Thread: How to Hold a Flat Washer While Reducing the OD

Christmas Dinner over as well as Boxing Day Lunch and its HOT.
I made some thick washers out of brass for a part on the steering of my WW II Jeep Restoration. I used a bolt as a mandrel while I machined a couple of brass nuts for the OD then rechucked and enlarged the ID threaded hole. That was simple and worked well. I dug out 4 flat steel washers to go under the nuts on the tie rods. The washers look very "agricultural" because they are too big (well I reckon they are) so I used a Bolt again as a mandrel but the bolt was too small so my reduced washers were off centre.

A got a hint years ago about a tapered mandrel that could centre the washer on the mandrel while you machined the OD. That would be OK for a few but I was thinking if you had to do a number how/what sort of a mandrel would be appropriate?

The few times I've done this I used your bolt mandrel method for the washers too, not the same bolt as you want to fasten with.

I go down a bolt size or two and select one long enough to have enough unthreaded shank below the head for a good chucking surface. Cut the head off the bolt, screw one nut on the correct end all the way till it binds against the end of the thread. Get a second nut and jam nut it against the first, chuck it and peck the end for a center.
Messure the od of the nuts to ensure they are smaller than the finished od of your washers. Don't need much clearance here. If you do need to trim a bit off the corners fit a third nut first. Trim to size remove the last nut then face the second nut on the threaded side all the way to the thread. Next do the samething but stop facing once you reach the id of your washer. Form a registry for your washer less than the washers thickness then use the third nut to lock your washer on the registry and go for it. Mark chuck jaw number 1 position in relation to the jam nuts before removing from the chuck

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I have no idea of the proper method for doing this, this method just uses the stuff I have at hand.

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As the OD is rarely as critical as the ID I usually fix them to the end of a correct size bolt and then put them in a lathe chuck . For small washers (<1/2" ID) I will often just put the bolt in a cordless drill chuck and spin the washer up against a full speed belt sander belt.

I do the same with many round headed type screws. The most common application is on M3 CS screws that are only 6mm long that I use to hold Arduino boards down on plastic or brass standoffs.

I also use one of the brass standoffs to hold the short screw to reduce the likelihood of the bet touching the drill chuck
ReduxeCSscrew.jpeg

Heres where the M3 sure has to go - ie not enough room for the standard M3 head size
ReduxeCSscrew2.jpeg

Turn a mandrel from some stock that is larger than the hole. Cut it slightly shorter by a blonde one one than the stack of washers you want to turn. Cut a thread into the end of the mandrel. Make a retainer smaller than the desired OD. Stack your washers on and screw the retainer on to clamp it all up. Your washers will come out as concentric as you make the mandrel in relation to the clamping end and the fit of the washer ID.
An expanding mandrel would probably work too but I have no experience with them so can’t comment with certainty.

Originally Posted by racingtadpole

Turn a mandrel from some stock that is larger than the hole. Cut it slightly shorter by a blonde one one than the stack of washers you want to turn. Cut a thread into the end of the mandrel. Make a retainer smaller than the desired OD. Stack your washers on and screw the retainer on to clamp it all up. Your washers will come out as concentric as you make the mandrel in relation to the clamping end and the fit of the washer ID.

That's how we do it at work, we'll usually stack 15-20 at a time. Our mandrels are made to suit a 1/2" or 5/8" collet in the headstock and a live centre in the tailstock.

Thanks for the replys. By the sound of things I will need to make a couple or 3 sizes to accommodate varying sizes of washers. The washers that we use now a days are probably good in Carpentry jobs where the larger size washers cover a larger area to spread the load over a bigger area. Doing Automotive/Engineering jobs with washers just marginally bigger than the nut you are using do look a lot better than the agricultural types

I have an idea flopping around in my head so I might have a play over the next couple of days and see where I end up

You could check into aircraft hardware as it isn't any bigger than needed to keep weight down. The AN (army/navy I think) and the later MS (military spec) were used on all the military equipment including jeeps so they would be the "proper" stuff. The bigger sizes will be spendy though. See if you can find an aircraft mechanic to scrounge some from.

Pete

Here is a supplier of aircraft stuff, mostly the homebuilt and ultralight market that have hardware. The AN960 washers should work for you.

Aircraft Spruce Australia. Pilot and Aircraft Supplies. Aviation supplies for pilots, headsets & helmets, Garmin GPS, radios, flying suits, intercoms, windsocks, Airservices Publications, Jeppesen

The supply of flat washers I have on hand are just the common variety from hardware stores. They are large in diameter and vary in thickness. What I ended up doing was to use 80mm of 16mm rod and cut two steps in it. The first step was machined to allow the ½" washers to slide on while the other was turned to fit 3/8" washers. I cut an 8mm thread on the end and made a cap to put pressure on the washers and I was away. I figured that I would not be doing a huge number to cut down so I can fit 4 washers on at a time. It works quite well. I need more practice to get a better finish off the tool. I used a HSS tool to do the job

One problem with reducing the diameter of a washer is that you are also cutting away the protective plating like zinc or cadmium letting them rust quicker. It is a lesser issue if the washers are stainless or you live in a desert. Bigger problem in places like this where the roads are white with salt in the winter when the slush dries. Of course it is an excuse to set up a plating station.

Pete

QC that's a top tip, never thought of aircraft suppliers before.

Another thing to consider is hardened washers usually available at agricultural supply stores ect

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Top tip until you see the pricing.. then not so much.

Hi Guys,

If you only need one or two, its as quick as chucking up a piece of steel slightly bigger in diameter than you need and turning to size then drilling a hole to suit your bolt, then part off as many as you need.