drill jug for drilling holes in washers

[Frank S]

Just today I explained to a younger friend,(Chef by Trade who I am teaching a bit about machines),about how washers are always a bit larger than the bolt or stud they are intended for and how by mixing Imperial and metric you can usually get a closer fit if needed.
The investment in those risers is certainly paying off.

Also different grades of washers have different Id's and OD's, washers also have a top and a bottom when installing. On softer lower grade s this will be noted by the rounded edges on 1 side and sharp edges on the other, for hardened or machined washers the top is denoted by a slightly larger bevel on the ID, these rounded or beveled sides should always be installed next to the bolt heads, this is to lesson the possibility of creating a pinch moment with the fillet radius of the bolt head which could result in a stress fracture of the bolt. the hole Id of washers are larger than the bolt diameters for much the same reason.