# 1.25" hole in 3mm stainless steel plate



## Florin Andrei (Jan 18, 2015)

I'm making the face plate for a control panel. I was able to cut the SS plate pretty easily, following the advice given by many of you here on this forum - thank you.

Now I need to cut a 1.25" round hole in the 3mm SS plate, to install an emergency stop button. I'm pretty sure brute-force drilling with a 1.25" drill bit will not work - I've made much smaller holes and it's quite difficult. The material hardens very quickly. The only thing that worked well for a linear cut was milling it with a carbide mill at slow speed while constantly moving the work.

What are my best options to make that big hole? I've access to a mini-lathe, mini-mill, drill press, and various hand tools.

The plate size is 8.75" x 3.5". The big hole is not in the middle, but closer to one end.


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## Douglasr (Jan 18, 2015)

Hole saw, back plate with wood.


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## nightowl499 (Jan 18, 2015)

My thought would be to drill hole out in steps to 1/2 inch then use the mill with a boring bar to take it the rest of the way out or if you have one a rotary table on a mill
 just my thoughts


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## chuckorlando (Jan 19, 2015)

You have a boring head or fly cutter? Step drill it. Jigsaw?


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## Dave Smith (Jan 19, 2015)

Florin Andrei said:


> I'm making the face plate for a control panel. I was able to cut the SS plate pretty easily, following the advice given by many of you here on this forum - thank you.
> 
> Now I need to cut a 1.25" round hole in the 3mm SS plate, to install an emergency stop button. I'm pretty sure brute-force drilling with a 1.25" drill bit will not work - I've made much smaller holes and it's quite difficult. The material hardens very quickly. The only thing that worked well for a linear cut was milling it with a carbide mill at slow speed while constantly moving the work.
> 
> ...



Florin----I would use a dremmel type tool with a cutoff disc to cut a square 1 1/4" hole or a 1" carbide tipped cement drill bit for a hole-----then you can put a carbide burr in your mill and clean up the hole to size needed--the hole doesn't have to be perfectly exact cause the mounting ring will cover outside----if you are handy with a hand die grinder with a carbide burr you could clamp your piece in your vise and make quick work of it---carbide burrs are very durable and fast and you can save your expensive endmills for better projects------another better option is to use an electricians 1 1/4"  knock out punch---- they work the best--- and buying a good set for your shop would be a continuous help--------Dave


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## 12bolts (Jan 19, 2015)

Like Douglasr, Holesaw and a thick timber backup, (19mm ply or similar) will make short work of it

Cheers Phil


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## hotrod (Jan 19, 2015)

12bolts said:


> Like Douglasr, Holesaw and a thick timber backup, (19mm ply or similar) will make short work of it
> 
> Cheers Phil


I just drilled three holes that size in 1/8 stainless pipe using a regular hole saw and a 50/50 mix of antifreeze and water. I ran the Bridgeport at 200 RPM and squirted the anti freeze mix on the drill continously with a spray bottle. It worked like a charm and the bit cut right through with no problem.
Dale


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## deyve (Jan 19, 2015)

yep - hole saw with tim:nuts:ber backing will do the job. Myself - I would use a step drill.


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## ki4byz (Jan 19, 2015)

hotrod said:


> I just drilled three holes that size in 1/8 stainless pipe using a regular hole saw and a 50/50 mix of antifreeze and water. I ran the Bridgeport at 200 RPM and squirted the anti freeze mix on the drill continously with a spray bottle. It worked like a charm and the bit cut right through with no problem.
> Dale



  Be careful using antifreeze as a coolant.
  If it contains ethylene glycol it can make you sick.
  If you must use antifreeze as a coolant please use one that is made with propylene glycol, it is much safer.


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## coolidge (Jan 19, 2015)

Greenlee knockout punch? http://www.amazon.com/Greenlee-730BB-1-1-Standard-Knockout-4-Inch/dp/B002NQZ0J0#productDetails


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## 12bolts (Jan 20, 2015)

Why is anyone using antifreeze as a machining coolant?


hotrod said:


> .... a 50/50 mix of antifreeze and water. ...





ki4byz said:


> .... If it contains ethylene glycol it can make you sick....If you must use antifreeze as a coolant please use one that is made with propylene glycol.....



Cheers Phil


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## JimDawson (Jan 20, 2015)

12bolts said:


> Why is anyone using antifreeze as a machining coolant?
> 
> 
> 
> Cheers Phil




It keeps the cutting edge from freezing up :roflmao:  Well, somebody had to say it.


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## Rob. Smith (Feb 28, 2015)

I once cut a 2" hole through a 1" thick steel plate .     I used a hole saw running at the slowest speed possible and plenty of cutting fluid.  The trick was to NOT force the tool and back out and clean the teeth and hole often.    It took a while and the hole saw is still good to this day .


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## Wreck™Wreck (Feb 28, 2015)

Florin Andrei said:


> Now I need to cut a 1.25" round hole in the 3mm SS plate, to install an emergency stop button. I'm pretty sure brute-force drilling with a 1.25" drill bit will not work


Why does drilling not work?


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## ProMetalShop (Feb 28, 2015)

Hi Florin, I would as others have said, use a bi-metal hole saw, ( good quality ) and run slow, with constant feed of cutting oil. Clean the area so the teeth are always cutting new surface. With 1/8th inch stainless you shouldn't have a problem being near the edge where it should be rigid enough with low amount of heat. Even if the hole saw wears a bit you can always go back in and clean it up with a boring head if one is available to you. Please post pictures of your results ! !


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## chips&more (Feb 28, 2015)

A good quality Unibit should work. Run it slow, keep it cutting, do not let it turn without cutting and use lots of cutting oil. They also sell hole saws now with Carbide teeth. That should also do the trick. But might need to be aware of having a ridged set-up so you do not destroy the Carbide…Good Luck, Dave.


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