Because forming doesn’t create chips, the heat must go into the tap or the material. During a tapping operation, heat enters the workpiece, tap and chips, he explained. “In addition to its high tensile strength and low ductility, titanium has very low thermal conductivity, meaning that it doesn’t absorb heat very well,” Gennuso said. Brittle materials, such as cast iron, do not flow well and cannot be form tapped. Material with a tensile strength of 160,000 psi and a maximum hardness of 36 HRC is about the limit for form tapping, although form taps for some materials up to 40 HRC are available.Ī range of metals can be form threaded, including aluminum, stainless steel, carbon steel, titanium and nickel. He estimates the ratio of cut taps to form taps used is about 100:1.įorm tapping requires a workpiece material that can actually flow to create the thread profile. But whether they call it form tapping, cold form tapping, thread forming, cold roll forming, roll forming, thread rolling, roll tapping or cold roll tapping, many metalworking professionals are unfamiliar with, according to Peter Gennuso, applications engineering supervisor for OSG Tap & Die Inc., Glendale Heights, Ill.Īl Zaitoon, marketing manager for YG-1 Tool Co., Vernon Hills, Ill., agreed that cut taps are more accepted and better understood. The process of displacing metal instead of cutting it is called many things. I've often wondered how many $billion the US automakers have blown over the last 30 or so years in producing cars with a mish-mash of metric and imperial dimensioned parts and hardware, all of which has added zero to the actual utility or value of the product.When the application is right, form tapping provides real production benefits. Metric stock, yeah, but at prices 2 to 3 times the price of the nearest imperial equivalent. Likewise, thinking the metric stock offerings from companies like Parker Steel would be a solution, would only be workable on parts where material cost has no bearing on final part cost. To imagine we're going to wake up one morning and find all the domestic metal producers now have all metric stock available, or that they've decided to spend a few billion to initiate a changeover, is wishful thinking. Obviously it doesn't make any difference in parts that are machined all over, but there's millions of parts made every day that don't fit that description. If we think we have trouble competing now, just think what it would be like if every part you looked at was fully metric in every dimension, and you had to compete with the rest of the world by using all imperial dimensioned stock while everyone else was starting out with metric stock. Part cost is high when doing things like that, but it was money the company was willing to spend to maintain uniformity, since something we designed and built that worked out well might also be built by the R&D divisions in France or the UK, using our drawings. So, a 12mm shaft with a 4mm keyway was made by turning 1/2" stock to 12, and cutting the keyway with a 1/8" endmill. Other than drills and taps, metric tooling back then (25 yrs ago) was unavailable for the most part on a ready basis, or ridiculously priced if it was available. We didn't do time killing stuff like machining 1/2 x 1 flat bar to 12 x 25 unless it was something for a replacement part in some of our test equipment that hadn't been built in house, but you still find out pretty quickly that the availability of material and cutter sizes is a big factor in the most economical manufacture of parts. When you work in one system for a while, be it imperial or metric, you begin to think in that system, so errors are less likely with uniformity. For simplicity, we would convert any imperial dimensions to metric. If you program some parts in metric, then you really need metric mics, metric thread mics, metric depth mics, metric height gages, jo blocks, etc etc etc, if you're going to avoid confusion at the measurement and inspection end of things.Īt Michelin, our shop was set up all metric to be uniform with the rest of the company worldwide. The shop's measuring equipment is another consideration too.
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