gasket999
getting there...
- Messages
- 370
- Location
- Manchester, UK
Hi - I'm looking for advice on choosing a grade of steel plate for a project and thought there may be someone on the forum who could help.
Wording it like an exam question: a bracket is usually attached with 4x grade 8.8 1/2" UNF bolts and 4x 8.8 nyloc nuts.
In this instance I need to replace the nuts with 4x tapped holes directly into in a piece of steel plate.
The rule of thumb I've always followed is that as tapped holes in typical mild steel aren't especially strong, the tapped hole should be to a depth of 1.5x the diameter of the bolt - that way the bolt becomes the weak point.
In this case the diameter of the bolt is 12.7mm. That would mean a typical mild steel plate of 19mm thick.
Due to space constraints, I only have about 12/13mm to play with - so that's the maximum thickness of the plate.
So the question is - could anyone suggest a commonly available grade of higher strength steel plate (that I might buy in a small quantity from a stockholder or engineering firm) in which a 12mm tapped hole would give comparable, or greater, tensile/rip-out strength to a common 1/2" UNF 8.8 Nyloc nut?
Obviously not looking for anyone to actually calculate this, just some experiential advice or perhaps a handy chart would be ideal.
The project is quite simple: attaching a recovery point onto the back of a defender. On later models the rear crossmember was made form thinner steel, necessitating a hefty spreader plate on the back - but the gap between the crossmember and the newly-relocated fuel tank is too tight to fit both a spreader plate and a nut. So the solution might be to use a slightly thicker spreader plate and screw the bolts straight into it. Land Rover got round this by fitting internal captive nuts, but they're attached to a weak part of the crossmember so can't be used for recovery and are being removed and replaced with thick crush tube straight through.
Wording it like an exam question: a bracket is usually attached with 4x grade 8.8 1/2" UNF bolts and 4x 8.8 nyloc nuts.
In this instance I need to replace the nuts with 4x tapped holes directly into in a piece of steel plate.
The rule of thumb I've always followed is that as tapped holes in typical mild steel aren't especially strong, the tapped hole should be to a depth of 1.5x the diameter of the bolt - that way the bolt becomes the weak point.
In this case the diameter of the bolt is 12.7mm. That would mean a typical mild steel plate of 19mm thick.
Due to space constraints, I only have about 12/13mm to play with - so that's the maximum thickness of the plate.
So the question is - could anyone suggest a commonly available grade of higher strength steel plate (that I might buy in a small quantity from a stockholder or engineering firm) in which a 12mm tapped hole would give comparable, or greater, tensile/rip-out strength to a common 1/2" UNF 8.8 Nyloc nut?
Obviously not looking for anyone to actually calculate this, just some experiential advice or perhaps a handy chart would be ideal.
The project is quite simple: attaching a recovery point onto the back of a defender. On later models the rear crossmember was made form thinner steel, necessitating a hefty spreader plate on the back - but the gap between the crossmember and the newly-relocated fuel tank is too tight to fit both a spreader plate and a nut. So the solution might be to use a slightly thicker spreader plate and screw the bolts straight into it. Land Rover got round this by fitting internal captive nuts, but they're attached to a weak part of the crossmember so can't be used for recovery and are being removed and replaced with thick crush tube straight through.
