Why use washers of one thickness over another thickness?

Brian Avila

Brian Avila

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Jan 2, 2011
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When researching the different types of washers and thicknesses, I find that everyone uses different thickness of washers and different materials. I can find different reasons for the different materials, but I don't hear about why using a specific thickness of washers over another?

I think I would like to try to make a lock back and a slip joint but use washers instead of milling or removing area around the pivot; as well as some liner locks. This would require my back spacer and springs to be different thicknesses than my blade on the traditional type blades and that is fine, but why would I pick one thickness over another?

Maybe it has to do with tolerances? Maybe it has to do with material types? I suspect that the thinner the washer the more likely it could bind (.005-.01") and if you have a little more space say .02" thick washers the less likely that is?

The plan would be to make my own washers out of teflon of whatever thicknesses I choose, eventually.
 
When stop pins have shoulders that may exceed thickness of blade by a bit . You have a blade that is .125 and your stop pin shoulder is at .135 you will have to add .010 of material to take the slop out (.005 x2). The hardware (stop pins and standoffs)will coincide with blade thickness as well. I'm terrible at explaining but it's simple addition and subtraction depending on a couple of variables.
 
Azbalisinging: I understand that, but I can make the stop pin, and the other hardware/spacers pretty much any thickness by lapping them. So I should be able to use any thickness of washer, theoretically. Maybe I am wrong...
 
Newbie here so I can only offer my experience of exactly one (1) folder completed. But washer thickness affects a few different things. The first two that come to mind are thickness and the detent ball. Obviously thinner washers equal an overall thinner knife, which can be desirable if you want something that can easily slip into a pocket. The detent ball thing really only comes up when you go on the thin or the thick end of washers. Thin washers means your detent ball has less room when the knife is in between closed and open, which is a problem with liner locks (scales/bolsters have to be relieved so the lock has room to bend back), but not with frame locks. On the other extreme end, massive washers mean your lock has to bend over farther or you need a bigger detent ball for it to contact your blade tang properly. I think washers being to thin is more of a common quirk to be worked around by makers than washers being too thin. Overall I think it matters little though, just pick what you like and what works for your system. It's really just like different washer materials: sure, one may be "stronger" or "lower maintenance", but the differences are so small that you see both cheapo production knives and customs use nylatron, teflon, and phosphor bronze.
 
I had almost forgot about the detent!!! Crap. Well if I use a 1/16" detent and need it to poke out .002" less than my washers odds are I will be between .01" and .02" thick for my washers.
 
Brian,

If you are making a lockback or slip joint, detent balls are not normally used, so that will not be a factor for you. For those knives I would use the thinnest washers available.

Now, for a liner lock, NeilJBorja explains it well. If your washers are .010 thick, your detent ball can protrude about .008 from the liner without you needing to releave the inside of the bolster and/or scale. A thickness of .010 to .015 or even .020 works well for liner locks. Much less will require release work. Frame locks are less sensitive to washer thickness since there is normally no scale or bolster to prevent the lock from moving out of the way.

Back spacer thickness obviously needs to be equal to the thickness of the blade + washers regardless of knife type.

Brian
 
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Brian,
There are so many variables that it is nearly impossible to predict the exact amount of "slop" room in the blade to liners area. The blade pivot area will be lapped and polished, the stop pin may have a few thousandths more or less that specs, and the screws/pins may snug things down more or less than planes.....all easily fixed by picking the right washer.
The washers come in different thicknesses to allow for picking the exact right one. The materials difference are mostly due to personal preference, but somewhat to use.
 
Good points!

So what do I need to think about about when choosing the thickness of the standoffs, washer thickness, and so when doing liner lock?

I have it working on paper but how do I account for the parts? Say get washer material that is .005, .01, .015, and .02" thick and start with the closest thickness when I get to that point?
 
Imo It's a ringer trying to order the correct hardware the first time. I used presision ground stock so I know where to start then go from there, lapping is still nesesary but you will be very close the first time around.
 
I understand getting the steel precision ground. But.... I want to use stainless. Since I have started I decided that I won't make knives that I don't want to make or like and I'm going to use the materials that I deem fit. It will bother the hell out of me if I don't. I'm not saying that to be rude or out of line, just explaining my thought process. I try to be meticulous when planning and working on my knives. So that's where most my questions come from.

I am going to use some type of stainless for the blade. And I don't have a mill or a surface grinder so I need to get over size close to what I want and then go to my granite plate.

Coming back to the washers in question. I plan on purchasing parts around the standoffs that I can buy. That will be the thickness i work around. And hope to have my blade between 1/8" and 5/32" when it comes for the liner lock.

Now when talking about a slip joint with washers. I plan on thin washers and getting the spring the same thickness as the blade plus the two washers, using my granite plate.
 
Until the blade is finished, you can't really calculate the washer thickness. Once it is done, the calculation is simple:
pivot bushing/stop pin width - blade thickness X .5= washer thickness.
 
I have to admit Stacy, I have no idea where that equation came from and I don't really follow you.

I was thinking: (standoff thickness)-(blade thickness) = (washer thickness)x2

The stop pin will be whatever the stand off thickness is plus liner thicknessx2.

Not sure what the drop pin thickness does to my washers.
 
Stacy E. Apelt - Bladesmith said:
Until the blade is finished, you can't really calculate the washer thickness. Once it is done, the calculation is simple:
pivot bushing/stop pin width - blade thickness X .5= washer thickness.
Click to expand...

Damn stacy, That is some scientific stuff.

@Brian Avila: I do friction folders and I simply wing it:o

It is kind of up to you if you want to meticulously plan everything out (which I have tried) but in the end EVERY folder i make needs some major "winging" and they always end up fine.

A good tip i have found is to err on the side of thicker phosphor bronze washers and you can thin them down if needed then mirror polish them for better smoothness.
 
(Assuming a shouldered stop pin) The pivot bushing and/or stop pin width ( space between the liners) is the fixed space measurement. Subtract the finished blade thickness, and multiply by .5 or divide by 2 ( same thing). That gives you the washer thickness. Using the spacer width only can be misleading, as the pivot can pull things in a few thousandths. This is sometimes planned into the measurements to allow some snugging down of the pivot screw to adjust the blade looseness. This tiny amount of play ( measured in .0001"s) matters a lot on autos. Switching to a slightly thicker of thinner washer can be the difference between a sloppy blade fit or one that seems to be on ball bearings.
 
I was planning on using Teflon to make my own washers. Can Teflon be lapped some to reduce thickness to make for a good fit.
 
For me Teflon is useless. If you compress it any it stays compressed. Get some phosphor bronze and use it. Here is my way to fit liner locks, remembering I do not have a surface grinder or milling machine. I do now have a fine Rod Nielsen disc grinder that helps. I used just the hand surfacing plate for many years. I do have a 2 X 72 grinder.
I decide how thick the blade is to be and finish it to that at the pivot area. I may decide what that thickness is because at the time that's what will work. Of course I use a hard pattern for the blade and liners. So now I make the liners and drill all the holes need in each. I have found that .015 is a good washer size. .010 is a bit thin, and .020 seems to look like a lot of unneeded space. I make the back bar or stand offs the wideth of the blade plus the washers. You may need further adjustments because the screw heads on the pivots are not cut flat on the bottom. You are now into the try area. By the way, I believe the this way of fitting is commonly used. Frank
 
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