Had a series of fails this afternoon- I'd drifted some holes in 3/8" square stock and then made a tenon - tried to put the tenon in the hole and then upset the tenon.  Holding it in my vise, when I'd smack the steel rather than upsetting the steel, it would slide out of the vise.  Granted, my vise is a post vise made from a couple of different vises (we'll call it Frankenvise) so maybe better equipment would make this job easier, but any advice from the crowd here?

I was at the high end of orange to yellow when I was trying to upset the tenon.

Greetings Jcornell, 

        Just make up some aluminum vice jaws to fit your vice. You will find that it will hold your stock much tighter on the smooth surface on your worn post vice. 

Forge on and make beautiful things 

Jim

or if the end of the other bar is flat (the one with the tennon) have that straight up on an anvil or upsetting block and pein it over.

Just curios, but got any pics of your vice? sounds interesting!

                                                                                                                 Littleblacksmith

Just a thought, put a piece of steel in the other side of the vice (if you insert your piece on the right side of the jaw, put the piece in the left most edge of the jaw) that is the same size or ideally slightly smaller.  Vices that get warn a bit will pull off center creating a less than parallel surface for holding your work piece.  With cold mild steel you have about 20% grip on a heavily warn vice without a spacer which gives you around 60% if it is slightly smaller (less than the thickness of your fingernail) than the workpiece.

All of the above, plus ... you are probably using a hammer that is too heavy

Seems to me the failure must be the vice not holding tightly enough, because everything else seems OK. I have found that light taps rather than heavy blows work best. Maybe you're hitting it a bit hard. If the metal is yellow it should peen over with little effort.