moisture indicator on any wood, it would register "0"
Microns is also used in measurement of a vacuum to tell when certain physical properties are no longer there.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on February 28, 2016, 1:23 am

No, it is not. Your tire gauge will read 0PSI when the absolute pressure is 14PSI. The tire gauge is a *relative* measurement but this is understood by its context.

All irrelevant.

...either relative or absolute.

Nonsense.

OK, but the sky is blue.

What *are* you jabbering about now?
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on February 28, 2016, 8:01 am

Smiling, http://www.engineeringtoolbox.com/standard-atmosphere-d_604.html
The tire pressure gauge reads 0 PSIg "g" is for gauge pressure. Not absolute.
Look at a low side refer gauge sometime. "0" on it is the divide between PSIg and hg

Well I was making a pitiful comment about wood to try and bring this around, back to wood, then I unfortunately through in the comment about microns used to gauge vacuum below a certain point for the purposes of ridding systems of H20 and other properties. Which I knew you would be clueless about. That was stupid of me and I am sorry.
So, please forgive me, and lets get back to WW'ing or should we be going to some gym and duke it out? LOL
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on February 25, 2016, 3:48 am
wrote:

What you said brought back memories, old ones. Like the vacuum gauge in inches of water column. Trying to use it for economy runs to save gas for a race. Watching that sucker jump around made it all pointless. In order to set injectors, or multiple carbs you had to use a manometer to sync them up. On motorcycles and their smaller engines and High rpms it was cortical, if a valve failed to seat or your fuel system flooded out, it was a definite boom time in the intake manifold. I've had more than one engine go up in flames, especially with stromberg 97's. ;)

that's ok, I meant it as a joke, "in my imagination" just letting it go wild to conjure up something. I believe that was first in response to Mikes comment on using imagination. Guess it didn't come across that way, sorry.

As long as he doesn't ask for money too. :)
I finally picked up an 1 1/2" hose for some of my small stuff, then realized I should cut that into smaller pieces and buy a few more fittings for it. I mistakenly had my hand holding the 2 1/2 hose when I hit to button to start the vac and boy did that hurt. that flex hose slammed closed in a hurry, pinching my skin and gave me instant blood blisters with that small hose hooked up. WOWEE! Then the small hose started whistling and stuff. I'm not sure how long that hose is, but it is so restrictive that I want to shorten it some to increase the air flow and cut down on the whistling at the same time. I'm thinking I am going to Rockler for those. they seem much better prepared with the fittings and hose then woodcraft where I picked up the hose on a whim. Where I am at there is only a woodcraft, and it is an independent store. Rockler is about 50-60 miles away.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on February 24, 2016, 1:45 pm
On 2/24/2016 12:49 AM, -MIKE- wrote:

stuck by lightning, but they are. There is a very low probability of people being struck by a meteorite but there is a recent story in the news about that happening.
There is a very low probability of a person being killed by a falling tree, but there are people who are cutting down their trees every day so they do not fall on them and kill them.
Low probability means exactly that, it can happen but infrequently.
Remember Murphy's law. Why tempt Murphy.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on February 24, 2016, 5:52 pm
On 2/24/16 7:45 AM, Keith Nuttle wrote:

The point is, there's a low probability in everything. If you want to worry about everything that is technically "possible" happening to you, go for it. Enjoy that life.
That's the kind of severely flawed logic that inhabits the brains of people who will never fly on an airplane but have no problem driving on the interstate, even though the chances of injury or death are almost unbelievably, exponentially higher when driving a car.
If people want to live in fear of everything that "might" or "could" happen to them, well... let's just say they make lots of pills for that condition. :-)
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on February 24, 2016, 5:58 pm
On 2/24/2016 11:52 AM, -MIKE- wrote:

You are more likely to cut yourself on a TS if you don't own a SS. ;~)
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on February 24, 2016, 6:34 pm
On 2/24/2016 12:52 PM, -MIKE- wrote:

accident, and taking steps to avoid a potential for an accident. You do not spend a lot of money installing things to prevent an 1 in a million probability of accident. However you don't ignore the possibility that it can happen. Sort of like walk under a ladder, the probability of something falling off of the ladder is remote, it is just good practice not to get in the habit of doing it.
There are other places where this applies. You buy home owners insurance even though there is a small probability that your house will be damaged or broken into. You make sure there are not children in the area where you are mowing even thought the probability you will hit something that will fly our and hit a child. Most people modify there behavior or make purchases based on low probability events.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on February 24, 2016, 7:06 pm
On 2/24/2016 12:34 PM, Keith Nuttle wrote:

And yet there are really no reasonable steps to take to keep saw dust from exploding because of static electricity in your DC, which is what this thread is about.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on February 24, 2016, 7:28 pm
On 2/24/16 1:06 PM, Leon wrote:

I ground my dust collector duct-work to fend off the mind control rays from outer-space. It also helps disperse those pesky chemtrails the gummint is using to make me more subservient.
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on February 24, 2016, 8:02 pm
On 2/24/2016 1:28 PM, -MIKE- wrote:

shop that make sparks and on a continuous basis. Like "any" electric tool or machine that has a universal motor. Yes damn near any hand held power tool. ;~)
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on February 24, 2016, 8:26 pm
On 2/24/2016 3:02 PM, Leon wrote:

and ALL of the problems that it may cause. You have installed a dust collector so the dust is controlled and diverted to safe areas.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on February 25, 2016, 12:54 am
On 2/24/2016 2:26 PM, Keith Nuttle wrote:

No I have not worried about excessive dust in the shop. I once buried my choc Lab under a pile on the out feed side of the planer. She was not worried either. ;~)
I got a dust collector because I got sick and tired of cleaning up and tracking dust into the house. I absolutely did not worry about any dangers other than breathing in that stuff. And again FWIW I was commenting about a spark creating an explosion not excessive dust or any other problems that it caused other than a mess.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on February 25, 2016, 1:37 am
On Wed, 24 Feb 2016 15:26:31 -0500, Keith Nuttle

Right. A safe area is anywhere that's not in my lungs. Other than that, a DC is a convenience.