I wonder about some of their treminology. I hear all the time the
term "Lag bolt" but to me a "BOLT" requires a NUT or it's a screw.
Now the "machine screw" can be either a screw (if it goes in a
threaded hole) or a bolt if it has a nut on it. But the "LAG" thing
hasent a chance of putting a nut on it, therefore it's a SCREW.
One other minor point is the washer that they called "finish" I
have used those for over 50 years and they have always been
Otherwise a good compendium.
There does seem to some ambiguity and overlap of terms in the industry.
The lead screw in lathes used the saddle as a "nut", and the ball
screws used in CNC's also use "ball nuts", so you'd think that they
might be called "lead bolts" or "ball bolts", eh? <g>
Here's an excerpt from Wik on screws (it touches on lag bolts):
 Differentiation between bolt and screw
Carriage bolt with square nut.
Structural bolt DIN 6914 with DIN 6916 washer and UNI 5587 nut.A
universally accepted distinction between a screw and a bolt does not exist.
In common usage the term screw refers to smaller (less than 1/4 inch)
threaded fasteners, especially threaded fasteners with tapered shafts
used in un-threaded substrates and the term bolt refers to larger
threaded fasteners that are designed to be used with nuts or in tapped
holes. The term machine screw is commonly used to refer to smaller
threaded fasteners that are used with nuts or in tapped holes. The term
lag bolt (also known less commonly as a lag screw) is used to refer to
larger threaded fasteners with tapered shafts.
Various methods of distinguishing bolts and screws exist or have
existed. These methods conflict at times and can be confusing. Old SAE
and USS standards made a distinction between a bolt and a cap screw
based on whether a portion of the shaft was un-threaded or not. Cap
screws had shafts that were threaded up to the head and bolts had
partially threaded shafts. Today a bolt that has a completely threaded
shaft might be referred to as a tap bolt.
ASME B18.2.1 defines a bolt as "an externally threaded fastener
designed for insertion through the holes in assembled parts, and is
normally intended to be tightened or released by torquing a nut." Using
this definition to determine whether a particular threaded fastener is
a screw or a bolt requires that an assumption be made about the
intended purpose of the threaded fastener, and as a practical matter
does not seem to be followed by most threaded fastener manufacturers.
It also conflicts with common usage such as the term "head bolt", which
is a threaded fastener that mates with a tapped hole in an engine block
and is not intended to mate with a nut.
It is possible to find other distinctions than those described above,
but regardless of the particular distinction favored by an individual
or standards body the use of the term screw or bolt varies. More
specific terms for threaded fastener types that include the word screw
or bolt (such as machine screw or carriage bolt) have more consistent
usage and are the common way to specify a particular kind of fastener.
The US government made an effort to formalize the difference between a
bolt and a screw, because different tariffs apply to each. The document
seems to have no significant effect on common usage and does not
eliminate the ambiguous nature of the distinction for some fasteners.
The definition is available online.
==================================================================== There is MUCH more juicy screw/bolt info on that site.
I've only used them for 45 years so I guess you have the upper hand.
But we always called them finishing washers. Walk into a large
hardware store ( not HD or Lowes ) and ask for a cup washer and when
you get a blank stare ask for a finishing washer.
A cup washer for me has a vertical wall that you snap a decorative cap
Just my 2 cents,
Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here.
All logos and trade names are the property of their respective owners.