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Posted

I have a basic question. When forging a bottle opener, why do all the examples I've seen have you punch out a rectangle and not a round hole? (See example attached I'm just getting into a little production run of openers and punching takes me such a long time. I was thinking of drilling a starter hole and then drifting out to the size I need. Is there any benefits with a rectangle over a round hole?

 

Thanks!

bottle opner steps.jpg

Posted

I don't see any that wouldn't work.   Never tried it.   I could see doing a quick starter hole and then using a press with a drift to open the holes.   You could probably even set it up so it has a ball punch built in so you can do it all in one go.  There may be an actual answer but I don't know it.  If you do try it let me know how it goes.  

Posted

Thanks Chad. I have a small 1 ton arbor press and will see if I can make that work. I just saw a video that gave me an idea. I'm going to try and fabricate some rectangle and round top and bottom dies for my guillotine tool to act like a double sided punch. (see attached) That might be faster and cleaner for me rather than just trying to punch one side, flip, line up and punch from the other. I'll also try drilling a starter hole as well and see which process works the best.

guillotine dies.jpg

Posted

That isn't a rectangular hole. It is slit, not punched at all.

The benefit of slitting and drifting for projects like a bottle opener is slitting doesn't remove much if any material leaving you more to work with around the opening for a stronger opener with more pleasing proportions. It's also much faster to drift a slit open and finish.

For example if you start with a 1/4" x 3/4" bar and punch a 1/4" hole 1/2" from the end you only have 1/4" around the punch to drift to your finish diameter. The added material necessary to make the enlarged opening Must come from the 1/4" remaining. Sure you can upset the corners into the center to gain some mass but your finished opener will have a very thin ring.

If on the other hand you slit it 3/4" centered 3/4" from the end it leaves 3/8" on both sides and the end so drifting doesn't have to stretch the remaining material to make the opening. The extra remaining material allows you a lot of leeway to get it just how you like it. 

The major benefits being, it's much faster with fewer heats and less material lost to scale, less work and more creative freedom.

Frosty The Lucky. 

Posted

The other advantage of slitting (which I was taught to call slot punching, at least if the tool as a narrow flat at the end) is that it makes more of the bar available to form the ring.  It's not easy to explain why in words, but imagine the ring you could make if the slot in your second picture extended almost to the bottom end of the bar.  

Also drilling removes more material than punching even a round hole, so going to a drill will be a bit of a double whammy.  On the other hand, if you have enough material, you have enough material.

Finally, if punching is taking significantly longer than drilling, it may be worth the time to practice your punching.  (At least for me, when I haven't punched for a while, it takes almost a conscious effort to strike the punch as hard as it wants to be struck.)

Posted

Right you ae Mike, A slot punch is different than what I use, I use a Brazeal type slitting punch, it only removes a tiny bit. It's easy to put a slitting punch exactly where you want it, it has a SLIGHT point and tapers slightly to the ends. 

My description of not losing material with a slitter wasn't too clear, I tried covering it above.

Done correctly punching is MUCH faster than drilling but like everything it's a little knowledge and a lot of practice.

Another thing that is easy when punching and drifting that's impossible drilling is you can punch and drift a 1" hole in a 1/2" rd bar. 

Frosty The Lucky.

Posted

Think of it as saving material and work. I use a slot punch that’s 3/4” x 1/16” and overlap the punching to get a 1-1/4” x 1/16” hole. The parameter of that is 2-3/4” pretty close to the 3.1” of a 1” diameter hole. The drift is reshaped the slot more than forging the material out thinner. Basically, reshape, forge the corners in, and it’s done. Make sure the 1//16” side of the punch is fully radiused… there’s a lot of stress there.

Slitting punch would work great, but I would have to grab a cutting plate. I’m not good at lining up slitting punches from opposite sides without lots of rag or cutting partially through from one side.

Keep it fun,

David

Posted

To slightly rephrase what others have said here, your drawing answers the question for you. The distance from the slot to the outside of the bar is the same all the way around, except at the corners. Once drifted round and with those corners easily forged in, the ring is of equal thickness everywhere. With a round hole, on the other hand, the distance to the edge is nowhere the same, which means that you have to put time, effort, and attention not only into forging out the ring, but to making (rather than simply keeping) it a constant thickness. 

IMG_0424.thumb.jpeg.80fd281f2199528fdfb199780be7fc5c.jpeg

Posted

the best way to know the answer to this question is to go and try it sometime, as it becomes self-evident when you drift a slot vs stretching a small hole.
I agree with the above as well in that if it takes longer to punch a hole than to drill it, then you need more punching practice!

i would personally guess that it should take less than twelve heats to do a simple bottle opener like that, one for punching, maybe two drifting, two stretching, two shaping the handle, then the rest for tweaking.

But like everything, its all about practice, and the first might take 16 heats while the tenth takes 7!

Posted

I have yet to make a good slotpunch, so any pointers?

I now use a round punch, it works, but the spreading of the material takes more work than I like

Posted

Regrinding chisels into slot punches works well enough if you radius the ends so the slot doesn't end in square ends, the sharp corners are weak points (stress risers) which are the initiation points for failures, breaks. 

Frosty The Lucky.

Posted
On 1/13/2025 at 1:56 PM, mutant said:

Is there any benefits with a rectangle over a round hole?

All the above are good answers, and I'm not sure it my response will add anything, but I were the first to respond I would have said:


The answer to this depends on the specific situation.  Sometimes yes, sometimes no.


Sometimes a round punch will do the job just fine, and the folks you mention above might merely be using a slot punch because that's what they have or are used to.
However, as mentioned above, if you want larger hole than your bar size you need to use a slot punch or slitting chisel (this is determined by the desired wall thickness in this situation).  Also, when punching holes there comes a point where the slot punch will drive through the stock easier than a large round punch, and it's much easier to "bend" the walls of a slot into big round hole than it is to "stretch" a smaller hole into a bigger hole.  It just takes some math to use slot punches for accurate hole sizes.

Posted

It's funny that when I first saw JHCC sketches I thought they were sketches for an iron grill work or gate.  Then I thought no, those are like the lock mechanisms in his attached photos!  

By the way John, have you ever been to this place;

 

The Bucyrus Copper Kettle Works - YouTube

 

Looks interesting!

 

 

Posted

Right you are Billy, sometimes a round punch is the right, even only right choice, say riveting. The original post asked about punching and drifting, for bottle openers to be specific. For which slotting or slitting is the better choice on all counts.

That's a great link Gazz, thank you!

Frosty The Lucky.

Posted
10 hours ago, Gazz said:

By the way John, have you ever been to this place

I have not, but it's roughly on the way from home to Quad-State. Maybe I'll stop in.

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