GTA
All Springer/NP/PCP Air Gun Discussion General => Machine Shop Talk & AG Parts Machining => Show us your Custom Airgun Parts (TRICKS-N-TIPS) => Topic started by: nced on July 18, 2021, 01:20:59 PM
-
I normally exceed the "max recommended" scope mount base screw torque on my HW95 so after "multiple excess torquings" the aluminum threads tended to strip. Well, the horizontal base screws for the UTG dovetail to Picatinny adapters I've been using have M4-0.7 size horizontal screws and indeed I stripped one of the threads so a repair was needed. The mount in question...........
(https://i.imgur.com/Xq1safx.jpg)
Preparing the base by drilling out the 4mm threads using a 5mm drill bit..........
(https://i.imgur.com/viEqmgT.jpg)
On to the minilathe to machine, drill and thread a scrap steel rod to make steel "press in" inserts............
(https://i.imgur.com/jvK8Enx.jpg)
Turn down the scrap steel rod to 6mm, then reduce the 6mm diameter to "press fit" into the 5mm drilled holes. The rod is reduced for about 3/8" length (about 2.5 thread diameters) leaving the 5mm diameter as a stop..........
(https://i.imgur.com/jvK8Enx.jpg)
Drilling the steel rod with a #30 drill (closest imperial size) for a M4-0.7 tap..........
(https://i.imgur.com/109drAc.jpg) (https://i.imgur.com/5RKeTlP.jpg)
Tapping the rod M4-0.7mm..........
(https://i.imgur.com/gCsUlG5.jpg)
Parting off a press in insert after breaking the sharp edges. I did find that my parting tool reduced the threads a bit at the part which required chasing the thread with the tap to restore the thread dimension..............
(https://i.imgur.com/E0S0YZV.jpg)
The inserts ready to be "oil blued" by heating oiled inserts with propane torch till they turn blue, then changing to "black" when cooling.........
(https://i.imgur.com/mxNfP3a.jpg) (https://i.imgur.com/E472gvY.jpg)
Securing the inserts with red thread locker (ran out of blue locker) however I "did a blunder" by using excess thread locker that got into the insert threads when using the base screws to pull the inserts into place. This caused one of the screws to be "thread locked" into the insert requiring heat to break the bond. Removing all the installed inserts with heat they were cleaned and reinstalled with less thread locker after chasing the threads with a M4-0.7 tap to clear out "thread locker residue"......................
(https://i.imgur.com/3AAncab.jpg) (https://i.imgur.com/xp7EcyY.jpg) (https://i.imgur.com/hDB2jYr.jpg) (https://i.imgur.com/1sPerXe.jpg) (https://i.imgur.com/vYBdFvi.jpg) (https://i.imgur.com/hDZWgq8.jpg)
Worked a treat so I did the same thing to the other UTG adapter used on the R9!
Garmic thanked
Quote
KWK
KWK
(@kwk)
Joined: 1 year ago
Posts: 264
June 23, 2021 21:44:20
Good repair. Better than new 👍
-
For those lacking creativity and a lathe another option is a helical insert. These are available from McMaster - Carr. They are not cheap but if you lack a machine shop they are an alternative. https://www.mcmaster.com/helicoils/ (https://www.mcmaster.com/helicoils/) They are also produced under the brand name Heli-Coil.
-
For those lacking creativity and a lathe another option is a helical insert. These are available from McMaster - Carr. They are not cheap but if you lack a machine shop they are an alternative. https://www.mcmaster.com/helicoils/ (https://www.mcmaster.com/helicoils/) They are also produced under the brand name Heli-Coil.
I have used many in 3/8" and 1/2". There is other brands that do basically the same thing, but slightly differently.
Well done Ed!
-
For those lacking creativity and a lathe another option is a helical insert. These are available from McMaster - Carr. They are not cheap but if you lack a machine shop they are an alternative. https://www.mcmaster.com/helicoils/ (https://www.mcmaster.com/helicoils/) They are also produced under the brand name Heli-Coil.
+1
Blue 242 loctite works great for high vibration/stress and stops the screws from coming loose over time.
-
For those lacking creativity and a lathe another option is a helical insert. These are available from McMaster - Carr. They are not cheap but if you lack a machine shop they are an alternative. https://www.mcmaster.com/helicoils/ (https://www.mcmaster.com/helicoils/) They are also produced under the brand name Heli-Coil.
Problem is that there really wasn't enough clearance to install a threaded coil. I initially tried to drill one of the existing 5mm screws that came with the mount and found that the crest of a M4-0.7 thread was larger than the root of a M5 thread so no go. Then I considered that I could tap a 5mm rod with a M4 tap so I sized the rod for a press fit in a drilled 5mm hole. Anywhoo, using M4-0.7 x 22mm screws to pull the insert in place worked well.
-
I think the way you fixed it is ultimately better than a thread insert. Now you can take it on/off as many times as you like without the concern of stretching the threads every time. Excellent work.
Dave
-
There's a locking insert it's male threaded and screws in the hole then your screw screws in as normal.
Nice job Ed...
Good tinker project for a boring nothing better to do day...lol
Lol.... For your worth per hour how many new rails could you of bought... Several?
Ya, been there
-
Good going-that ought to hold up! :D
Didn't somebody (maybe you) do this another time not all that long ago? I got a complete Deja Vu feeling when I pulled up this thread...
Jesse
-
There's a locking insert it's male threaded and screws in the hole then your screw screws in as normal.
Nice job Ed...
Good tinker project for a boring nothing better to do day...lol
Lol.... For your worth per hour how many new rails could you of bought... Several?
Ya, been there
"Good tinker project for a boring nothing better to do day"
Yep! Took one and a half hours which is less time than going to a local WallyMart and back to buy mediocre pellets! :o
Ordering stuff online gives a lot of "boring nothing to do better today" time! Problem with new rails at about $17.50 each is the fact that they would still have new aluminum threads with a max 25 in/lbs torque limit, not so with the steel inserts
-
Lol.. it take me a hour to dig out a bit . Gosh forbid there organized in there coffee cans.
I guess a guy could of made it sweat fit to hold them in tight?
If you fell like doing another try this next level
( not saying there's anything wrong with what you did / I like them. I say good job.)
Them medcore under $6 Walmart pellets seem fine for 40 yards off used T- post sawhorses a old 2x10 and a jack block with a old tee-shirt stuffed sock as a bench/ rest.
The R9 don't seem to mind them at all.
-
Lol.. it take me a hour to dig out a bit . Gosh forbid there organized in there coffee cans.
I guess a guy could of made it sweat fit to hold them in tight?
If you fell like doing another try this next level
( not saying there's anything wrong with what you did / I like them. I say good job.)
Lol.. it take me a hour to dig out a bit . Gosh forbid there organized in there coffee cans.
I guess a guy could of made it sweat fit to hold them in tight?
If you fell like doing another try this next level
( not saying there's anything wrong with what you did / I like them. I say good job.)
Them medcore under $6 Walmart pellets seem fine for 40 yards off used T- post sawhorses a old 2x10 and a jack block with a old tee-shirt stuffed sock as a bench/ rest.
The R9 don't seem to mind them at all.
Sweat fit??? Kinda hard to sweat steel to aluminum. Actually, the press fit of the machined adapter is sufficient to prevent the insert turning when tightening the base screw but I used thread locker simply as a precaution and there was no need to tap the base for the insert.
-
Good going-that ought to hold up! :D
Didn't somebody (maybe you) do this another time not all that long ago? I got a complete Deja Vu feeling when I pulled up this thread...
Jesse
Well....years ago I had one of the front stock mounting screw holes stripped and used commercial threaded inserts to repair...........
(https://i.imgur.com/Vyc6AZG.jpg) (https://i.imgur.com/IDIV19L.jpg)
I also "posted" all my HW stock screws with home turned screw cups and posts...........
(https://i.imgur.com/G4znrw4.jpg) (https://i.imgur.com/UTKu4Vs.jpg) (https://i.imgur.com/mvh5tuz.jpg) (https://i.imgur.com/PmXQtlw.jpg) (https://i.imgur.com/z0pARoA.jpg) (https://i.imgur.com/hrh2PNW.jpg)
-
Not that kind more compression fit
Drill hole slightly undersized put insert in freezer when ready to install heat up hole as hot as you can to expand it then quick press cold ( contracted) inset in and when to all comes to ambient air temp the hole contracts and the insert expands and puts a tight choke hold on it. . We just on the job call it sweat on a fitting unlike soldering...lol.. my bad
P.s..
I like the caps.
-
Good going-that ought to hold up! :D
Didn't somebody (maybe you) do this another time not all that long ago? I got a complete Deja Vu feeling when I pulled up this thread...
Jesse
Well....years ago I had one of the front stock mounting screw holes stripped and used commercial threaded inserts to repair...........
I also "posted" all my HW stock screws with home turned screw cups and posts...........
OK-now I'm hearing twilight zone music in the background.... Because what I swear I remember was someone doing the exact same thing you just did on the scope mount.... Red Loctite, oil blue, everything.... ???
Aha! Found it-you had already posted up this (most excellent) fix on June 7-I'm not crazy :D
https://www.gatewaytoairguns.org/GTA/index.php?topic=188106.0 (https://www.gatewaytoairguns.org/GTA/index.php?topic=188106.0)
Jesse
-
Good going-that ought to hold up! :D
Didn't somebody (maybe you) do this another time not all that long ago? I got a complete Deja Vu feeling when I pulled up this thread...
Jesse
Well....years ago I had one of the front stock mounting screw holes stripped and used commercial threaded inserts to repair...........
I also "posted" all my HW stock screws with home turned screw cups and posts...........
OK-now I'm hearing twilight zone music in the background.... Because what I swear I remember was someone doing the exact same thing you just did on the scope mount.... Red Loctite, oil blue, everything.... ???
Aha! Found it-you had already posted up this (most excellent) fix on June 7-I'm not crazy :D
https://www.gatewaytoairguns.org/GTA/index.php?topic=188106.0 (https://www.gatewaytoairguns.org/GTA/index.php?topic=188106.0)
Jesse
Ooooppppssss....thanks for the "mind clearing" because I thought that post was only on the "other forum" so I THOUGHT I'd simply re-posted it here.
Red faced and embarrassed nced! :-[
-
Don't be embarrassed.. nothing wrong with refreshing help and tips.. threads get buried over time.. keep it out there for new guys to easy find .
I thinknk your stuff is good interest to me.
-
That's OK, no big deal :D
Jesse