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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/27/2012 at 15:19
DANNY-L View Drop Down
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Just recently started lapping my rings useing the wheeler kit,upon completing a set of rings I noticed a small crack near the ring mount,question is I got the replacement ring but can ya lap just the 1 ring or do you set it all back up and just leave the ring that was already done a bit loose.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/27/2012 at 18:25
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The reason I lap my rings is to make sure that both rings are acting as one unit,also make sure the rings will be lined up straight so that there will be even amount of flex on the scope!
Do not leave a scope ring loose as you can destroy your scope in as little as one shot.Make sure you torque the correct amount as per the manufactures specs.
 
Since I've started using better rings[Aadland,Badger,Tally tactical to name a few]I have not found the need for ring lapping.You pay a little more for the rings but you get better quality.
 
Of course this is not to say that the holes on the barrel are lined up or have been drilled correct!I have always found by taking off about 60%of the dye on the inside of the ring is about as far as I'm comfortable with.This of course is only on the bottom of the ring.You might have taken off too much of the ring & that's why it cracked.
 
Buy another set of rings if you can't get the rings to work in harmony with each other,better a $100 set of rings than a $750 scope!
Welcome to the OT! 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/28/2012 at 17:27
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Thanks and before doing my first I would never have thought that rings could be so off set. 1 set of leupold I did was only making contact with about 15-20%,I was surprised.
I did a search on lapping scopes and found this site,lots of information for sure here.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/29/2012 at 09:50
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Align or bed the bases, buy quality rings, and sell your lapping tools.

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/29/2012 at 17:45
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I don't mind giving it the do it yourself touch just like reloading.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/29/2012 at 18:52
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Originally posted by DANNY-L DANNY-L wrote:

I don't mind giving it the do it yourself touch just like reloading.
 
I am all about DIY myself.
 
It is just you will never be as precise with lapping as the manufacturer is when machining the rings.  For instance, TPS rings have a two mil gap machined in the right side.  You start lapping, and that gets out of whack. 
 
I only use one piece rails, and bed them to the reciever, leaving everything perfectly square.  Then I mount quality rings (TPS lately), and get 100% contact without lapping.
 
If you really want to get custom contact with your rings, bed the rings to the scope.  If I ran into a spot where I had to use two piece bases, I would bed the rings, if needed.
 
I have lapped a bunch of rings, but now I don't.
 
Here is my rail bedding video:
 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/30/2012 at 07:57
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Originally posted by Bitterroot Bulls Bitterroot Bulls wrote:

 

It is just you will never be as precise with lapping as the manufacturer is when machining the rings.  For instance, TPS rings have a two mil gap machined in the right side.  You start lapping, and that gets out of whack. 
 
I only use one piece rails, and bed them to the reciever, leaving everything perfectly square.  Then I mount quality rings (TPS lately), and get 100% contact without lapping.

That's exactly the way I believe as well. 
How would some dude with some lapping compound, armed with a lapping bar, ever get those rings as "square" as a the factory, (TPS in this case), can get them? 

Good post, BB.  
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/30/2012 at 14:09
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That's a really interesting video. I'm a bit hard of hearing (not enough volume on my computor)so I couldn't hear the first part does this work with any base or only certain ones. This is the first I've heard of bedding a rail or base. I appreaciate the video and advice.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/30/2012 at 14:23
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By bedding the rail it insures that the entire base makes contact with the reciever, which takes out any type of twist that may occur when ya torque them down, which keeps the rings in perfect alignment so no ring lapping would be needed. Am I understanding it correctly?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/30/2012 at 15:12
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Originally posted by DANNY-L DANNY-L wrote:

By bedding the rail it insures that the entire base makes contact with the reciever, which takes out any type of twist that may occur when ya torque them down, which keeps the rings in perfect alignment so no ring lapping would be needed. Am I understanding it correctly?


kinda. if the base is bedded to the rifle it will have 100% contact to the rifle/action, so no moving when shooting. You can remove it and it will go back to the same spot everytime you put it back with 100% contact. it will also make it feel firmer (more solid) as it will be. Now this only works if you use a straight cut base from the start, but you will have a problem if the base is bedded or not in that case. also, if the base is bedded and you still want to lap the rings you will have a more ( not perfect) platform to lap them too, as the base will not wiggle as your lapping. I have never had 100% contact on any rings I have used 95%+ alittle was the best I have had so far. I see no point in lapping rings as they should work well if the money is spent on the rail and rings on the first go around. I have been made into a firm Bi-liver in " you get what you pay for" in the ring and base subject.

Hope that made some cents.lol



Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/30/2012 at 15:26
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You can have the most precise rings ever manufactured, and that has little to do with why lapping is beneficial.  If you are using 2-piece rings/bases, USUALLY lapping is beneficial.  The reason is simple -- the rings are mounted on a receiver using socket head or Torx cap screws only.  There are several things that can cause alignment errors, any one or combination of which lapping can correct:

1.  Misaligned mounting holes on the receiver.
2.  On stepped receivers like Rem 700, variations in the receiver top surface height, front to back, such that the height deviates from nominal dimensions the rings were designed for.
3.  Clearance between the o.d. of the mount screws and the i.d. of the mount base screw holes allows some radial deviation from true 12:00 top dead center.

In short, it is a misconception that precisely made rings eliminate the need for lapping.  I've mounted many scopes, and I've never seen any brand of 2 piece horizontally split rings mounted on any rifle receiver that didn't benefit from lapping.

One piece bases are a different story, since the rings on a well-machined 1-pc base or integral base/ring assy maintain concentricity as long as the top of the receiver isn't so far out of round that the mount assy flexes when the screws are tightened down.

As a general rule, IMHO.... 2 pc bases = lap the rings; 1 pc = maybe not, but check with alignment bar.

Even if you choose not to lap, as long as the rings are within a couple .001" or so of being concentric, you're not going to damage the scope and you're o.k.... even though lapping the rings still technically results in a better mounting job, as it ensures more surface contact and less stress on the tube.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/30/2012 at 18:29
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My comment about 100% contact was an exaggeration of course.  However, it is somewhere around there.  BigDaddy is absolutely right about having a straight and square base to start with when bedding.  The bedding job won't straighten the base, but it will alleviate some problems at the base/receiver interface.

No matter what when lapping, you end up removing material by hand, and that is a less perfect process than CNC machining, IMO.
 
Bedding a one-piece base mitigates or eliminates Ted's three base mounting issues.
 
When using quality rings on a properly bedded (and true) one-piece base, you should not need to lap the rings.
 
Bedding rings is still a good solution with two piece horizontally split rings.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/30/2012 at 23:04
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Originally posted by Bitterroot Bulls Bitterroot Bulls wrote:

It is just you will never be as precise with lapping as the manufacturer is when machining the rings. 


Actually, just the opposite is true, depending on the method of machining that's used.  If the i.d. of the rings are turned or milled, lapping (like grinding, honing, and reaming) is capable of achieving straighter, truer surfaces than conventional machining can achieve.  Much tighter tolerances between mating parts are always possible when surfaces are lapped rather than machined only.  Even if the i.d. of both rings are perfectly concentric with each other, lapping removes the crests of the tool marks, resulting in greater contact surface area with the scope tube.  This is of course dependent on how straight and true the lapping bar used is.  You really cannot screw up the i.d. of the rings as long as the bar is of the correct diameter and is taper-free because the bar forces alignment and will not allow you to deviate from true alignment due to its stiffness and bearing length.  This is why match-grade custom barrels are always lapped after drilling, reaming, and rifling.  It's also why precision mating surfaces in engines such as valve seats are lapped after being machined.  Lapping is similar to honing, except honing really just polishes the surface, whereas lapping trues and polishes the surface.

Even when using one piece bases or integral base/ ring systems, the rings can get out of alignment with each other if the receiver it's mounted to isn't perfectly straight, which isn't uncommon with mass-produced products.  Everything is made with predetermined acceptable production tolerances to meet cost and productivity targets.  If, for example, a turning insert starts to fail while a round receiver is being machined in the lathe, the result is a cylinder that has varying diameters along its length.  A receiver with eccentric mounting surfaces will stress 1 pc bases when tightened down, causing the ring saddles to move out of concentric alignment with each other.

The bottom line is even the finest, most precise scope mounts must still be mounted to a rifle receiver that may or may not be made to sloppy tolerances.  If either mounts or receiver isn't made to very tight tolerances, misalignment occurs when the two components are mated together because of tolerance stack-ups and error accumulation. 



Edited by RifleDude - April/30/2012 at 23:09
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/01/2012 at 08:28
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Originally posted by RifleDude RifleDude wrote:


Actually, just the opposite is true, depending on the method of machining that's used. 
I agree.

 
Originally posted by RifleDude RifleDude wrote:

lapping removes the crests of the tool marks, resulting in greater contact surface area with the scope tube.
 
I disagree here, as there should be no "crests" if the tolerances are tight enough, as they are in quality rings.  The lapping is done by the factory to extremely tight tolerances.
 

 
Originally posted by RifleDude RifleDude wrote:

This is of course dependent on how straight and true the lapping bar used is.

It is also dependent on how firmly fixed the rings are to the bases, the bases are to the receiver, and how stable the gun is in the vise.  Also if you remove the bases and remount them, your lapping may no longer be true, as the rings may be mounted slightly differently.
 
 
Originally posted by RifleDude RifleDude wrote:

You really cannot screw up the i.d. of the rings as long as the bar is of the correct diameter and is taper-free because the bar forces alignment and will not allow you to deviate from true alignment due to its stiffness and bearing length. 
 
You can screw it up due to variations in pressure (from the person using the kit and gravity) taking more material from different areas of the ring.  Hand lapping has no tolerances.

Originally posted by RifleDude RifleDude wrote:

This is why match-grade custom barrels are always lapped after drilling, reaming, and rifling.  It's also why precision mating surfaces in engines such as valve seats are lapped after being machined.  Lapping is similar to honing, except honing really just polishes the surface, whereas lapping trues and polishes the surface.

Barrel lapping and precision machine part lapping are also governed by tolerances.  Barrel lapping also has a significant advantage in bearing surface length.

Originally posted by RifleDude RifleDude wrote:

Even when using one piece bases or integral base/ ring systems, the rings can get out of alignment with each other if the receiver it's mounted to isn't perfectly straight, which isn't uncommon with mass-produced products. 

This is the real problem with ring alignment, and if it is solved or at least substantially mitigated (by epoxy bedding), the need and advantage to lapping is reduced or eliminated.
 
Even when there is misalignment, hand lapping will never be as precise as bedding rings to the actual scope tube the rings will hold.
 
These are just my thoughts on why I don't lap rings anymore, and to be a bit of a pain in the apple.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/01/2012 at 08:42
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This is a really good thread! 

BB beat me to it, but as he mentioned, what happens when you take the rings off and then remount them? Are your lapped surfaces affected by that? I would think so. 

Also, what if the scope tube itself is out of whack and not a true 1" or 30mm?

Not trying to argue here, Gents. Just trying to understand. Bucky 
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Also what if you want to use those rings on a different rifle after you have lapped them to fit?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/01/2012 at 11:12
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Get a Surgeon 591 with the integrated rail and some Seekins rings. No lapping necessary. (You will have to make other sacrifices though!)
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/01/2012 at 19:51
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OK, a couple things here...

Ring lapping is a lot like stock bedding in that it may not provide any noticeable benefit in some cases, but it never hurts to do it.  Even if it's only a small improvement of questionable benefit; better alignment is still better alignment, and lapping rings is neither hard to do nor especially time-consuming.

Most scope rings aren't lapped or otherwise super-finished after machining.  They are usually just machined then grit blasted and either blued, anodized, or coated (depending on the material used).

ALL conventionally machined surfaces have peaks and valleys left by the feed marks from the insert or mill cutter used, unless the surface is reamed, honed, lapped, or ground after rough machining.  The degree to which this is or isn't an issue depends entirely on the machining method(s), tooling, and cutting parameters (feed rate and cutting speed) used to produce the rings in question. 

Lapping is a super-finishing method that trues up and removes small imperfections in machined surfaces, whether those surfaces are inside match grade barrels or scope rings.  The goal is the same.

Contrary to common belief, lapping rings DOES NOT increase the inside diameter of the rings, if the lapping bar used is the correct diameter, which is a few 0.0001" to maybe 0.001" undersized from nominal scope tube dia (to allow room for the grit displacement of the lapping paste used).  Remember, when the ring caps are tightened down against the lower ring halves, the ring actually distorts to somewhat conform to the scope tube, but never with full 360-deg contact.  No matter how much force you exert on the rings during lapping, the lapping bar diameter and straightness determines the diameter and squareness of the lapped rings.  The bar doesn't grow in diameter, and it has no cutting edges.  You simply monitor the % of finish removed from the i.d. of the rings while lapping and stop when you have at least 70% or so cleanup, which you can easily see as the % of polish on the ring surface.  You aren't removing much material when lapping; you're only moving the surface down a tiny amount and squaring it up.  Without lapping, you aren't getting full circumferential contact between rings and scope tube on conventional horizontally split rings.  At best, you're getting line contact in a couple places.  Even after lapping, you aren't really getting full contact, but you do get increased surface contact, which means gripping force spread over a larger area of the scope tube.  The reason this is so is because the i.d. of your rings is almost never exactly the same size and geometrically the same roundness as the scope tube and your scope tube is sitting on the "peaks" of the machined or blasted finish.  You only have to run a lapping bar through the rings and look at the uneven "cleanup" to see that this is so.

When you're lapping rings, the mounts and receiver are already screwed together into a fixed relationship, as long as the mounts are secured tightly to the receiver.  Provided the mounts are tight and remain so, the only remaining variable that affects ring to scope fit is the lapping bar size and the amount of time spent lapping.  A good lapping bar will be surface ground and straight.  The quality of the lapping job is the direct result of the quality of the lapping bar.

Yes, if you remove the mounts from the receiver and remount it on another gun, even the same gun, the lapped surfaces are likely no longer aligned... however no less so than the rings would have been before lapping anyway.

Lapping certainly doesn't cure all scope mount ills, but doing it is never a step backwards, and other than a little extra time and effort, there aren't any real disadvantages to doing it.


Edited by RifleDude - May/01/2012 at 20:08
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This is what got me to change my ways and it made sense to me, from TPS:
 

INSIGHT INTO THE WORLD OF TELESCOPIC SIGHT

MOUNTING

The inherit problems of proper scope ring alignment is as old as the first rifle scope.

Anyone who has attempted to mount their own scope, using various manufactures

ring and bases have all encountered the same thing, whether or not they identified

the problem is another topic. The scope rings, which hold the scope onto your rifle

or handgun, are not perfectly aligned together. The misalignment of your scope

rings is why we are here, taking you through the process to explain why your scope

rings are misaligned and how to prevent it from happening ever again.

It has become an acceptable procedure in past years to do something called

"Lapping" your rings. The individuals who have become aware of the fact that their

rings are not aligned correctly are implementing the only way of correction that has

become apparent to them. Today, however you are about to become aware of not

only a different and unique way, but the only correct and proper way to aligning

your rings.

First and foremost, the customer, being yourself, must understand a couple things

about the manufacturing of firearms, scopes, rings and scope bases. Virtually, every

firearm that is manufactured in the world, past and present has the same inherited

problems. They are all unique. Unique in the fact that no two are the same, and the

areas that mates with your scope ring bases are the areas that is of concern today.

The receivers on rifles and handguns are machined and then polished, typically by

hand. By hand polishing along with typical machining tolerances, you have

irregular radiuses, surfaces and dimensional heights to which you must align and

eventually mount your scope ring bases onto. Because of these differences, is what

causes your scope rings to be misaligned, which is why the attempted correction has

been to "Lapp" your rings.

All components, such as your firearm receiver, scope rings and bases all have

dimensional "manufacturing" tolerances in them. However, you will typically find

that most quality oriented manufactures in the scope, scope ring and base market

provide an accurate product, since they are typically machined on the critical

surfaces, compared to a firearm receiver which as been polished by hand.

If the world were perfect, your firearm receiver would as well. However, we know

this not to be true, so we accept the problem and find means to correct it. The

Basebed™

Alignment Bar aligns your bases, even if they themselves may not be perfect. The

alignment bar aligns your bases together, in three (3) different planes, and then

allows you to mount the bases in their aligned state of position perfectly to your

firearm receiver. In using the Basebed™

Alignment Bar, you will have eliminated the largest aspect of misalignment in the

mounting of your scope. Nothing can take the place of precision and accurate rings

and bases, so we highly suggest that when decide to purchase your next set of rings

and bases consider the quality and accuracy of both in regards to how they mount on

your firearm.

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I read a post by glen seekins once against lapping as well. He even talked about how just lapping the anodizing off will make them oversized.

I am not sure how lapping could not make them larger. The ones i have done in the past it was pretty obvious a bunch of material had been taken off the rings. Most of it coming from the bottom ring.
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Sorry to revive an old thread, but I haven’t been able to log into the site much since the last post, and I think this is an important and oft-misunderstood topic. 

BB, that summation from TPS is correct, but if you read it carefully, it doesn’t say lapping isn’t beneficial so much as explaining why rings are almost never perfectly aligned, and why they recommend another alternative to lapping.  For certain, lapping isn’t always needed.  The goal of lapping is near-perfect ring alignment, and if that goal is achieved by other means, then “rock and roll hoochie-koo”… lapping ain’t needed.  If TPS holds the extremely tight tolerances they say they do (and I have no reason to believe they don’t), lapping would indeed not be necessary IF you also mount their rings to a precision ONE PIECE base and ensure that the top of the action it’s mounted to is either perfectly straight or bed the base. Notice that TPS doesn’t offer 2-pc bases, which almost certainly introduces misalignment.  By the same token, if you mount their rings on lower quality bases or 2-pc bases, there’s no way they can say with 100% certainty that lapping isn’t necessary.  They can’t control what they don’t make.  Of course manufacturers are going to advise against lapping, because the outcome is totally out of their control, and they have no way of knowing whether the person doing the lapping knows what they’re doing or not.  Plus, if they advise people to do it, they run the risk of consumers thinking there’s something wrong with their products, and as has already been discussed, a good portion of the reasons why ring misalignment occurs has nothing to do with the rings themselves. 

Saying “no lapping is necessary” makes great ad copy, but it ignores reality.  How can a scope ring manufacturer ensure that any possible receiver their rings may be mated to is straight, when that is totally outside their control?  Unless the same manufacturer made the receiver, bases, rings, and scope and fitted each piece together as individual assemblies, nobody can guarantee that everything always lines up perfectly 100% of the time with all possible combinations of receivers, bases, rings, and scopes, especially when different companies made different parts of the assembly.  It’s not possible.   All of the components in the rifle/mount/scope assembly, just like all other products, are made to design tolerances, and actual dimensions will vary from stated nominal dimensions within those tolerance ranges, resulting in tolerance stack-ups and therefore misalignment.  With all the variables in play, it is actually more likely that you will have misalignment than not.  You then have 2 options:  either ignore that possibility and mount your scope anyway, or address the misalignment.  If you choose the former, you may be o.k. if the alignment isn’t great, but if the misalignment is great, you will torque your scope tube, causing ring marks and reduced W/E adjustment travel, and even degraded optical performance in worst cases.  If you choose the latter, you WILL either have to lap or ream the rings, bed the base(s), or choose a ring design that self-compensates for misalignment, like the Burris Signature rings with inserts.

Even if perfectly concentric rings are mounted to a perfectly straight 1-pc base, if the receiver it’s mated to isn’t perfectly round and/or straight, the mount base will flex when the mounting screws are torqued, pulling the once perfectly aligned rings out of alignment.  To determine if you will have alignment problems with a 1 piece base & mount system, fasten the front end of the base firmly down to the receiver ring, without installing the rear screws.   Then, check to see if either of two conditions exist:  1.  The rear portion of the base makes contact with the bridge and begins to exert upward torque on the base before the front screws are fully tightened, or 2.  There’s a gap between base and receiver bridge even after the front screws are fully tightened.  If either exists, you WILL have misaligned rings when you torque down all base screws unless you lap the rings or bed the base.  Even if you use TPS’s alignment bar method, if the receiver the mounts are installed on is not geometrically perfect, the alignment bar is merely torqueing the receiver and/or mounts while it’s secured in the rings.  As soon as you release the bar, the rings will spring back into misalignment again.

ST, if a correctly sized lapping bar is used, lapping doesn't make rings oversized, it only squares them up and polishes.  It’s reasonable to ask how it’s possible that material can be removed and yet the clamping diameter remains unchanged.  This is one of those things that’s much easier to demonstrate in person than attempt to describe in words, but bear with me here, and I’ll attempt to do so. 

The only way lapping will enlarge the clamping diameter is if either the ri

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Excellent post Ted.

Am I the only one that thinks we are all mostly in agreement here?

I may repeat some info from my earlier posts, I apologize if that is the case:

I think lapping rings can, and does, increase contact on the scope tube, which is good. I think this method is not as good as bedding a one piece base. We have touched on the disadvantages of lapping already, inlcuding that they are likely again misaligned if removed and remounted.

Ted, TPS' alignment bar was only to be used as an alignment jig to then bed the bases stress-free to the action. Once the epoxy was cured, the bases would then be true to each other, and would not spring back into misalignment when the bar was released.

If properly bedded in a stress-free manner, a one piece base would not arc or twist on the action when torqued, because those imprefections were cured with the epoxy (pun intended).

As far as lapping removing material to make the ID oversize, I understand your point. I think the problem is that, as you move the centerline of the ring ID down, you are closing the gap between the ring halves. This is especially problematic with TPS rings, as they are designed to not have a gap on one side.

For me bedding has more advantages, as I can switch scopes from one rifle to the next without worry. I prefer to customize the bases to the rifle, rather than the rings to the bases. You can also resell your rings later.
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stickbow46 View Drop Down
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Very good write up guys.I've always lapped my rings till recently using Robert Hart lapping bars,the reason I don't any longer is I've switched over to Picatinney rails on all my rifles.
 
I have found to many discrepencies in the rails these companies are machining & I am talking the top of the line rails.No I have not yet tried bedding the rails but that will come next set up.I have however tried to lap my aadland rings & found they were very even[took same amount of dye off on each ring].All my rifles now are riden by Aadland.
 
I have called 4 different top of the line ring manufacturers & have gotten 4 different replies when it comes to the question of lapping[2 in favor & 2 against]so it seems here lies the problem for all us average do it your self people,if you can't get the manufacturers to agree,I guess it's left up to the individual.Kind of like the topic to Season or not to Season a new barrel?
 
As I was a  tool & dye maker for 5 years I do know my way around lapping equiptment & I have to disagree with the statement that You can't make a ring larger by lapping.If the person doing the lapping is not going straight with the bar they will ultimately wind up with an eccentric hole kind of like a cam or egg shape,pluss they will also create a weak spot on the ring,causing it to possibly break & this is where this thread first started Loco 
 Again much thanks for all the great infoExcellent


Edited by stickbow46 - May/27/2012 at 15:29
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I don't think you could "wear a weak spot in the ring", simply by running a lapping bar over, my friend.
I do see where you could make the ID of the ring bigger though, but not as much as would have any consequence. 

Aren't we assuming that all the scope tubes and lapping bars are perfectly round here, Gents?   
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The i.d of the rings and the "effective clamping i.d." once the rings are assembled to bases and rifle are two entirely different things when said rings are misaligned.  All custom barrel manufacturers lap the hell out of match barrel bores -- entirely by hand -- to create the final bore finish, without oversizing bores, and still hold +/-0.0002" (two ten-thousandths) TIR straightness from breech to muzzle because, like a lapping bar in rings, the lapping slug has a long surface area that ensures self-alignment and distributes the lapping paste evenly.  If you're using a precision bar that's round, straight, and of the correct size, you will not oversize your rings, nor reduce the gap between upper and lower ring halves to any noticeable degree.  This assumes you use common sense, don't spend a solid week lapping the rings, carefully monitor clean-up on the ring i.d faces, and know what to look for. 

If you plan to mount and dismount your scope often, don't buy 2-pc bases.  With some rifles, 1 pc bases block the ejection port or there are no 1 pc bases available.  When I use 2pc bases, I intend to never remove the mounts from the rifle they're installed on, so the fact that lapped rings are no longer in alignment anymore when removed and reinstalled is irrelevant. 

Yes, using an alignment bar, in conjunction with using a precision made 1pc base and precision rings, in conjunction with bedding the base is an effective alternative to lapping.  In fact, it's probably a superior method.  Missing any of those elements, however, and lapping is your huckleberry.

You can also just use a ring design that self-compensates for misalignment like those that use the "gimbal" type inserts and do neither.
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