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Durkin Tactical Franklin Armory
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Posted: 7/19/2010 3:09:07 PM EDT
I have a mount that has two capture points on the rail for an optic

the threads on one side are messed up.....

the original size was 10-32

I am going to re-tap in 12-32

my question is is the 12-32 screw too big for the slot in a Picatinny rail?...

so someone with a 12-32 screw handy please check....

I know that that the screws are supposed to have a major diameter of .216 and the rail slots are supposed to be between .206 and .214

someone check please....
Link Posted: 7/19/2010 3:14:57 PM EDT
[#1]
Have you tried using a 10-32 tap to chase the threads?
Link Posted: 7/19/2010 3:20:25 PM EDT
[#2]
Quoted:
Have you tried using a 10-32 tap to chase the threads?



no

as the threaded area is smooth to the tune of .192 or so where it pealed the aluminum....

I did not torque down on it when it did it but it did it...and I do not want to buy another mount ($175.00) as they do not sell the base separate....and it is a flip to the side type mount.....
Link Posted: 7/19/2010 3:30:42 PM EDT
[#3]
Quoted:
I have a mount that has two capture points on the rail for an optic

the threads on one side are messed up.....

the original size was 10-32

I am going to re-tap in 12-32

my question is is the 12-32 screw too big for the slot in a Picatinny rail?...

so someone with a 12-32 screw handy please check....

I know that that the screws are supposed to have a major diameter of .216 and the rail slots are supposed to be between .206 and .214

someone check please....


It is probably not going to fit, but you could "force" fit a few thous if your rail is aluminum and you don't mind gouges in the anodizing.  You could probably just thread it through and it will work itself in without much force at all.

But a 12-32 is a UNEF so it's not exactly an easy tap to find at the local hardware store.   Major is .212-.215 on a #12 2A.   That increases to .213-.216 on a #12 3A...    


Or, try a heli-coil type threaded insert to repair the bunged hole.    

Or retap to 12-28 and get a stud that is 12-28 on one side an 10-32 on the other - run that through the rail and nut on the 10-32 side.



Link Posted: 7/19/2010 4:01:42 PM EDT
[#4]
Quoted:
Quoted:
I have a mount that has two capture points on the rail for an optic

the threads on one side are messed up.....

the original size was 10-32

I am going to re-tap in 12-32

my question is is the 12-32 screw too big for the slot in a Picatinny rail?...

so someone with a 12-32 screw handy please check....

I know that that the screws are supposed to have a major diameter of .216 and the rail slots are supposed to be between .206 and .214

someone check please....


It is probably not going to fit, but you could "force" fit a few thous if your rail is aluminum and you don't mind gouges in the anodizing.  You could probably just thread it through and it will work itself in without much force at all.

But a 12-32 is a UNEF so it's not exactly an easy tap to find at the local hardware store.   Major is .212-.215 on a #12 2A.   That increases to .213-.216 on a #12 3A...    


Or, try a heli-coil type threaded insert to repair the bunged hole.    

Or retap to 12-28 and get a stud that is 12-28 on one side an 10-32 on the other - run that through the rail and nut on the 10-32 side.





I most likely will retap to 12-28...thank you for the help sir...
Link Posted: 7/19/2010 6:30:29 PM EDT
[#5]
Why not just helicoil it?
Link Posted: 7/19/2010 6:36:57 PM EDT
[#6]
Quoted:
Why not just helicoil it?


In true arfcom fashion helicoil both holes while you are at it.  
Link Posted: 7/19/2010 7:07:28 PM EDT
[#7]
Quoted:
Quoted:
Why not just helicoil it?


In true arfcom fashion helicoil both holes while you are at it.  


because I have never seen this tell me more please gentlemen....I am also doing research but help fill the common mistake gaps with said helicoil.....
Link Posted: 7/19/2010 7:15:06 PM EDT
[#8]
ok...now that I am convinced...where can I purchases said helicoil kit....
Link Posted: 7/19/2010 7:17:36 PM EDT
[#9]
a helicoil should solve your problem look into it
Link Posted: 7/19/2010 7:25:20 PM EDT
[#10]
Quoted:
ok...now that I am convinced...where can I purchases said helicoil kit....


You could try a local machine shop, they tend to have plenty of things to un-fark holes.

Or to get a helicoil kit, try a GOOD autoparts store, like a Napa.  Or look up local branches of Motion industries or MSC.

You will want the helicoil kit ~$50-60 (with tap, drill, install tool, and a bunch of inserts ) , not just the inserts which are about $1-2/pkg.

Drill the hole clear through with the drill bit in the kit, then use the special STI tap in the kit to cut the thread for the helicoil, then use the instalation tool to put the helicoil into the hole.   The helicoil is like a big slinky that mates between the thread you just cut and a 10-32 thread.  Worth their weight in gold.

Here is the common 10-32 kit good for holes as shallow as 3/16".

10-32 Helicoil Set @ MSC
Link Posted: 7/19/2010 8:12:34 PM EDT
[#11]
Link Posted: 7/20/2010 12:14:55 PM EDT
[#12]
Quoted:
Quoted:
ok...now that I am convinced...where can I purchases said helicoil kit....


You could try a local machine shop, they tend to have plenty of things to un-fark holes.

Or to get a helicoil kit, try a GOOD autoparts store, like a Napa.  Or look up local branches of Motion industries or MSC.

You will want the helicoil kit ~$50-60 (with tap, drill, install tool, and a bunch of inserts ) , not just the inserts which are about $1-2/pkg.

Drill the hole clear through with the drill bit in the kit, then use the special STI tap in the kit to cut the thread for the helicoil, then use the instalation tool to put the helicoil into the hole.   The helicoil is like a big slinky that mates between the thread you just cut and a 10-32 thread.  Worth their weight in gold.

Here is the common 10-32 kit good for holes as shallow as 3/16".

10-32 Helicoil Set @ MSC


+1 to the above. You'll probably also need a tang breaker, but you can easily make one with a nail and a hacksaw. Cut a slot in the end of the nail, then slide the nail down in the hole and turn until you feel the slot slip over the tang. Twist the nail counterclockwise a tiny bit and then back clockwise...the tang should break right off. If you don't remove the tang, it can jam the screw(depending on screw length).

The other option is a thread insert....basically a steel tube that's threaded inside and out. You drill the hole oversize and tap for the insert, then screw the insert in and you're done, no special tools required. All of them I've used have used standard hardware store drill and tap sizes.
Link Posted: 7/20/2010 2:22:42 PM EDT
[#13]
Quoted:
Quoted:
Quoted:
ok...now that I am convinced...where can I purchases said helicoil kit....


You could try a local machine shop, they tend to have plenty of things to un-fark holes.

Or to get a helicoil kit, try a GOOD autoparts store, like a Napa.  Or look up local branches of Motion industries or MSC.

You will want the helicoil kit ~$50-60 (with tap, drill, install tool, and a bunch of inserts ) , not just the inserts which are about $1-2/pkg.

Drill the hole clear through with the drill bit in the kit, then use the special STI tap in the kit to cut the thread for the helicoil, then use the instalation tool to put the helicoil into the hole.   The helicoil is like a big slinky that mates between the thread you just cut and a 10-32 thread.  Worth their weight in gold.

Here is the common 10-32 kit good for holes as shallow as 3/16".

10-32 Helicoil Set @ MSC


+1 to the above. You'll probably also need a tang breaker, but you can easily make one with a nail and a hacksaw. Cut a slot in the end of the nail, then slide the nail down in the hole and turn until you feel the slot slip over the tang. Twist the nail counterclockwise a tiny bit and then back clockwise...the tang should break right off. If you don't remove the tang, it can jam the screw(depending on screw length).

The other option is a thread insert....basically a steel tube that's threaded inside and out. You drill the hole oversize and tap for the insert, then screw the insert in and you're done, no special tools required. All of them I've used have used standard hardware store drill and tap sizes.


well I did a lot of reading and and I am going to buy and go with the heli-coil type repair...there is not enough metal on the part to do the basic thread insert type.....but there is plenty enough for the heli-coil  ...there was the next larger size at work and it would have fit but I want to stay with 10-32....and the 12 sizes will require a slight modification to the rail so 10-32 is much better

I do not know why I have never heard of these before...they are awesome....thanks guys....

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