Help punching square holes

[territorialmillworks]

Need to punch a series of 1/4" and 3/8" square holes in 1/8" thick angle iron. Tried punching with square punch but then couldn't knock the plug out from the backside because of the thine material deforming. A round bolster was even worse. If I made a square bolster I don't think I could get it lined up with the punch and the work piece. I thought about making a handled punch and trying to do this on the power hammer.......appreciate any help.....

[HWooldridge]

To prevent the deformation, I would try drilling holes where you want them with the drill diameter equaling the width of the square hole, i.e. 1/4 and 3/8, then just clean up the radii with a drift. An even better way would be to broach it to finished size but I'm making the assumption (perhaps inaccurately) that you may not have the means to do that.

[Ten Hammers]

I would agree that drilling and drifting would work (for me). Keep the vise jaws open a crack so you can just fit the angle in them to straighten any deformaties and of course use the hammer and anvil too. I would just use the prtichel hole and have a bucket of water on the underside. When drifting, I have the stock bloody hot. Backpunching angle may present a problem in that you cannot reach the pritchel. This may require making a bottom tool from some heavier plate that has a hole close to the edge so you can have a backup when you flip the angle. Sometimes a piece of heavy pipe with an ear wleded to it and the ear clamped in the vise will give you a place to drive through. Depending on the needs and the vise you have, you may can just use the jaws cracked open a bit.

[John B]

Need to punch a series of 1/4" and 3/8" square holes in 1/8" thick angle iron. Tried punching with square punch but then couldn't knock the plug out from the backside because of the thine material deforming. A round bolster was even worse. If I made a square bolster I don't think I could get it lined up with the punch and the work piece. I thought about making a handled punch and trying to do this on the power hammer.......appreciate any help.....

Make two punches from round stock 1/4" sq and 3/8 sq (You could also make other sizes at a later date)

Then you use three "plates",

The top plate is the guide for the punches, it also acts a as a stripper plate,

This "plate" wants to be thick enough to use as a guide for the punch, and about 2 to 3 times longer than the width of the angle, mark out for, and drill a hole slightly larger than the punch's diameter at the distance from the inside of the angle, to the centre of the square hole position, this will give a consistent size for repeatability

The second plate is a spacer slightly thicker than the angle, and is positioned far enough back to allow the vertical angle side to fit up snugly to the front datum (where you marked out the position for the hole in the top block)

The bottom plate is the bolster plate, ideally you will need two of these, one for the 1/4" and one for the 3/8 "
Punch and clean up a square hole in each one of these plates where the appropriate square punch in situ in the top block can be positioned directly into the into this punched hole

Stack the "plates" in this position, drill and tap and secure them together, use 1/4 diameter holes for 1/4" threaded screws to ensure accurate location when changing the bottom bolster plate.

The clearance around the punch, and punched holes should be minimal, and I would suggest a square face on the punches as this tends to shear the metal rather than deform the bottom side which a radiussed or diamond point will do.
To get alignment of the punch to hole, Mark on the centreline of the hole on the top block, and If you put the punch into the hole and mark the position of this centre line onto the punch shank, when these are aligned, you are in the right place.

This tool could be used under the flypress, treadle hammer, or on the anvil with the hammer.

To get the pitch of the holes if you are doing a series on pitch, just make a length bar to use as a spacer from a punched hole to the side of the top block, a round pin the same size as the punched hole in one end of this bar will drop into the previous punched hole, the other end will fit against the top block, and it will ensure repeatability.

Hope this makes sense and helps

[bigfootnampa]

I do this by using a punch that is about 3/16" square on the tip ground to a shallow pyramid shape at the point and tapered. I punch the hole using a slightly oversize round bolster and just punch clear through. Then I flip the material and use my angle grinder and flap wheel to grind the plug and rough edges off and quickly back to the anvil to hammer the punched area flat again. If the hole is to be rough and not too big I will just use the tapered punch to drift it as I punch the holes but I get a nicer finish by reheating and drifting (after the grinding/reflattening steps). This goes quite swiftly with a bit of practice. I use this method to create square holes for my handmade nails in angle, flattened hook ends and straps.

This method leaves you with a hole that is slightly "dipped" or countersunk from the topside but that is fine for my applications and it is simple and FAST.

[JNewman]

All the above is good advice, another option if you have a lot to do and this is a paying job is to find someone with an ironworker and pay them to punch them for you. Sometimes paying for an hour of someone else time can save you a days work.

[HWooldridge]

I do this by using a punch that is about 3/16" square on the tip ground to a shallow pyramid shape at the point and tapered. I punch the hole using a slightly oversize round bolster and just punch clear through. Then I flip the material and use my angle grinder and flap wheel to grind the plug and rough edges off and quickly back to the anvil to hammer the punched area flat again. If the hole is to be rough and not too big I will just use the tapered punch to drift it as I punch the holes but I get a nicer finish by reheating and drifting (after the grinding/reflattening steps). This goes quite swiftly with a bit of practice. I use this method to create square holes for my handmade nails in angle, flattened hook ends and straps.

This method leaves you with a hole that is slightly "dipped" or countersunk from the topside but that is fine for my applications and it is simple and FAST.

I think your suggestion is probably the best and fastest way to do it.

One problem with punching angle iron is that it tends to curve if much deformation is made along only one leg.

[Frank Turley]

As a long retired horseshoer, I found that hot countersinking and punching increases the length of each branch of a horseshoe. I therefore, agree with HWooldridge about possible distortion.

Turley Forge and Blacksmithing School : The Granddaddy of Blacksmithing Schools

[pkrankow]

I finally got a punched hole to work making a nail header today. I noticed that driving the burr out the metal needs to be slightly cool so it shears instead of deforming. I also noticed that use of punch lube is very important. I tried two of Hofi's recipes, the salt lube and the wax lube. I had very good results from the salt lube, but had a punch jam badly with the wax based lube.

I Forge Iron - BP1025 Salt Lube

I Forge Iron - BP1024 Wax Lube

Hope this helps some
Phil