Socket Head Cap Screw Head Diameter
	Post Reply		Forum

Posted by: Larry767 ® 11/14/2005, 16:22:55 Author Profile Mail author Edit

We are working on some old equipment that has some 5/8" socket head screws that need replacing. We ordered new fasteners and the heads came in at the standard 0.938" diameter. The old fasteners we are replacing have a head diameter that is approx. 0.860". The counterbores in the part are sized accordingly so the new fasteners will not fit. My question is, was there a change to the ANSI standards at some point to increase the head diameter or are these fasteners just non ANSI (i.e. produced in some non-ANSI abiding country)? Is it possible to buy a 5/8" sockete head cap screw with a smaller head diameter anywhere?

Replies to this message

Re: Socket Head Cap Screw Head Diameter
Re: Socket Head Cap Screw Head Diameter -- Larry767	Post Reply	Top of thread	Forum

Posted by: Larry767 ® 11/15/2005, 16:02:22 Author Profile Mail author Edit

Found some additional info here: www.techsavvy(dot)com/industry/file/national/03v3f/6.html?id=107842&comp_id=03V3F&base_region=* Now, can anyone point me to a chart specifying the head diameter of a 1936 Series socket head cap screw? I am being told that it is .860" by another internet surfer on the newsgroups. Modified by Administrator at Tue, Nov 15, 2005, 17:08:51

Post Reply | Recommend | Alert

Where am I? Original Top of thread

| |

Re: Socket Head Cap Screw Head Diameter
Re: Re: Socket Head Cap Screw Head Diameter -- Larry767	Post Reply	Top of thread	Forum

Posted by: kelly_bramble ® 11/15/2005, 17:26:42 Author Profile Mail author Edit

Well, I don't know about the standard you are reffering to, however the 1947 ASA B18.3 American Socket Head Cap Screw Standard says the following: Head Diameter Max. 7/8 Head Height Max. 5/8 Socket Width Accross Flats 1/2 6 Flutes What is the size of the internal hex on you original fastener?

Post Reply | Recommend | Alert

Where am I? Original Top of thread

Re: Socket Head Cap Screw Head Diameter
Re: Socket Head Cap Screw Head Diameter -- Larry767	Post Reply	Top of thread	Forum

Posted by: kelly_bramble ® 11/14/2005, 16:55:27 Author Profile Mail author Edit

Sounds like you are actualy replacing a Hex Socket Shoulder Screw. Check out ANSI/ASME B18.3. The Hex Socket Shoulder Screw has a max head diameter of .875 and min. .853. This type screw performs differently than a regular socket head. The shoulder relief is there to take a little bending load.

Post Reply | Recommend | Alert

Where am I? Original Top of thread

| |

Re: Socket Head Cap Screw Head Diameter
Re: Re: Socket Head Cap Screw Head Diameter -- kelly_bramble	Post Reply	Top of thread	Forum

Posted by: Larry767 ® 11/14/2005, 21:41:52 Author Profile Mail author Edit

It is not a shoulder screw. There is no shoulder (unless it is a 5/8-10 with a 5-8" shoulder ;-). If I put the old fastener beside the new they look identical except the old fastener has the slightly smaller head diameter. The head has not been machined down either - it has the factory marks on the O.D. just like the new one.

Post Reply | Recommend | Alert

Where am I? Original Top of thread

| |

Re: Socket Head Cap Screw Head Diameter
Re: Re: Socket Head Cap Screw Head Diameter -- Larry767	Post Reply	Top of thread	Forum

Posted by: Gary Kemp ® 11/18/2005, 02:33:00 Author Profile Mail author Edit

I think the standard changed in 1960.

Post Reply | Recommend | Alert

Where am I? Original Top of thread

| |

Re: Socket Head Cap Screw Head Diameter
Re: Re: Socket Head Cap Screw Head Diameter -- Gary Kemp	Post Reply	Top of thread	Forum

Posted by: Larry767 ® 11/18/2005, 07:54:15 Author Profile Mail author Edit

I have since discovered that prior to 1960 these were produced under different dimensions that are available today under the "1936 Series" name. Older copies of Machinery's Handbook apparently have the dimensions listed and that is apparently what my fastener is. The cost of these special fasteners is prohibitive though so we're better off enlarging the counterbores or turning down the heads of the new fasteners if strength is not an issue. Thanks all.

Post Reply | Recommend | Alert

Where am I? Original Top of thread

| |

Re: Socket Head Cap Screw Head Diameter
Re: Re: Socket Head Cap Screw Head Diameter -- Larry767	Post Reply	Top of thread	Forum

Posted by: randykimball ® 11/19/2005, 00:06:53 Author Profile Mail author Edit

Before World War II fasteners were made about anyway the maker wanted to make them. During the war the MIL-SPEC system was established to make all fasteners one common size so that we could make parts to jeeps, trucks, aircraft, tanks and so forth all over the country and expect them to fit. At that time the current quality control methods were born, too. With a 1936 bolt you are most likely to find about anything. It would be wise to counter bore to fit modern specs so in the future the bolt can be replaced without additional problems. Working with these old machines don't be surprised to find odd sized bolts with strange numbers of threads per inch. It may be wise to tap out the threaded portion with a modern tap while you are there. Good luck. The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them. Modified by randykimball at Sat, Nov 19, 2005, 00:10:38

Post Reply | Recommend | Alert

Where am I? Original Top of thread

| |

Re: Socket Head Cap Screw Head Diameter
Re: Re: Socket Head Cap Screw Head Diameter -- randykimball	Post Reply	Top of thread	Forum

Posted by: kelly_bramble ® 11/21/2005, 09:31:06 Author Profile Mail author Edit

The following link has a little about the history of thread standards. https://en.wikipedia.org/wiki/Unified_Thread_Standard I'm actualy amazed it took so long for a standard to be created.

Post Reply | Recommend | Alert

Where am I? Original Top of thread