Punching eyes in steel, not people | Power Hammers and Presses | Forum

I have two different suggestions. Start with thicker metal so that you end up with the right thickness after the thinning caused by the punching. I don't know what shape you are punching with, but I was taught to punch hammer eyes with a round punch, you then flatten the side and you end up with an oval eye.

I may be wrong but I would think containing your stock on the sides would reduce the drag down, because the metal cannot swell to the sides. It can still flow to the ends but being contained some of the metal should start coming up.

James

Could you you post a video of you punching the eyes, or some photos. It may be easier to give some advice then. The photo of the slot drift in my article gives a pretty good idea of the geometry of the tooling I use. Maybe try duplicating something similar. The tool in the article makes 30mm holes, the tip is about a 22mm by 5mm oval (from memory) and the taper transition from this to full round is about 75mm. The tip is rounded all over. A chisel edge is of no use with the pressure/heat used. It will quickly round up (unless frequently withdrawn and cooled ... v. tedious) and may spread wider than if it had been made "pre-round" (I hope this makes sense). My tools are H13 heated to a good orange and air cooled. I guess I should temper them but they've stood up without so far. I do cool it with a cup of water occasionally.

I can't work out the diameter of the cylinder you are using but it looks similar to mine. You're also using a 10HP motor so if the pump is suitably sized you should be moving the ram at a good speed. That said, hose diameter is quite critical. You're moving a lot of fluid in a short time. From memory (I'm at home not the w/s) my hose are about 3/4". Given the distance of your motor to cylinder, too small a hose could slow things significantly.

You will always get a small degree of drag down around the holes. The thinner the tip and the longer the taper the less this is when done at a good heat. In effect my tooling is a slot punch and drift in one tool. Doing it this way it has too push a lot of metal somewhere after the slot is punched, Most of this goes to the sides but some causes the metal to get thicker in the OTHER plane (ie along the tool axis). You get a strange situation where you both make the metal slightly thicker and have a small amount of drag down. That said it keeps the shape pretty well .... but that said I very very rarely punch round bar, it's nearly always square or rectangular. Even when making hammers from round stock I forge it square first.

I'm sure you've found out but starting the slot BANG IN THE MIDDLE of the bar is VERY important

James my gut reaction is that the small x section of the tip combined with a good taper is at the heart of good punch/drifting. I kinda think the chisel edge will quickly blunt under power. It works a treat by hand though where the tool is often and rapidly withdrawn and cooled

Not enough taper there James. I haven't done any comparative experiments to prove it but to quote Terry Clerk, I know a good woman when I see one and I know a good car when I see one and I know that punch hasn't got enough taper.

Photo shows a selection of the punches I use. Note the taper on them all. Punch in my hand makes a 30 x 12mm rectangular hole, tip is 25x 5 mm, taper is over about 70mm

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Notice they all have domed tips, not chisel points, almost the shape you'd get if you went over a chisel point with a flap wheel