- Thread starter smashweld
- Start date
When you get the 12.9 bolt remember to get a 12 grade nut or you will be wasting your time. Also the tightening torque is increased on as you go up the grades.
Info here
http://www.thomsonrail.com/Technical Resources/A short guide to metric nuts and bolts.pdf
Info here
http://www.thomsonrail.com/Technical Resources/A short guide to metric nuts and bolts.pdf
pedrobedro
Man at Matalan
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As the tensile strength goes up the bolts get more brittle in shear so are not always the best choice for a given application where an 8.8 would bend and still hold
Fortunately bolts don't work in shear/bending forces isn't it. To put it in context a 12.9 isn't far off taking double the load of a 8.8 in tensile. Outside bolts you can talk about shear but a bolt is simply designed to work at the correct torque in tensile strength.
Agroshield
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Replies so far have ignored a quite crucial line in the original post, viz. "Is there such a thing as a high compressive strength bolt?".
The OP states that the bolt he is replacing is bent, so clearly it has been subjected to bending forces. This may point to a design problem with the machine.
We need to find out more what the purpose of this bolt is.
What follows is pure speculation....
Looking at his exploded parts diagram and noting part number 44, it may be that the bolt is acting as a stop and is thus subject to compression forces, with the bending due to buckling.
If this is so, a solution is to increase the stiffness of the assembly or reduce the cantilever. A quick and dirty solution is to use a long coupling nut in place of the standard 44. Another solution is to make something out of hexagon material the same size A/F as the original bolt, with a short threaded section on the end. This loses the adjustability however. An intermediate solution is to do the same and use different thickness washers for adjustability.
Again, if the bolt is a stop, does the full perimeter of the head touch down at the same time? If only one edge or one corner touches down, this will induce a significant bending force in the bolt. A spherical end to the stop and a pad (like a G-clamp) could help here.
just realised the exploded diagram prob doesn't show how it works very well!
the bolt's for adjusting the height of the beams but when it's folding there must be pressure on it...there's other bolts to loosen/slacken when adjusting the height of the beams but they were loose when I got it which could be the cause of the bent bolt. Tried jacking the beam up to full height then tightening those bolts at the side but when folding it slips back down to resting on the bent bolt so the bolt must take some of the pressure?
also...I need to look again but fairly sure the bottom of the arm is threaded on mine and there's no nut (part 44)
The bolt..
The other 2 bolts
on the side
Agroshield
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Nut 44 is not essential to the operation of it. The bolt should thread into the bottom of the arms as you say. 44 is just a locknut to stop the adjuster bolt turning when you don't want it too (e.g. due to vibration).
I think you have solved your own problem. The bent bolt is currently taking all the force from the bending when what it should be doing is only supporting the weight of the beams in the correct position until the proper beam clamping bolts are secured. Find out why the bolts at the side are not locking the beams securely in position, persuade or coerce them into doing their proper job and your bent bolts will not appear again.
Can you say which numbered parts in the first diagram are the clamping bolts that don't work.
Set beam in correct position, weld securely, problem solved. To adjust beam position, slacken using Makita 5" rat-tailed spanner.
I hadn't paid full attention to the diagram tbh...the bolts for locking the beams aren't in that diagram...they're maybe out of shot..bottom right
maybe I just need to tighten them more (bit wary of threading them...) but as I say they were all loose when I got it so hopefully it's just that...although doesn't explain why they were loose in the first place..
also considered just putting a packer in as it'll be fun trying to get it out!
good point...will make that first priority before tackling the bolt...
maybe I just need to tighten them more (bit wary of threading them...) but as I say they were all loose when I got it so hopefully it's just that...although doesn't explain why they were loose in the first place..
also considered just putting a packer in as it'll be fun trying to get it out!
good point...will make that first priority before tackling the bolt...
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