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Rifles, Reloading, Optics, Equipment
Gunsmithing
Just finished a Lothar Walther barrel
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<blockquote data-quote="Trickymissfit" data-source="post: 1228051" data-attributes="member: 25383"><p>Forty RPM is not too bad for the surface diameter, but the issue is never the RPM. It's the actual surface speed. Valenite make special inserts for 17ph-4 steel. The steel is tough, and will work harden quickly. 17ph-4 likes to be crowded when cutting. Light cuts will get you in trouble sooner than later. BUT if you hate this stuff, then try MAR-10 ( a pre-treat form of 17ph-4 re-arc melt). I've cut a lot of both, and never had a surface finish problem. The steel is odd to ream, and I've found .005/.0075" to be about right preside. I have reamed less than .0035" with little trouble. Single point thread can be a bitch! I tried all sorts of inserts, and suspect a ceramic might be the ticket. </p><p></p><p>You really will separate a good lathe from an also ran with 17ph-4. Really a heavy load on the spindle bearing pack. Tool loads are heavy enough to cause the cross slide to back off, so I recommend clamping the slide down. It's never going to cut well on a Bridgeport, but if you do; then learn how to change the bearings in the quill. Drilling and tapping isn't too bad, unless you get larger than .500". Forget milling pockets, and things like that. Yet a generic K&T knee mill does it effortlessly. </p><p></p><p>gary</p></blockquote><p></p>
[QUOTE="Trickymissfit, post: 1228051, member: 25383"] Forty RPM is not too bad for the surface diameter, but the issue is never the RPM. It's the actual surface speed. Valenite make special inserts for 17ph-4 steel. The steel is tough, and will work harden quickly. 17ph-4 likes to be crowded when cutting. Light cuts will get you in trouble sooner than later. BUT if you hate this stuff, then try MAR-10 ( a pre-treat form of 17ph-4 re-arc melt). I've cut a lot of both, and never had a surface finish problem. The steel is odd to ream, and I've found .005/.0075" to be about right preside. I have reamed less than .0035" with little trouble. Single point thread can be a bitch! I tried all sorts of inserts, and suspect a ceramic might be the ticket. You really will separate a good lathe from an also ran with 17ph-4. Really a heavy load on the spindle bearing pack. Tool loads are heavy enough to cause the cross slide to back off, so I recommend clamping the slide down. It's never going to cut well on a Bridgeport, but if you do; then learn how to change the bearings in the quill. Drilling and tapping isn't too bad, unless you get larger than .500". Forget milling pockets, and things like that. Yet a generic K&T knee mill does it effortlessly. gary [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Gunsmithing
Just finished a Lothar Walther barrel
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