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Steel vs Aluminum scope bases.

 
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  #15  
Old 01-24-2012, 08:28 AM
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Re: Steel vs Aluminum scope bases.

Broz outta know because he fiddles with them for a living. I'm just a hobbyist.

Sounds like a messy job to me. I guess I could fixture the receiver and indicate the parallelism and height differential between the adjacent bases as it pertains to post mounting, Right now I use the 'feel method' to sense any misalignment and lap off the high spots using an appropriate sized bar (0.100" or 30mm) placed through both bases and some Clover fine lapping compound.... Somewhat tedious but I have lots of time. I considered mechanizing the process, tantamount to line boring, but it would be even more tedious to set up and execute.

Appropriate sized drill rod is readily available from most metals suppliers.

One thing that most consumers don't realize or take into account is that metal, any metal, is always moving. Not a lot, but it continuously moves with temperature changes and even the way a particular part is packaged can adversely effect the trueness and parallelism over it's length and cross axis. That includes the rings and the optic itself.

It has to do with grain structure and a whole bunch of things technical and not germane here.

It becomes apparent when using precision measuring instruments that indicate in tenths (0.0001) or better, something I deal with in the shop.

2 good examples come to mind. One is bench grinding wheels and surface grinding wheels (for me). never purchase a grinding wheel that's laying on it's side, on the shelf, in a store, because gravity has deformed it, they must be stored on end.

The second example is cylinder liners for diesel engines. They also must be stored vertically because, if stored on their side, gravity will cause the bore to become oval.

Gravity affects everything metal and non metal. You could purchase a rail thats been packaged with it's center point resting on some high point in the packaging and laying flat on a shelf for a period of time and that rail will be higher in the center than it is on the ends and that will show up in ring misalignment and the misalignment won't be consistent because the the center point in the packaging may be or not be centered on the rail in the first place.

In other words, any rail can be in misalignment prior to mounting and the receiver's metal can also be misaligned, causing even more problems, problems that can become apparent when shooting extreme long range versus a hundred yards or so. The longer the shot, the more critical alignment of the respective components becomes and the more 'metal movement' comes into play.

Every part coming off the CNC is created equal or at least as equal as the machine can make it within it's designed accuracy parameters. As the part ages and sits, metal movement can and will change the initial dimensions and can adversely impact your end use, which is why lapping or seating the rings in respect to the optic is a good idea.

Remove as much misalignment as possible before clamping the assemblies together and while on the subject, it's important to adhere to each respective manufacturers torque specification for respective components. Over torquing fasteners not only increases the chance of breakage, it will deform the part or assembly that's being secured by the fasteners in the first place, so no matter how carefully you try to correct misalignment, cranking down on the respective fasteners will negate and possibly amplify the misalignment you just spent a gob of time trying to remove......

I adhere to the above procedures all the time in my shop. It has nothing to do with firearms but is just accepted shop practice when working with accuracy in metal parts.
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  #16  
Old 01-24-2012, 10:08 AM
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Re: Steel vs Aluminum scope bases.

Quote:
Originally Posted by brentc View Post
Jeff, did you find the need to bed the bases on your custom actions?
Yes, I bed every single rifle I put a base on, for the same reasons we bed actions. The reason may not be from only a misaligned or non-parallel mounting planes, but rather the need to fill gaps even if the base torques down and remains flat on top. Some bases have a void under them due to the way they are machined that is intended, and some simply because they have no way of knowing what receiver you are using so they use a standard radius ( like the 700 Rem) problem is the 700 Rems vary a ton from action to action. So yes, I feel it is necssary to bed them all, customs too, and most base mfg's recommend it. Remember, those little #6 or #8 screws are not what does the majority of the holding of that heavy scope on top. It is the clamping of two mated surfaces that do a great deal of the holding. This is why I want two perfectly matched surfaces between my action and base with 100% contact area. This insures me it will stay put and it is true.


SidecarFlip, I am simply a hobbiest too. But I find myself tinkering with these rifles all the time. I use to race cars and build some pretty wild engines, now I tinker with rifles, rifles have a much longer life expectancy than a wedge head making 3000 HP. But I did relate to your post and agree with you. You should see how I store barrels and things I want to keep true. Oh, and I have never layed a crank shaft or camshaft down flat and left it over night. Nor would I ever torque down a crank in a block that is only supported by one end hanging on an engine stand. I do it with the block fully supported on a flat surface. I have seen the ill affects of other ways, you are correct, metal moves, grows and flexes.

Jeff
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  #17  
Old 01-24-2012, 08:49 PM
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Re: Steel vs Aluminum scope bases.

Jeff...

Without violating any tennets of this site, lets just say I manufacture custom and high performance motorcycle accessories in stainless and aluminum.

And I tinker too, with guns, mostly target pistols, which is my passion and of course reloading because one, I'm cheap and two I like controlled ballistics.

When I removed the rail on the Savage (I removed it primarily to indicate each mounting boss and counter a post in another thread that the 111LRH rail comes in a 0 (flat base). It's a 10 degree cant. Either that, or the receiver is tapered and I don't believe it is.... The base is radiused to match (I assume) the od of the receiver. I didn't check the radii on either the base or the receiver (with Dykem) I just reattached it and put a dab of blue threadlocker on each of the 3 mounting fasteners and torqued them to 35 inch pounds. There was no discernable rock in the rail in either axis prior to reattaching. I physically attempted to rock it in both axis. I did check the rail with a good straight edge (Starrett diemakers square) and it was square and parallel with no evident twist.

Is that acceptable or should I remove it, blue it and recheck it? I have the capabilities of fixturing the entire action on a surface plate and checking all dimensions for squareness and parallelism but it seems a bit of overkill. I'm a long, long way from being even a run of the mill long range bullseye puncher....

Just getting into this LR stuff and LR is like ultra precision machining. A little error compounds the end result appreciably.

Your input would be appreciated.

You obviously (at least as I see it) get your hands dirty with this stuff more than I ever have.
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  #18  
Old 01-24-2012, 10:35 PM
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Re: Steel vs Aluminum scope bases.

Quote:
Originally Posted by SidecarFlip View Post
Jeff...

Without violating any tennets of this site, lets just say I manufacture custom and high performance motorcycle accessories in stainless and aluminum.
.
Hmmmm, some how I believe our paths might have crossed. You would not happen to know a good friend of mine from DesMoines, Ia named Jim would you??

Anyhow, Maybe you have noticed that to achieve a "good fit" some rail base mfg's will hollow out a void in the middle of the rail where it contacts the receiver. This way it fits like a saddle only touching on both sides and not in the middle. I especially want to bed these to maximise surfase contact.

I will not say if you don't bed your base you will have problems. But I will say I have seen problems and with the heavy scopes I bolt on top I want all I can get. Next time you have it off dykem it and see what it says. You may then choose to bed it. or not?

Jeff
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  #19  
Old 01-24-2012, 11:24 PM
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Re: Steel vs Aluminum scope bases.

Jeff...

It's not relieved in the center of the underside, the radius extends uninterrupted across the entire bottom. Looks to be ball milled with an appropriately sized cutter. I can see the tooling marks. Actually I was surprised it didn't have a milled Vee down the centerline, a common practice in machining.

I've had the action out and did a look-see inside. Savage Arms are very impressive internally. I appreciate quality machining and fit of intrinsic parts and this firearm has excellent fit and finish throughout, at least visually. I know the proof is in the shooting and we'll get to that.....

The exception was the adjustable cheek. The fixing bolts were basically oxide coated carriage bolts with a cobbly knob and the bolt shanks stuck out past the knob surface. I fixed that with 18-8 Stainless polished dome headed carriage bolts with the shanks ground to length (to be flush with the knobs tightened) and some nice knobs in hard black plastic.

We might have crossed paths. I have customers and friends all over the country, actually worldwide. I do more business offshore than here, a couple patents and a very active imagination. My best ideas come when I'm reloading of all activities.. It's tedious and repetitious so my mind is elswhere, coming up with ideas that I sketch and later prorotype and build into marketable parts....sometimes. Sometimes they wind up in the scrap can.....

Yes, a couple around Des Moines and over near Council Bluffs. We could have crossed paths at any time, I meet a lot of people in my travels... I've had my sidecar outfit in shows all over.
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  #20  
Old 01-24-2012, 11:38 PM
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Re: Steel vs Aluminum scope bases.

Koenig Engineering is my good friend. He has built some bad azz drag bikes, boats you name it. I too am a sucker for fine machine work and I have been lucky to know some real artists.

Jeff
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  #21  
Old 01-25-2012, 12:09 AM
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Re: Steel vs Aluminum scope bases.

Not familiar with them..... I'm into vintage British bikes, Triumphs, Nortons, Beezers, AJS, that sort of bike. Restored to showroom condition.

I'm good friends with Randy Baxter in Marne, Iowa. Actually he's my only domestic dealer and his place is the mecca of vintage Brit bikes.

I collect Triumphs and have a garage full of late and early models and I make aftermarket parts and high performance acessories...for Late Model Triumphs..... Actually the front of the machine shop is the bike shop, heated in the winter and cooled in the summer....

My car stays outside.......

There are lots of collectors in the Des Moines area and Council Bluffs plus a couple of shows that we make every year. Mine is a trailer queen but I do ride in local rally's at every show and around here.

We are off thread, so I digress....
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