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Mach4 General Discussion / Re: Mach 4 Thread Milling
« Last post by joeaverage on July 11, 2025, 08:35:25 PM »Hi,
I work with automotive instruments and on occasion require very small screws. The smallest I done successfully is a 13BA thread, which has a major diameter of 1.2mm
and a thread pitch of 0.25mm or 102 TPI!!
I was lucky and got off EBay five new Kyocera 98M11-0250LFA1 threadmills for $15USD. They are 1.1mm dimeter with a 0.25mm clearance, two flute. I could and did the external
thread of the screws above at 1.2mm major diameter. I made them in 316 stainless with a 3mm thread length. They were for a classic Jaguar tachometer from the fifties.
The smallest I could do an internal thread with these ultra tiny endmills is 1.4mm, but still pretty damned small!
The trick is to use a large number of very shallow passes otherwise the tool flexure beats you when it does not break the tool outright. That in turn requires that your machine can
do circular interpolation with micron type repeatable circularity. My machine made these screws and measuring with a micrometer found a ovality of about 0.02mm, which I thought was
pretty fair.
Craig
I work with automotive instruments and on occasion require very small screws. The smallest I done successfully is a 13BA thread, which has a major diameter of 1.2mm
and a thread pitch of 0.25mm or 102 TPI!!
I was lucky and got off EBay five new Kyocera 98M11-0250LFA1 threadmills for $15USD. They are 1.1mm dimeter with a 0.25mm clearance, two flute. I could and did the external
thread of the screws above at 1.2mm major diameter. I made them in 316 stainless with a 3mm thread length. They were for a classic Jaguar tachometer from the fifties.
The smallest I could do an internal thread with these ultra tiny endmills is 1.4mm, but still pretty damned small!
The trick is to use a large number of very shallow passes otherwise the tool flexure beats you when it does not break the tool outright. That in turn requires that your machine can
do circular interpolation with micron type repeatable circularity. My machine made these screws and measuring with a micrometer found a ovality of about 0.02mm, which I thought was
pretty fair.
Craig