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I Forge Iron

Need some advice on making a square hole.

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I know everyone is thinking "use a square punch, duh." Well, its not as easy as that. I need a 1/4" square hole in the end of a 1/2" square bar, about 1" or so deep. In other words it is not going all the way through. 

This is my plan right now. Do it the same way socket cap bolts are made. Drill a hole in the end about the size i need, then use a square punch and drive it in to "shave" the sides square. There will be a little rag in the bottom but i do not think that will hurt anything as long as the rod goes in far enough. 

To give an idea i have to make some door handles, the lever type. The hole will accept the square rod that a door knob would attach to to make the bolt move back and forth. I thought about punching the piece all the way through then welding on the handle portion but i do not want the ugly welds around it, and i am afraid trying to forge weld such a thing would just deform the hole to where it would be a wasted effort. 

Anyway, am i on to the best way to do it? Or is there a better way? Thoughts and suggestion welcome. 

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The idea sounds like it would work. I'd be curious to hear others ideas.


One possibility is to drill and tap the 1/2" square bar make the end of the 1/4" square rod round then thread it. Then drill and tap the side of the 1/2" bar for a set screw to keep it in place.  

Just an alternative idea if I'm reading what you are saying correctly.

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Your plan for broaching a round hole square is a proven  method. If you hollow grind the end of the broach slightly the cuttings will curl into the center of the hole and you can clear them with the drill bit. Just be careful the bit doesn't gall and jam. Slow and easy does the trick.

You'll probably need a Dremel spherical stone to put a hollow grind on 1/4" sq. That's probably going to be the tricky part.

Frosty The Lucky.

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Thanks Frosty, i could not for the life of remember "broaching". 

Das, that is also an interesting idea. 

Thanks for the input ya'll. 

So i went out an tried it this AM. Getting chilly out, 34* with a light on and off snow. Yeah i know Frosty that is shorts and t-shit weather for you. Here is what i have learned. First it is a PITA to make a hollow grind on a 1/4" square, and it is better to have broach slightly tapered. This i discovered after getting it stuck in the hole and severely deforming it, oh well just make another and drive on.

Anyway a little off center and not quite straight but this is just a practice piece to get the method down. May go up to a 5/8" or maybe even 3/4" bar and draw it down to size. May look a little better on the door anyway. 


Rusty, i am sure someone makes it. Here is a piece of tubing i am turning parts off of at work right now. Unfortunately it is 12L14 and does not forge well, crumbles under the hammer. And no, yall cant have any one my tasty tasty mint fudge cookies. 



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the way I used to do it is this..   use a longer straight single sided cold chisel with a taper only on one side.. of the square. You need to chisel all 4 sides but you will end up with a really nice square hole.. 

Something that is overlooked many times is even in the 1700's they had special machines and punches they used for making such things..   For us simpletons the chisel is the easiest way. 

Ideally showing a sketch of what you are after might yield better suggestions..  

Today drilling and then rotory broaching would be ideal and pretty easy with a metal lathe..   But, without this. it can still be done.. 

Again, a sketch of what you are after often can result in better suggestions. 

If you really want to do this hot, you use several sizes of prepunches till you get to the last size of straight.  

The other way is to make the item as a punched or drilled short section and then rivet it onto the shaft size you want. 


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Jennifer, brilliant suggestion. 

These are basically going to replace the missing door knobs on an old set of doors. I was going to do thumb latches but the doors already have some gorgeous brass plates for the lock mechanism and i want to keep them. The doors are original to the house built in the 1880's. The rod going through is square with a set screw on the knob. There will be one on each side of the door so the rod has to be inserted then the handles attached, or at least one not attached. 

However, i think i may found a work around after looking at some of the old doors in my house. I was going the hard way, like usual. Many of my doors the knobs are round threaded holes and the square rod has threads cut on the corners so that the knob is screwed on then a set screw holds it in place. This would also let me forge a much nicer handle then just drill and tap a hole when complete.  

But here is a quick sketch.


But hey, at least this got us talking about the subject of broaching a hole to shape. 

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Billy:  In the early 20th century houses I have renovated the door latches worked like this:  The square spindle that goes through the square hole in the latch mechanism is threaded on the corners (edges) of the square.  Those thread into the female threads in the door knobs which are secured with a set screw at 90 degrees to the spindle.  When I say threaded on the edges I mean that it was run into a threading die sized for the diagonal measurement of the spindle.  So, only the edges of the square spindle would engage the cutting threads of the die. 

The same could be a solution to your problem,  Instead of cutting a square female hole in the handle to engage the spindle, drill a larger round hole the same size as the diagonal measurement of the spindle in the handle and thread it.  Then, cut threads on the square spindle and thread the handle on.  Drill and tap a hole in the side of the handle to intersect the spindle threads and use a set screw to lock it all together.

You can buy pre-threaded square spindles at large hardware stores or architectural salvage places and, I'm sure, the internet.

I'm pretty sure that 1880's hardware worked the same as that installed 20 years later. 

"By hammer and hand all arts do stand."  

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Daswolf hit it on the head. No forging needed. Drill a hole the size of the diameter of the square bar. Use your drill size chart for the proper tap and die. Thread both hole and shaft. Screw together. 

I also drill and tap for a set screw placed in a non visible location.

Ive made a lot of hardware. Often the lever is separate from the shaft that goes into the lock set. Ive often forged a square tenon on both ends of this shaft. One is rivited to the lwver and the other  square goes into the lockset.

Hardware like this is a good business and fun to do.

EDIT: I should of read before posting. Like minds and all that.


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So, if you are really looking to have it be a 3 piece design, you can go another way as well..   Nice sketch.. :) 

Have you ever gotten a punch stuck in a hole when punching it hot? 

If you only need one clear end... Like a 1/4" rod all on it's own then you can forge it slightly undersized and drive it into the hot end you are punching..  It will take a little experimenting but you can actually use it as a hot riveting system that is blind..  

To Add to Georges information...  Thread the rod while it's round then file to square..  threading a square rod is no fun.. Well unless you are cutting thread with a file. :) 


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There is a blind mortise and tenon joint that requires no external hardware and is permanent.   It's mostly used in wood work, but I see no reason it can't work here as well. at least for one handle.   The mortise is tapered, with bottom of the hole being wider than the top. The tenon is split, and a wedge started in the split, Then the tenon is driven into the mortise, the wedge bottoms out, and expands the tenon to fit tightly.   I've done this several times, and there's no non destructive way to take it apart.

Actually, it's more like a blind dovetail.

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A blind tenon in iron is not hard. Drill a hole, tap with a standard tap, tap again with a bottoming tap and bottom it out. Thread a flat bottomed stud so threads dont stick above the hole, peen the stud like any ole tenon.

The bottoming tap is critical. A drill bit leaves a rounded bottom. The bottoming tap cuts threads and creats a flat bottom, fully threaded hole. If you leave the rounded bottom, when you peen the head, the tenon tends to be loose in the hole.

Ive used this to join some styles of door handles to the spindle(thanks, George, i had a senior moment on the word spindle)

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George, that is exactly what i discovered on the doors in the rest of the house. What threw me off is that i have 1 knob and 1 rod that is made with out the threads and the hole in the knob is square, the threads for the set screw on this are also in the rod and not the knob. Anyway i saw the knob and rod and went with it rather than thinking it through for an easier way. And an easier way was just going to the bathroom and looking at the door knob. I can be my own worst enemy with things like that. 

Das, after re-reading your post i am thinking that what i discovered is what you were saying. When i read it i was thinking you meant a round shaft all the way through.

I was going to go with 3-d on the sketch but i could not locate my T-square for the drafting table. :) 

Ever got a punch stuck in a hole? I had to make 3 square punches to get what i got becuase of them getting stuck and severely deformed getting them out. Well, really same punch just much shorter now than when i started. 

Anvil, i am having a real hard time envisioning that. How do you peen the end if it does not stick out? I work in a machine shop so bottoming taps are no big deal to get for me, well actually we make them. Cheaper for us to get regular taps then put them on the surface grinder in a fixture and cut the tap to what we need. We do the same for the drill point. Some of the parts i make there is a spec on the angle of the bottom of the hole. 

Natkova, not quite. It is a blind hole and does not go all the way through. But a file is a square suggestion. ;) (thought we missed that didnt you?)

Anyway thanks again everyone for your input. Sometimes i just need the obvious pointed out to me. 


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6 hours ago, jlpservicesinc said:

Bluerooster..  Doing this kind of thing is metal is tough..  It can be done, but..   It's kinda the same thing as doing the hot upset.. 

Putting the tapered hole in is the problem with only access from one side..  this becomes chisel work.. 

Yes, I can see it being troublesome.

Drill the round hole, square it with the chisel, and at the same time taper it on two sides with the chisel.  Doesn't require much of a taper.  I think I'll give it a go next time at the forge.

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Since the mint cookies are off the table, I will be un-available for further un-expert advice, but... 5/8" round stock with a thru hole (diagonal measure of your 1/4" stock for diameter)bored the length of it. Heat and forge to 1/2"on a lubed 1/4" mandrel. If mandrel gets stuck, you can drive it out from the opposite end, since you have a thru hole.

Cat skinning 101...I think


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Or! Do a section of the half inch, drill then through punch it square. And then weld it to the rest of the stock and grind/sand smooth. Speaking of skinning the ol cat. But. I'd never skin an actual cat. Dunno where the phrase came from. Hopefully metaphorically. I do understand they are pests to some. 

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I used to have a 'shop cat', that would hang out in the shop with me, and bring me 'snacks' (usually moles). He would hop on the anvil for rubs and scratches.

When we got him, he needed a name, he was a black cat with a white V on his chest and he had pointy ears, so he got the name Vulcan. I started playing with metal after we got him, so the name fit him pretty well.  I miss my shop buddy.

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