high tensile bolts

[petersto]

I am changing the engine mounts for my md11c in my centaur. The angle iron on which the mounts are fixed are attached to lengths of wood(plywood I think) which are run the length of the engine space and supported by glassed in wooden supports. My question is this the angle iron is bolted to the wood with high tensile bolts(hard on hacksaw blades)) is this really 1970's overkill or is it the correct way. Why high tensile when its in wood.
Thanks in anticipation.

 

[john_morris_uk]

If they are high tensile, I bet the only reason is that its what was to hand and fitted when the engine was put in. Is it the original fit?

 

[earlybird]

I don't think high tensile bolts are really necessary from a strength point of view, though 8.8 grade are often more readily obtainable than mild steel at engineers suppliers. These shouldn't really offer much difficulty for a decent high speed steel hacksaw blade ( don't use a cheap carbon steel blade ). I would consider stainless bolts & nuts anyway. Happy sawing!

 

[halcyon]

Most bolts were high tensile.
What else are you thinking of using?

Brian

 

[Eygthene]

I would take an angle head grinder to cut them off, if they are proving too hard for the hacksaw. As above, I would either use stainless steel nuts and bolts when replacing them, or I would use well-greased mild steel bolts which would be quite good enough strengthwise, into plywood.

 

[petersto]

I am using off the shelf bolts from a local supplier these are quite hard but not as hard as the ones I have managed to get out. They were a blade per bolt.

 

[colinmi]

Id think it was more to do with the thread pitch, than the high tensile material per se. High tensile bolts will by design have a very fine thread to enable them to be tightened to the higher torques. On an engine mounting application the fine thread is desirable for close adjustment of the alignment with the shaft.

Colin

 

[Avocet]

Old and slightly rusty bolts can form a bit of a "skin" which makes you think they're harder than they really are once you get through it. As for the strength of the bolts, it really depends how they're loaded. If, for instance, it's subject to a bending load, rather than pure tension or shear, it might require a stronger bolt than you'd think, based on the fact it's going into wood. Metric bolts of grade 8.8 are considered the lowest grade of "high tensile" bolt commonly available and they're pretty easy to cut with a half-decent hacksaw blade. After that, you'd get grades 10.9 and 12.9 and even they aren't impossible to cut with a hacksaw!