Monday, February 27, 2012

How well will G-10 hold a screw?

This question has come up so often asking me how well G10 holds threads that I thought it was a good subject to go over. If you are a knife nut you are likely quite familiar with G10 material. This glass filled epoxy material is time proven for knife handle applications with machining and carving or shaping ability that far exceeds most of the other things we have open to us as makers to use as handle materials. G10 is virtually immune to weather changes such as temp. variance and humidity, it is immune to oils, chemicals, acids, heat and flame and many other factors such as chipping or cracking from drying out over time. Even with the safety issue of having to really watch how much of this dust you breath in by using the best respirator you can afford since it is basically like breathing volcanic glass G10 brings a lot to the table as Cold Steel and Andrew Demko have proven in their severe abuse testing of some of this material when used on folding knives.

Way back in 2009 I had a post for this question which I recently found again. My answer was so complete that I decided to make that post a sticky on my forum and to place that same info here. Here is my answer complete in it's original form pasted from my own words when the question was put to me yet again.

The question: 

I wanted to do a quick mod on a knife. Will G-10, if tapped, hold a screw well or am I wasting my time?

My answer: 

G10, Micarta, FRN/Zytel 'can' work to hold threads indefinitely and as I always tell folks when I flip these clips to tip up carry for them the same things I'll just tell you now so you know. Of course this depends on using the proper size numbered drill sizes to drill your holes and the proper size tapper to thread those holes after they are drilled. For softer materials such as these a number 48 drill will work just fine with a thread forming tap for a 2-56 size from Enco or MSC Industrial supply.  Be aware of the three rules of thumb for threading these materials without liners of nickel silver, brass,  stainless or titanium behind them and you'll see that it will go a long ways for you before you ever have to fuss with it again. Those three rules are:
1) Never overtighten the screws. They need only be snug to work. An occasional check is ok but just be careful to not overtweak them. One half twist too far can severely weaken the bite and hold down ability of your new threads. 
2) Don't use loctite or super glue on the threads. While it is debatable here I don't recommend using it in this case. Doing so in my experience may be responsible for premature weakening of the threads when you are relying on just G10, Micarta, or FRN (fiberglass reinforced nylon) The more you wear the threads down the more likely they will lose their bite and hold down ability. For the glues it can be such that when you do end up having to remove the clip for whatever reason after gluing them in it can strip out the threads entirely or severely change them to weaken them in some places you can't see the first time you do remove or re-tighten a screw later.
3) Don't make a habit of taking the clip on and off whether you use glue or loctite or not. Frequent removal like this increases the risk of cross threading, or overtightening, both of which are quite easy to do if you are not careful.  The more you use it the weaker and weaker the threads get. In fact its more than an argument really. They will weaken more with use. The key to making the threads last is to simply leave the clip in place once it is mounted.

In some knives depending on thickness of the scales I have used shorter screws to hold the clips but threaded into the material much deeper. Later if a short screw strips or no longer holds you can simply get a longer one and find fresh never used threads deeper that will still work so you can cheat your way to longer life this way also. 

I've done a countless number now of clips threading them into handles made out of all of those materials over the years and some of those jobs are upwards of 17 to 20 years old or more now and still holding threads for folks using them so it can work if you follow these guidelines. In the event that a screw does strip you can always send it to me then and get the backing plate or some threaded inserts installed on the underside of the scale so there is metal to screw down to. (see pics attached to this post) Generally speaking if you follow these three simple rules though, its trouble free and it won't come to that. In the event that one does strip out though there may be other options. 

In my testing I've never had any issues doing it this way, and quite honestly the fears and stories of the G10 ripping out are nonsense. Thats never happened to any I've tested. The clips break way before the G10 would give out and if you notice the G10 is very secured and bolted down both at the lanyard on most Spydercos and the screws holding the knives together. It makes for a very strong body. I believe Cold Steel and Andrew Demko have proven just how durable and strong G10 actually is. Just watch some of the videos on youtube.

I've done so many now its old hat and I have some knives in my safe of my own threaded like this that are first test pieces so to speak that are old Cold Steel FRN knives from way back still holding threads no problem. Way back when a lot of companies, Spyderco included made those pocket clips integral with the handle of the same FRN or Zytel material and often times those had to be replaced from bending out, deforming or one time one melted somehow. I forget how now. Seems like it had something to do with insect repellent now that I think about it. Anyway, there are a ton of old knives out there by me with new clips done this way and some are probably still floating around the forums that folks here have had me do so just do what I recommend and you'll be fine. 

As I said, if and when it ever needs work again just print my work order form found in one of my sticky threads about contacting me and mail it off to me or fix it yourself with a little bit of work after dissassembling it by installing two or three inserts in the bottom side of the scale. Use spade or two flute type drills in the proper sizes and not the twist drills and you can save time by not having to clamp pieces down. Twist drills pull the piece in and on something very thin like a scale it can snap clean through right quick if you are not careful. A starter hole using one of the two flute carbides from MSC followed up to the proper depth with a correct size end cutter flat bottom drill and it is ready to have the insert placed. I usually buy one 1/8" pivot barrel already threaded for the 2-56 size screw. Then I slice off thin end cuts off the end of that stainless barrel using my thin kerf cut off disc and my rotary handpiece holding the barrel firmly with a small vise grip plier. Once a 1mm slice is off I insert them in 1/8" shallow holes on the undersides making sure to cut the slices so the last little bit of material holding the slice on the barrel has to be snapped off. This leaves a little splinter or nipple end protrusion that you can use to grip into the G10 keeping it from spinning when its tightened down. After the clip is placed you can spot some super glue over the back side of the three inserts and its basically on there ready to roll after that. Reassemble the folder and you are good to go with metal backing now to secure the clip.

Hope that helps and answers your questions. Thanks for stopping by my forum to ask. 


click any picture to enlarge

shown above are two thin stainless 1/8" pivot barrel slices placed into holes drilled to precise depths to allow the sleeves to sit flush once pulled in and seated by tightening down the screw. This is of course a shot of the underside of the scale on both shots here.  Once the folder is put back together it looks like any other folder with the unseen threaded inserts hiding on the inside. 

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