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Acme vs Trapezoidal Threads

Acme vs. Trapezoidal Threads – What’s the Difference?

Acme threads appeared sometime in the late 1800’s, as an improvement on the square thread form. Square threads were the first choice for motion transfer and heavy loads. But, square threads were difficult to produce with available cutter technology. Although the square form was relatively efficient for the purposes required, it was inherently weak at the base of the thread due to the sharp 90-degree angle of the flank. Modifying the included-angle to 29-degrees widened the base of the thread making it stronger. Over time, standards in Acme diameters and pitches were established, all with Imperial Inches in diameter and Threads-per-Inch units of description.

 In Europe, similar standards followed using metric units of measure, and the slightly different included flank angle of 30-degrees. Metric standard trapezoidal threads are covered under DIN103. Diameter and pitch descriptions are in metric units of measure.

                            Acme Threads

Acme Threads

                              Trapezoidal Threads

Trapezoidal Threads

Both thread forms serve the purpose of producing linear motion when rotated, usually under heavy load. Some common uses include; lead screws for linear actuation on CNC machinery, table lifts, clamps and vises, valve stems, medical diagnostic device drives, trailer jacks and jack-stands. The American Acme form has an included flank angle of 29-degrees. The metric Trapezoidal thread is at 30-degrees. The uses for these thread forms are essentially the same. In fact, taking manufacturing tolerances allowed into consideration, they may be interchangeable when TPI (threads-per-inch) is the same.

 The demands placed on the tools that produce these threads are higher due to the amount of material being removed, per tooth, in the process. Controlling “chip-load” is critical. In order to design a tap for these threads, North American Tool requires specific detail on the application. Information on the material being tapped, tapping depth, condition of the hole (through or blind), and Class of Fit, is essential to engineer the proper tap. General purpose taps are available, but are definitely not suitable for every application.

So what’s the difference between Acme and Trapezoidal? Not much physically. Although the American Acme thread-form is used and accepted throughout the world, the choice of which to use is usually dictated by the origin and user destination of the finished part. To that manufacturer, the difference is everything!

 

Tags: AcmeThreadsTrapezoidal

North American Tool is a tier 1 manufacturer of special taps and dies with many taps having a 24hr lead time. Call us today for a quote!!

Grinding Wheel Productivity

We posed the following question on social media last week and have John Thompson of Pferd to thank for a fantastic answer!!

“4-1/2, 5″, or 6″ what is your favorite size grinding and/or cutting wheel? Jumping from 4-1/2 to 5″ is an easy way to get more bang for your buck with your existing grinder but will a 6″ wheel justify the cost of a new grinder?”

We asked John Thompson of Pferd USA to use his technical expertise and many years of experience running abrasives to answer this questions for us. Though John works for Pferd, this information is applicable across all brands and industries. We really appreciate John spending the time to put this information together for us!! Without further delay, here is his answer to our question…

Improving Productivity and Performance in Grinding and Cutting

Being competitive in any fabrication process requires a continuing process to improve productivity and reduce labor costs. You may have found the right formula for bending, shearing, welding and material handling to reduce labor and improve process flow to keep the bids low and the work coming in. As these improvements can be very expensive a lot of thought goes into the type of product and overall cost. Long term savings are often the result from a logical investment in the math required to determine the return on any investment and the overall payback time from lower labor and material costs. This is how a fabricator stay competitive and keeps the team invested in the company growth.

But some of this savings can be lost when the productivity of grinding or cutting for preparing material for welding or cosmetically finishing material for paint or powder coating is left up to antiquated equipment or ideas about the difference between Price and Cost when it comes to abrasives. This is NOT a discussion about different grades of Bonded or coated abrasive product. That subject has been beat to death by every abrasive supplier with new grain or new special formulas that promise faster grinding and longer life. THIS IS a discussion with a simple math lesson on improving productivity and reducing overall costs based on the extra life of a slightly larger diameter product.

This is a simple look at the increased performance and reduced costs for applying simple math to improve the volume of material going through the fabrication process and shipped to the customer as a finished product i.e. “Payday”.

There are two false ideas that must be addressed.

One: that the shop worker doesn’t care about getting their part of the job done on time and with minimum effort on their part. They do care as they need that job and the pay it offers to live. The faster they can complete a task with minimal effort means they can move on to the next task and complete the job on time so everyone can be paid and secure that the company is competitive.

Two: Constantly applying pressure to a supplier of consumable product such as abrasives, weld wire, band saw blades and other consumables will make the company competitive even if they do not change the process of grinding prep or finishing procedures. This false idea that high consumption of cheap or small diameter product based on price will offset lost productivity and allow a company to be more competitive. It is the Labor to use the abrasive NOT the Price of the abrasive.

  So how can we improve operator productivity and reduce labor costs to keep some of the lost money due to old process issues? Look at the interaction of RPM, Diameter and power tool Weight to work Faster NOT Harder.

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