Looking for a source for Metric Carriage Bolts

Hi Everyone,
I am having trouble finding what I would call a carriage bolt, it looks just like a carriage bolt except that it has a spline round shape under the head instead of a square shape that is usually under
the head of a carriage bolt. The round shoulder under the head is a fine spline that looks about 8 mm long.
The bolts are used to secure a steel gas tank support arm to the frame of a truck.
I need a source of supply I can order from here in the USA but I'm having trouble finding this item.
Thread specs = 10 mm OD X 1.5 mm pitch Length under head = Need at least 40 mm long but can cut down a longer bolt if needed. Head diameter = Approximately 20 mm OD, but can use a little larger if needed. Grade = Prefer a 10.9 class or whatever the strongest grade available is. The round spline shape or shoulder that is directly under the head has an 11 mm OD.
I have tried local hardware and autoparts stores along with www.mcmaster.com. I also looked through the www.auveco.com/ catalog but have not found anything yet.
Does anyone have an idea of where I might find something like this ?
Thanks John
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John2005 wrote:

If this is just to hold the support arm use a standard hex head grade 8 bolt with a washer to spread the load. The only reason for the spline is to make assembly faster as the splines hold the bolt in place so only one socket is needed.
--
Steve W.
Near Cooperstown, New York
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Thanks Steve,
I was thinking of using a grade 8 bolt and washer myself, but was not sure if there was a functional reason for the spline carriage bolt.
I've never even seen carriage bolts in a grade higher than 5, but it makes sense to use a grade 8 hex bolt.
This seems to be a non-standard bolt, perhaps custom. It looks like a common wheel stud (with a fine & short spline) but with a standard carriage bolt head.
John
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John2005 wrote:

Yep, Special purpose bolt. Designed like many of the other "special" bolts on the vehicle to save time during initial assembly. No reason why a standard bolt couldn't be used. During assembly it is faster if the worker only has to grab a nut runner and put a nut on the bolt and torque till the bolt seats. No second wrench to hold the head or drop by accident. Same reason why there are many nuts with tabs welded to them or speed nuts used in place of standard fasteners.
--
Steve W.
Near Cooperstown, New York
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ace hardware stores. old john
Hello, John2005! You wrote on Wed, 17 Sep 2008 23:29:04 -0700 (PDT):
J> I am having trouble finding what I would call a carriage bolt, it J> looks just like a carriage bolt except that it has a spline round J> shape under the head instead of a square shape that is usually under J> the head of a carriage bolt. The round shoulder under the head is a J> fine spline that looks about 8 mm long.
J> The bolts are used to secure a steel gas tank support arm to the frame J> of a truck.
J> I need a source of supply I can order from here in the USA but I'm J> having trouble finding this item.
J> Thread specs = 10 mm OD X 1.5 mm pitch J> Length under head = Need at least 40 mm long but can cut down a longer J> bolt if needed. J> Head diameter = Approximately 20 mm OD, but can use a little larger if J> needed. J> Grade = Prefer a 10.9 class or whatever the strongest grade available J> is. J> The round spline shape or shoulder that is directly under the head has J> an 11 mm OD.
J> I have tried local hardware and autoparts stores along with J> www.mcmaster.com. I also looked through the www.auveco.com/ catalog but J> have not found anything yet.
J> Does anyone have an idea of where I might find something like this ?
With best regards, snipped-for-privacy@comcast.net. E-mail: snipped-for-privacy@comcast.net
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