Anyone who has ever needed to change the ID of a washer knows that it is not all the difficult just lock it in the groves of the jaws in a 3 jaw chuck enlarge the hole with a cutter like that of a boring bar. Simple for 1 off or maybe a few but the process becomes arduous and time consuming. Chucking squaring boring checking the ID removing the burr then removing and repeating the process for as many as you require.
But what if you require a batch of several?
Today I needed 8 washers with a 1.610" ID and no more than 2.5" OD. 1 1/2"USS flat washers are 3 1/2" OD & 1 5/8" ID nominal SAE flat washers hold tighter tolerances but are 3" OD & 1 9/16" ID Neither came close to suiting my requirements the USS would have been tool large an OD and ID the SAE would have been too large OD with too small of an ID
A while back I made a mandrel that would allow me to turn the OD of a 1 1/2" washer and the USS with the 1 5/8 ID could have worked but they cost over $2.00 each plus the local hardware store only had 4 , I needed 8
1" USS washers are 2/1/2" OD perfect 1` 1/16" ID plus they had a box of 10 for $6.75
Now just boring out 8 pieces wouldn't take much time but what's the fun in that next time I might need 200 PC.
I decided to make a fixture like those I made years ago but no longer have. Simple right just hog out a piece of stock then thread the OD for the part to be chucked in the lathe and hog out another piece then thread the ID for the clamping nut The only thing was I didn't have any suitable stock fpr the project. Time to search for something else.in my usable scrap. What I found was the Male and female threaded portions from a stick of 2 7/8" Oilfield tubing Nice and hard already close to the proper bore. Just a matter of sawing off what I needed and a little turning tack weld in a couple of other washers chuck the fixture clamp in 8 washers and bore as required.
Next time I need to modify some 1" USS washers to another size I will have the fixture