Helicoil thread repair?

TheJon

TheJon

Joined
Apr 12, 2014
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I have an aluminum scales for a Benchmade that had the threads for the pocket clip strip out. It's sat for probably a year while I debated what to do with it. So I'm debating how to fix it.

Has anyone ever tried using 2-56 helicoil to repair stripped knife threads? I debate if it would be worth it, or if I should drill and tap for a size up
 
That would be a tough insert to insert, being so small. You would probably need a prewinder to install it. I had to do a bunch of 5-40 helicoils and they were bad enough to get started without a prewinder.

How much to replace the scales?
 
What about using loctite?
Some are strong enough for slipfit
 
Can you simply drill and tap the hole(s) bigger , drill the holes in the clip bigger and put in bigger screws ?
I have done a train load of helicoils but I don't think it would be worth the effort in this case unless . . .
somebody can say why " bigger " would not work out .

PS : alternatively a pocket slip. A couple of my medium / Largish knives I prefer without a clip and carry in a slip or belt pouch , e.g., Cold Steel 4" Ti Lite .
 
Helicoils are often used to put machine screw threads in plastic and Carbon fiber scales. It helps if you have a drill press and a hand tapper. You need a Helicoil tap drill, a tap for the coil, an insertion tool, and the coils. It might not be a good investment for 1 knife. I have also drilled and tapped Aluminum and Titanium scales for #2X56TPI pocket clip screws.
 
Look up Keenserts. They’re FAR superior to Helicoils IMO.

I know they make down to size 2-56, but they require a certain minimum depth for proper engagement. I think ~1/8” for 2-56 iirc.
 
Another possible option might be these 2-56 threaded inserts. They're stainless steel and come in two lengths, 1/8th" and 3/32nds". Available from Macmaster-carr for $5 and change for a pack of 25, plus shipping. You can find them by searching Macmaster-carr for either part number 92985A814 (1/8th"), or 92985A813 (3/32nds"). If you use them I recommend drilling the holes using a size 31 drill bit for a snug fit.

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I was going to suggest drilling bigger and using a threaded insert, like the ones above. Could even use Loctite to fit them. I would not go the Helicoil route for something that small; cost of tap, tool, etc.
Going a size up in screw could be easiest, if you have space (is there space for the screw heads on the clip? Bigger screw, bigger head, same hole spacing. Also, can you source screws and tap in desired size.

One of our customers (aircraft engine maker) has insisted on us using some Keenserts for stuff they want to mount to our machine. Not my sub assembly, but I have been hearing a lot of grumbling because special tools are required for installation. Might also be availability, there has been a LOT of grumbling! We usually specify locking Helicoil Classics in imperial sizes, but it is recognised that the tangs are a royal PITA to remove from blind holes in the smaller sizes, and locking is unreliable in 4-40 and smaller.
 
C_Claycomb said:
One of our customers (aircraft engine maker) has insisted on us using some Keenserts for stuff they want to mount to our machine. Not my sub assembly, but I have been hearing a lot of grumbling because special tools are required for installation. Might also be availability, there has been a LOT of grumbling! We usually specify locking Helicoil Classics in imperial sizes, but it is recognised that the tangs are a royal PITA to remove from blind holes in the smaller sizes, and locking is unreliable in 4-40 and smaller.
Click to expand...
Curious what special tools they need for the Keenserts? They're really easy to install unless you're talking about an extra-hard or resistant material, like hardened steel or Ti. Then you do need their special broaching tool to pre-cut a path for the keys. I can install them in my garage with nothing more than basic hand tools (and have) even into mild steel.
 
SpyderPhreak said:
Curious what special tools they need for the Keenserts? They're really easy to install unless you're talking about an extra-hard or resistant material, like hardened steel or Ti. Then you do need their special broaching tool to pre-cut a path for the keys. I can install them in my garage with nothing more than basic hand tools (and have) even into mild steel.
Click to expand...
I will have to ask. Curious now!!!
Two different projects. One was into 7050 aluminium (I think. Not one of the 6000s, probably not 2014, although we have used that a lot). The other is 17-4PH H1025. The tool grumbling was definitely on the 17-4PH. Possibly when the housing cost more to machine than most family cars, there is more interest in how the inserts get fitted 😄.

Sounds like they might be a better option for the OP than Helicoils, if you have been doing them fine at home with hand tools.
 
C_Claycomb said:
I will have to ask. Curious now!!!
Two different projects. One was into 7050 aluminium (I think. Not one of the 6000s, probably not 2014, although we have used that a lot). The other is 17-4PH H1025. The tool grumbling was definitely on the 17-4PH. Possibly when the housing cost more to machine than most family cars, there is more interest in how the inserts get fitted 😄.

Sounds like they might be a better option for the OP than Helicoils, if you have been doing them fine at home with hand tools.
Click to expand...
Haha, yeah, the 17-4 is gonna be a bit difficult to cut after HT lol. That stuff sucks after HT, we use it a lot in aerospace, especially in the wind tunnel models I work with a lot.

Generally you just need standard drills and thread taps for the Keenserts, and a hammer/punch to set the keys.

One other thing I've considered which could be problematic with replacing threads for a pocket clip is hole spacing. With either type of thread replacements, the original holes need opened up to a significantly larger size. If the holes are too close together, there might not be enough room.
 
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C_Claycomb said:
is there space for the screw heads on the clip
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no prob ; jess chuck 'em up in the old lathe and turn 'em 'til they snuggle . 🤓😎
DO NOT tell me we are trying this without a lathe, a TIG Welder and a Swiss Army knife.

If it were my choice no self respecting male (OK person) would be allowed out of the nursery with out "the basics".
else it will all end in tears ; mark my words .
 
SpyderPhreak said:
Curious what special tools they need for the Keenserts? They're really easy to install unless you're talking about an extra-hard or resistant material, like hardened steel or Ti. Then you do need their special broaching tool to pre-cut a path for the keys. I can install them in my garage with nothing more than basic hand tools (and have) even into mild steel.
Click to expand...

Many decades ago when I worked in manufacturing, we called those things PEMs. Don't know if that was a brand name or an acronym. We would drill the hole to fit the cylindrical section and use a manual press to embed the toothed part in the metal. You would embed it so that tightening the screw would pull the toothed piece further into the metal. Otherwise, torquing the screw would pull it out of the piece if you pushed it in from the top instead of inserting it through the bottom. You are deforming the piece in which you are embedding the Keensert, so if it falls out you may not get a good seat from a second try.
 
I had added a clip to a vintage Gerber FS2, and they also stripped, I triued loctite, did not last long, then I used epoxy that lasted a but longer but still failed. I think the only thing to do is go a size up.
 
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donnord said:
I had added a clip to a ventage verber FS2, and they also stripped, I triued loctite, did not last long, then I used epoxy that lasted a but longer but still failed. I think the only thing to do is go a size up.
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Loctite is a brand with many varieties.
When I suggested it above I should of specified which type.
680 is Very Strong. It's (green) it's for slip fits.
A loose/stripping screw would be IN there, probably never to be removed again. This is not thread locker, Heat would be needed to remove. Which would probably melt the handle. Close to being permanent

I like to clean all parts with alcohol, then dry, then apply as directions. It's fast acting 10 mins approx. But let cure overnight
 
Crag the Brewer said:
Loctite is a brand with many varieties.
When I suggested it above I should of specified which type.
680 is Very Strong. It's (green) it's for slip fits.
A loose/stripping screw would be IN there, probably never to be removed again. This is not thread locker, Heat would be needed to remove. Which would probably melt the handle. Close to being permanent

I like to clean all parts with alcohol, then dry, then apply as directions. It's fast acting 10 mins approx. But let cure overnight
Click to expand...

We used green Loctite on screws for military hardware and you had to grind off the screw if the bracket clearance was outside the specification. I was under the impression that green was permanent, or at least we treated it that way.

You might ask a local machine shop if they have a Helicoil kit with the thread you need and ask if they would insert one for $10. I remember needing 3 or 4 tools in the kit to install them.
 
Sharp Steel said:
We used green Loctite on screws for military hardware and you had to grind off the screw if the bracket clearance was outside the specification. I was under the impression that green was permanent, or at least we treated it that way.

You might ask a local machine shop if they have a Helicoil kit with the thread you need and ask if they would insert one for $10. I remember needing 3 or 4 tools in the kit to install them.
Click to expand...

Yes, I consider 680 permanent. High heat is needed to remove.
 
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