GT40s.com - View Single Post

killroy · 09-10-04, 04:37 PM

If you are replacing a grade 5 bolt, a good stainless bolt with rolled threads and a good heat treat should be able to do it, because grade 5 is pretty weak. The required tensile strength is 120 KSI with 14% elongation.

Grade 8 is 150 KSI with 12% elongation. That's very hard to match with stainless.

Elongation is the measurement of the fasteners ductility. As the tensile strength goes up, elongation goes down. A bolt with very little elongation will look good untill it snaps. A bolt with more elongation will strech before it breaks and in that stretch area, the diameter of the fastener will be reduced.

If it were easy to make grade 8 bolts, we would only have grade 8 bolts. We have grade 5 because we needed a spec for the cheaper bolts.

With stainless, the elongation is what kills you, it's easy to find a stainless alloy with high tensile strength, but it's very hard to make an alloy with good elongation. I'm sure some one could make a grade 8 stainless bolt, but it will probably loose some of the corosion resistance that stainless is known for and it will be $$$.

09-10-04, 04:37 PM	#10 (permalink)
killroy A Tenth Join Date: Jul 2004 GT40: Silicon Valley Posts: 121 Rep Power: 6	Re: Stainless suspension bolts ? If you are replacing a grade 5 bolt, a good stainless bolt with rolled threads and a good heat treat should be able to do it, because grade 5 is pretty weak. The required tensile strength is 120 KSI with 14% elongation. Grade 8 is 150 KSI with 12% elongation. That's very hard to match with stainless. Elongation is the measurement of the fasteners ductility. As the tensile strength goes up, elongation goes down. A bolt with very little elongation will look good untill it snaps. A bolt with more elongation will strech before it breaks and in that stretch area, the diameter of the fastener will be reduced. If it were easy to make grade 8 bolts, we would only have grade 8 bolts. We have grade 5 because we needed a spec for the cheaper bolts. With stainless, the elongation is what kills you, it's easy to find a stainless alloy with high tensile strength, but it's very hard to make an alloy with good elongation. I'm sure some one could make a grade 8 stainless bolt, but it will probably loose some of the corosion resistance that stainless is known for and it will be $$$.