A Lawnmower Punch Press

Robo_Pi

Registered
Registered
Joined
Feb 18, 2016
Messages
451
I couldn't find a forum for lunatic ideas so I'm posting this here.

I'm in dire need of a small cheap punch press. I only need to punch out small pieces from thin brass sheet so I don't need to huge punch press. I'm looking to build one for FREE materials because I'm cheap. :grin:

Today I was able to acquire a free lawnmower. It doesn't run. I don't know if it could be made to run, but I already have several lawnmowers and don't need another one. It turns smoothly when pulling the cord so the crank and connecting rod are most likely in good shape.

Lawn Mower.JPG


My thinking is that this crank and connecting rod would make the perfect basis for a punch press the size I need. I can build the rest of the frame for the punch press from scrap metal salvaged from old farm equipment.

I searched YouTube and Google for examples of others who have built a punch press using a lawnmower crankshaft to get ideas. But low and behold I couldn't find a single solitary example. I confess that this kind of surprised me because I can usually find examples of people who have already built crazy things like this.

In any case, I thought I'd post the question here:

Has anyone ever seen a homemade punch press built around a lawnmower crankshaft or something similar?

I'm sure I can build one even without seeing an example. But it's always nice to see how other people might have done it. I'm pretty sure the stroke will be long enough to punch out 0.6 mm brass sheet.

I haven't taken this lawnmower apart yet. I doubt that I'll be able to use the bearing case. I'm thinking worst case I'll just grab the crank and connecting rod and piston assembly. Then make my own pillow blocks to hold the crank on the newly constructed punch press frame.

Surely there has to be someone out there who has done this? This is the first idea that came to my mind when I needed to build a punch press. Surely I'm not a pioneer in converting an old lawnmower into a punch press?
 
I'm going to take a shot in the dark and assume that this is in relation to the Curta build from another thread. In addition to the eccentric, you will need some sort of clutch mechanism, ram guides, flywheel and you are starting to get complicated. For the 42 parts you want to punch, the effort required to build the tool will greatly exceed the work required to make the parts. If it were me, I would look at getting a small arbor press. You might even be able to accomplish the task with a drill press.

If you are determined to set up a punch press, PM me. I have a small table top inertial press that is not being used.
 
I'm going to take a shot in the dark and assume that this is in relation to the Curta build from another thread. In addition to the eccentric, you will need some sort of clutch mechanism, ram guides, flywheel and you are starting to get complicated.

Yes, I'm aware of how a punch press works. I used to work in tool and die. I actually made quite a few punch and dies. And also maintained the punch presses they were used on.

For the 42 parts you want to punch, the effort required to build the tool will greatly exceed the work required to make the parts.

First off, I'm not so sure I agree with you on this. Trying to make 42 microscopic gears all identical is nothing to sneeze at.

Also, my idea is that if I actually build the Curta I'd like to have the potential to build more than one of them. Maybe as many as 10 or more. Now we're talking more like 420 gears, or more.

Finally, I have been wanting a small punch press for years. I've actually had the idea of building one using a lawnmower crankshaft for quite a long time. Now I have an excuse to actually do it. :grin:

So it wouldn't be just for the Curta project. It would be nice to have this little punch press around for other projects to. I'm build robots. You can probably imagine how many small parts I could make for my robots with a nice little punch press.

So yeah, I agree, if a person wants to build just one Curta Calculator and quit, then building a small punch press might be overkill.

It seems to me to be a waste to only build one Curta. There are going to be a lot of special fixtures and jigs required to make even one. May as well take advantage of all that tooling and make some more too. In fact, I'm thinking that most of the work on the Curta project is going to be building the tooling to build it. Making the actual parts will be secondary.

We're working on making the transmission gears right now. But this part is a piece of cake compared with the next part we need to build -
The Setting Shaft.

When we set out to build the Setting Shaft we are going to need to build special tooling for that too. I don't recall exactly, but I think there are only 8 setting shafts required. But what a shame it would be to only make 8 setting shafts after having made the tooling to make them. May as well make 80 shafts and build ten Curtas. :grin:

Why stop at 8?

I openly confess that I'm thinking mass production here. Not serious mass production obviously, but mass production for a "handcrafted" item. These will all need to be meticulously hand finished. So making even ten will be a major undertaking. But hey, if done properly they could fetch a grand a piece. That could be a $10,000 pay off in the end. Finally a hobby that will pay for itself. :grin:

And yes, that's about all it will be doing - paying for itself. It's going to take a year to complete this project. It's not going to make anyone rich to be sure.

But what would I do with just one Curta?

Nope, I want ten of them. I'm GREEDY! :grin:

To be honest, I wouldn't have even bothered with this project at all if I thought I was only going to build one Curta.

Plus I want this punch press for other projects too. So the punch press isn't just for the Curta project.

But yeah, I'm talking about punching out more like 420 gears. Not just 42.
 
If you are determined to set up a punch press, PM me. I have a small table top inertial press that is not being used.

Picking up an actual punch press is not "off the table". I might consider going that route yet.

But at the moment I have a FREE lawnmower in my backyard. and old farm equipment in the field that is calling to me. "Use us! Use us!"

Don't want to disappoint the poor things. :grin:

They want some love and attention.
 
Last edited:
Hey why not :) You know how a punch press works and how to build one, so no problem there. The stroke might be a little long for a small press, but it should make a 1.5 ton or so based on the journal sizes. Once you have the frame built, you can always build a new crank & rod if it doesn't work the way you want it.
 
If your determined to use a lawnmower crank let me suggest you get a much larger HP engine and older is better cast iron block type crankcase.
The journals will be stronger and the counter weights heavier. You'll still need a heavy flywheel which on older engines is heavy duty cast iron . On mower engines the flywheel is aluminum , they use the blade as counter weight.
 
Hey why not :) You know how a punch press works and how to build one, so no problem there. The stroke might be a little long for a small press, but it should make a 1.5 ton or so based on the journal sizes. Once you have the frame built, you can always build a new crank & rod if it doesn't work the way you want it.

That's what I'm thinking. I'm certainly not a punch press expert by any means. My experience as a tool and die maker was well over a half a century ago. But at least I do have some memories in tact. :grin:

I confess that I too am concerned slightly with the stroke size. I'm with you guessing that the journal size should easily handle 1 to 2 tons. And I'm also hoping that my small brass material will have perforating pressures well under that. I haven't actually done the calculation yet, I have the equations in hand. I'm just busy right now. I just cut down some trees and brought the logs into my sawmill for making lumber. Real life projects continue on in the background. :grin:

Edited: Here I forgot to post these pictures,...

Logs (1).JPG

Logs (3).JPG

I'd like to cut down one more large oak tree and bring those logs in as well before I set up to start cutting lumber.

Busy, busy, busy. No time to build any punch press one would think. But I don't think like that.

We'll have to wait and see what happens. I could very well be biting off more than I can chew. But the Curta project is just a hobby. I personally have no deadline to get it done. I know Racer would like to finish his in a year. But he doesn't even have access to a machine shop yet. At least I already have a lathe and mill. And I don't have the year time limit. I can just build it in whatever time it takes. No rush to build a Curta here.

I'll try to keep up with Racer. Don't ask me why, but I don't foresee that being a problem. Hopefully I'll be wrong about that and he'll beat me to completion.
 
Last edited:
If your determined to use a lawnmower crank let me suggest you get a much larger HP engine and older is better cast iron block type crankcase.
The journals will be stronger and the counter weights heavier. You'll still need a heavy flywheel which on older engines is heavy duty cast iron . On mower engines the flywheel is aluminum , they use the blade as counter weight.

I just took an old 18 HP single lung tractor engine to the metal scrap yard last year! What a mistake that was!

I agree starting with a larger engine would provide a stronger punch press. But we're only talking about punching out 0.6 mm brass sheet. Surely this small lawnmower crank can handle this.

I also agree with the counterweight. I wasn't planning on using the lawnmower flywheel as the counterweight. I might use the original flywheel to mount the counterweight on though. I actually have a nice large heavy counterweight candidates on some of this farm equipment.

Again, I'll only be punching out thin brass sheet. I don't think I'll need to build a 5 ton punch press. I'm thinking 1 to 2 tons should be plenty.

I'm trying to get Racer to do the calculation for me in his homework. But I may end up needing to do the calculations myself. They are easy calculations. I might do them when I break to eat dinner.
 
Is that that same as a 'fly press'? Just curious, I've not heard the term "inertial press" before.

-frank
I hadn't heard the term fly press before. According to Wikipedea, a screw press is also known as a fly press. https://en.wikipedia.org/wiki/Machine_press https://en.wikipedia.org/wiki/Screw_press

An inertial press (my term) uses the inertia of a flywheel driving a eccentric to provide the force required to punch or form the material as opposed to hydraulic press or a mechanical press using levers, gears or a screw.
 
Back
Top