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Gunsmithing Scope base makin day. . .

LRI

LRI

Lance Criminal
Full Member
Minuteman
    • Mar 14, 2010
    6,346
    7,709
    53
    Sturgis, S. Dakota
    www.longriflesinc.com
    #1
    Finishing up a 6mm Dasher bag gun for a feller. Have to make him a base for the "hubble" going on top.

    Thought I'd share the process:

    Here's the action: Arnold Arms Model AP (no longer around)
    DSC_0009.jpg

    Here's the blank: 416 SS bar stock
    DSC_0010.jpg

    And the single shot follower I made last night. Bling Bling!
    DSC_0011.jpg

    Some more CAD doodles:
    DSC_0013.jpg

    1st op: Roughing out the general profile and cutting the "trough" where it'll settle on top. Doesn't look like much yet as I'm just getting material out of the way right now. This SS is pretty gummy and the rougher "corn cob" endmill I'm using has been around the block once or twice. (I generally run these things right into the ground (that means till they break) cause of how expensive they are) Luckily were leaving some material on it yet so that when the finisher comes in it'll clean up nice n perty.

    More to come, back to work!
    DSC_0012.jpg
     
    #2
    Re: Scope base makin day. . .

    Now it's startin to look like sumpthin.

    Instead of dealing with multiple set ups and/or complex surfacing to machine the facets where this thing is actually going to register on the action I'm using a 1/2" OD 60* included angle spot face drill made from carbide. These little buggers work awesome for chamfer endmills if used properly. Saves a ton of extra work when using simple angles. (in this case 30* since that what the facets are on the action)

    DSC_0015.jpg


    DSC_0019.jpg
     
    #4
    Re: Scope base makin day. . .

    Profiled and angles cut now we check the work. I like to leave the center section unsupported in my scope bases. This way there's a touch of compression by the screws and they tend to stay put a little better. It also seems to center a little easier. We've got a .015" gap between the top of the receiver and the bottom of the base. That's what I like to see.

    I ran the 3/8" EM over the top again to nick all the burrs off. Now she's got clean corners and edges all the way around. Next step is to whack off the slugs on the end to make it easier to qualify when I flip it over. This is a 20MOA base so the next set up will require a little extra work. I could go through the trouble of a sine plate and all that goes with it. With CAD all I'm going to do is compute the taper per inch and then wiggle this thing in the vise and check with an indicator till I get what I need. Then it'll be a pretty simple task of adding the geometry for the 1913 mil spec base features.

    DSC_0023.jpg


    DSC_0024.jpg
     
    #6
    Re: Scope base makin day. . .

    Instead of resetting the part in the vise and fiddling withe the indicator, why don't you just ramp the cutter from xz while your milling the 30' feature to begin with? A .0058" tpi is a doable ramp angle for any cutter as long as you mind your p' and q's and play nice.

    Just curious, love reading your posts you really are an artist, i wish more people could/would appreciate the versatility of cnc.
     
    #7
    Re: Scope base makin day. . .

    The reason for not using an X,Z move is the surface won't be flat. You'd end up with a slight convex (or is it concave?) radius on the top surface of the part. Doesn't matter how big a diameter the cutter, you'd still have a "dish" for the top feature. Plus all the lugs would end up being a staggered height the whole way through and wouldn't be square to the top surface. I guess I could surface the sides but cripes that'd take forever to machine. It'd be different if I had a rotary 5 axis head, but even then the programming complexity would be pretty big.-even with software.

    Just less work this way.

    Thanks for the kind words. Always nice to hear.
     
    #8
    Re: Scope base makin day. . .

    Gotcha...concave/convex, depends on your perspective I guess.

    I just reread your post, I am saying run the cutter at a ramp when you are milling the feature that mates to the reciever. It would eliminate resetting the part in the vise and having to indicate the slope. When you flip the part to cut the lugs it would be the same set up as you have now.

    Lugs would still be cut nice and square.
     
    #9
    Re: Scope base makin day. . .

    Outside has been profiled to finish size with the 3/8 finisher.
    Then I plowed a quick pass through the center just to give the indicator a good finish to run on.

    From here it's pretty simple. Just zero the indicator and then move one inch in X. From there I fussed with moving the part up/down till I got .0056" of Z change.

    Then I just zero the indicator again and verify using the DRO of the mill. Took a few tries but I got it: .0056" taper per inch on the money. I verified this in CAD first just to be sure that it equals 20 minutes of angle inclination.

    Were spot and and now ready to start the fun stuff.

    More to follow. . .

    DSC_0028.jpg

    DSC_0029.jpg
     
    #10
    Re: Scope base makin day. . .

    Judging by the burrs left behind and how you stated that the material was "gummy" leads me to believe that the SS you are using is 300 series not 416. This observation is based on my own experience using both types of SS. The 416 SS i have used in the past has been "free machining" and a pleasure to work with. It almost machines as easily as 1018 or 8620 etc. Also the surface finish you get with 416 looks a little "frosty" as compared to 300 series SS whichs gives you a mirror like finish. Just an observation.
     
    #12
    Re: Scope base makin day. . .

    i could never remember what was what. but i think like this. concave goes in like a cave. the back of your eyeglass lens is concave. the front of the lens is convex. most times anyway.

    CDixon, im always amazed at your work. so clean, so precise. thanks for sharing
     
    #14
    Re: Scope base makin day. . .

    Nice one Chad, just when I think Im getting good you go and do this again. Very tidy work for sure. Ive never heard of those actions. Do you have a link to them.
     
    #23
    Re: Scope base makin day. . .

    FWIW:

    I'm fortunate to have some really good relationships with folks in this industry. Historically discussions about this site/forum have sort of settled into a common denominator: "it can be a really tough crowd so be careful..."

    That being said I'd also like to point out how positive it can also be.

    I'd like to thank everyone for the nice words and constructive (rare these days) comments/suggestions that my threads seem to generate.

    Very encouraging and nice to hear. Enjoy your weekend.

    C


    This morning's project is to make a bolt stop for this action.

    Grrrrr. . . I'd rather be out flying! Winter is right around the corner but for now we've got some pristine weather.

    Werk sux sometimes. . .

     
    #25
    Re: Scope base makin day. . .

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: toolmaker64</div><div class="ubbcode-body">Judging by the burrs left behind and how you stated that the material was "gummy" leads me to believe that the SS you are using is 300 series not 416. This observation is based on my own experience using both types of SS. The 416 SS i have used in the past has been "free machining" and a pleasure to work with. It almost machines as easily as 1018 or 8620 etc. Also the surface finish you get with 416 looks a little "frosty" as compared to 300 series SS whichs gives you a mirror like finish. Just an observation. </div></div>


    303 machines nice.
    304 is gummy crap.
    316 is tough.
     
    #27
    Re: Scope base makin day. . .

    I've been jabberin off/on about this dumb follower.

    Here's the idea. I don't like the idea of the thing floundering around inside the action magazine mortise. Sooo, I attached it to the stock. Whipped up a couple pillars from brass and stuck em in the stock, then machined the scab line in the bedding from claying the receiver till I just got into the wood again. Drill/tap a couple holes and 'poof' were done.

    As soon as I get the tang features cleaned up it'll be ready to flip to finish off the trigger guard.

    DSC_0045.jpg


    DSC_0046.jpg
     
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