Need a 3/4" square hole through the centre of a piece of round bar 2"dia x 3" long. Have bored a 3/4" hole through
the centre.
Any advice on heating, punching etc would be greatly appreciated.

drift with a square shaft.

Is it crucial to maintain the current outer dimensions? If not, then what Steve said. If so, then you might consider squaring it out by filing.

At the ABANA 2010 conference at Memphis Mark Aspery used a cape chisel to cut out the corners to make a square hole.
Not sure if he has a youtube video of doing this
Cape chisel has one flat side and the other side is wierd but once you saw one you know what it is

A diamond point is meant to open up corners. It may be called something else as well. Chiseling out with cold chisels is interesting work, I have done it in an ASO that needed a hardy.

Phil

What I've seen done is, drift the opening with the appropriate sized drift then using an upper and lower square swage, swage so that the opening conforms to the size of the drift tightly.

Is it crucial to maintain the current outer dimensions? If not, then what Steve said. If so, then you might consider squaring it out by filing.

Would like to keep the outer shape as near as possible.

Then I'd file or, as someone suggested, chisel it, then finish with a file. A square broach would also be a good solution, but if you had that capabililty you probably wouldn't be asking the question. And setting up for broaching a hole that size isn't something you'd do for a one-off. ($$$)

ever considered rotary broaching for an application like that? It's a little too deep for a typical broaching tool, but may be worth investigating

Drift with tapered sq punch then reheat, put the drift back in and hammer the sides back to "spec". (Of course then the tickness may be a bit off and you can then flatten and re-drift----repeat until satisfied or you just give up!)

Drift square as others have said and true up the outside by turning the bulges off in a lathe.
Rotary broaching looks cool but very expensive, also the broach depth would be a problem.

If the application doesn't require the hole to be square all the way through, you could bore the middle portion to a larger inner diameter on a lathe. Squaring just the two ends would be much easier.

I think the "Forging" a square hole as already been well covered, so how is the project progressing?

As Machining has started to creep into the options, how about using a slotting machine or a shaper?

or electro machining (EDF?) all of these will not distort the outer diameter of the shaft and are very accurate.

Post a picture and your method of choice when done please.

Phil

Hind sight is 20 / 20........ 1/2" hole would have been best..........for that method.........you probably won't get a 3/4 sq. hole from what you have now

I would slit it, upset the slit, then drift it first round, then square. Francis's cookbook gives lengthways for the hot slit. This will give you about half the thickness on the sides and looks great. If you punch or drill the hole first, you lose a lot of material.

Oops, just noticed the 3" length. In thus case, start with a longer piece, then do the above and cut to length you need.
If you don't want to change the outside dimension, you could drill to 3/4",then make a shearing tool that has a 3/4" tennon on the end and is 3/4" square above and hardened. This will remove the corner material using an 8 lb hammer or so. When I have done this, my tool is handled, but can be hand held as well

anvil

Sounds like a job for a Die Filer.

How do I punch and/or drift a square hole?

I can forge a square punch or a square drift, but it's not a perfect square.
The four faces of the square are slightly differant and looking at the working end, the two diagonals are not identical.

I usually strike a few blows from one side (side 1) and then turn the work over and strike a few blows from the opposite side (side 2).

The problem is, when I turn the work over to drift from side 2, the drift will not exactly fit the work because the drift was not exactly symetrical. I end up with a more or less square hole but the corners are a little rough. Having the hole not exactly square is okay, but I have to use a file to clean up the corners with a file. I'd like not to have to use a file to clean up the corners.

Does any one have a suggestion, aside from forging an absolutely square drift?

Thanks

Forging the drift square is a matter of practice. Make sure when you are starting to flatten the second side that you get it square at that point, it is much easier to keep it square than to correct it once it goes diamond shape. Working all four sides rather than just two can help as well.

When you are drifting, drive it in, knock it out, then turn it 90 degrees and drive it in again. This will help to correct for any imperfections in the drift.

If I want a square hole I prefer punching square rather than round, because it can be hard to get rid of a round mark on the flat sides of the hole.

If your punch is slightly out of square you are not going to punch from both sides and expect them to punch through square.

You don't say how thick your material is, or what size square you are trying to punch, and how far in you are when you try to punch it from both sides

Try punching as far through as possible, until it becomes very firm when struck, leaving mabe 1/16" thickness in the base, then flip it over and punch through using the dark or shiny spot as your location.

If you haven't got a square drift, you need more forging practice, or file/grind it square and to size

The punch should be smaller than the drift,

Alternatively obtain a piece of stock the finished size of the square you require, taper at both ends and use that as a drift

John's suggestion is a good one. Or just dress your not-quite-square punch with a file or grinder until it is square.

Yes, it is easier to square the tools than to correct an inaccurate hole. If you must file the hole you could have filed the tool instead. I usually get mine quite close but finish by grinding to even better accuracy. Corners can often have a slight radius... depending on what fits into the hole. It is, again, easier to soften the corners of tenons than to keep a sharp cornered hole.

How do I punch and/or drift a square hole?

I can forge a square punch or a square drift, but it's not a perfect square.
The four faces of the square are slightly differant and looking at the working end, the two diagonals are not identical.

I usually strike a few blows from one side (side 1) and then turn the work over and strike a few blows from the opposite side (side 2).

The problem is, when I turn the work over to drift from side 2, the drift will not exactly fit the work because the drift was not exactly symetrical. I end up with a more or less square hole but the corners are a little rough. Having the hole not exactly square is okay, but I have to use a file to clean up the corners with a file. I'd like not to have to use a file to clean up the corners.

Does any one have a suggestion, aside from forging an absolutely square drift?

Thanks

I guess I pressed the wrong button.
You could try punching a slot and then drifting with a square drift for opening up a slot. There are pictures of the tools in "Slitter Geometry" on the first page.

so today I took a quick break from my regular fab work and decided to try out one of my punches I have. This friend of mine gave me a bucket of tools he had lying around his shop. Now he had worked for Vulcan Tool in Weymouth, MA. for about 25 years or so, they are a modern day blacksmith shop and make tools. So I have this 1/2" square punch I decide to try out. Pretty neat I'm thinking, I pre-drilled a 5/16" hole in the drill press thru a piece of 1" x 1/4" flatbar. I stick it in the forge for a heat and when it's ready I try punching it thru...came out really good... ya I know, no big deal but it was my first, I mean I used to run cnc punch presses at the sheetmetal shop and hadn't run a single station punch in a while so this was like way back in time so to speak I was traveling..... anyway, just sayin..... the tooling I have from my buddy are all heat treated so it's really a blessing I happened onto this stuff... I have an idea for making motorcycle shifter pedals for a future project..... cheers and thanks for reading.....