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Speaking of Precision

Speaking of Precision is a knowledge preservation and thought leadership blog covering the precision machining industry, its materials and services. With over 36 years of hands on experience in steelmaking, manufacturing, quality, and management, Miles Free (Milo) Director of Industry Research and Technology at PMPA helps answer "How?" "With what?" and occasionally "Really?"
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Distinguishing Bolts from Screws

Posted January 25, 2011 8:15 AM by Milo
Pathfinder Tags: bolts Fasteners nuts screw threads tapped threaded fasteners

Yes, bolts and screws are both externally-threaded fasteners. But how can you tell the difference?

Bolt - torque the nut

Bolt - externally threaded fastener that is

  • designed for insertion through holes in assembled parts
  • normally intended to be tightened (or released!) by torquing a nut

Screw - torque is applied through the head

Screw - externally threaded fastener that is capable of

  • being inserted into holes in assembled parts;
  • mating with a preformed internal thread, or forming its own thread;
  • being tightened or released by torquing the head.

A bolt is designed for assembly with a nut.

Nuts are required for bolts, optional for screws.

A screw has features in its design which makes it capable of being used in a tapped or preformed hole in the work. Because of basic design, it is possible to use certain types of screws in combination with a nut. Any externally threaded fastener which has the majority of the design characteristics which assist its proper use in a tapped or other preformed hole is a screw, regardless of how it is used in its service application.

Source: Distinguishing Bolts from Screws, US Department of Homeland Security, March 2006.

Bolt

Screw

Nut

Editor's Note: CR4 would like to thank Milo for sharing this blog entry, which originally appeared here.

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RDGRNR
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#1

Re: Distinguishing Bolts from Screws

01/25/2011 2:14 PM

Interesting, and quite correct. Maybe my question was answered in the editors note. I couldn't open the link but why in the world is the Department of Homeland Security interested in bolts and screws?

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Milo
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#2
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Re: Distinguishing Bolts from Screws

01/25/2011 2:22 PM

Homeland Security includes Customs.

Customs has to know if the "goods" are bolts or screws in order to apply proper duty, tariff, or exemption.

The publication is printed, i have a copy) as far as I can tell never made it online.

Milo

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Chankley
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#8
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Re: Distinguishing Bolts from Screws

01/26/2011 4:26 AM

Why they need to differentiate between screws and bolts and have different tariffs beats me. It is interesting that they fiddle around with these minutiae when they don't even have logical categories for many classes of electronic equipment in the harmonised tariffs.

For instance a laptop (8471.30.00) does not come under Chapter 85 (electrical equipment). Instead it comes under:

CHAPTER 84 - NUCLEAR REACTORS, BOILERS, MACHINERY AND MECHANICAL APPLIANCES; PARTS THEREOF

71 Automatic data-processing machines and units thereof; magnetic or optical readers, machines for transcribing data onto data media in coded form and machines for processing such data, not elsewhere specified or included

.30 Portable automatic data-processing machines, weighing not more than 10 kg, consisting of at least a central processing unit, a keyboard and a display
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#9
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Re: Distinguishing Bolts from Screws

01/26/2011 2:30 PM

Computers are in chapter 84 because of their history. They are descended from the old lever crank adding machines which were originally not electrical.

In the 2005 rewrite of the tariff by the WCO (World Customs Organization) they finally moved monitors and printers out of the computer parts category and into the proper headings. The tariff is an ever changing organism but it is written and controlled by a huge bureaucracy and it takes years to make any meaningful changes. The electronics world is changing much faster than the WCO can move.

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lyn
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#3

Re: Distinguishing Bolts from Screws

01/25/2011 6:12 PM

Whadda ya call them little pointy things ya screw into metal or wood?
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#4

Re: Distinguishing Bolts from Screws

01/25/2011 9:57 PM

Nobody ever says "Go bolt yourself!"

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#5

Re: Distinguishing Bolts from Screws

01/25/2011 10:33 PM

Ahh, now i get it.

There was this news item about a lunatic escaping from the asylum, happened to catch a lone woman washing clothes at the river...the headline said "Nut screws washer and bolts"

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#7
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Re: Distinguishing Bolts from Screws

01/25/2011 11:30 PM

Milo

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#6

Re: Distinguishing Bolts from Screws

01/25/2011 11:29 PM

Screws utilize Screw drivers as Flat, Phillips, Square and star. All others require other than previously mentioned and host an array of different style heads to be used with different type tools, although the threads may also appear to be rolled in the form of what one would consider a wood type screw that is not quite right. So , half right/half wrong.

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Milo
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#11
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Re: Distinguishing Bolts from Screws

01/26/2011 2:56 PM

Not sure I understand what you are trying to say.

Milo

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#10

Re: Distinguishing Bolts from Screws

01/26/2011 2:37 PM

I keep that publication near at hand. There is a revised edition that came out in 2010

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#12

Re: Distinguishing Bolts from Screws

01/26/2011 8:56 PM

Screws are slang for prison warders in the UK.

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#13

Re: Distinguishing Bolts from Screws

01/28/2011 3:43 PM

For any of us who complain of being screwed by the regulations, the company, the government, the ex-wife... there is now a clear way to determine whether you've been screwed, or in fact, bolted.

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