06-14-2015, 02:31 PM
Hi Johno,
I'll be going with 20mm pins (a little over 3/4", near as dammit 0.786") in the local equivalent of 4140 CrMo (709M40 aka EN19A, bluebell), hardened and tempered (I'm building a little HT oven at the moment, 5"x5"x12", designed to be fairly airtight so I can flood it with argon to prevent decarburising), the yield strength in tension would then (worst case heat treatment!) be a minimum of 26 tons, should give a shear yield strength of around 16 tons *per hole per pin*, so a total shear yield point (assuming, dangerous, equal loading) of around 64 tons, so it should give about a 3x safety factor - I think it's worth the extra on a decent alloy for the safety factor!
Earlier in the thread, Vinny described his (store bought) 25-ton press, which has 3/4" pins in a very similar frame, they're 1018 (aka "mild steel") with a considerably lower yield stress in shear, he didn't mention any snappages ;)
Anyone with better ideas, please feel free to criticise / constructively comment!
I'll be going with 20mm pins (a little over 3/4", near as dammit 0.786") in the local equivalent of 4140 CrMo (709M40 aka EN19A, bluebell), hardened and tempered (I'm building a little HT oven at the moment, 5"x5"x12", designed to be fairly airtight so I can flood it with argon to prevent decarburising), the yield strength in tension would then (worst case heat treatment!) be a minimum of 26 tons, should give a shear yield strength of around 16 tons *per hole per pin*, so a total shear yield point (assuming, dangerous, equal loading) of around 64 tons, so it should give about a 3x safety factor - I think it's worth the extra on a decent alloy for the safety factor!
Earlier in the thread, Vinny described his (store bought) 25-ton press, which has 3/4" pins in a very similar frame, they're 1018 (aka "mild steel") with a considerably lower yield stress in shear, he didn't mention any snappages ;)
Anyone with better ideas, please feel free to criticise / constructively comment!
Rules are for the obedience of fools, and the guidance of wise men...
(Douglas Bader)
(Douglas Bader)