Bolt question

[JHZR2]

Hi,

I am making a new HD negative battery cable, and the connection point is a bolt with a 13mm head. I can get standard (imperial) size holes for the cable end. What size shaft would a bolt that has a 13mm head have?

Thanks!

 

[XS650]

The ANSI, ISO and DIN standards all use a 13mm hex on 8 mm threaded fasteners as the standard size. JIS doesn't normally use a 13mm hex

8mm = 5/16 within a gnat's eyebrow.

In the US we use the US Customary system of units for inch measurements, not Imperial.

As spasm3 has inadvertently pointed out, standards aren't always followed.

 

[spasm3]

I measured a bolt with a 13mm head i had laying around, the shaft under the bolt head measured 9.5 mm i think that works out to 3/8

 

[andyd]

mebbe so but 5/16= 7.95 mm. You can run a 8mm coarse bolt through a 5/16 coarse nut.

 

[spasm3]

Home depot has a neat little measurement card thats a buck or so. it has bolt holds, measures outer and some inner diameters etc. Its call " Gage-it hard ware gauge"

 

[UncleS2]

Speaking of Home Depot & bolts- is HD (maybe Lowe's too- I don't get to either one very often, but will probably drive right by some tomorrow) a good source for some grade 5 bolts, probably 7/16"- 1/2" dia, to mount a frame mount rcvr hitch? I'd need bolts, nuts, lockwashers, maybe flatwashers.

 

[Tempest]

They should have that. I'd go up to a grade 8 if you only need a few bolts. Couple of dollars is worth the extra peace of mind to me.
The Ace hardware stores here have a much better hardware section than HD or Lowes.

 

[NJC]

Originally Posted By: andyd
mebbe so but 5/16= 7.95 mm. You can run a 8mm coarse bolt through a 5/16 coarse nut.

The pitch is .003" off between the two: 5/16 - 18 = .056" and M8 x 1.5mm = .059" That's a fair heap so I'm surprised it works ... I'll check when work's slow.

 

[UncleS2]

Thanks Tempest- our small local Ace hw is only ~3 miles from home, & has a very good selection for a small store. I'm always going there for bolts, fasteners & stuff, will probably just stick with them. It'd be mighty disappointing to go through all the hassle of getting into a big HD or Lowe's- park way out, hike in, etc- just to find I'd have had equal or better choices right at home. Bailey's Ace won't even mind if I bring the hitch in!

 

[The_Jeff]

HD and lowes often bag their hardware as well making it hard to screw stuff together to check threads.

ACE packs 10 lb of stuff in a 5 lb bag, but their marketing/advertising is incredibly bad.

chart: http://www.boltdepot.com/fastener-information/Bolts/Metric-Bolt-Head-Size.aspx

 

[onion]

Generally speaking, a bolt with an 13mm head will have an 8mm X 1.25 thread. It's very close in size to a 5/16" thread, but the thread pitch is different- using them interchangeably will damage the threads.

But without actually seeing the bolt and knowing the application, this is only a guess. I've seen bolts with a 13mm head that have a 10mm X 1.5 thread, too. And I've seen them with a 9mm X 1.0 thread. And an 8mm X 1.0 thread. There really isn't enough information in the OP to give a definitive answer... but 8mm X 1.25 would be the most common for a 13mm head.

Also, this "grade 8" business does not apply to metric bolts. Metric bolts will be stamped on the head with a number like 8.8, 9.8, 10.8, 12.8, etc. And 10.8 is roughly equivalent in strength to a grade 8 standard bolt. 8.8 is roughly equivalent to a grade 5.

But whatever you do, don't cross-thread a standard bolt into the hole.

 

[Kestas]

Why would anyone recommend a graded bolt for a battery cable job? Is joint strength really an issue? If anything, I would recommend the softest bolt available. Years down the road, if he finds the setup has horribly corroded and can't unbolt it, he could easily cut, drill, or grind the fastener to take it apart.

 

[NJC]

Originally Posted By: NJC
Originally Posted By: andyd
mebbe so but 5/16= 7.95 mm. You can run a 8mm coarse bolt through a 5/16 coarse nut.

The pitch is .003" off between the two: 5/16 - 18 = .056" and M8 x 1.5mm = .059" That's a fair heap so I'm surprised it works ... I'll check when work's slow.

Given a late hour, I can offer the absolute finest incorrect information. If a M8 x 1.5mm exists, it's VERY rare.

5/16 - 24 = .0416" thread pitch
M8 - 1 = .0394" thread pitch

These 2 bolts are very close (.002") in pitch, but are fine threads. And the typical M8 cap screws I use are 1.25mm pitch.

 

[NJC]

Originally Posted By: Kestas
If anything, I would recommend the softest bolt available. Years down the road, if he finds the setup has horribly corroded and can't unbolt it, he'd be able to easily cut, drill, or grind the fastener to take it apart.

SS would be a good fit - corrosion resistant and stretchy.

 

[XS650]

Originally Posted By: NJC


5/16 - 24 = .0416" thread pitch
M8 - 1 = .0394" thread pitch

These 2 bolts are very close (.002") in pitch, but are fine threads. And the typical M8 cap screws I use are 1.25mm pitch.


You wouldn't need Loctite.

10 turns would be 1/2 thread pitch off

 

[mechtech2]

I'd get the one that fits the hole. Why substitute??

A very good option is to leave the stock cable in place [with clean ends and seats] and use ANOTHER cable at a good location.
Consider this method of attack.

 

[Tempest]

Quote:
Also, this "grade 8" business does not apply to metric bolts.

Yes, and nobody was. Stuart was asking about fractional bolts for a TRAILER HITCH and a good place to get them.