The most common broken/worn part make/model specific

[muskrat man]

I'm curious to hear from other mechanics what the most common broken/worn part they encounter in a specific make/model of knife (other than blades)

I see a lot of broken backsprings in the Schrade 55UH and 55OT linerlock knives
I also see a lot of broken springs in the one piece schrade lockback knives. More so than the ones that utilize spring steel wire in a holder like most of the LB7's

[tjmurphy]

I'm certainly not a mechanic, but I've noticed that SCHRADES, especially UNCLE HENRY's, have weak snap. Also, that WWII era, military issue, CAMILLUS tend to have excessive tang wear on the primary blade. These are just observations and do not necessarily hold true for all.

[glennbad]

The mainspring on the stainless Camillus demo/utility knife is notorious for breaking.

I also work on a lot of 72's, and mostly because the main blade gets used the most, it or the spring always has unusually bad wear. I also run into a lot where the pivot pin loosens and the knife parts separate. The tang of the knife then wears poorly, and there is always an area of tang that has more than the rest because it has slipped past the spring.

Bails are almost always mangled beyond repair or missing entirely.

[glennbad]

Also, my fingernail has a habit of breaking on the TL-29 screwdriver blades...

[orvet]

I'm certainly not a mechanic, but I've noticed that SCHRADES, especially UNCLE HENRY's, have weak snap. Also, that WWII era, military issue, CAMILLUS tend to have excessive tang wear on the primary blade. These are just observations and do not necessarily hold true for all.

I agree with everything you say TJ.

My theory & I think MM will agree, is due to the design, Schrades are designed with less snap.
Schrade in later years, say 1960 & later used more round tangs. They are rounded like the lobes on your camshaft. The cam action of the rounded tang lobes do not push out the back spring as far as the square tangs found on a lot of older knives, (pre-WW II) and also used today on many patterns by GEC. The square tang also gives the knife a half-stop.
Essentially you have the difference between a low-lift cam and a high-lift cam. There is more travel with the high lift so there is more tension on the spring causing stronger snap.
In new knives (not subject to wear) both type of tangs function equally well, one is easier on the fingers and the other makes a louder snap, which some people equate with quality. I think the reason some people think more snap equals quality is back in the day where the square tang & half stops were the norm; a knife that didn’t snap probably did have a weak spring.


I have observed, and I am sure MM will back me up on this, that weak springs are not as common as one might think. The usual problem I find on an old knife with weak snap is that the lobe has worn off the tang. The tang wears down to where it is completely round and provides no lift to the spring and therefore no snap! I have seen the same thing on square tang knives, it usually takes longer to wear those down.
IMO the biggest factors for worn tangs are dirt & lack of lubrication.

Also, my fingernail has a habit of breaking on the TL-29 screwdriver blades...

I had problems with broken nails also until I started taking 3 capsules of gelatin as a dietary supplement.
If I run out of the gelatin for more than a week, I start breaking nails again.
It really works well for me!

[knife-nut]

With scout knives it is usually the punch blade tipped and the bail missing.

[muskrat man]

Dale nailed it ,

[just bob]

I'm no mechanic either but I've noticed that on the Case Scout knives from the 1980's that the big blade tends to loose snap or have really poor snap while the other tools seem to have really great snap on the same knife. Also I think it has been posted on here before about the tendency of the big blade on the 87 pattern to wallow the back spring out. I have 2 knives like this.

[orvet]

I'm curious to hear from other mechanics what the most common broken/worn part they encounter in a specific make/model of knife (other than blades)

I see a lot of broken backsprings in the Schrade 55UH and 55OT linerlock knives
I also see a lot of broken springs in the one piece schrade lockback knives. More so than the ones that utilize spring steel wire in a holder like most of the LB7's

I agree 110%!!!
When Schrade went away from the old style spring for the lock backs (the one using the spring steel wire) and went to the 2 one-piece flat springs, I think it was a huge design mistake, (or perhaps the problem was in heat treating the steel for the springs). I have several dozen of the new springs for the 3OT. I have installed them on several knives and usually they don't survive the testing and adjusting!

I suppose they were cheaper to make and easier for a small knife like the 3OT, but I have given up on replacing springs in 3OTs. If I need to fix one, I will make an old style one to use the spring steel wire.

I have noticed problems with the new one-piece flat springs in the 3OT, 5OT and all variations of those as well as all models in the LB series when they have the new one-piece flat springs in them.

I am not sure if it was a design or an execution problem, but IMO the one-piece flat springs are 5 times more likely to fail on average than the earlier spring steel wire design!




PAL problem-
I have noticed that all the Pal knives, (Pal Blade & Pal Cutlery Co), have a tendency to loose snap due to the rounding off of the square end of the tang. They seem to be worse about this than any of the other companies making military knives of the same design.
Granted a lot of these military knives were used in combat under the harshest of conditions, probably full of sand and with little or no lubrication. However considering the easy opener jack made for the military; I see more rounded tangs on the Pal jacks than I see on Imperial or Camillus jacks, and I have seen this pattern & these three brands in about equal numbers, but I rarely find a Pal that still has much snap left in it.

My hypothesis is that Pal tangs were not hardened to the same hardness as their springs.
The difference in hardness was so great that he tang nearly always wears down and rounds off.