Another desporterization project

[Brian Alpert 0]

Painting is a great idea.  I am amazed how tough the coating is.

[eb in oregon 0]

31 minutes ago, Brian Alpert said:

Painting is a great idea.  I am amazed how tough the coating is.

Trying to remove the plating by bead or sand blasting isn't a good idea, hard chrome is called hard chrome for a reason. And as it is a plating process (controlled to a specific thickness) the best way to remove it is to de-plate; reverse the process and it comes off. However how thick is that plating? As it is a controlled process it can be tenths or thousandths, so to remove it could cause tolerance problems. Paint is cheap, you can touch it up as needed, the part is hidden inside the front of the receiver, and nobody will notice unless the barrel is taken out for observation. And as mentioned, hard chrome is ideal for wear and corrosion resistance. I'll also mention that hard chrome is pretty near impossible to machine, it is usually ground to a final dimension if needed. The best way to trash an endmill is to try to machine hard chrome. It's even hard on carbide.

[C P 0]

Does anyone know if the dovetail slot for the real sight corresponds to a standard dovetail size?  Or is it proprietary?

 

[eb in oregon 0]

2 hours ago, C P said:

Does anyone know if the dovetail slot for the real sight corresponds to a standard dovetail size?  Or is it proprietary?

 

If you use a genuine Johnson rear sight or a reproduction it should fit. I can't answer if the JRAR's rear sight dovetail was an industry standard dovetail but I know that there were some different sizes in different firearms, and that sort of indicates that some were proprietary to the maker. However, you'll need a 1941 Johnson sight as no other would really work as it is sort of specific.

[C P 0]

Progress on the rear sight. If anyone want's to use my measurements, feel free!

[C P 0]

[butch 0]

Looks good! How do you plan to attach the dovetail ?

[eb in oregon 0]

2 hours ago, butch said:

Looks good! How do you plan to attach the dovetail ?

I've been wondering that myself. Tig weld, spot weld, or a high temp silver solder is my guess.

[C P 0]

rosette weld, or spot weld so yeah.

  I'm not sure if I should heat treat this part or just leave it as is.  Does anyone know if the original sights were heat treated?

[eb in oregon 0]

57 minutes ago, C P said:

rosette weld, or spot weld so yeah.

  I'm not sure if I should heat treat this part or just leave it as is.  Does anyone know if the original sights were heat treated?

I don't know but an educated guess is "maybe" as the steel should be springy enough (depending on the material) and to heat treat such parts as that is problematic at best. They have a tendency to warp, twist, or otherwise deform. It's quite possible they made them out of spring steel in the first place as the sight appears to be a stamping which could have been heat treated before forming.

If only the factory drawings and manufacturing process documents were still available. 

[C P 0]

I'll heat treat a test piece then and see how it turns out.  Thanks.

[Joseph Scott 0]

I have previously made rear sights and they were definitely heat treated.  Spec. is annealed, 1095 high carbon steel, heat treated after bending down the little tabs and spot welding parts together..  Otherwise they snap off.  1095 is a water quench material.  My first ones were oil quenched and did not harden properly.  They must be tempered down somewhat to prevent snapping. Dovetail were originally spot welded but I had no luck with this and used riveted screws from the bottom.  Measuring dovetails is tricky.  I used 2 #55 drills under the lips to get a known dimension.  Even so, sometimes I had to peen the lips slightly to get a good fit. The male dovetail must be exactly 90 deg to leaf.  The upright back-end is also a challenge but are soft steel.  I had my parts laser or water-jet cut.  1940's machining used lots of go-no-go gages for such dimensions.   Good luck.

[eb in oregon 0]

22 minutes ago, C P said:

I'll heat treat a test piece then and see how it turns out.  Thanks.

You might be better off putting it in a foil bag and in a proper oven rather than using a torch and your eyeball.

[C P 0]

Got another question: Does the windage screw knob have spring detents?  Or is it kept from drifting by friction?

[eb in oregon 0]

8 hours ago, C P said:

Got another question: Does the windage screw knob have spring detents?  Or is it kept from drifting by friction?

Four clicks per revolution, .005 lateral sight movement per click. I measured twice with dial calipers. And you have to be careful to measure the same spot each time. The edge of that sight isn't exactly parallel to the sight ear. No idea how big a ball is being used, but it's quite easy to rotate.

Edit: I'm not taking mine apart to see, but I'm guessing that the spring and ball are in the knob as that sight ear is a bit thin for a hole with a ball and spring.

[C P 0]

Thanks!  That answers my question.

[C P 0]

 

Progress.

[butch 0]

Looking really good! Are you going to put the windage adjustment marks on too? 

[C P 0]

I don't have anything precise enough to make those markings unfortunately.  I would need either a proprietary stamp or some form of etching.

[butch 0]

 I wonder if the edge of a file could be used to make a stamp using the existing teeth. I count 15 marks in .375" on the leaf. Maybe something to experiment with first. Just a thought.I 

[eb in oregon 0]

On 5/12/2021 at 5:27 PM, butch said:

 I wonder if the edge of a file could be used to make a stamp using the existing teeth. I count 15 marks in .375" on the leaf. Maybe something to experiment with first. Just a thought.I 

A person would have to be real talented to scribe 15 identical marks exactly .025 apart with a file. There are shops however that do laser engraving. That might be worth investigating.

[butch 0]

If you have a milling machine you may be able to clamp your sight in the vice and have a stamping tool in your quill to mark it. That would make it easy to move it .025 at a time if you make one mark at a time. Not sure how hard the material is to stamp a mark into, but it should be pretty accurate that way. With a hard pointed tool you could drag a line whatever length you need. They aren't very deep so it may work. Mine are .150" long. Just throwing ideas out there.

[eb in oregon 0]

12 hours ago, butch said:

If you have a milling machine you may be able to clamp your sight in the vice and have a stamping tool in your quill to mark it. That would make it easy to move it .025 at a time if you make one mark at a time. Not sure how hard the material is to stamp a mark into, but it should be pretty accurate that way. With a hard pointed tool you could drag a line whatever length you need. They aren't very deep so it may work. Mine are .150" long. Just throwing ideas out there.

Actually an engraving tool would be the way to go (basically a sharp pointed carbide single flute end mill). It can be done, but it would be a PIA and the operator would need be careful about depth. Those fine lines are just that, really fine and only a few thousandth's deep. I have the tools and machinery but Alaska is a bit far away.

 

[C P 0]

After finishing the prototype sight and learning some lessons and revising dimensions from that one I built a second one out of tool steel.

The first sight was made out of low carbon steel and just wouldn't take heat treatment, so I couldn't make it springy enough. 

For the second tool steel sight I tried some different welding techniques like resistance welding and brazing.  If and when I build a third sight I think I'll use brazing exclusively since that worked really well.    

[eb in oregon 0]

You are talented and doing a good job.