How can I punch holes in a plastic caps? (a cap similar to the caps on soda bottles)

branpalm · Feb 19, 2016

So I need to figure out a way to punch a 5/8" hole in a 1.25" plastic cap (similar kind of cap that you would find on a jug of juice or soda bottle, etc.) The cap also has a soft poly-something gasket stuck in the top of the cap that needs to be punched with cap also. I need to punch a lot of them so I need something effective and efficient.

I have virtually no knowledge of presses, punches, or any other tools/machinery that might be used in such a way. If anyone could help me out, I'd be very grateful. As I have virtually no knowledge of this kind of work, please be specific and detailed! Thanks!

JRIowa · Feb 19, 2016

You need to be much more specific.
What's "a lot"?
What's your budget?
What equipment do you have for using the punch?
What equipment do you have for making the punch?

Depending on the quantity, I might look at water jet. If you don't have a press, and the quantity is in the thousands, you should probably look at farming it out.
JR

EPAIII · Feb 19, 2016

Since you are doing a lot of them, making a custom punch and die would probably be best. The die could be made to the inside dimensions of the cap so it would self center. I would make the punch with a very sharp edge, possibly hollow ground in the center. Of course, both should be hardened for longer life. Others can probably suggest a good steel for them.

rke[pler · Feb 19, 2016

I'd just whack it with a gasket cutter. If you have a bunch to do then you might want to go with a punch tool that looks like hand pliers or even the bigger one looking like lock cutters (I'm at a loss for the generic term for these tools even having them).

gwbolton · Feb 19, 2016

Use an incline type press. Punch and die installed in in a die set. Sheet metal track to load the lids into position. Gravity will allow the part to fall after piercing with maybe a little help from an air blast, allowing the next part to be fed into position. Pierce inside to outside so that the hard plastic is against the die. Use spring ejector on punch to help eject slugs. No lube on the parts, run totally dry. Good luck.

jscpm · Feb 19, 2016

Define "a lot".

Your definition should include two things: the number of parts and the amount of time in which those parts need to be produced.

(seriously, this is the kind of crap I have to deal with every day :ack2:

)

FredC · Feb 19, 2016

If a lot of them is 200 pcs or less then you can make a punch and a die out of aluminum on a lathe. Make the punch first so that it can be chucked in the tailstock. The punch should be a couple of thousands larger than your minimum hole size. Turn the die so that your 1.25 cap fits on it drill and bore a hole that is a few thousands larger than the punch. Face the die flat and you are in business.
I did one of these to make some shims out of .020 thick Teflon sheet and the results were so good you might of thought a professional did it. I sure fooled them!

Chip Chester · Feb 19, 2016

"...please be specific and detailed! Thanks!"

Yes, this. In addition to the questions above, are the caps sitting on your bench, or are they tamper-proof sealed on a bottle of toxic goo?

And, does the thing that punches them stay in place (like an old-time oil spout) or do you need a perfectly round, centered hole with the scrap not in the bottle of (whatever it is)?

Chip

branpalm · Feb 19, 2016

Sorry for not giving more information.

My budget is fairly low, few hundred dollars at the most as I'm looking to lower my cost of these caps. I can buy the whole caps for $0.08 each but to buy them already with the hole punched out they are $4.80 each.

Quantities in the hundreds, they don't need to be produced extremely quickly, but I also don't want to spend too much time slaving over them (after initial set up at least). The caps are alone, not on any kind of bottle or anything. However the gasket on the inside of the cap is glued in, so any ideas of removing the gasket from the cap and punching them separately is impractical at best. The holes need to be visually centered and round, but they don't need to be perfect.

For equipment, I have most things you would find in an average man's garage. However, no metal working equipment, no welder. The only thing semi-related I have is a small drill-press, which I know probably isn't any help.

I wouldn't mind investing in a small arbor press with a punch and die, however I've never used an arbor press nor any punch and die equipment. So I do not know what kind of punch/dies I would need nor how to set it up properly.

CougarMountain · Feb 19, 2016

EPAIII said:
Since you are doing a lot of them, making a custom punch and die would probably be best. The die could be made to the inside dimensions of the cap so it would self center. I would make the punch with a very sharp edge, possibly hollow ground in the center. Of course, both should be hardened for longer life. Others can probably suggest a good steel for them.

A polyurethane stripper on the punch would be a big help and easy. As little tonnage as this should punch, the above die assembly could be run in a hand powered arbor press for an extra margin of safety.

CougarMountain · Feb 19, 2016

branpalm said:
Sorry for not giving more information.

My budget is fairly low, few hundred dollars at the most as I'm looking to lower my cost of these caps. I can buy the whole caps for $0.08 each but to buy them already with the hole punched out they are $4.80 each.

I wouldn't mind investing in a small arbor press with a punch and die, however I've never used an arbor press nor any punch and die equipment. So I do not know what kind of punch/dies I would need nor how to set it up properly.

I think a Unipunch frame could be set up to do the job, with an arbor press, depending on the cap height. The example below would work with the lower die holder modified (shortened, and a sleeve added to hold the cap centered). The punch and die size you would need is probably an off the shelf item from Unipunch or ebay. You need to pay attention to the frame size when ordering, as there are many different configurations.

FredC · Feb 19, 2016

I found the tooling in the cabinet of my old South Bend. Doing several hundred at a time would not be much trouble even stripping them off the punch by hand.

The initial punch and die are on the left, the punch in front. Instead of making the punches one piece, I drilled a 1/2 hole in them and chucked a piece of 1/2 bar stock to center the punches on the tailstock. The punch on the right has a step for lining up the hole punched in the sheet. The waste plugs and a couple of the finished washers are on the lower right. Quick and dirty made out of scrap, with a good result.

A machinist in your area could mount this stuff on a punch press for you or if you ever stumble over a nice bench lathe you could build this yourself in an a short time then you have a lathe to do other stuff. If your drill press has a 1/2 chuck stuff like my photos could be mounted on it.

Heavey Metal · Feb 19, 2016

Forstner bit

jscpm · Feb 19, 2016

With no metalworking equipment there is no easy way to set it up, because you have align the punch which means you need to have a fixture which means you need to have a precision machining capability.

You could use a hydraulic knockout punch but the cycle time will be about 30 seconds per unit.

Danny VanVoorn · Feb 19, 2016

I didn't see any tolerance noted but an Arch punch will put a hole it them. If putting them in a certain location and an odd size hole a button die and punch with a simple nest would do. I have a little press with easy instill punches and dies that would be pretty easy to add some simple locators to and do that job.
Dan

Silent_Man · Feb 19, 2016

Maybe you can use your drill press to make a fuxture and also as a punch. Im not sure how well it would work due to slop in the spindle though.

Steps:

Drill a hole in a plate the od of your cap.

Remove plate

Clamp a different plate on the drill press table and drill a 5/8 hole.

Clamp first plate on top of 2nd plate centering the holes as closely as you need.

Grind the end of a 5/8 steel rod FLAT.

Chuck the rod in the drill press (You may need a bigger chuck or turn down one end of the rod end to a smaller diameter so your existing chuck will work.)

Make sure the rod goes through the hole. Aluminum might be a good choice for the second plate btw so it wont damage the steel punch it they hit. If the rid does not go through due to misalignment, unclamp the plate and reclamp it with the rod sticking theough the hole.

Drop a cap in and punch out a hole.

Repeat

Also, make sure the slugs drop through the center opening of the drill press table... preferably into a trash can. You definitely dont want to have to pick them out of a blind hole every 4 or 5 pieces

Davis In SC · Feb 19, 2016

I have a job where a hole is punched in a polyethylene disk. Takes only a few hours for a person to punch 2500 pieces. There is an aluminum nest, nothing fancy, to hold the part. In the center is a hard drill bushing, pressed in, sitting flush, with the top ground sharp. Punch is an ejector pin. Set it up in an old BP mill, center, and lock the X & Y, set the z stop, and start punching. Slugs fall out via a through hole and a slot in the bottom.

Bill D · Feb 19, 2016

does the hole have to mate with something or is the diameter not critical?
Bill D.

branpalm · Feb 19, 2016

Bill D said:
does the hole have to mate with something or is the diameter not critical?
Bill D.

No, the diameter is not critical. Need 5/8" to 11/16" diameter hole

Limy Sami · Feb 19, 2016

5/8 wad punch -like this https://www.acklandsgrainger.com/en/product/MIB356450

How can I punch holes in a plastic caps? (a cap similar to the caps on soda bottles)

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