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-   -   Borrow scope lapping tool??? (https://www.calguns.net/calgunforum/showthread.php?t=1531668)

audiopro74 05-09-2019 12:29 PM

Borrow scope lapping tool???
 
Anybody near Newark got a 30mm lapping tool I can borrow? Or rent for a six pack or something?
Just being cheap, and donít plan on doing enough to ďneedĒ to buy one.

desertrider 05-09-2019 6:32 PM

I'm not going to knock lapping rings as a waste of time and effort, because there are situations when it may be the best option, but have you already eliminated all other variables causing the misalignment you're experiencing?

Do all mounting screw holes in the receiver align properly?

Are you using a one piece scope base or two piece?

If you're using a one piece scope rail, does it sit flush with no gaps?

Are you using name brand rings? (Beware of cheap, poorly machined rings)

Remember, you are combining several different systems, probably all manufactured in different facilities on different machines. All provide an opportunity for different tolerances between each other.

There's a good chance that if you eliminate all tolerance inconsistencies between the mating parts it may not be necessary to lap your rings.

audiopro74 05-09-2019 6:52 PM

One piece steel rail, only has a super thin sheet of paper gap on the front. Rings are high end matched, matched rings. Not sure they need lapping, just trying to give this rifle every chance to bang steel at 1000. Itís my first foray into the long range game, and I donít wanna it any corners.

desertrider 05-09-2019 7:30 PM

I'm in the same boat right alongside you right now.

I recently bought a used 700P (PSS?) in .308 and I'm in the process of scoping it right now. I'm using a bunch of old components that I happen to have on hand.

Rem 700 action - Leupold MK IV one piece steel rail - Badger Ordnance steel rings - SWFA SS 10x42 scope.

I know I will have a tolerance stacking situation since there is a very slight gap between the receiver and rail at the back of the receiver. I'll bed the rail to correct that this weekend though.

Once I'm satisfied with the rail bedding, I'll use some green plastigage on the ring surface to look for any abnormalities in fit once the cap screws are torqued.

audiopro74 05-09-2019 7:51 PM

Quote:

Originally Posted by desertrider (Post 22985811)
I'm in the same boat right alongside you right now.

I recently bought a used 700P (PSS?) in .308 and I'm in the process of scoping it right now. I'm using a bunch of old components that I happen to have on hand.

Rem 700 action - Leupold MK IV one piece steel rail - Badger Ordnance steel rings - SWFA SS 10x42 scope.

I know I will have a tolerance stacking situation since there is a very slight gap between the receiver and rail at the back of the receiver. I'll bed the rail to correct that this weekend though.

Once I'm satisfied with the rail bedding, I'll use some green plastigage on the ring surface to look for any abnormalities in fit once the cap screws are torqued.

That should be a nice shooter. Are used to shoot my uncles PSS, that was his competition gun in the Navy. Love that thing! Iím waffling back-and-forth on lapping the rings, as I bought a nice set of matched MDTĎs. I like the idea with the plastic age though, I may try that. My alignment is perfect, my only concern is mating surface. So I guess Iíll see.

sigstroker 05-09-2019 9:38 PM

The plastigage thing is for bearings, which are supposed to have a certain clearance. Scope rings aren't supposed to have any clearance.

audiopro74 05-09-2019 9:58 PM

Quote:

Originally Posted by sigstroker (Post 22986208)
The plastigage thing is for bearings, which are supposed to have a certain clearance. Scope rings aren't supposed to have any clearance.

True, but it will give you a good idea of mating surface. Run 2 strips. One on each edge.

sigstroker 05-09-2019 11:09 PM

Did you read somewhere this was a good idea? The point of lapping is to have even contact along the whole surface of the ring. The plastigage won't tell you anything about that because if there are high spots, you won't be able to tell. Those high spots won't compress.

audiopro74 05-09-2019 11:24 PM

And logically, if itís not compressed, you know you donít have good contact. Which would require lapping.

Running matched rings, thereís varying opinion on whether they need to be lapped. This could be used as an indicator.

And yes I know, lapping is always better. Iíve got plastigage in the tool box, but not a scope lapping tool.

desertrider 05-10-2019 4:37 AM

Quote:

Originally Posted by sigstroker (Post 22986391)
Did you read somewhere this was a good idea? The point of lapping is to have even contact along the whole surface of the ring. The plastigage won't tell you anything about that because if there are high spots, you won't be able to tell. Those high spots won't compress.

I've never read of using plastigage for this application, it's just something I've done to see if the mating surface is uniform.

If the flattened plastigage isn't uniform in it's spread I'd attribute that to imperfections in the machining of the rings.

At that point I'd consider lapping the rings, especially if I've done everything in my control to ensure proper fit starting at the receiver and working up.

I'll be mounting up my scope this weekend. Over the years I've mounted several scopes and have never found it necessary to lap a set of rings yet. That's been my experience, I'm no world class marksman, but I shoot reasonably well.

MarikinaMan 05-10-2019 4:43 AM

I’m in West LA. I’ve got the Wheeler tool kit.

75 bucks cash deposit, get 65 back on return. Shipped at your cost. Pick up ok.

I’ve lapped a few rings. All of them showed high and low spots. Some more than others. You clamp down on imperfectly mounted or made rings, never seen perfect ones, you run the risk of torquing the scope tube. What happens when it’s torqued? Tracking can be affected. “can” not do sho.

Some designs, like some vertical splits rings from Warne and Aero Precision don’t benefit from lapping due to the way they clamp down.

desertrider 05-10-2019 5:08 AM

Quote:

Originally Posted by audiopro74 (Post 22986411)
And logically, if itís not compressed, you know you donít have good contact. Which would require lapping.

Running matched rings, thereís varying opinion on whether they need to be lapped. This could be used as an indicator.

And yes I know, lapping is always better. Iíve got plastigage in the tool box, but not a scope lapping tool.

I agree with you on the above point, especially if you have a matched set from a reputable manufacturer.

Not being a professional on this subject, I believe that if you paid good money for a set of matched rings and find that there is uneven pressure being applied to your scope tube, it is most likely a result of tolerance stacking where something else just isn't fitting together right.

So if you choose to lap the rings to accommodate the inconsistency of the poorly fitted parts, you no longer have a matched set of rings. You've just modified them to fit the combination of tolerance inconsistencies in your build.

Like I wrote in my first reply, sometimes lapping may be the best option for some situations though. For instance, what if the problem is with the receiver? The cost to have a 'smith strip your gun down to just the receiver and match the surfaces would be a heck of a lot more than the cost of a lapping bar for your rings. That's for damn sure.

If that were the case, I'd spend the coin and get a good lapping kit. Personally, I'd buy the Kokopelli Accurizing Kit and be done with it. http://www.kokopelliproducts.com/acckit.htm

desertrider 05-10-2019 5:13 AM

Quote:

Originally Posted by MarikinaMan (Post 22986562)
Iím in West LA. Iíve got the Wheeler tool kit.

75 bucks cash deposit, get 65 back on return. Shipped at your cost. Pick up ok.

Iíve lapped a few rings. All of them showed high and low spots. Some more than others. You clamp down on imperfectly mounted or made rings, never seen perfect ones, you run the risk of torquing the scope tube. What happens when itís torqued? Tracking can be affected. ďcanĒ not do sho.

Some designs, like some vertical splits rings from Warne and Aero Precision donít benefit from lapping due to the way they clamp down.

I was typing my reply when Markina Man replied.

For only ten bucks plus shipping, that might be your best bet audiopro.

smoothy8500 05-10-2019 5:40 AM

If planning to use shims, Plastigage would make sense in determining the "gap" when installing the one-piece rail on the receiver. Bedding the rail with some sort of epoxy is easier though.

Spyder 05-10-2019 7:20 AM

If theyíre ďhigh end matched ringsĒ, donít lap them.

Spyder 05-10-2019 7:26 AM

Dykem would be a much better plan than plastigage. Or a sharpie.

sigstroker 05-10-2019 9:10 AM

Yeah, plastigage needs to be compressed. Installing one screw on a rail probably wouldn't compress it enough to tell you anything.

Plastigage is an automotive tool designed to be a cheap way to tell you if you have enough clearance in bearings. All of this scope mounting discussion concerns things that should have no clearance at all.

smoothy8500 05-10-2019 9:45 AM

In doing a fair bit of research, it appears that placing rings too close to the turret body and over-torquing the rings creates greater issues that lapping can't fix. Squeezing the tube close to the turrets causes binding of the erector assembly or parallax adjustment.

Lapping rings may not improve fit, but it can't hurt. But, if the scope is not correctly mounted, lapping didn't help a bit.

Ramsh00ter 05-10-2019 10:14 AM

I lap all steel rings! Does it do any good, I don't know. But it eliminates the possibility. Shooting to me has a certain about of head games to it, so eliminating every variable I can just helps my head.

Got into a debate with a Leupold tech about lapping rings when I asked if they could supply a 34mm lapping bar. They tried to tell me their rings were near perfect and did not need lapping..... Really....

After having a 34mm bar ground from an old rail gun barrel, I lapped the 34mm Leupold rings, they were not round and had high spots.

I have lapping bars for 1" 30mm, & 34mm.

Pay the shipping and promise to return it, you can borrow it.

The 1" and 30mm were cheap to make, just order the bar stock from McMaster Carr and a handle. The 34mm was a different story, had to have one ground.

Drill a hole, tap, screw in the handle and you are ready to go.

I lap with four different compounds, 300 grit, 600 grit, 1200 grit, and Ultra Bright Tooth paste.

I can post a picture of what I made when I get home if you would like, they are easy.

PM me if you want to borrow mine.

NiMiK 05-10-2019 1:44 PM

Quote:

Originally Posted by smoothy8500 (Post 22986630)
If planning to use shims, Plastigage would make sense in determining the "gap" when installing the one-piece rail on the receiver. Bedding the rail with some sort of epoxy is easier though.

I agree with epoxy method. Lapping the rings is one thing but will the base make full contact on the receiver? That was one of my concerns before I decided to bed the scope base on my rifles.

Spyder 05-10-2019 3:24 PM

Quote:

Originally Posted by smoothy8500 (Post 22987412)
Lapping rings may not improve fit, but it can't hurt.

It most definitely can.

hambam105 05-10-2019 6:01 PM

I'd say the professionals know the purpose and ability to use a scope lap ring tool properly.
Therefore, my vote is to deploy a used HB electric grinder with a wheel no smaller than 8 or 9 inchs under low light conditions.

shafferds 05-10-2019 6:46 PM

Odds are you will do more damage than good. Put it together first with proper torque of screws and scope placement.

jtv3062 05-10-2019 7:17 PM

Quote:

Originally Posted by audiopro74 (Post 22985686)
One piece steel rail, only has a super thin sheet of paper gap on the front. Rings are high end matched, matched rings. Not sure they need lapping, just trying to give this rifle every chance to bang steel at 1000. Itís my first foray into the long range game, and I donít wanna it any corners.

You paid big bucks for rings and then your going to ruin them? Bed the base and be done with it, that is if you bought quality base.

Preston-CLB 05-12-2019 6:23 AM

Please forgive my ignorance, but I have two questions:

1. What is 'Scope Lapping'?
2. Why is it done?

Thanks, gents,
-p

mtenenhaus 05-12-2019 6:35 AM

here's an example of one of the commercially available kits to lap riflescope rings.
https://www.brownells.com/gunsmith-t...rod126532.aspx

Basically it helps you both to align the rings so there's no undo pressure on the scope body...and it makes sure that the contact surfaces of the inner aspects of the rings are near perfectly inline and in contact with the scope body. In effect improving upon any mismatch or machining irregularities in the rifle mounting relationship.

Hope that helps.

LynnJr 05-12-2019 8:49 AM

Quote:

Originally Posted by Preston-CLB (Post 22993333)
Please forgive my ignorance, but I have two questions:

1. What is 'Scope Lapping'?
2. Why is it done?

Thanks, gents,
-p

It's a process that is supposed to allow for 100% contact between the scope rings and the scope tube.
It is done because the scope tube and the scope rings are machined parts and have tolerances.

Preston-CLB 05-12-2019 11:15 AM

Thanks for explanation, gents!
-P

hambam105 05-12-2019 3:30 PM

Who needs 100% scope body to scope rings contact, and who needs precision machined parts when 'Good-Enough' will do?
:saddam:

ar15barrels 05-12-2019 3:48 PM

Quote:

Originally Posted by desertrider (Post 22985609)
I'm not going to knock lapping rings as a waste of time and effort, because there are situations when it may be the best option, but have you already eliminated all other variables causing the misalignment you're experiencing?

Do all mounting screw holes in the receiver align properly?

Are you using a one piece scope base or two piece?

If you're using a one piece scope rail, does it sit flush with no gaps?

Are you using name brand rings? (Beware of cheap, poorly machined rings)

Remember, you are combining several different systems, probably all manufactured in different facilities on different machines. All provide an opportunity for different tolerances between each other.

There's a good chance that if you eliminate all tolerance inconsistencies between the mating parts it may not be necessary to lap your rings.

The main reason to need tp lap rings is that the scope base does not fit correctly and the person has chosen to tighten it down to the reciever and twist the base instead of bedding the base to the reciever.
If you bed the base to the reciever so that the base is not twisted AND you use good quality rings, the scope will set in the rings and slide like it's on air bearings because everything is in alignment.
When the base is twisted or the rings are NOT square, then the scope tube binds and lapping will cut out the misalignment.

People don't realize that if you put the rings on different slots on the base after lapping that the rings are no longer straight to each other if the base is warped by being force fitted to the reciever.
This is not the case on a straight bedded base though.
You can move the rings and maintain alignment when the base is straight.

Lapping should be the last ditch effort to fix misalignment.
The FAR better method is to bed the base.

ar15barrels 05-12-2019 3:49 PM

Quote:

Originally Posted by sigstroker (Post 22986208)
The plastigage thing is for bearings, which are supposed to have a certain clearance. Scope rings aren't supposed to have any clearance.

Plastigauge will show angular misalignment very well though.

ar15barrels 05-12-2019 3:51 PM

Quote:

Originally Posted by sigstroker (Post 22986391)
Did you read somewhere this was a good idea? The point of lapping is to have even contact along the whole surface of the ring. The plastigage won't tell you anything about that because if there are high spots, you won't be able to tell. Those high spots won't compress.

I take it you have not used plastigauge.
It will absolutely tell you if you have misalignment.

ar15barrels 05-12-2019 3:52 PM

Quote:

Originally Posted by desertrider (Post 22986555)
If the flattened plastigage isn't uniform in it's spread I'd attribute that to imperfections in the machining of the rings.

29 times out of 30, the problem is the base being twisted on the reciever, not the ring machining.

ar15barrels 05-12-2019 3:58 PM

Quote:

Originally Posted by Preston-CLB (Post 22993333)
1. What is 'Scope Lapping'?
2. Why is it done?

The use of a mandrel and abrasive (lapping) compound to correct misalignment within the rings to eliminate angular misalignment stress on the scope tube.

It's a "hack" fix for parts that don't fit correctly to begin with.

LWP 05-14-2019 12:51 PM

Quote:

Originally Posted by Ramsh00ter (Post 22987524)
I lap all steel rings! Does it do any good, I don't know. But it eliminates the possibility. Shooting to me has a certain about of head games to it, so eliminating every variable I can just helps my head.

Got into a debate with a Leupold tech about lapping rings when I asked if they could supply a 34mm lapping bar. They tried to tell me their rings were near perfect and did not need lapping..... Really....

After having a 34mm bar ground from an old rail gun barrel, I lapped the 34mm Leupold rings, they were not round and had high spots.

I have lapping bars for 1" 30mm, & 34mm.

Pay the shipping and promise to return it, you can borrow it.

The 1" and 30mm were cheap to make, just order the bar stock from McMaster Carr and a handle. The 34mm was a different story, had to have one ground.

Drill a hole, tap, screw in the handle and you are ready to go.

I lap with four different compounds, 300 grit, 600 grit, 1200 grit, and Ultra Bright Tooth paste.

I can post a picture of what I made when I get home if you would like, they are easy.

PM me if you want to borrow mine.

I agree with you, if you have the tool and are able to do it, which is very simple, why not. It only makes sense, especially after you start lapping for a few minuets and confirm from the results where the high and low points inside the rings are. And if there aren't any you'll know quickly and can stop. No harm no foul.

boyguan 05-14-2019 9:55 PM

Hitting steel at 1000 was easier than I thought. All this work isn’t needed if your goal is a24x24 at 1000

Mute 05-15-2019 8:11 AM

If it ain't broke, don't fix it. Shoot your set up first and see if it actually performs as needed.


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