Home Made lapping bar.

[MalleeFarmer]

So I've never lapped scope rings before. So I made a lapping bar out of a piece of 30mm shaft. I think it will cost me around $15 (haven't got the account from the steel shop). I used 400grit emery paper to clean it up. And then I drilled a 3/8 hole and threaded it 16NC and cut a rusty bolt off and polished it up cut off the head and shortened the thread and used a drill press as a lathe to get the top cut straight and then filed it smooth and the edges off while in the press to make the handle. I have checked the shaft in a scope ring and it's a perfect 30mm fit.

1. Make Sure You Use 30mm SHAFT not just 30mm bar or rod. Shaft is made to a higher tensile and level of precision than just bar or rod.

2. Drill a pilot hole and then drill out to desired size. Also I used a 1/2 drill bit. To de burr the top of the threaded hole. And then filed the burrs off of that. And then sanded the whole bar to a nice finish.

[MalleeFarmer]

Also I was wondering what lapping compound you guys use??

[<<Genesis93>>]

oh no..... not the lapping subject again

Good work MF....
I think I paid about 20bucks for a length of 1inch rod a while back....compound I got off the bunnings boutique shelf...

Eggspurts will chime in soon and tell you 'how to do it' or go to the other thread...

[MalleeFarmer]

I DON'T want to know how to lap I can find that on Google but it's pretty straightforward from what I've seen. I was just wondering if anyone had suggestions on what compound to use. I was actually thinking of using toothpaste.

Also I am interested in Linseed Oil Bluing so I decided I'd just heat the handle up in a gas torch and dunk it in pale boiled linseed oil then I repeated 3 times and got quite a good dark blue I think It could do a very good job if you were willing to repeat 5-6 times.

[<<Genesis93>>]

the eyeroll is not at you, its at what will follow.....

Standard lapping compound....not toothpaste

[MalleeFarmer]

Oh ok I thought the grit in toothpaste might be enough for a light lapping job. Oh well I'll get some valve lapping compound or something I can get off eBay.

[on_one_wheel]

I thought about lapping in my rings ...
Then I thought " I'm going to blow a day stuffing around with a rifle that shoots .5 moa off a perfect rest just to get it shooting somewhere near .5 moa so I can head out into the field using my side mirror as a rest, with the engine running, vibrating the s**t out of my rifle resulting in a 3 moa ... I'd be better off spending a day stuffing around with my side mirror."
Stand by for the modified shooters side mirror thread

I must admit, I admire the lengths people will go to get every last .001moa out of their rifles.
Thats dedication.
Your lapping tool looks the goods.

Ps ... that's what Genesis meant by

[MalleeFarmer]

I thought about lapping in my rings ...
Then I thought " I'm going to blow a day stuffing around with a rifle that shoots .5 moa off a perfect rest just to get it shooting somewhere near .5 moa so I can head out into the field using my side mirror as a rest, with the engine running, vibrating the s**t out of my rifle resulting in a 3 moa ... I'd be better off spending a day stuffing around with my side mirror."
Stand by for the modified shooters side mirror thread

I must admit, I admire the lengths people will go to get every last .001moa out of their rifles.
Thats dedication.
Your lapping tool looks the goods.

Ps ... that's what Genesis meant by

Yea I understand that and agree I have 3 rifles none of which have lapped rings. but since I'm going "all out" with the varmint rifle I'm building I thought the extra time to lap my rings just to eliminate a stress point on the scope and action would be worth it I'm also going to glass bed the action and the rail. I figure if I'm spending 4K on a rifle build I should isolate as many issues as I can. It's also not going to be a ute window rifle.

[Apollo]

4K on a Rifle, Gee... that's a cheap one..

I have 3 Scopes that are worth that each and there is no way they would get mounted in Rings, no matter how expensive or well made, unless they were lapped or at least checked with a Lapping Bar.

These Rifles if built these days with scopes would be over 10K each.

Even a cheap Sako 85 is lucky and gets Optilocks to achieve the same result...that result is an expensive Scope that is protected and looks like Brand New even after years of use.

BTW. The Lapping Equipment I have used comes from BRT and is an Undersized Bar with a sheet of Emery Paper that takes a few seconds to lap. Be it 25,30 and/or 34mm.

If I paid more than a hundred bucks or so for a scope then it gets lapped.

I have one and seen many scopes that are very badly damaged by cheap rings, over tensioned and other errors that people make that has produced very badly damaged scope tubes.

[on_one_wheel]

Sounds like it's going to be pretty flash. I'd recon it'll be all worth it on a decent varmint build.

[MalleeFarmer]

Sounds like it's going to be pretty flash. I'd recon it'll be all worth it on a decent varmint build.

Yea that's my thoughts. I don't have as much money as Apollo.. So 4K may as well be the whole earth at the moment I was lucky the wife bought me my scope for an anniversary gift.

[MalleeFarmer]

4K on a Rifle, Gee... that's a cheap one..

I have 3 Scopes that are worth that each and there is no way they would get mounted in Rings, no matter how expensive or well made, unless they were lapped or at least checked with a Lapping Bar.

These Rifles if built these days with scopes would be over 10K each.

Even a cheap Sako 85 is lucky and gets Optilocks to achieve the same result...that result is an expensive Scope that is protected and looks like Brand New even after years of use.

BTW. The Lapping Equipment I have used comes from BRT and is an Undersized Bar with a sheet of Emery Paper that takes a few seconds to lap. Be it 25,30 and/or 34mm.

If I paid more than a hundred bucks or so for a scope then it gets lapped.

I have one and seen many scopes that are very badly damaged by cheap rings, over tensioned and other errors that people make that has produced very badly damaged scope tubes.

How did you stop the emery slipping on the bar?

[Apollo]

I have a hold of it...with my hand...

Sorry, I'm in a happy mood.

The bar and emery are long enough and the bar has no handle so I can grip the butt end.

A little different to what you have designed but serves the same purpose as long as the bar is perfect in size.

I like your idea of Toothpaste, it might work and the idea being that it is not going to remove any great deal of material if only the finish inside rings but give you and idea of any high / low points. Valve Grinding Paste also maybe but the very fine one. Been 30-40 years since I ground valves.

Anything that is very, very fine abrasive wise.

I can't remember the grade of emery that I used with the BRT gear but it was super fine grade.

Now, Aluminium Rings are way softer than Steel so apply to suit. From memory my Kelbly Aluminium Rings took one turn, the Ken Farrel Steel Rings a few turns and a short pull. These are top end CNC Machined Rings worth a few hundred bucks but also near perfect so one little light touch. Some other cheap rubbish might take a bit of work but don't go too far and reduce the diameter inside.

Then after all that I use a Tension Wrench on all my Rings and Bases.

[Gwion]

Lapping compound that came with my kit is 220grit. You can get valve lapping compound or order various grits from online engineering suppliers.

[Arth]

1. Make Sure You Use 30mm SHAFT not just 30mm bar or rod. Shaft is made to a higher tensile and level of precision than just bar or rod.

So 'shafts', 'bars' and 'rods' are different things as far as a metals catalogue goes?

[MalleeFarmer]

Depends button what I have gathered from working with all sorts of equipment is if a shaft is 30mm it's designed to fit inside a 30mm bearing or (sprocket, gear, pulley etc.) so it has to be perfect (what you're after in a lapping bar) bar and rod will be close but don't require the precision that a shaft does. Also shaft is a higher grade of steel (to handle torsion when driving something) so the lapping compound will be less likely to shrink the shaft compared to the bar or rod.

[Gamerancher]

Me thinks Arth"s question about "shaft", "rod" and "bar" having different meanings may be in reference to their meanings in a "non-steel catalogue" setting.

[<<Genesis93>>]

What about billets and wire?
Rod, bar, shaft, billets and wire.....

[Gamerancher]

What goes on in the bedroom, stays in the bedroom.

[MalleeFarmer]

Me thinks Arth"s question about "shaft", "rod" and "bar" having different meanings may be in reference to their meanings in a "non-steel catalogue" setting.

Arth is on the wrong forum I think...

[huccl]

What goes on in the bedroom, stays in the bedroom.

Everyone loves a late night lapping