Why can't I cut holes like the big kids?

[shoshin]

Hey all,

Long time lurker/some-times poster here. I'm building my eHerms system, and I admittedly bought some of the cheapest tools available (https://www.harborfreight.com/knockout-punch-kit-10-pc-60575.html) for the job. I used the 1-1/4 knockout punch to try to cut a hole in the side of my HLT (10-gallon stainless stock pot) for a 5500w heating element, but the darn thing won't cut. I've cut a few other holes in some other components with this kit and they worked just fine, but it simply refuses to cut this 1-1/4 inch hole in the side of my HLT, and in trying, the cutting edge of the punch is dulling and nearly flattening. I followed up with a step drill bit to try to cut the hole (https://www.harborfreight.com/2-pie...oated-high-speed-steel-step-drills-96275.html) but this drill bit won't cut. The bit will turn and turn and it looks like there's a ton of heat being generated, enough to deform the hole near the bit and almost turn it red hot, but the step bit won't advance.

Am I simply falling victim to the perils of using cheap tools (i.e. should I drop the $50-60 to get a Greenlee knockout punch, or $65 to get a professional step bit), or could there be something else going on here? Thanks in advance for any useful suggestions.

Cheers,

shoshin

 

[Warren Boese]

You buy this and cut through it like butter!
https://www.brewhardware.com/product_p/holesaw32.htm

 

[Bobby_M]

You are lucky the 1-1/4 conduit punch didnt cut. Thats too big for a weldless element install. You need the 1" conduit punch which makes a 1.25" actual hole size. Since you already have a hole for the punch, you cant use the tungsten bit at this point and you have work hardened the opening now.

 

[FloppyKnockers]

IIRC stainless steel gains in strength when subjected to heat and friction. The best approach when drilling stainless is slowly with a lot of lubricant.

 

[shoshin]

Ah. Thanks all. I did not use lubricant, I went fast and hard, and in true noob fashion I think I did indeed work-harden the steel.

Regarding the size of the knock out I mis-stated ... I had first used the 1-1/4 conduit punch on a metal box cover to find that yes it was way too big - I switched to the 1” punch which makes a hole slightly larger than 1-1/4.

Any suggestions on how best to proceed? I now have a hole that is approximately 1” in diameter with some tooth marks around it from a failed conduit punch. Is there any good way to save this hole (and the SS pot)?

 

[MaxStout]

The metal is probably work-hardened. You could take a Dremel with a small grinding stone and slowly work your way outward from the pilot hole. Wear ear plugs, it will be very loud!

 

[day_trippr]

Pictures might help...

Cheers!

 

[shoshin]

 

[day_trippr]

Looks pretty well toasted.
I'd try a good quality step bit run at lowest speed with lots of oil and hope it'll cut through the obviously hardened area.
Assuming it does a bit of hammering with a backer should straighten out the edges, then use a flat silicone gasket instead of an O-ring...

Cheers!

 

[kh54s10]

Yes. It will now take a very high quality bit. Or a grinder. If you use a Dremel get a lot of grinding bits you will use quite a few. How many?? It will also take quite a long time. I once worked a hole that was less than half the size of the threads on the weldless fitting and it took over an hour of grinding. Work around and try to keep the metal from heating.

When drilling, go as slow as possible, use cutting oil and a lot of pressure. Stop if you see smoke.

 

[grampamark]

Get a hole saw like the one in the link a few posts above. Then, put a block of wood over the inside of your existing hole and wedge the block in place with a piece of wood just slightly longer than the distance from the back side of the block to the opposite side of the kettle. If you have a woodworking clamp, of the type where the jaws can be reversed so that the clamp pushes rather than pulls, the block would be held more securely than using a wedge. Just make sure that the clamp pad contacting the wood block isn't aligned with the pilot bit of the hole saw.

The wood block will provide a solid start for the pilot bit in the hole saw. You don't have to start the hole saw perfectly centered on the existing hole, as long as you're close enough for the saw to overlap the edges of the hole.

 

[shoshin]

Thanks all, this is helpful I have half a mind to seal it up (maybe with a bulkhead fitting with a cap on each side?) and cut another hole elsewhere

 

[kh54s10]

I would give it some work before trying to seal the hole. I wouldn't want the obstruction on the inside of the pot. But that is just my OCD.

 

[shoshin]

You buy this and cut through it like butter!
https://www.brewhardware.com/product_p/holesaw32.htm

Wish I had seen this before I started anything!!! Thanks for the recommendation. #nexttime

 

[shoshin]

Get a hole saw like the one in the link a few posts above. Then, put a block of wood over the inside of your existing hole and wedge the block in place with a piece of wood just slightly longer than the distance from the back side of the block to the opposite side of the kettle. If you have a woodworking clamp, of the type where the jaws can be reversed so that the clamp pushes rather than pulls, the block would be held more securely than using a wedge. Just make sure that the clamp pad contacting the wood block isn't aligned with the pilot bit of the hole saw.

The wood block will provide a solid start for the pilot bit in the hole saw. You don't have to start the hole saw perfectly centered on the existing hole, as long as you're close enough for the saw to overlap the edges of the hole.

Near suggestion - I’ve done this with woodwork before but I wasn’t sure how I would secure the backer - wedge is a great idea

 

[golfindia]

Step bits suck for drilling SS, its Pure physics. Since there are only 2 small blade sections per step, it's not going to work well in tough metal. Carbide hole bits and a few drops of 3-in-1 oil will do the job. If I were you, I'd just pay someone to weld a TC fitting over the screwed up hole.

 

[mirthfuldragon]

If I were you, I'd just pay someone to weld a TC fitting over the screwed up hole.

+1. It helps if you know somebody who welds, but I would spend the money to fix it right. Any decent welding shop will be able to fix it properly. Better than chasing your tail and buying expensive tools for a single use.