Thursday, August 19, 2010

Pocket clip flip and other knife modifications

Seen here are three knives I bought for myself recently that simply surprised me at how nice they each are for the money. Top folder is a Sanrenmu 939 as it comes from the factory. Next is a Sanrenmu 710 which I've modified. Middle is a Boker Anti MC Plus with ceramic blade and last is the Sanrenmu 939 after modification. All of these came with just one mode of carry for the pocket clip. I prefer tip up carry so my first order of business with each one was to proceed to the shop and change some things to suit me.

As you can see from looking at these folders, there are some other things besides pocket clips that I did before I was finished with them. Once these folders arrived I might have had each out for an hour before I was in the shop changing things to suit me better. First thing I did was make a custom titanium pocket clip to fit them for tip up carry. By the way, you can click any picture to enlarge it out to full size to get a better zoom shot of the details.

So once that original clip was off I was mapping out a new pocket clip design of my own on some scrap titanium right quick. I drilled some holes for a 2-56 threaded screw sizes after marking where I needed the holes on each model and then threaded them into the stainless handles to create my new mount areas. These handles are hardened stainless on both the Sanrenmu knives and titanium on the Boker Anti MC Plus model.

I used a number 46 drill size as opposed to the normal number 47 I would use in most everything else. I normally select the 46 for slab threading jobs. It seems to bind less the deeper it goes but you still have to be very careful. This slightly bigger diameter number 46 drill bit size improved my chances of successfully threading the thick slabs and reduced the chances of breaking off a tap and getting it stuck in the hardened stainless steel handle. Another way to do this is to simply drill the hole too large for the threader 3/4 of the way through the thickness and simply thread the last 1/4 of the slab only. I opted to simply thread the entire thickness with weaker threads. In my tests doing this on junk knives the clips break long before the screws pull out. Come to think of it. I've never pulled the screws out so to me it seems to hold just fine using a number 46 and a thread forming tap.

Once the new clip was done I simply cut the original clip for that 939 so its mount plate could still be used on the knife. I did this by zipping it off at the first bend. I did this using a thin kerf cut off disc to give the original mounting plate a new purpose. Now its a lock stop to prevent over travel of the lock or hyper extension of the lock out the wrong way which can cause the lock to lose spring tension.

Sometimes in the heat of a moment like during an adrenaline rush in an emergency its easy to over extend the locks on these open frame designs. The fact that so many manufacturers take the lock cuts to thin the lock slabs down so thin makes this scenario that much more plausible. While not common I've read of it enough to warrant this preventive device. I felt since the original pocket clip is no longer there to serve this purpose after my new one was installed that I still needed the benefit of a physical block for the lock travel. In the end I did another plate making one up from scrap titanium to fit the Boker for the same job.

Without some block there to prevent over travel out the wrong way when the lock is released you just never know when you might accidentally take the lock out too far one day. This is easier done than you might think when a lock sticks and binds on the contact on the blade. If it requires a bit of force to release the lock, as this Boker does, its very easy to envision a situation where spring tension could be lost. This physical block will prevent that from happening.

Now move to the rear of the folder looking at it on the outside as shown in the first picture. Having the lock cut in the rear of the folder on the outside as opposed to the inside where it is not as easily seen can create a challenge for flipping a pocket clip to tip up carry mode on these open frame lock style folders.

The lock cut is the dished out part of the handle in the slab where its thinned down. Look at the first picture of the 939 model. Note at the tail end of the original pocket clip and you can see that the original pocket clip shown there almost curves and points right to the lock cut or dished out area I'm speaking of if you look right at clip tail. This lock cut is there to thin the slab to allow it to be easier to bend the lock to put spring tension on it so it blocks the blade from closing and to allow the user an easier operating lock since the thicker slab would have too much resistance. Its these cuts that can be taken down to extremes at times.

I have a Strider PT folder with .125 slab lock thickness that the lock cut is taken down to .032 on. This Boker shown here is .034 from .100 thickness. Both the stainless Sanrenmu knives shown here are .039 plus or minus from an original thickness of .100. So you can see they take them down pretty thin at times. This makes the actions work easier but unfortunately it can also make hyper extension of the lock out the wrong way that much easier also.

That spring tension must remain in the memory of the lock or you cannot rely on the blade to be secured safely for use. Whenever these lock cuts are on the outside I have to really be careful where I put the new pocket clip. That lock cut, when on the outside can catch the rim of the pocket if the clip is positioned wrong and if the clip is sitting in the wrong place where it can pinch the pocket rim into the lock cut as you extract the folder for use it can cause the knife to catch and snag getting hung up on the pocket and cause one to drop their folder.

Looking once more that the Sanrenmu 939, once I figured out how I wanted to handle both the overtravel issue for the lock and the new pocket clip positioning I simply reprofiled the blade shape and made it so it had a better splinter picker point for my own tastes> You can notice the original blade shape in the very bottom (last) picture. Compare that to my new reprofiled shape and you can see that its hard to tell its even the same blade. In the end I'm quite happy with this knife. So happy I'm ordering more of this model just to have a few in the safe for in case I beat this one up or lose it one day.

These San Ren Mu knives are quite nice for the money. I also bought two of the 710 model. One in black. These are great travel knives for when crossing state lines just to have something on you that is little to fuss over should it be lost or taken at a traffic stop. Something I've had to endure once before unfortunately and it was a much more valued knife then. After shipping I have about $20 in this 939 and about $12 each for the 710's. I won't cry over that if its taken as my last one was. .

As stated earlier, the Boker shown here is one equipped with a Ceramic blade. Ceramic is good for straight cuts only as it is a very brittle material. Lateral stress can snap one of these blades quite easily so I'm not sure just how much it can take but I liked the sleek lines of the design and figured I'd give it a try for $50 plus shipping. Ceramic is suppose to cut for a very long time since it is so hard. Edge keeping was my primary reason for wanting to try this but also the price made it easy to get into one compared to ceramic blade knives I've priced in the past. Thanks for looking.

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