Monday, May 18, 2009

GN 711 Metric Size Self-Adhesive Rulers

Diane here, with another one of our featured products. Today we look at our series GN 711 metric size self-adhesive rulers. These are handy for use in coordination with control knobs when you want to add a means of measurement to your machine, and are one of the items offered in our Section 9, Control Knobs.

Three models of this self-adhesive ruler are available and all are RoHS compliant. The stainless steel version is scale etched and 0.6 mm thick. A white plastic version is highlighted in silver, scale printed, and 0.3 mm thick. The transparent plastic version is scale printed and 0.3 mm thick. Six different figure sequences are available, and the rulers are offered in 100, 200 and 300 mm lengths.

To apply the ruler, the protective strip is removed from the back and the ruler can then be affixed to the specific surface. Meanwhile, we also offer GN 711.1 indicator arrows in all three materials for use with these rulers.

Thursday, May 14, 2009

Put a Toggle Clamp on the Barbie

Diane reporting today, and I'm in a summer mood. That's because this past week a clever do-it-yourselfer who calls himself “Arctikdog” posted to the Weld Talk message board all about his latest project. He built himself two double walled and insulated cabinet smokers, just in time for barbeque season.

I was interested to read his post, not because I can weld, or even because I like brisket. No, I was interested in his use of some of J.W. Winco’s components: our series 431 toggle clamps. I can see why these clamps were an elegant solution to Arctikdog’s design challenge.

As he writes, "The door closure system that I used was a pull down clamp. This gives me a positive closure on the door, and also allows adjustment if your gasket ever gets compressed over time. They were easy to position and weld for me, and I didn’t have to 'invent' something. I got them from J.W. Winco, and they have a large selection of goodies to choose from."

I can see why Arctikdog chose these latch-type horizontal mounting base toggle clamps for his application...I'm sure they serve the purpose perfectly. (By the way, these clamps made of zinc plated sheet metal steel with a red vinyl hand grip, come in three sizes, and are also available in stainless steel.)

Sure, we like it when we can sell a component to an engineer whose project involves a mass-produced machine. But it's also nice when one of our parts just helps a guy have a tastier summer.

Friday, May 8, 2009

Bolt Tensile Strength

Diane here, posing the question: What’s the difference between my world (the world of the marketing person) and the engineer’s world? Answer: I only deal with three fasteners: staples, clips and tape. Engineers deal with a staggering number of fasteners when creating a design, and even after they’ve selected the appropriate fastener—say, a bolt—there are still numerous things to consider. Today we’ll look at just one: tensile strength.

In my very simplified world of fasteners, my options might boil down to this: which kind of clip will have the strength to hold this number of pages together? The regular staple? The ginormous binder clip? Well, that’s not really an accurate analogy to tensile strength, but the point is, an engineer must be much more particular than I, math- and physics-wise, to confirm the bolt of choice can handle the stress of the job.

Stress of this kind is typically measured in psi (pounds per square inch) or MPa (meter-pascals). Those are measures of pressure, so what you’re looking to find out is the amount a pressure your bolt can handle. This is not a simple question, even if you know the strength of the material used for the bolt. Other factors involved are size of the bolt, whether it’s square or round, whether the threads are fine or coarse pitch (fine threads, logically, are stronger), and much more.

Because of these complexities, bolts are given ratings to simplify your choices. SAE or DIN/ISO grades will provide you with an accurate measurement of the stress a particular bolt can handle. Our Web site’s Technical Section includes a handy chart of bolt minimum tensile strength.

But what exactly is meant by tensile strength? A lot of things, and you can break it down more specifically. First, you have Proof Strength, which is used to determine tolerable torque, and is ~95% of Yield Strength. Yield Strength is the point at which your bolt will start to deform. And lastly there is Ultimate Tensile Strength, the point at which your bolt will break.

There are other factors that influence the stress a bolt can handle in a particular application. For one thing, tensile strength ratings assume the nut is fully threaded onto the bolt. Meanwhile, the nut itself needs to be adequate strength and support the shear load. The machine is assumed to be operating under typical room temperature, and the torque on the bolt needs to be greater than the load torque so that tension changes don’t result in fatigue. There may be other factors besides load that effect the bolt. In an application that is subject to vibration, that means additional stress as the load on the bolt repeatedly reverses.

When I think about all this, I have one of those rare moments when I’m glad I’m not an engineer. I can pretty much eyeball whether I need a paperclip or a ginormous binder clip. If you become as baffled as I am about selecting the right bolt, just call our Technical Sales Associates for assistance. Bolts are included in our Section 19, Fasteners and Seals.

Tuesday, May 5, 2009

The Wonders of Bearings

Diane posting, and I just want to share my great admiration for those splendid components known as bearings. Bearings can trace their origins back to the royal halls of ancient Egypt, you know. The logs that were used to roll immense stone blocks for the pyramids were some of the earliest bearings.

I admire bearings because they can be used to outsmart the laws of physics. Well, actually, nothing can outsmart the laws of physics, but smart engineers use some laws to outsmart others. In the case of bearings, we are battling against both friction and gravity, for the purpose of increasing machinery speed and efficiency.

When designing a bearing, the engineer must be at his best. If you’re creating, say, a U-handle, you can err a bit in size and configuration and still have the part perform its function. Not so with bearings: they require precision, or they will do more harm than good to a machine.

You’ll find these durable, high precision components in applications such as computers, VCRs, cars, trains, planes, construction equipment, machine tools, refrigerators and fans.. .wherever there is a requirement for high speed rotation, minimal vibration and noise reduction.

Plain bearings were developed for the automobile industry in the 1920s. Since then, all manner of these useful components have been developed. For example, rod end bearings such as our DIN 648 have an integrated rod that can be used to mount the outer bearing ring. Shown here is the female tapped version; there is also a male version with threaded stem. Various combinations of bearing types can be combined in one housing to manage bearing loads from several directions at once.

For simplicity’s sake, let’s look at how a plain bearing works. Check out our GLRSW Stainless Steel Series K Spherical Plain Bearings for a good example. You have an inner ring and an outer ring, between which may be sandwiched a set of balls, pins or rollers, which are lubricated (the GLRSW uses chrome plated steel ball bearings). One of the rings is fixed, and the other is free to rotate. Some sort of clamping or pressure fit will be used to affix the stationery ring.

The material used for a bearing is key. For its inner ring, our GLRSW uses a special high-strength bronze (CuSn8) with a PTFE liner.

Proper and stable mounting of the bearing are also essential to good performance. Looseness will result in vibration and noise, shock loads relative to speed, and eventually the actual destruction of the bearing and adjacent parts. Meanwhile, seeing as friction always creates heat, wear and tear, lubrication is an essential part of a bearing. Otherwise, once again bearing destruction is the result. The bearings shown on this post have nifty PTFE liners which make them, in fact, self-lubricating and maintenance-free.

You’ll need to bring your engineering expertise “to bear” when calculating the appropriate bearing for your application, taking into account things like static and dynamic load ratings and limiting speed. Fortunately the bearings we offer have all this information included in the dimensional tables, and you can always consult with our Technical Sales Associates for any information you need about our components.

For our selection of bearings, and various components and accessories that work with them, visit our catalog Section 13.