Stripped threads

[markthenewf]

Well, I trashed the internal threads on the frame (aluminum) of my Kimber CDPII for the grip screws....or those bushings or whatever they are. Either way, the soft aluminum just can't take much torque load from tightening those steel bushings so the threads are all but gone and the bushing is completely loose. I'm ticked-off to say the least.

I've read here that everyone is retapping the holes and putting in 'ovesize' bushings to suit, but what gets me is the amount that this ocurrs. I spoke to an engineer from Crimson Trace who says he sees strippped threads on aluminum frames all the time. That's rediculous.

I'm not planning to retap (I've got the dexterity of a bear) and here in Houston everyone tells me that they'd take a month to do it for me (gunshop, etc.). I'm just going to clean out the hole, get a regular sized bushing, and use a few dabs of JB weld on it. If that holds ok. I'm also going to remove the other bushings and put some blue thread lok on them in order to make sure this doesn't happen again.

Hasn't anyone come up with an alternative to this rotten bushing-scew setup? Someone needs to invent some sort of back-face scew-on compression fitting (countersunk into the back of the frame) so that when you screw in a grip, it pulls it tight against the frames opposite face when the screw grabs ahold of its threads. That way you can only fuddle-up those two pieces of which you can always have a spare or two of.... heck of a lot better than having to retap or JB weld!

Anyone else do a "JB job" on ther grip fasteners?

[log man]

Well, I trashed the internal threads on the frame (aluminum) of my Kimber CDPII for the grip screws....or those bushings or whatever they are. Either way, the soft aluminum just can't take much torque load from tightening those steel bushings so the threads are all but gone and the bushing is completely loose. I'm ticked-off to say the least.

I've read here that everyone is retapping the holes and putting in 'ovesize' bushings to suit, but what gets me is the amount that this ocurrs. I spoke to an engineer from Crimson Trace who says he sees strippped threads on aluminum frames all the time. That's rediculous.

I'm not planning to retap (I've got the dexterity of a bear) and here in Houston everyone tells me that they'd take a month to do it for me (gunshop, etc.). I'm just going to clean out the hole, get a regular sized bushing, and use a few dabs of JB weld on it. If that holds ok. I'm also going to remove the other bushings and put some blue thread lok on them in order to make sure this doesn't happen again.

Hasn't anyone come up with an alternative to this rotten bushing-scew setup? Someone needs to invent some sort of back-face scew-on compression fitting (countersunk into the back of the frame) so that when you screw in a grip, it pulls it tight against the frames opposite face when the screw grabs ahold of its threads. That way you can only fuddle-up those two pieces of which you can always have a spare or two of.... heck of a lot better than having to retap or JB weld!

Anyone else do a "JB job" on ther grip fasteners?
Before I would use JB I'd use Loctite 271 and be sure to use the primer also for max strength and cure. Loctite 620 is a retaining locker that works in up to a .015" gap.

LOG

[Jolly Rogers]

I would not disturb any bushing that hasn't shown signs of loosening. Particularly in an aluminum frame 1911. I guess JB would work. I'm not sure Locktite would work after the hole is stripped. I suggest biting the bullet and letting Kimber fix it. They will weld,retap, replace the frame as necessary. Once your frame is addressed by a non factory repair facility the frame is yours to deal with in the future. Let Kimber have a swing at this to restore the frame to undamaged condition. Staking the bushings in an aluminum frame seems counter productive to me. It over stresses a thin soft area unnecessarily. If the frame is undamaged Loctite 271 is the route I would take. I don't know of a "molly bolt" solution to the grip screw bushing issue.
Joe

[markthenewf]

Thanks for the input, guys. After a few discussions with other vendors and 2 gunsmiths, I've come to the conclusion that those aluminum frames with thier easily stripped threads are a design flaw therefore I won't be asking Kimber to fix it. I'll be brininging it to a local smithy here to retap and set the larger bushing for the ruined hole and then getting him to add a drop of lok-tite to the others for good measure. Up until now I've been ok with Kimber, but this is quite unacceptable for what should be an exceptional product.

[tmbg]

putting torque on a steel fastener in aluminum has been stripping threads LONG before kimber came along...

[markthenewf]

Uhhhh, yeah. Just because that's the way it's been done for years doesn't mean it's right. Things should evolve, and as far as I'm concerned this is a design issue that has not proceeded to a better arrangement. I still like the Kimber, but it's a bug to say the least.

[BacAway]

More like a bull in a china shop for an OP. Just how much torque do you think the bushings or the grips screws really need?

[markthenewf]

???????????????

:rolleyes:Yeah, more usefull input. Thanks. I needed the condescension since 'Log man' and 'Jolly Rogers' had me feeling too good about the situation.

How much torque do you know is needed? Do you set yours to a certain lb-ft rating? I don't have a torque guage to mount for the driver but I've been around enough steel and aluminum (struct. engineer) to know what it's good for. In fact I know I didn't overtighten them as I've noticed that the other screws have failed to stay tight in the grip after one outing at the range. I've got a feeling that because I didn't tourqe them enough (for fear of damaging the threads) that the threads rode around a bit in the grooves causing just as much damage as overloading them.

How about next time you provide info as to how to know what the correct torque is rather than letting everyone know how smart you could be.

[Jolly Rogers]

If you inspect the diameter of the threads in the frame and the pitch of the threads on an undamaged bushing...just snug with thread locker on them. ;) Wait for a cure (overnight)and then you can tighten the grip screws with a standard handle screwdriver pretty good. The bushings are steel,carbon or stainless, so the threads in the bushing for the grip screws are pretty durable. The fit between the bushing and the frame is where the difficulty lies.
I don't have a torque driver at home nor do I know the torque specs for the parts so I'm basically no help here. :D
Joe

[niemi24s]

Sometimes folks tend to overtighten the grip screw because they loosen up when firing and this can lead to stuck grip screws and/or stripped bushings.

One way I've heard of to keep grip screws from shooting loose is to install them with O-rings underneath their heads. I'd think size AS-006 would do.

Regards

[BacAway]

Well Mark, I don't have the AMU T.O (that's Army Marksmanship Unit Technical Order) in front of me, but I do recall that it does specify a torque value. As for measuring the torque I have a 1/4" drive torque wrench that measures in in/lb, as well as a Wheeler FAT Wrench (http://www.midwayusa.com/viewproduct/?productnumber=718023). Wonderful tools for maintaining firearms.

Now from an engineering and/or metallurgy standpoint, it long been known that iron (grip screw bushings in this case) is harder than aluminum (your 1911 frame). That said, over-tightening any fastener that is mating in a material softer than the fastener itself, is asking for trouble. I think we can all admit to doing so at one time or another. Whether it be a grip screw bushing in a 1911 frame, or a wood screw in a piece of wood - bad things happen - but hopefully we learn from them.

For my money, and in your circumstance, I use Locktite (for its intended purpose) and because it does have some 'filling' capabilities, and I use the a torque wrench on all the screws/nuts, on all my firearms - grip screw bushings included.

Enjoy your 1911.

[Rick McC.]

I've got three alloy framed Kimbers, and none of those has stripped out. I have had to deal with some of the bushings coming out with the grip screw. Blue loctite took care of that.

The small o-rings do work great in keeping the grip screws from working loose. I was having a problem with that in my "harder" material grips. kimber will send you the o-rings for free; and they probably would fix the frame for you, too.

Take care,

Rick

[niemi24s]

FWIW, found this torque calculator http://www.futek.com/boltcalc.aspx which gave 26.8 in-lbs (2.23 ft-lbs) with the info I poked in the boxes, using T6 aluminum for the frame. However, have no idea what kind of aluminum alloy's used for 1911 frames. If you knew its yield strength, that could be entered using the custom selection.

If you select custom size, you can even enter 0.236" major diameter & 60tpi.

Futek's is the most versatile torque calculator I've found so far.

Regards

[markthenewf]

The possibility of that happening again totally turned my stomache, so I went ahead and got it 'fixed': rethreaded w/bigger bushings+loctite+staked. I think from here on in I'll avoid aluminum frames.