# 5 Things To Know About Triangle Effect, Pseudo-Roundness, and Lobing

Pseudo-roundness is best defined as any shape not perfectly round, which exhibits constant dimensions when measured in any direction between two parallel planes, ie, with a  2 point micrometer.

1. A non-round (pseudo-round) workpiece can mike as if it were round using only customary two- point, two- plane gage;
2.  A pseudo-round can be detected with a three point gaging system;
3. Given  the number of lobes from using a 90 degree V-block and indicator,  a savvy shop hand can choose the proper included angle V-Block to determine the difference between R and r;
4. Salvage of individual parts is  possible given sufficient stock to remove;
5. Bars exhibiting lobing can be ground to the next incremental size and the lobing eliminated with attention to details of wheels settings, support plate location and geometry, and rotational speed.

In centerless grinding, a geometric condition can be encountered that puzzles most shop hands and often stumps the old pros. That geometry condition is called pseudo-roundness, lobing, or the triangle effect.

Pseudo-rounds have odd numbered crests , which because of the exact opposition of their high to low spots always have a constant  “Miked “ Dimension.  This is explained by the fact that the gaging planes of R and r are tangent to the arcs of the profile, and perpendicular to both radii which belong to the same common center. That is:
Miked Dimension  = R (center to apex) + r (center to low spot)=Constant value

I first encountered this when I had a batch of material that miked fine but didn’t pass the customers roundness test. That material was lobed.
I’ll spare you all the geometry lesson, but here are a half dozen facts that I know from my 30+ years experience in the bar business :

1. Everybody will tell you it can’t be fixed. They would be wrong.  Round gage pins are held to millionths of an inch of roundness, and they didn’t start off life at that level of perfect roundness before grinding
2. Yes, it seems impossible to be able to fix it if you know that the centerless grinder has the high spot hitting the regulating wheel while the pressure from the grinding wheel holds the work down against both the regulating wheel and the blade support, since the diameter obtained in centerless grinding is determined by the distance between the regulating and grinding wheel. But as I mentioned above, the fact that a constant diameter results does not assure perfect cylindricity.
3. In order to assure a more perfect circle, adjustments of the geometrical arrangement of the grinding and regulating wheels, support blade need to be made. In my experience, increasing the speed of rotation also seems to help.
4. While you can regrind to eliminate the lobing, that doesn’t mean that A)it will come in both round and B) within your originally desired tolerance. Unless you have left a great deal of stock on the workpiece, there is usually insufficient material to true up to your hoped for diameter.
5. Use a three point micrometer if roundness / cylindricity is a critical feature on your product. The sketch above shows you how a constant diameter solid workpiece can in fact not be a perfect circle. A two plane gage will not reveal this to you.
6. A standard 90 degree V-Block and indicator will do, but if you want to measure the difference between R and r  (R-r) you will need V-block of the angle given by the following :

2A = 180-(360/N)

where N is the number of high points or lobes. For a three lobe configuration, A becomes 30 degrees, (the half angle) and the V-Block should be 2*A or 60 degrees included angle.

Kennedy and Andrews.

# Three Ideas To Improve Employee Engagement

Thanks to Tim Waters via LinkedIn Goups for the great thought-starter Question!

1) Be sincere and respectful when employees engage you.
2) Determine their PASSION, then allow them more degrees of freedom and discretion in that area.
3) Join them in their world. Have huddles in their space. Be present where the action is.
As managers and executives it’s easy to listen to an employee’s ‘issue’ and think- “Well that’s about the most unimportant thing that I have heard and I’m not going to waste my time on it.” But in the employee’s world that issue or need  just might be the speed bump that keeps them from running the process profitably. Listen and respect what they have to say to you, if they have taken the time to share it with you, it is important to them.
How can we not trust someone with what we know is their passion? Letting someone operate at their highest and best use is win-win-win for all involved. It’s what the folks in the Pentagon refer to as a “Force Multiplier.”
Being a presence on the shop floor means that you have more and better information. And that you are approachable, that you care.
WARNING: If you are in our space and aren’t wearing the Personal Protective Equipment that you make us wear, you will lose our engagement because of the hypocrisy.  Show us that you are one of us by your actions, not just your words.
Employee engagement is powerful. What tips would you like to share to help us better engage with each other at work and in the shop?
Cartoon

# Prices Rise As Manufacturing Recovers

The prices of all raw materials that we track rose as follows over the past year:
Aluminum: Up 23% from July 2009.
Brass: Up 28% from July 2009.

Copper: Up 17% from July 2009.
Nickel: Up 70% from July 2009.
Stainless: Up 37% from July 2009.
Steel, Busheling: Up 51% from July 2009.
China Coke, Up 3% from July 2009.

We track these items as they indicate the direction that we wll be paying for our raw materials in our precision machining shops, Steel, Aluminum, Brass and Stainless barstock. These items are critical to the manufacture of those materials.

# ARTICLE – Corrective vs. Preventive – What IS the Difference?

Published September 2010

By Monte Guitar

# ARTICLE – PMPAs Social Networking—A Tool You Can Use

Published September 2010

By Miles Free III

In just one year, we can document more than 65,000 page views on PMPA’s blog, SpeakingOfPrecision.com.

# Glad We Are Not On This Chart

Manufacturing is unremarkable, when the Government talks about workplace fatalities.
That’s a good thing!

The real good news in the  latest BLS report is that “the number of fatal work injuries in both the private and public sectors declined by 17% in 2009.”
The preliminary total  for 2009 was 4340, down from 5214 fatal workplace injuries in 2008.
While economic factors certainly played a part, we believe that the 17% decrease in fatalities  is more than just a reflection of the 6% decrease in hours worked in 2009 vs 2008.
The four most frequent types of  fatal workplace  injuries  1992-2009, according to the BLS are Highway incidents, Homicides, Falls, and Struck by Object.
For the record, Manufacturing accounted for 304 fatal work injuries,  and a  fatal work injury rate of 2.2 per 100,000 full time equivalent workers hours worked.
Get the BLS news release.