Hello
I bought a PTG two peace bolt for Remington 600 with .062 firing pin hole. Can I just turn my factor pin down or do I need to pick up a new firing pin. Or would a new one with new spring be best.
A Leaphart
I've turned down hundreds, if not thousands of striker pins to fit a bushed hole or a new bolt face fitted to a smaller diameter. It does not take a grinder. All you need is the right tool.
Machine tooling 101 as it relates to this:
Grab most any insert graded for turning ferrous materials of any sort. What do you have? By and large edge prep is NOT sharp. There's a corner radius out on the nose of the tool and the actual cutting surface by and large looks and feels dull.
Why is that? Its because these tools do not "cut" the way a knife slices your finger. They rely on tool pressure. That pressure is exerted by the rigid casting, way surfaces, and ball screws in the machine. The pressure creates friction and that transforms the material into a plastic-like state. It becomes semi-molten and it tears from the substrate. The bulk of the heat is transferred to the chip coming off the part. It's how the chips look amber/blue yet the part itself is maybe only lukewarm.
Now, nonferrous materials such as brass, aluminum, etc. Machine these and watch the spindle load meter. You can lean into them exponentially more aggressively provided you have two things: Horsepower and flood coolant (aluminum especially because it likes to weld itself to the cutting tool) When you buy insert specifically for these kinds of material the edge prep is remarkably sharper. They'll slice the snot out of you if you're not careful.
These types of tools require far, far less tool pressure because they are actually shearing material off the parent rather than ripping through it like a snowplow. Chips come off cooler and the surface finish is equally bright.
How this all works for you in this instance:
Know first, you're going to burn through inserts a little faster, but who cares? It's a striker pin. I do around 100 of these a month and our burn rate is somewhere between 3 and 5 inserts a month. The trick your pulling with this is reducing the tool pressure exerted against that small diameter sticking out several times its own diameter (unsupported) from the face of your chuck. That is the trick to getting both an accurate cut, and the appropriate surface finish on the part. Doing this makes the job a snap. Dimensions are easy to control this way because the tool will actually peel a .001" off the part instead of rubbing, increase DOC, rubbing, increase some more, then followed by, oh %$#@ and ripping an additional .003"+ off the darn thing because it finally chewed through the work-hardened surface and tore out its guts. -Or worse, deflected the part to where it climbs on top of the insert and snaps the tip off completely.
Experience is never cheap...lol.
I like the CXS series boring bars from Sandvik for this job. Just run the spindle in reverse and get on the +side of the X-axis and feed it directly with your carriage. Set your compound up to match the general angle where the tip transitions to the larger body taper. When you get to that point, transition your hands to the compound and walk it out till it runs off the part. Anticipate this so that one hand is already there, that way the tool does not dwell and cut a ring around the tip right where its at a potential shear point.
Clean, simple, uniform surface finish, no abrupt fillets or corners that will fatigue and snap off.
Easy!
Good luck.
