August 19, 2014
If a tool gets too hot to hold while grinding, you have already ruined it. You knew that, right?
A bit of circa 1965 “Knowledge Retention” from the archives of Lester Detterbeck Enterprises Ltd.
By the time the heat gets to your hands and is too hot to hold, you have already lost the temper on the edge being ground. If you then put it in water to cool it down, depending on the material grade, the water quench is likely to help form untempered martensite, a very brittle microstructure.
The tool will lose properties, and fail in very short order. Often with catastrophic consequences.
The point of grinding is to take very small amounts of removal by abrasion, not to create lots of heat by hogging the material off.
Heat treated tools are actually very sophisticated system involving the interaction of material chemistry, microstructure, mechanical properties (including hardness) and design.
Out of control grinding practices can destroy this system with a single temperature excursion above the tool’s last tempering temperature and formation of untempered martensite by water quenching.
Thanks to John Detterbeck at Lester Detterbeck Enterprises Ltd for sharing the above cartoon and confirming the failure mode.
August 14, 2014
Our post on No Gloves When Working on Grinders has prompted a number of responses.
Here are some additional reasons why you should not even need gloves when working on grinders and grinding machines.
Issue: “There are sharp edges or burrs that will cut me if I hold the part. The grinding will be to remove the burrs.”
Response: Use a file to knock down the burrs so that you can safely hold the part for grinding. Or use leather finger cots to grip the part for grinding.
We permitted these for use on belt grinders for holding small parts.
Issue: “The part gets too hot to hold.”
Response: Then you are grinding wrong. Here is a list of some of the things that can go wrong by letting the heat of grinding get out of control:
- Remove the temper from Steel. Especially on tools, loss of temper means loss of tool hardness and edge life. A drop from Rc63 to about Rc48 for a couple of tenths (0.0002-0.0005) can contribute to side wear and edge failure.
- Crazing or checking on Carbide can be caused by burning during grinding.
- Work Hardening. Overly shiny surfaces are usually the clue that work hardening has occurred.
- Creation of untempered martensite.
Untempered martensite can be formed in high carbon and alloy steels by getting high surface temperature from grinding- red heat- then quenching in water.
- Untempered martensite is very brittle and reduces toughness.
- Keeping the work cool continuously while grinding is an important aspect of preventing damage to work, the wheel, and injury from occurring to the worker. Hogging off material and infrequently quenching is a great way to destroy a tool by grinding
- Water needs to be plentiful to absorb the heat from grinding, and frequently used to reduce heat buildup in the work.
- Take multiple small passes and cool in between in a large bath of water while grinding to minimize heat build up.
Of course, wearing the required PPE, making sure the grinding wheel is properly dressed, all guards are in place and properly adjusted are also key to safe grinding in our shops.
Bottom line: If the work is too hot for your fingers, it may be approaching the danger zone regarding loss of mechanical properties and function in end use.
August 13, 2014
If there is a worse combination than grinders and gloves, I don’t know what it is, except perhaps for gloves and a drill.
We posted a really cool video on our career blog about making a light saber sword here. But we were shocked to see the guys in the video wearing heavy leather gloves while working with grinders.
Never wear gloves with grinders. Or operate grinders with guards removed.
By “grinders,” we mean abrasive belt grinders, bench grinders, pedestal grinders, surface grinders, and also abrasive cutoff machines.
Sanders, polishers, and buffers that involve rotating wheels or transversing motion are also included in this classification for the purposes of hazard analysis.
Here are 6 reasons to not wear/not permit the wearing of gloves while working with Grinders or Grinding Machines
- General duty of employer to provide a workplace free of recognized hazards
- Gloves can catch on rotating equipment and pull operators hands into the equipment
- Rotation of grinding wheels is at high RPM’s
- Operator cannot get hand out of glove when it catches
- Equipment horsepower and machine material properties exceed those of the operators flesh
We did a quick calculation and a 12″ grinding wheel and 3600 rpm and arrived at a speed on the periphery of 120 miles per hour.
No time to react.
More info on preventing amputations from OSHA
August 6, 2014
Baby-boomer demographics continue to shape industry and employment.
According to Peter Coy with Bloomberg,”…older workers’ share of the workforce briefly dipped below 12 percent in the early 1990s but has risen steeply ever since. The population bulge of the baby boom is the big factor, of course. The peak birth year of the baby boom was 1957. Those peak boomers, no longer babies, reached age 55 in 2012—the first year older workers’ share of employment hit 21 percent.”
As managers we need to
- Understand that this cadre of talent has (is!) our tribal knowledge;
- Find ways to help them share and preserve this knowledge;
- Find new talent to learn from them;
One more item to think about- many baby-boomers will not be taking traditional retirements for various reasons-
- They enjoy their jobs,
- They are still too fit to “retire,”
- They can’t afford to,
- They decide to keep working to assure that they won’t run out of money when they finally do retire.
We will need to make some accommodations in our shops to keep them safe for older workers.
Bloomberg Story and Graph
August 5, 2014
We remain optimistic for the outlook for manufacturing for the next three months based on the latest ISM PMI and PMPA Business Trends Indicators.
The latest Institute for Supply Management PMI (Purchasing Managers Index) increased 1.8 points to 57.1 for July. The July value was the 14th consecutive month of manufacturing expansion; the 62nd consecutive month of expansion in the broad economy, and the highest value since April 2011.
Using the July reading, this value indicates an expansion in manufacturing, but if annualized, is also consistent with a 4.6% rate of increase of real GDP according to ISM.
If the January through July data is annualized, the corresponding GDP growth would be about 3.7%.
PMPA’s June 2014 Business Trends Report showed a seasonal decline in shipments for the month of June, but the average for the year to date is 123, up 6 points (~5.1%) from last year’s 117 year end average.
PMPA’s Business Trends Indicator for Sales/ Shipments sentiment was strongly positive in June, with ~88% of respondents expecting sales to remain the same or increase over the next three months. and 89% of respondents expecting lead times to increase or remain the same for the next three months.
July ISM PMI GRAPH courtesy St Louis Fed
July 2014 ISM PMI Report for Manufacturing
July 31, 2014
Openings for skilled workers as older workers retire are seen as the biggest challenge facing manufacturers in this economic policy report from Connexus Indiana and CBER Muncie.
When these workers leave, we will need people with skills to replace them. What’s your plan?
“The most significant challenge facing Indiana’s manufacturing firms is the very high percentage of workers nearing retirement age (more than one in six workers over the next 10 years).”-CBER Manufacturing and Labor Market Frictions, Connexus Indiana, CBER Muncie Indiana.
“Since 1998, the share of manufacturing workers aged 55 to 64 has grown from 9.8 percent to 16.8 percent, which is a 71 percent increase in share in less than a generation’s time. This rapid growth is due to the movement of the baby boom generation into near-retirement and retirement years.
Although this transition is occurring across the economy, it is larger and growing more rapidly in manufacturing.” CBER Report
And it is not just in Indiana. This trend can be seen nationwide.
Skilled workforce. Our greatest challenge.
What is your plan?