Caliper friction washers

Been cleaning up some tools I inherited a while ago, and found that some of the larger Moore & Wright calipers have a friction washer of some sort under the domed nut. This unfortunately seems to be breaking up and coming out, which will make the joint a lot looser.

So, what are they made of (looks like some sort of fibre or heavy paper to me), and how best to replace them?

It looks like I'll have to grind off the peened over end of the joint screw, but will I do more harm than good - will there be enough thread left to reliably re-assemble? Are they actually necessary and once they have fallen out, could I just tighten up the joint by tightening the hex head screw?

Thanks.

Rob

If you can make a screw on cap for the hinge, you can try different friction materials. Occasionally there is a black very hard thin paper based card in the packing of certain products, a bit like fibre washers, that might work.

You could try looking up Belville or Crinkle/Wobble washers.
Some of the latter are quite thin and my be available in suitable sizes.

Bill

Thanks guys, I'll have a go at taking one apart. The Belleville washers sound like a good idea, or I've been wondering if a washer made of plastic (from a milk container, maybe) would give a stiff but movable joint.

The soft plastic you are thinking of will likely extrude and break down, better to have a stiff solid materiel as a friction washer. Vulcanite comes to mind if you can find some thin enough. easily dressed down to a thickness required.

Red fibre washers? Or cut your own specials from a sheet of red fibre material that you can buy at engineering suppliers. (No idea if there is a proper name for that red fibre, that's all I've ever heard it called.)

Or you might investigate what type of friction material is used in steering dampers on vintage motorcycles. Many had a disc 2 0r 3 inches diameter of friction material about 1/16" thick that was clamped between two steel surfaces by a big knob on a threaded rod coming up through the steering head.  Probably available from vintage parts suppliers for AJS, Matchless, BSA, Triumph etc etc. One steering damper disc would supply enough material for a bunch of caliper sized washers.

Edited By Hopper on 22/01/2020 09:19:30

How about this: **LINK**

https://www.vintagecarparts.co.uk/products/ca584-hard-red-fibre-sheet-0-8mm-thick

Russell

Edited By Russell Eberhardt on 22/01/2020 09:29:05

Maybe a bit of leather from an old shoe or belt. Definitely what would have been used before they invented plastic. Make a new longer screw with a locknut.

Many thanks for all the ideas and information, I'll look at getting some of that fibre sheet.

Hi All

Disassembled one of the calipers - as it turned out, I picked one where the washers were still intact, but never mind. I found the screw is not peened over, so that's a good thing, and the washers are 5/8" OD, 3/8" ID and 15 thou thick (measured at 14 but assuming some compression has occurred). Cleaned and reassembled, good as new. Took some pictures if anyone is interested, not sure how to add an album to a posting, but I think you can see them if you click on my username.

There seemed to be some writing on the friction washers, which were quite a tough material, white in colour, which said (I think) "TENNEX", but cannot find anything relevant with a Google search.

FYI on red fibre washers .

https://plasticwashers.newprocess.com/product/custom-washers/vulcanized-fibre-washers

I m,ade 150 pair of calipers for the Christchurch Indoor Bowls Ass, I put a washer made of shim brass (about .010" Between the legs, and held them together with a brass rivit. Seems to work OK, just a light tap on the rivit if it gets a bit loose. I have never looked at my Moore & Wright gear, but I would go with Clive, a hard plastic.

Ian S C

Thank you all for the insight and suggestions, I may well go with some brass shim.

Cheers, Rob

Presumably, the calipers were for measuring woods?

Kiaora!

Comparing the distances 'twixt woods and jack, I would guess - I inherited a handy little string and ivory gizmo for the same purpose from my grandfather.

I expect you are right but one would need a steady hand to avoid disturbing the status quo (I assume they were firm joint calipers).

Of course, you don't need to measure if you can do this

Vulcanised fibre was actually patented in 1859 and is available in a number of different colours. It's amazing stuff.

That said, I have various calipers made by my grandfather in the early 1900s with no shim or washer in the joint, and they are still in regular use. All that's needed is enough oil to prevent rust in the joint, and a tap with a hammer every generation or so to take out any looseness.

George B.