VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc Bolts vs Screws

On another thread there was questions about the bolts/screws holding the oil pan to the block. Answers to the issue have prompted the following:

I need educating on whether a device for holding two parts together is a screw or a bolt.

I have always thought that if the threads weren't spiral and tapered they were bolts. Screws pointed, spiral threads increasing diameter from pointed end to head whereas bolts same diameter for the length of the threaded surface. No matter the size.

I think you all know what I'm talking about even though I may not explained my dilemma.

Please educate me on this issue. Technically speaking what is the definition of a bolt as opposed to screw? I don't think the terms are interchangeable according to size and function.

Thanks,

Charlie

A screw can be used by itself to fasten items while a bolt is used with a nut or other threaded attachment. .

I beg to differ. Stove Bolts are round head screws, Head bolts are not used with a nut. When I go to the hardware store they have round head screws and hex head screws. Call them what you will. No harm done.

Taken from https://www.melfast.com/blog/2010/11/what-is-the-difference-between-a-bolt-and-a-screw/

I have added a few words of my own in brackets [].

• Bolts and screws are both Building Fasteners that help to position objects and hold them together.
• If it has a head on one end it is a screw. The head is driven or turned with a screw driver or sometimes with a wrench. The diameter ranges vary to meet demands and needs of specific products. Screws are generally turned into an object, like a piece of wood, so the head needs to be bigger than the surface. This prevents the screw from being turned further than the length of the screw itself.
• Bolts are screws that rotate into a matched nut [or threaded hole] to tighten it. Bolts have a bigger head than the shaft, with a few exceptions. Carriage bolts and J-bolts are among those exceptions. The shafts of bolts are not tapered, whereas many screws are tapered. The main difference between a bolt and a screw is that a typical screw can work on its own and a bolt requires a nut [or threaded hole] to secure it.

So, bolts are a subspecies of screws.

Cheers, Dean

Very good Dean. I was going to get my Machinist Handbook and quote it but with your explanation it is not needed. Good Job

I have added to my above post. Both screws and bolts have many various types however if a screw it can be used alone and if a bolt it is used along with an attachment-be it a nut or other matching threaded item.

So the things that keep the taillight doors attached to the assembly are bolts and the little devices that connect the brushes in the generator are bolts also.

According to the responses then instead of calling them screws they are actually bolts. Makes sense to me.

Charlie

since you brought up taillights I have a question for you. Are the nuts that hold the taillight onto the bracket on the 1931 and 1932 Square nuts or Hex nuts?

BR,

You're asking the wrong guy. I have no idea. How about trying Chip/ or one of the other really, really old guys that got their first driving lessons in one.

Best,

Charlie

Careful about those old Guys. I'm one of then. VCCA#28

I have always referred to fasteners that have a hexagonal head that require a spanner to turn as bolts and those that use a screwdriver (either flat or phillips head) as screws then there is the oddball self drilling (tek screws).
Tony