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do both ring halves need lapping?

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/30/2007 at 07:48
rooshooter View Drop Down
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can anyone tell me whether both halves of rings need lapping, or is it just the bottom?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/30/2007 at 08:03
silver View Drop Down
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Yes, the tops are easy, just run them up and down the lapping rod until things are close and then assemble everything so that it all lines up for the final work. 

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/30/2007 at 08:30
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do you mean bit by bit? i thought you just tighten the rings down on the rod firmly and lap away doing both halves at once. is that correct?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/30/2007 at 08:53
silver View Drop Down
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Roo,

 

It all depends how out of spec things are...  To start out set everything up and make sure that the gap on mountings screws are the same.  Give things enough passes so that you can pull things back apart and see how much work is needed.  Things get worked in pairs.  If the tops are messed up then work them togther.  If it's the bottoms, then the bottoms get worked together.  When you get close again put it back together and start again.

 

You should not have much, if any, gap between the top and bottom rings and that gap should be uniform when you are done.  In some extreme cases you may have to dress the screw flanges of the rings to get what you want. YMMV

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/30/2007 at 13:17
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There are conflicting opinions on this.  Most gunsmiths I know recommend only lapping the bottom because the tops aren't in a fixed position to the base, so they just follow the tube.  They are also thin, so they can flex to conform to the tube.  That said, it certainly won't hurt anything to lap them both; you just may not gain anything.  I used to lap both, but now I only lap the bottom halves. 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/30/2007 at 13:46
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some makers (NF) recommend only the bottoms as the lower part is over sized on purpose and NF tubes are slightly more than 30 mm.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/30/2007 at 13:55
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Let expound on this a bit more.  In a perfect world you should not have to do anything.  The rings are cast, machined, polished and blued.  All those steps have heat, that can twist, contract or just plain warp.  Now if the problem is were your rings made before coffee break... The afternoon before a holiday break...  Friday about beer thirty... Or with the boss looking over everybody? YMMV  

 

I really don't like the rings should conform under torque school of thought. Because the thing you are really torqueing on is the scope tube. Each maker is a little differant in how they handle things. YMMV

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/30/2007 at 16:11
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Originally posted by silver silver wrote:

Let expound on this a bit more.  In a perfect world you should not have to do anything.  The rings are cast, machined, polished and blued.  All those steps have heat, that can twist, contract or just plain warp.  Now if the problem is were your rings made before coffee break... The afternoon before a holiday break...  Friday about beer thirty... Or with the boss looking over everybody? YMMV  

 

I really don't like the rings should conform under torque school of thought. Because the thing you are really torqueing on is the scope tube. Each maker is a little differant in how they handle things. YMMV

 

 

But remember, it isn't just the rings that contribute to misalignment.  If you're using 2-piece bases, the rifle's receiver holes may be out of alignment front to back and there may be some taper on the top of the receiver.   Plus, screws by themselves are not able to precision locate the bases because there's clearance between the screws and the screw holes.  So, no matter how precisely a set of rings are made, you may still need to lap.

 

As for the rings conforming under torque concept, I agree with you that in most cases you're stressing the scope tube.  However, unlike the bottom ring halves of horizontally split rings that are securely attached to the bases, the top ring halves aren't secured to anything, so they will self-orient to the scope tube, and therefore can't twist the tube.  There's enough clearance in the screw holes of the top ring halves that it allows for compliance to the tube orientation. 

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/31/2007 at 05:47
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are all scope rings made with enough clearance in the screw holes of the top half? i have the hinge type weavers. yes i knoe they're crap in most people's opinion, but they hold the scope to the gun. lapping should improve that fit. what else do you need?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/31/2007 at 05:50
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one other thing, can you use any abrasive paste such as the sticks of it you use on bench grinder buffing wheels, or does it have to be specific? i want something readily available if at all possible.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/31/2007 at 13:39
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If you are doing Weavers, then the base is about all you have to work with. 
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