what to do when step bits overheat?

[raney]

okay so I am working on an ebiab build and have successfully drilled my entire control panel and 3 out of 4 holes in my ss pot, then got stuck on the very last hole...and of all holes, it only needs to be 1/2"! The hole heated up just a couple of steps away and now I am stuck. I was re-oiling every step or 2 and everything else was going well...but I must have been drilling too fast. Most knockout punches need a 1/2" pilot hole, so I'm not too sure what my other options are. I can try putting a little force into it but don't want to ruin the pot in the process so I want to save that for last resort. Anybody have an idea of what I can do?


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[ChocolateMaltyBalls]

That's pretty much how the last couple of holes I had to drill were. The step bit had bit the dust, probably because the drill motor I was using didn't have much of a low speed high torque setting. Anyway if you're using a knockout punch then all you need is a hole big enough to fit the draw stud, and since you're removing all the metal around it, you can do whatever necessary to enlarge the hole. Just make sure there's something in the kettle to catch molten metal bits. If the step bit is completely shot, you can get a 1/2" metal bit or go to work with a round file attached to your drill.

BTW I think the greenlee punches I have all use 5/16 draw studs, or maybe 3/8, but certainly smaller than 1/2. Though there's lots of variability it's worth double checking.


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[raney]

the hole only needs to be 1/2" and I don't think they make punches that small. the step bit I was using on this hole was actually brand new...if the metal has been superheated will a 1/2" metal bit get through it?


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[ChocolateMaltyBalls]

the hole only needs to be 1/2" and I don't think they make punches that small. the step bit I was using on this hole was actually brand new...if the metal has been superheated will a 1/2" metal bit get through it?


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Oh I see, in that case you don't want to overheat that metal. A 1/2 coated bit can break though work hardened metal, but depending on how big the hole is now it will likely leave a pretty jagged finished hole. How many holes have you cut with that step bit?


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[raney]

that particular bit had only been used on the one hole it got stuck on which is why I was kinda confused. the hole is probably .3" or so and I just need to get to .5"


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[The_Doktor]

Stainless work hardens like mad. You want to use low speed and lots of feed pressure. Good quality cutting oil helps a lot.

Cheap, high RPM drills are a sure ticket to failure. I would recommend something under 25 FPM with a HSS bit in stainless.


Ed

 

[ChocolateMaltyBalls]

Do you have a round file? I'd first try to remove the work harden edge with a file and then try the step bit again with plenty of lubricant, maybe a different drill if you have one. Low speed, high torque, and pressure. If there's not a metal ribbon or fly pieces of metal stop immediately, don't wait for it to get red hot.


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[The_Doktor]

25 FPM would be ~190 RPM at ½", slower is no problem. 100 RPM would be even better.

 

[raney]

thanks for all of the help. I'm sure it's an easy fix but I've almost tripled my budget as is so I want to try and make this one work. I don't have much experience working with metal so you guys are a huge help - I'll go at it with a file first and then take it slow with my drill. thanks for all of the responses, I'll post back with results!


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[Facinerous]

Most likely you have a bad step in the bit. It happens all the time. As the hole becomes larger and you keep running the bit though step by step it heats up.

All I do when I have a bad step in the bit is set your drill to a low speed, put pressure on it, and wobble it side to side. It'll run though. It will just take some effort. If your using a punch after the step bit you wouldn't need to worry about any irregularities in the hole, the punch will take care of that.

There is a punch that uses a smaller pilot stud (1/4 inch) to knock out to the larger 1/2 inch. They are out there.

 

[raney]

Thanks for all of the help in here! I didn't have a file small enough and was too impatient to wait, so I went back at it with a different step bit and drill...just went slow enough and pushed it through and it worked! The edges were burnt I didn't think my drill had it in her. Thanks for the advice - I'm a newbie working with metal so it helped





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