Home made ring lapping tool

[gitrdun]

I've been looking for a ring lapping tool without any sort of success at the Calgary stores. Russel's used to have them for around $50.00. I decided to build my own using 1" cold rold bar stock. I'm going to drill and tap it for a handle, make it 7" long and use valve grinding paste to lap the rings. Am I on track or out to lunch with this idea?

[hunt_and_fish]

Makes sense to me. Pretty simple tool when you think about it. As long as you have a good piece of straight steel that is the correct diameter, it should work fine.

[Pathfinder76]

It needs to be 100% concentric and the proper diameter. It it isn't, it could cost allot more than $50. IMO it's reverse economy. Look at Sinclair International.

[gitrdun]

Originally Posted by chuck

It needs to be 100% concentric and the proper diameter. It it isn't, it could cost allot more than $50. IMO it's reverse economy. Look at Sinclair International.

I measured the cold rolled steel with a micrometer, it's about .003" undersize. then I measured three 1" tube scopes, they average about .004" oversize. So, I'm kinda thinking that the .007" difference ought to allow for the lapping compound. And of course, you're right, the steel has to be concentric and straight to work properly. I'm going ahead with the project, on a cheaper set-up of course before I apply it to my BR gun.

[elkhunter11]

I made my own lapping tool by chucking a length of 3/4" pipe in the lathe, zeroing it perfectly, then turning it down to exactly 1".I left a not quite smooth surface finish,so it holds the lapping compound better.

[IR_mike]

Originally Posted by elkhunter11

I made my own lapping tool by chucking a length of 3/4" pipe in the lathe, zeroing it perfectly, then turning it down to exactly 1".I left a not quite smooth surface finish,so it holds the lapping compound better.

What was the original OD?

[elkhunter11]

What was the original OD?

I made it so long ago,I don't remember the OD,or even the pipe schedule.

[sinawalli]

I made one out of 30mm turned and ground steel from work. Drilled and tapped a hole for a 3" bolt, about half way, and it works very well!

[deanmc]

Might I suggest you use actual hard shaft as it will be far more true?

[gitrdun]

Originally Posted by deanmc

Might I suggest you use actual hard shaft as it will be far more true?

Sounds good.

[bwcweld]

bass pro carrys the wheeler kits

[berjerkin]

i bought a wheeler kit from p&d. they just mailed it to me. came with the 1" bar, lapping compound, locktite, torque screwdriver and bit set. works great. $100.

[vic1]

Don't use cold roll steel, use T&G 1045 shaft, it is grind shaft to perfect 1".
Just call around steel suppliers.

[deanmc]

Originally Posted by deanmc

Might I suggest you use actual hard shaft as it will be far more true?

Far more true??????? i hope the grammar police dont see this thread.

[sinawalli]

Originally Posted by vic1

Don't use cold roll steel, use T&G 1045 shaft, it is grind shaft to perfect 1".
Just call around steel suppliers.

X2! Although it is theoretically impossible to get "exactly" 1" od, it will be close enough for your needs.

[gitrdun]

In theory I will agree with the use of a steel composition that is harder than the ring material. But practically, elkhunter11 has made one out of pipe which is much softer than the materials suggested, and it apparently works for him. I'll give the cold rolled shafting a try for now. I'll mike the bearing surfaces before and after use.

[deanmc]

Cool idea. Let us know how it works out. I would like to try it on one.

[gitrdun]

So I make my tool by simply drilling and tapping 1/4"-20UNC and screwing in a handle. I am using a 220 grit lapping compound.

Here, the tool sits in the lower rings. I've coated the bottoms with the lapping compound, and coated some on top of the lapping bar.



Now, I've installed the upper halves of the rings. At first I only tighten the ring screws very lightly. Start turning the lapping tool back and forth and slide it forward and back. As resistance eases off, I'll tighten the rings screws just a bit. I also make sure that the gap between the flats of the upper and lower ring remains even throughout the operation. I use a feeler gauge for this purpose.



Here we have the finished bottom front ring. Note the shiny spots. Top half of this ring looks similar.



This is the finished bottom rear ring. Again, the top half looks similar.



I don't know to what extend, but this has to be putting some stress on a scope tube. Don't know whether it would be detrimental, but based on what I'm seeing, I think that I'll be lapping all my rings.

[berjerkin]

looks like it worked out ok. you will definetly have less stress and a better hold on your tube now. nice job!

[elkhunter11]

I use the bar as much as an alignment tool,as a lapping bar.
Before I start lapping,I put my bar in the rings in place of my scope and torque it down.I then give the bar a few raps with a soft hammer,and then retorque the ring screws.This helps to make sure that the rings are aligned before I start lapping.I then remove the top halves,and lap until I see good contact across the lower ring surfaces.

Just looking at the pattern,your front ring may not have been perfectly aligned, before you began lapping.

[deanmc]

Very interesting and educational. Thanks for posting.

[deepstuff]

Should a lapping bar be slightly undersize or exactly 1.000" in diameter?

[qwert]

I keep a similar piece of 1" cold rolled and use it with good results as you suggest, but only on standard quality rings with 2 piece bases.

I do not lap my high quality rings mounted on 1913 P rails as lapping is not recommended by NF and will void warranty. I epoxy bed rails carefully to avoid any distortion when tightened, as this avoids the need for lapping.

Good Luck, YMMV.

[Duke1]

Bore a hole in in the center of 1 end along the axis of the bar and thread to 3/8 UNF. This allows the use of a power drill with a flex shaft to spin the bar for the coarse grind, making the job go much faster. For the coarse grind I use Permatex 474G automotive valve grinding compound (can be acquired from NAPA or other parts store for about $10.00 per 115ml cup). Be careful not to remove too much material and wipe it clean before the fine grind. Bore 2 holes on the radial side of the bar in line with each other, 1 in the middle and 1 at the opposite end of the axially bored hole, thread to 3/8 UNF. For the fine grind I use 2 - 3/8 UNF threaded handles about 3" long with knobs, allowing the use of both hands for better control and faster cutting (1 handle can be threaded out to remove the bar when the ring tops are in place). I use Wheeler 220 grit lapping compound for the fine grind. elkhunter11's method is very similar to mine and works good.

[Bushrat]

I always number and index the top rings to the bottom so when you take them off to install the scope that they don't get reversed or misplaced front to back or your lapping efforts are wasted.

[Au revoir, Gopher]

Originally Posted by gitrdun

Here, the tool sits in the lower rings. I've coated the bottoms with the lapping compound, and coated some on top of the lapping bar.

My goodness, that is a lot of lapping compound! It's like Brylcream, a little dab will do ya.

Originally Posted by Bushrat

I always number and index the top rings to the bottom so when you take them off to install the scope that they don't get reversed or misplaced front to back or your lapping efforts are wasted.

Yup. Centre punch and hammer... one dot top and bottom of one pair, two dots on the other pair; only mark one side. That way they will go back on the same way every time.

ARG

[lake side]

I made mine out of a piece of Induction hardened (IHCP) 30mm T+G. super hard and the lapping compound wont cause wear. Works like a charm.


L.S.

The founder of premier reticle in the USA suggested folks use copper pipe/tubing. On a typical ruger (where Reaming works best) I suppose it could be done. All things relative, low cost solutions often work best for low cost items .... I guess this is where buris signature RI gs would be better then a cheap lapping tool. A quality tool can always be rented out to reduce its cost. Given the cost of rifles, optics and components I don't understand the benefit of this idea. In pinch........maybe.....lesser evil I suppose...

[xcaribooer]

sorry to re boot an old thread but I am wanting to make my own 30mm lapping tool as well.
I have access to some shaft steel that measures about 1 5/32" or slightly over29mm (I haven't used a micrometer to check exactly)
my question is are 30mm scope exactly 30mm? will using stock slightly undersize by half a mm be a bad thing?

[gitrdun]

My Sightron SIII tube measures 30.01 mm. Since posting, I've purchased a Wheeler kit. The bar measures 29.79 mm.

Your 1 5/32" (1.15625") converts to 29.368 mm. The next size up would be 1 3/16" (1.1875") which converts to 30.162 mm (too big in my opinion). Close, but possibly not close enough, although since undersize wouldn't hurt to try. I could turn an exact dimension bar on the lathe. However, I'm in Alberta and you're in BC. I'm certain a local machine shop could turn one for you. If I were you and plan to get a machine shop to turn one, I'd ask for 29.79 mm or 1.172 ". I certainly hope this helps and isn't too confusing, and good luck.