New coupler says "Top Holes Not For MTG"

[Darren Nemeth]

I am close to putting my new coupler on the trailer. The last sentence of the stamped in warning says "Top Holes Not For MTG". I'll assume MTG means "mounting."

What are they there for then? There are two of them and I plan to bolt one.

 

[boat1010]

Re: New coupler says "Top Holes Not For MTG"

I am not sure. Maybe a picture a little farther back might give us a little better view. I always just used the holes in the sides of the couplers to mount them.

 

[pnwboat]

Re: New coupler says "Top Holes Not For MTG"

I had a hitch a few years ago that had the same thing stamped on it. I also assumed the MTG means mounting. I mounted mine using the bolt holes on the side. I suspect that what they are trying to say is don't use ONLY the top bolt hole(s) to mount the hitch? As long as you mount it with the holes in the side, you should be OK in using the top one too. Just don't use the top one by itself I guess?

What is it there for? Who knows. Maybe the safety chains? Although I attached my chains on the side.

 

[Bifflefan]

Re: New coupler says "Top Holes Not For MTG"

I had a hitch a few years ago that had the same thing stamped on it. I also assumed the MTG means mounting. I mounted mine using the bolt holes on the side. I suspect that what they are trying to say is don't use ONLY the top bolt hole(s) to mount the hitch? As long as you mount it with the holes in the side, you should be OK in using the top one too. Just don't use the top one by itself I guess?

Hit it right on the head...

Use the holes on the sides only.
Bolts mounted in shear are stronger then ones mounted in tension.

 

[Darren Nemeth]

Re: New coupler says "Top Holes Not For MTG"

It looks like I am okay then.

I am using one through bolt on the rear top hole, two small bolts through the side rear holes and a 4 inch through bolt in the front holes. the safety chains will go on the 4 inch bolt.

Over kill, I guess. lol!

 

[dave11]

Re: New coupler says "Top Holes Not For MTG"

I am just replacing mine. I have the Dutton 5000# 2 inch coupler. It just uses the two through bolts on the side. I went outside and checked the old one, and there is no bolt in either of the holes on top.

FWIW it also says "Use D-L parts only. Do not substitute."
I would use through bolts on the side. Do what ever you want with the top holes. Bifflefan brought up a very good safety point I was not aware of.

You are talking literally pennies. Don't scrimp on those bolts.

 

[kenmyfam]

Re: New coupler says "Top Holes Not For MTG"

Side holes are good. Agree with not cheaping out on bolts !!! it's the difference between velcro and weld.
Just my 2 cents

 

[Silvertip]

Re: New coupler says "Top Holes Not For MTG"

Look at the coupler and you should be able to figure out why they don't want you to use the top holes only. The coupler is essentially an upside down "U". If you bolt through the top only, the upward force on the coupler where the ball sits would make the coupler fold like a cheap suit -- meaning the sides of the coupler would bend outward and the ball socket would bend upward wherever the tongue ended. The only bolts you need are two long bolts that pass all the way through the tongue and therefore "capture" both sides of the coupler. The through-bolt method also prevents side loading on the tongue which would occur if you used separate bolts to bolt each side of the coupler. You likely can't reach the back holes with separate bolts but I have seen this done and almost always the tongue and coupler are bowed outward due to the stress.

 

[jeeperman]

Re: New coupler says "Top Holes Not For MTG"

The top holes are not meant to be used to bolt the coupler to the tongue. Those couplers are rather thin sheet metal in most cases. And most backyard installers would merely install bolts with no washers other than maybe a lock washer.
Other than what Silvertip said about the coupler folding upward, it would be rather easy for a bolt head or nut to get pulled thru that sheet metal if only top bolts were used.
Especially after years of bouncing down the highway being pounded all the time.
I see those holes used most often when the coupler is welded to the tongue via plug welding.

 

[jeeperman]

Re: New coupler says "Top Holes Not For MTG"

The through-bolt method also prevents side loading on the tongue which would occur if you used separate bolts to bolt each side of the coupler. You likely can't reach the back holes with separate bolts but I have seen this done and almost always the tongue and coupler are bowed outward due to the stress.

I am trying to visualize why this would be if the proper size coupler is used on the tongue.
I have seen the use of long bolts going from one side to the other over torqued and collapsing the coupler and tongue.
Can't do that by using seperate bolt for each hole.
That being said, I use seperate bolts on all holes other than the up front holes.
There I drilled the holes out a bit bigger to match the max. bolt size that would go thru the safety chain links. I then used one stud threaded from each end, enough for two nuts and washers sandwiching the tongue and coupler on each side. (One nut inside the tongue and another outside the coupler.) The last safety chain links are on that stud inside the tongue. They are not wrenched down but are floating on the stud with washers in between the chains to fill the remaining space on the stud.
Over kill I know, but look at how your safety chains are attached to the tongue. On mine the last link had a tongue bolt thru it but the next link prevented the last link from laying flat to the coupler surface. So when the bolt is torqued down the chainlink is tilted, which is putting the wrong load on the bolt. Like the link is bending the bolt head off. Un acceptable for me.

 

[rbh]

Re: New coupler says "Top Holes Not For MTG"

Bolting them in with a grade #8 is the way to go for me, I also like a couple of welds just to be on the safe side.

 

[Silvertip]

Re: New coupler says "Top Holes Not For MTG"

An individual bolt at each side of the coupler is still going to allow outward bowing of the coupler, taking the side of the tongue with it due to the upward bending moment of the coupler ball socket. Granted, it can only bow a certain distance before one of two things happens. 1) the tongue simply can't bow any more or 2) the tongue rips open. Obviously if the tongue material is thicker than the coupler material the tongue would need to deform before the coupler. Through bolting can indeed deform the tongue inward but the bolts (properly tightened) prevent the coupler and the tongue from spreading. The bolts therefore control the stresses - not the material in the tongue or the coupler. If individual bolts at each side of the coupler were the best way to do this, trailer manufacturers would be doing it. Individual bolts are certainly better than using only the top holes which is what this is about. I can't believe anyone would do that but then I thought I'd never see a trailer used on the highway with wheel barrow tires either but I did. The load of landscape rock scattered all over the highway was not pretty.

 

[CatTwentyTwo]

Re: New coupler says "Top Holes Not For MTG"

I don't know if this is right or not, but it seemed like a good idea at the time. I used through bolts and cut a couple of spacers from 1/2" galvanized pipe to fit over them. I was then able to torque the bolts down real good without deforming the tongue.

 

[Bigprairie1]

Re: New coupler says "Top Holes Not For MTG"

Sometimes extra holes found in equipment or products are tied more to the original manufacture and fabrication of the item. It might be that the tooling used to form and make that item had a couple of locator pins or similar through there.
BP

 

[Floatsum]

Re: New coupler says "Top Holes Not For MTG"

Having been in the industry,,,,

Top holes are for manufacturing. They locate the raw steel plate in the forming press (s) during manufacturing to make everything symetrical per design.
When pressing to form, without a anchoring system the dies could pull the plate off location giving a ill formed product. Like too much material on one side of the ball socket, not enough on the other for example.

That's all they are for, and probably a basterdized size (as relevant to bolt sizes).

You're welcome.

 

[Darren Nemeth]

Re: New coupler says "Top Holes Not For MTG"

Thanks.

I spent $2 on the stainless bolt, nut and washer so I may as well use one of the top holes to bolt it to the trailer. But now I will know for next time jsut to use the sides.

 

[dave11]

Re: New coupler says "Top Holes Not For MTG"

Thanks.

I spent $2 on the stainless bolt, nut and washer so I may as well use one of the top holes to bolt it to the trailer. But now I will know for next time jsut to use the sides.

Sure don't want to waste so much money.

 

[jay_merrill]

Re: New coupler says "Top Holes Not For MTG"

I don't really care about the bolt holes - I weld mine on.



???

 

[kenmyfam]

Re: New coupler says "Top Holes Not For MTG"

Sometimes extra holes found in equipment or products are tied more to the original manufacture and fabrication of the item. It might be that the tooling used to form and make that item had a couple of locator pins or similar through there.
BP

Great point.
In the automotive metal stamping business we want as many "tooling holes" as possible to assist with alignment in the die and to achieve part quality and production speed.

 

[NYBo]

Re: New coupler says "Top Holes Not For MTG"

Very interesting discussion regarding through-bolts vs separate bolts. My trailer came with a through-bolt aft and separate bolts forward, and that's how I mounted a replacement coupler.

I don't know if this is right or not, but it seemed like a good idea at the time. I used through bolts and cut a couple of spacers from 1/2" galvanized pipe to fit over them. I was then able to torque the bolts down real good without deforming the tongue.

This makes a lot of sense to me. How about it, Silvertip, et al? Is this a good way to go?