Blade play - so what?

[Siggyhk]

The majority of knives I've owned had some sort of blade play. Sometimes there is so little, it's very hard to detect. I've done my best to weed out the ones with play, but it's been a struggle. When I find one that has no movement after it's been used, it's usually a keeper for me. I'm not real keen on sending a knife in for repairs, so if it's not like I want it, it's gone.

 

[rifon2]

Blade play is inevitable on mass produced knives. If all components were specified, inspected, selected and assembled to preclude any play, pocket knives would start at $100 and go up from there.

Just a quick question for all the zero play allowed crowd: At what temperature are you determining zero play? Since the pins used in assembly are not generally the same material and heat treat as the blade, or the liners, or the scales, or the backspacer there will be differential expansion/contraction with temperature changes. A folding knife with zero play at 72 degrees may rattle at 10 degrees and stick open or shut at 110. It may not matter if you never go outdoors, but I work outside a lot, and where I live, we have a temperature range from -10 to 110 degrees in an average year.

Sorry about the rant, but I am with the original poster on this subject.

Must disagree with you about blade play being inevitable on mass produced knives.

Jjust about every knife I've bought over the past 7-8 years or so has had zero blade play, with the exception being some slipjoints.

And those were either returned or repaired.

Even some CRKTs I recently bought - closeouts at ridiculous prices, to use as beaters - locked up beautifully. No blade play whatsoever.

 

[yablanowitz]

I thought that might stir up a few of you. Now, let's define zero. When I say zero, I mean ZERO. As in less than one thousandth of a micron. If there is ZERO clearance between parts, how can there be movement between them?

I have worked with taper fit parts presicely fitted to the point that 50 degrees difference in temperature meant the difference between falls apart and can't get them apart with a hammer. I have worked with parts fitted precisely enough that if you got one side of the 24 inch diameter locking ring 0.003 of an inch ahead of the other, it would wedge in place on the shaft. I have some idea of the difficulties involved with assembling parts fitted to those kind of tolerances.

I doubt that I would notice play on the order of one one thousandth of an inch. I kind of doubt that anyone else would either. That does not mean it isn't there. So if by zero play you mean that with the handle of the knife clamped in a vise, applying a pressure of 50 pounds of force perpendicular to the blade will result in less than one thousandth of an inch of deflection at the tip of the blade, fine. I can accept that. It isn't my definition of zero play, but I will accept it as yours.

If I only accepted knives that fit my definition of zero play, I wouldn't own any folders.

 

[SilverFoxKnows]

Nothing in my EDC rotation was more than $50. If an FRN folder develops a little wiggle after extensive use I don't fault the tool. After all, it was just a low end, mass produced, plastic handled folder. My Native has a little play but I've done a couple of dumb things with it. Hardly Sal's fault. If I were paying big bucks for my knives it would probably bug me. But a tiny bit on an under $50 blade? Not a big deal.

Frank

 

[hardheart]

I thought that might stir up a few of you. Now, let's define zero. When I say zero, I mean ZERO. As in less than one thousandth of a micron. If there is ZERO clearance between parts, how can there be movement between them?

There can't, which AFAIK, is how a lock is supposed to work. If there is flex in the part, that's one thing; which would still bother me depending on how much force is needed to cause distortion, but there shouldn't be any space between a lock and tang, or stop pin.

 

[rebeltf]

If a folder has play in the blade and I cannot fix it , I wont use the knife and unless it is something very special it will be relegated to the bottom of the sock drawer.

 

[MORIMOTOM]

blade flex in a fillet knife and blade play in a folder are two completely different things.

in a folder blade play when in the locked position makes the knife weaker at its already weakest point, the hinge. enough play can also disengage the locking mechanism, and with most locks it wouldnt take much.

 

[tirod3]

So what we see here is one informed response from an experienced technical viewpoint, and pretty much all the rest uninformed consumer opinion.

Let's get one thing clear - all moving parts have clearances, clearances are measurable, and measurements have tolerances. These are known as manufacturing standards. When those standards allow the consumer to notice blade play may or may not be an actual quality concern. Engines are built with 2 to 10 thousanths clearance, and you can feel it in the rings, bearings, gears, and dozens of other parts. I don't consider it poor quality, I KNOW it is proper function and design.

Folding knives must have clearance at the pivot or they just won't open. Whether you notice or not is entirely subjective, and without measuring the amount in precise dimensions, you don't know what you're talking about.

Now, back to my original point - what are the specifics? What are the measurements? Get out the calipers and let us know what you think is poor blade play.

"Zero play, rock solid " is BS in the manufacturing world.

 

[DaveH]

So what we see here is one informed response from an experienced technical viewpoint, and pretty much all the rest uninformed consumer opinion.

Duh, does this look like a technical forum?

Sorry the great unwashed thought they could respond to your thread in a helpful manner. Oh please great god like technical expert, show us they way!

:barf:

 

[knarfeng]

Maybe we should look at what we mean when we say "zero blade play".

To me, "zero blade play" means that when I lock up the knife, I can't wiggle the blade in either vertical or horizontal planes using the amount of force I would normally use to cut.

Is there some movement? Undoubtedly so. As tirod3 points out, there has to be some clearance or the knife won't move. Can I feel the movement in a locked up position? I cannot. Not for most of my knives. Got a couple of Gerber EZ-outs that wiggle a bit if I work at it. Can't feel any movement in my Spydercos and Benchmades.

Just an aside. I would not expect the tolerances to change significantly over a change of 120F. The CTE of 400 series stainless is on the order of 7ppm/°F. So if the temp changed by 120°F, a 0.125" thick blade would change in thickness by 0.00000075". I don't think I could detect that with my bare hands.

 

[tirod3]

Duh, does this look like a technical forum?

Sorry the great unwashed thought they could respond to your thread in a helpful manner. Oh please great god like technical expert, show us they way!

:barf:

A great post!

What better example could I ask for??

If you can't quantify the problem, belittle the messenger. Totally emotional and useless. No help at all.

And yes this is a technical forum. I guess you missed all the long and boring posts on the compositions of steels, edge angles, blade grinds, and handle scale material strengths. It's what keeps some of us late from work.

It's ok if you don't own a caliper, most consumers don't know they exist - and used to make every knife they buy. And their cars, TV's, disposals, washers, A/C - hey, what if precision was kicked out the window and we went back to the horse?

Most people have no clue about the precision standards that make their life comfortable, and enjoy being ignorant, delegating power over their life to others - who charge a darn good price for what they know.

Willing subservience to technical gods. Not my idea of how to live. That's why we share knowledge, and in the process learn what we don't know, to understand what is important - like knives have play in them whether you know it or not.

Sometimes it's hard to handle the truth, but you'll be better for it.

 

[tirod3]

Knarfeng, I doubt I could detect the difference in a hot blade or cold blade either. It's the .002" clearance between the pivots that raise hackles with some. If they can feel it, they think it's a crap knife.

I'm just asking, what is it precisely they feel? I have no doubt 1/8" could be a significant indicator of sloppy workmanship in a particular case. Fitting a knife blade in pivot washers with a pin involves tolerances that in some cases stack up on the large side. For those who got one, we'd like to know - specifically. After all the threads started over 420J and 420Hmod, this is more important. There seems to be an unwarranted expectation of perfection in a man made object, and the emotional letdown is directed as a quality concern against good makers doing their best for the price.

Sure they could send it back - but like lots have said, tighten it yourself. There is the dividing line today - those who can, and those who can't tighten a pivot screw (warranty aside - and a convenient excuse.)

If they tried, they'd learn just how close a fit it is, and how difficult a 1/8 turn can make things. Then they would have knowledge - not baseless expectation.

 

[ginshun]

Just a quick question for all the zero play allowed crowd: At what temperature are you determining zero play? Since the pins used in assembly are not generally the same material and heat treat as the blade, or the liners, or the scales, or the backspacer there will be differential expansion/contraction with temperature changes. A folding knife with zero play at 72 degrees may rattle at 10 degrees and stick open or shut at 110. It may not matter if you never go outdoors, but I work outside a lot, and where I live, we have a temperature range from -10 to 110 degrees in an average year.

Sorry about the rant, but I am with the original poster on this subject.

Um no.

The equation for themal expansion is E*t*l Were E is the coeficent of linear expansion, t is the temperature change and l is the lenth of the object.

E for mild steel is .00065 for a 100 degrees and even less for hardened steel, although I don't know the number off the top of my head. With a l in fractions of an inch on the parts that you are talking about and a temp change of only 120 degrees, your talking about parts changing in size by like a ten thousanth of an inch, if that. That is not enough to cause any significant play in the blade.

As far as my thoughts on it, I can deal with a very small amount of play in low and medium priced knives. Very small, as in I can grab the blade and try to wiggle it and feel it move a tiny bit. Anythink more than that and it goes back to the manufacturer for fixing or to be replaced. Oh higher dollar knives, ie anything over about $150, if I can feel any play it goes back.

Any knife that I can just shake the knife and feel the play is getting returned.

 

[knarfeng]

I think rifon2 put his finger on it for me in post #12.

"A wiggly blade is like a rattle in a car." rough quote.
Does the car still work? Yup.
Does it annoy me? Oh yeah. Drives me nuts.

A wiggly blade still works. It just bothers me. I buy mostly low $ knives. (Got teenagers to feed ) So it's not reasonable for me to send in a loose bladed knife. But I can also find ones that are low $ that lock up solid. Those are the ones I try to buy and those are the ones that end up in my EDC rotation.

 

[enduraguy]

A slight amount of blade play never bugged me. Even though most of the knives I've owned like Spyderco usually have none to almost none. Even if over time a slight amount develops, as long as the knife still performs reliably...I could care less. I've however never understood the whole "centered blade" thing. Other than aesthetics, what's the big damn deal if the blade is not perfectly centered when the knife is closed? There's nothing wrong with the knife, but I've seen grown men throw the biggest hissy fits over such a mute issue.

 

[Kaizen1]

I thought that might stir up a few of you. Now, let's define zero. When I say zero, I mean ZERO. As in less than one thousandth of a micron. If there is ZERO clearance between parts, how can there be movement between them?

I just don't like noticeable play in my knives, for the most part. I also don't have extreme weather and temperatures to deal with in my location. If that becomes a factor, then I'll consider it. Until then, I like no "noticeable" blade play during use. Nothing wrong with that.

 

[tirod3]

A slight amount of blade play never bugged me. Even though most of the knives I've owned like Spyderco usually have none to almost none. Even if over time a slight amount develops, as long as the knife still performs reliably...I could care less. I've however never understood the whole "centered blade" thing. Other than aesthetics, what's the big damn deal if the blade is not perfectly centered when the knife is closed? There's nothing wrong with the knife, but I've seen grown men throw the biggest hissy fits over such a mute issue.

Yes, more, bring it on. What is the deal?

 

[Kaizen1]

There's nothing wrong with the knife, but I've seen grown men throw the biggest hissy fits over such a mute issue.

I'm not trying to be confrontational and I understand where you're coming from. I'm not one of these guys who are bothered by this particular problem. I do my best not to whine over small stuff, but it happens every so often when I'm not paying attention. My thing is, everyone has at some point complained over things that others may not complain about. I know I can't judge others about this because I get caught complaining about stuff sometimes. I do think that if you ever complain about something that someone else wouldn't complain about, you'd be a hypocrite to say this.

 

[hardheart]

Trying to portray this as a technical discussion when it is really just a fanboy response to the complaints of sloppy QC of Striders (which I have not experienced firsthand) is hilarious. Taking offense at being belittled when you are the one belittling everyone else who is a consumer and expressing their subjective opinion without providing you with hard numbers to argue for the adequate build quality of My Favorite Maker X is simply trollish behavior. Nobody has to assign a numerical standard, and no one has to agree with yours.

 

[Rhesus Feces]

Trying to portray this as a technical discussion when it is really just a fanboy response to the complaints of sloppy QC of Striders (which I have not experienced firsthand) is hilarious. Taking offense at being belittled when you are the one belittling everyone else who is a consumer and expressing their subjective opinion without providing you with hard numbers to argue for the adequate build quality of My Favorite Maker X is simply trollish behavior. Nobody has to assign a numerical standard, and no one has to agree with yours.

+1:thumbup: