Thread: Bolts for couplings

Originally Posted by Camoco

We should be grateful for fellas like yonnee who spend as much time helping others as they could probably be in the shed enjoying themselves.

Cheers Cam

here here

Well bugger me, I log on to post this exact question about what type of bolts to use on my coupling and also to attach my Alko IRS with and look what I find

My hitch (a cast Carter?) does not have a flat mounting face and in fact has a raised foot under each bolt hole so based on the above I should be using MS to fit the hole size (14mm). Are there different grades of MS, if so what grade to use and am I best of using course thread?

Now for the Alko IRS, the mounting is pressed steel so not a nice machined flat surface and two bolts on each side (so four all up). I assume that this should also use MS in the 14mm course thread to fit the holes?

Just double-check that 14mm will fit. Most of those couplings (Carter Wesco, AL-KO, Trigg,) only ever had holes to fit 1/2" bolts.

The AL-KO axle you can use either. Most of the load force is downward, compressing the trailer to the axle, so not alot of force on the bolts by comparison with the coupling. But I would recommend using a large diameter flat washer against the slotted hole of the AL-KO bracket. And another comparison, 95% of trailers sold have their axle attached to the springs with MS U'bolts, along with MS bolts mounting the spring eye to the hanger.

Thanks Yonnee, yeah 14mm will fit as I think the last owner may have drilled it out. It is only going on for the short term until I can decide which off road coupling to use. My plate has been punched out to 14mm to match.

Vehicle manufacturers and towbar manufacturers all insist on towbars being attached to each other with HT bolts
Towbars that have a bolt on tounge use HT bolts
Manufacturers of 4WDrives with recovery hooks use HT bolts.
4WDrive after market accessory manufacturers insist their recovery hooks are joined to the 4WD with HT bolts. I've uninstalled and installed recovery hooks on various vehicles (Jackaroos/Hilux's/Rodeos) and most hooks do not have a machined surface where it joins to the chassis of the vehicle, it is a raw cast surface
My boat trailer (2t boat on trailer) and two 7x4' box trailers were all supplied with HT bolts

There is typically more clamping force with HT bolts as generally they are finer threads, BSF or UNF (yes there are some course pitches out there too).

My double ended stiff bar which has a 50mm coupling on each end, has the couplings bolted down with HT bolts.

Also I would not use a coupling only designed for two bolts, I will even avoid couplings designed for three bolts, will go out of my way to find/purchase/use a coupling with four bolts all the time, even if the four hole coupling costs more.

Cheers,
Wahoon.

Thanks for everyones input...has been most informative...and based on my original question as to whether the VSB1 or other specifies the bolts to use...I think my question has been answered.

Cheers