Re: [CAD_CAM_EDM_DRO] Re: Thread milling

R Rogers <rogersmach@...> wrote:



////I was taught and its common knowledge within the ranks that there is no such thing as a size range on collets. Collets are ground to specific diameter. Using them on any other diameter will disfigure them and is referred to as "the cardinal sin of collets". Installing a larger or smaller than intended diameter in their bore will result in 3 points of contact within the spindle and risk triangulating the taper. To hold a tap shank which none of them are nominal, simply make an adapter in the lathe with a nominal O.D and setscrew to secure. There are some commercially available with collapsible collets like tapmatic uses if memory serves me correct.

Ron


There are dozens of various collet designs, some of which have a set size, some have an acceptable grip range. Many old school machinists say to never use collets with taps or end mills, yet I work in an aerospace shop where we use collets with end mills and taps 16hrs a day, six days a week. They hold tight tolerances (+/- .0002) and thread mill almost daily. For many threads, odd fine internal threads on large diameters, thread milling is the feasable way to get it done. Have any of you seen a 4"-32tpi tap laying around, and if you have, what do you chuck it up in?

Rob.





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