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. We have tried anything in between S3555 and S300, thinking that might help.The shop's measuring equipment is another consideration too. The recommended RPM for a Balax M2 is S3555. ![]() The speeds and feeds in this code are generic. So it is not just that individual mill that can't tap. Additionally, most of the parts have M3 STI holes in them that we cut tap. These parts run in multiple locations throughout the shop. Some have may six M3 holes, some may have fifty eight M2 holes and eighteen M2.5 holes. This is a package of parts that gets assembled by our customer. So the breakage is likely related to the tap diameter. As the taps increase in size, the tap breakage is less often. Mostly we cut tap or thread mill on parts for other customers. M2, M2.5, and M3 are the only 3 form taps we are struggling with for this customer. Thanks everyone! A lot of great stuff here! Any help or advise would be appreciated, Thanks Maybe there's something I just don't know about. Maybe there's something simple that I just haven't thought of. And some other off-brand, thick as molasses, tapping compound. We've tried Tap Magic for aluminum - comes in a red/white spray can and is supposed to be cinnamon scented. ![]() I'm not a fan of the coolant, but there's no getting away from it. The coolant we use is a local brand I think, AFT (Advanced Fluid Technology) 619M2. We have purchased an Emuge Softsynchro high performance tap holder. Probably another 5 or 6 brands that I can't remember. Using appropriate size solid carbide drills - 118° drill tipįormula for determining appropriate drill size for 75% metric threads: Tap O.D. Spotting with a 1/4" x 120° NC spot drill Tapping retract is set at 4, but we've tried both slower and faster Torque specs for the assembly screws are mandated by our customer's customer.Ģ015 Haas VF-4SS. Form taps and thread percentage is mandated by our customer. Trying a drill the next size up drops the thread percentage causing ripped threads at assembly. 5 holes in aluminum with 75% thread percentage. ![]() Long time Forum reader, first time poster.
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