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I upped to full member so I could post pictures. I also found out don’t take much time putting together your post or it will time out and erase it.
There is no evidence of the aperture being staked in the sight.
Neither JWA nor Joe has ever seen anything but 10-48 threads on these sights.
The sight drawings does not specify a thread size
A thread pitch of 48 / inch has a thread width of 0.020833”
We (USA) use a standard 60 degree thread.
The formula I have seen most often for thread depth is: 0.5412 X pitch and would equal 0.0113” thread depth
I have a pre-serial number Marlin80-DL with the Marlin 12R aperture that appears almost NIB. The threads in that sight are the same as the 69.
The pictures show a #10-48 tap not being able to go into either sight enough to get to the first whisper of thread on the tap.
A #8-48 tap is a sloppy fit.
Aluminum stock was drilled with a #18 bit to give a theoretical 75.8 % of 10-48 thread (thread depth 0.00856”). Best % there is on the drill chart. Joe’s aperture correctly screws perfectly in as I would expect.
As close as I can get with my caliper for thread ID (and compared to drills that would and would not fit).
Winchester 69 in question 0.165”
Marlin 80-DL 0.165”
Aluminum stock threaded with a new 10-48 tap 0.170”.
The #18 bit fits through the 10-48 in aluminum stock
It takes a #20 drill to fit through either of the rifle sights
Drill size for #8-48 is allusive. I used the drill size calculator from Newman Tools https://www.newmantools.com/tapdrill.htm
Using tap diameter of 0.157 48TPI and 75% thread calculated drill size 0.1367025”
Using a tap diameter of 0.160 yielded a drill size 0.1397025
From my favorite Decimal Equivalents chart:
#29 at 0.1360 is closest for 0.157”
#28 0.1405 is closest for 0.160” and yield 72% thread
Yep a #8-48 is a sloppy fit
This was better than worrying about frozen water pipes in the last storms
k7sparky said
I have a pre-serial number Marlin80-DL with the Marlin 12R aperture that appears almost NIB. The threads in that sight are the same as the 69.
Since you can’t easily shoot both rifles at the same time, why not use your Marlin disk in the 69? We won’t tell on you. Then you can worry about your water pipes.
Marlin doesn’t have a disk either.
If you read the original Humeston patent description for this sight it says the disk is optional.
I haven’t read any of the old stuff that refers to Ghost Ring sights, but that’s today’s vernacular for disk out.
The temperature is up to 55 so far today. Pipes are fine. Several surrounding communities with “city” water are shut off till the piped are replaced.
I’m off to do battle with magazine catches on LR10s. Ding dongs making them appear to think 0 to – clearance is a good thing. They are making them about 0.250″ wide for slots specified 0.250 +/ – 0.004″. Not real good at getting the stud centered top / bottom either. What’s that? YES! I would like a small glass for my whine!
Hi k7sparky,
You will not see any evidence of the staking on the 96A or 96B sight base. The aperture was threaded into the sight base and then a center punch shaped staking tool was inserted into the aperture hole on the thread side of the aperture that protrudes through the base tab. After it is struck it expands the protruding threads slightly wider than the tapped hole and prevents the aperture from backing out by very slightly mushrooming them outward. When a staked aperture is forcibly removed by unscrewing it forces the now slightly larger diameter aperture threads through the tapped base hole in the sight base sheet-metal tab and enlarges it.
So, having described that process, it is certainly possible that the actual original size of the aperture threads is 8-48 (I don’t have any documentation that actually states what the original size was). If all of the holes were enlarged with the removal of the aperture that would explain why Joe’s 10-48 fits most sights. If your aperture was never staked you could have an original (un-enlarged) hole. I have plenty of original sights with the aperture still staked in place but there is no good way to measure the threads or the diameter of the hole since the swaging of the aperture enlarges the accessible protruding diameter.
Again, that is just a possible theory, and again, I do not know what the actual original thread size and pitch is supposed to be as it is not specified on any drawing I have seen. Joe’s dimensions came from his actual measurements of sights but I don’t know if he took into account the swaging and/or possible enlargement of the aperture mounting hole. His apertures do fit into the typically enlarged holes though (except for yours).
It is an interesting mystery and hope we can solve it.
Best Regards,
Edit – I suppose we could take a sight with the original aperture staked in place and grind off the swaged protruding threads on the inside face and then carefully unscrew the aperture. That would reduce the possibility of deformation and allow a better measurement of the original tapped hole in the sight base and aperture threads. I don’t currently have a scruffy 96A or 96B sight to dissect but will keep it in mind for future experimentation.
WACA Life Member #6284 - Specializing in Pre-64 Winchester .22 Rimfire
k7sparky said
The formula I have seen most often for thread depth is: 0.5412 X pitch and would equal 0.0113” thread depthAluminum stock was drilled with a #18 bit to give a theoretical 75.8 % of 10-48 thread (thread depth 0.00856”). Best % there is on the drill chart. Joe’s aperture correctly screws perfectly in as I would expect.
As close as I can get with my caliper for thread ID (and compared to drills that would and would not fit).
I don’t like undefined constants. Been bit on the posterior too many times by them.
On wikipedia https://en.wikipedia.org/wiki/Unified_Thread_Standard
and in Machineery’s Handbook 17th ed page (where the wiki info came from) starting on page 1727 gives the information. Start with 100% thread which is sin of 60 degrees (0.866) then desired % thread .75% and more comes up to 0.514 or a bit more depending on class of thread fit.
Second quoted paragraph I used 75.8% times 0.0113 to get 0.00856″ I shouldn’t have used the % again. YEP not knowing the derivation of the constant bit me again.
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