Screw size for older Lyman Receiver sight

Ian

Notorious member
The challenge with going to 8-40 for me hasn't so much been drilling and re-threading the hole as much as it has been enlarging the counterbore on the mount/base. Difficult to do without a vertical mill and a way to indicate dead-concentric with the original screw hole and counterbore.
 

Pistolero

Well-Known Member
HMMM. IME, a slightly oversized drill, if the part is held in a drillpress vise, because it WILL tend to
be grabby and the vise is held but permitted to be free to move slighty laterally, will self center very well. And
the hole bottom not being flat, should not be an issue, the outer perimeter if the screw should hold it
down fine.

If you drill it up, partial depth, don't "unflatten" the bottom of the counterbore, then use a mill cutter, which
will now fit in, not touch the sides, you can then deepen the counterbore and maintain a flat bottom.

I will add that I have not done this on a receiver site, but have on other, similar items.

Bill
 

Jeff H

NW Ohio
HMMM. IME, a slightly oversized drill, if the part is held in a drillpress vise, because it WILL tend to
be grabby........Bill
If you care to dedicate a twist drill to this specific task, you can grind a much steeper angle on the leading edges of the drill and it will be much less grabby in plastics. I started using the same drills to enlarge holes in aluminum and it works very well. I go by eye, but believe I'm putting only one or two degrees from horizontal on the edge. I've done this with twist drills for enlarging holes in aluminum, not so much for making a new one. I fill the drill flutes with Crisco and it lubes while holding the smaller chips and keeping them from getting between the drill and walls of the hole. It's more of a pain to clean out of drills and taps, but an old toothbrush does the trick.

This will still leave an angled bottom in the hole.
 

Charles Graff

Moderator Emeritus
The challenge with going to 8-40 for me hasn't so much been drilling and re-threading the hole as much as it has been enlarging the counterbore on the mount/base. Difficult to do without a vertical mill and a way to indicate dead-concentric with the original screw hole and counterbore.
I guess, I am just simple minded, but the sight base could be held tight on the receiver with one 6-48 screw and then a 8-40 tap drill can be run into base and through the receiver, making for concentric holes. Tap and tighten with 8-40 screw, remove 6-48 screw and do it again. With the receiver firmly locked to DP table, replace tap drill with a proper size small end mill and do the counter sink.
 
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Ian

Notorious member
"Firmly locked to DP table" is kind of an oxymoron with my flimsy drill press, but otherwise a sound method.
 

Charles Graff

Moderator Emeritus
I have a good 17" Jet floor model drill press bolted to the floor. She don't move! Before I bought it, I checked with Lee Jurras on Jet quality. He was making 1,000 yard bench rifles at the time. He told me that Jet machine tools were all they used in his shop.
 
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Ian

Notorious member
Jet is a great brand, very expensive too but you get what you pay for. I got to use a big floor model recently and it's even better than our old Rockwell in the shop here. I use a $200 Ryobi bench model at home and it is the definition of flimsy.
 

JWFilips

Well-Known Member
The challenge with going to 8-40 for me hasn't so much been drilling and re-threading the hole as much as it has been enlarging the counterbore on the mount/base. Difficult to do without a vertical mill and a way to indicate dead-concentric with the original screw hole and counterbore.
Well this is my big issue also: First off; I found out that the only receiver sight that will work without bolt interference on my Mod 39 Arasaka is the old steel Lyman 57! I wanted to use an old redfield but the inboard side sets the disk too far back so I would have to move it too far forward! The 57 seems to have equal draft inboard & outboard so centered on the receiver there is good clearance on bolt lift.
Since I have a good supply of Brownell's 6-48 screws I'm going with those because they fit the sight base without alteration. However I did order a new 6-48 carbon tap since my HSS one is worn (and a problem if I were to break it off)

Since in my shop it is Drill press drilling and hand taping I need all the help I can get!
This Jap rifle it built like a "Brick S-H" Now I'm worried that the receiver is heavily case hardened!
I pulled apart my share of old German Mauser's but these have them beat in quality construction! At least the early 20th century versions ( mine was built in the first decade of the 20th C) The inletting is impeccable and everything is over engineered!
 

Snakeoil

Active Member
Hillman is the company I'm famliar with. Lots of their stuff is from Asia. Finding slot head screws is becoming a challenge. Most are now that foolish phillips/slot combination.
 

Charles Graff

Moderator Emeritus
Well this is my big issue also: First off; I found out that the only receiver sight that will work without bolt interference on my Mod 39 Arasaka is the old steel Lyman 57! I wanted to use an old redfield but the inboard side sets the disk too far back so I would have to move it too far forward! The 57 seems to have equal draft inboard & outboard so centered on the receiver there is good clearance on bolt lift.
Since I have a good supply of Brownell's 6-48 screws I'm going with those because they fit the sight base without alteration. However I did order a new 6-48 carbon tap since my HSS one is worn (and a problem if I were to break it off)

Since in my shop it is Drill press drilling and hand taping I need all the help I can get!
This Jap rifle it built like a "Brick S-H" Now I'm worried that the receiver is heavily case hardened!
I pulled apart my share of old German Mauser's but these have them beat in quality construction! At least the early 20th century versions ( mine was built in the first decade of the 20th C) The inletting is impeccable and everything is over engineered!
I put a tight fitting drill bit for the hole in the drill press chuck, shank down. I adjust the work until the drill shank is a smooth fit to the hole I want to enlarge. I then lock the work down to the table and have at it. No need for a mill. A good mill is a delightful thing, but cost more money than I care to invest in a home shop. Of course the "gear heads" think it is a must have machine, I don't.
 
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JWFilips

Well-Known Member
I guess I never Finalized this thread!
I put the Old Lyman Receiver sight on that Old Arasaka !
Everything went very easy ! Yes I used the 6-48 Screws My HSS tap worked fine! No Hardened receiver
And The old girl is shooting outrageously good! Just love the look of the old sight on the old gun. Will probably replace the front sight with an old Lyman 17 Globe with aperture insert also That will then match my GEW 98!
 
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FrankCVA42

Active Member
Bought one of the British steam engine model kits many years ago. the kind of kit where you have to D&T all the holes, assemble the parts and adjust and run the engine in. Did the base plate and stand and for whatever reason lost interest in the project. Came with screws and a couple taps. Sat on my workbench for quite sometime. Buddy came over to shoot the breeze and saw how far I had progressed. I just handed it to him and said go for it. Couple weeks later said come on over. He had completely finished it and had it running on a small air compressor. But he had a small machine shop in his basement. Mill,drill,lathe and surface grinder. Not hobby stuff, full on big machine shop style. Bought all of it when the aero space industry on Long island went bust. Literally had to take the stairs out and piece by piece lowered into the basement and reassembled. While I have the Brownells taps and die sets for scope and sights all I've used them for is cleaning up the already D&T'd holes. Also bought the Brownells screw assortment sets. Now that has more than paid for itself when your having a receiver sight and no screws. Seen too many rifles done by bubba swiss cheesed with screw holes and none of them line up. Beautiful Swiss K31 for $50 because bubba had at it with holes in the receiver both front and rear,sidewalls and where one would normally mount a receiver sight. So my hats off to all of you who do your own sight work. Sorry for the long post. Frank
 

Missionary

Well-Known Member
Only 6-48 screws I have that failed were on a Springfield 03A3 that someone milled the top rear sight area far to thin. So not the screws but the holes failed.