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What kind of material(s) would make a good friction disk, or disks, for a friction hinge, or torque hinge? This will be for the hinge on an arm that needs to be adjustable and also hold it's position with 1 to 10 pounds on the end. The hinge may be a vertical tilt hinge or a horizontal swivel joint.

The two pieces that will swivel against each other are flat metal with 2 surfaces of 1.5 inch diameter of overlap where the friction disk will be. I plan to use a bolt with a spring washer to supply the pressure.

The specifics above are to give an idea of the scale of the forces. My question is generally about what materials are used for friction disks.

Brass or nylon washers are sometimes used for hinges or joints when you don't want friction. I want the opposite of that - I want friction.

I want something durable enough that won't wear out quickly or disintegrate, and grippy enough to hold without slipping. The hinge may be repositioned several times per day. The worst thing would be a hinge that slowly slips over time.

Ideally, the materials would slide without making noise, like scratching or grinding sounds.

Edits: I reduced the weight from 40 down to 1-10 lbs.

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  • $\begingroup$ Holding 40lbs (at 6", 20 lb-ft, about 30Nm) with a 1.5" diameter friction hinge sounds hopelessly optimistic, unless you have counterbalance to eliminate almost all the force. $\endgroup$ – Brian Drummond Dec 21 '16 at 23:38
  • $\begingroup$ Oops, it will have 1.5" area of contact on either side of the hinge. So 2x 1.5". And, I reduced the arm to 4 inches and the weight to 35 lbs. $\endgroup$ – tbird Dec 22 '16 at 2:24
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Gem Products friction hinges use a sandwich of different metal washers, for example, phosphor bronze, stainless steel, and phosphor bronze. Their patent says:

The washers 135 of the present application can provide advantageous properties relative to conventional friction hinges. For example, the washers 135 may be made from phosphorus bronze, beryllium copper, brass, stainless steel and 17-4 PH hardened stainless steel, for example. The inventors of the present application discovered that the above materials are advantageous when used in washers for a friction hinge configuration like that shown in the figures. For example, the inventors discovered that a three washer configuration including a first washer made of phosphor bronze, a second washer made of stainless steel, and a third washer made of phosphor bronze, frictionally coupled together with advantageous wear properties. That is, the three washer configuration discussed above provides sufficient friction to ensure the desired angular position of the hinge 100 even after many rotations. Likewise, the inventors discovered that washers 135 made of beryllium copper, brass, 17-4 PH hardened stainless steel or any combination of the above materials, are advantageous for wear properties.

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The first problem I see is that static friction doesn't care about movement direction. So if you have e.g. 40 lbs worth of holding force in the "downwards" direction, you yourself must apply 80 lbs of force to move the screen upwards. This is because in upwards movement, you'll have both the weight of the screen and the friction working against you.

Another problem is that your surfaces are made of aluminum, which is a very soft metal. To avoid wearing them out, you will have to at least mount a flange of more durable material around the hole. This mounting must be strong enough to transmit the 30 Nm torque to the aluminum.

In general this kind of problems are solved by using a spring to take up most of the load, so the required amount of friction is much lower. You might try looking into mechanism that are used to hold windows and lids open; they usually have both a gas spring and the friction mechanism combined into one device.

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  • $\begingroup$ My question is about the materials used for friction disks. $\endgroup$ – tbird Dec 22 '16 at 14:27
  • $\begingroup$ @tbird a google search for "friction materials" is in order $\endgroup$ – DLS3141 Feb 21 '17 at 0:44

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