Work hardened steel?

[fusa]

Just tried drilling a hole for my thermometer/sight gauge and at 1/16" from the size I need, my corded drill would not drill anymore. I used a lot of metal cutting fluid, but might have used too much speed. Previously I used a cordless drill, which was a little slower. I'm waiting for the battery on my cordless drill to recharge, and try that since it has a torque adjustment (kicking myself for not getting a corded drill with torque adjustment )

Is there anything else I can do? Or any tips on how to work with work hardened steel? Or would this be normal, the final size will be 13/16" and I remember the final 1/16 or so was slower using my cordless drill, but it also ran out of battery power.

 

[pattatat]

If its anything like our shop its old crappy worn out dull bits...?

 

[fusa]

The bit has only been used once before to drill a 13/16 hole for the bulkhead. The steps on the bit feel the same and look the same from each step to the other.

 

[Homercidal]

Stainless? I was told by a guy at work to go slow, keep good constant pressure on the work and use a bit of fluid. He said that for that kind of sheet metal, runnign to fast or too light can heat it up and make it harder.

He actually recommended using a hole saw for this. He said they used to cut a few holes in some work for a customer's stainless product and that was what they used. I said ok as long as I can use the company's bits! But I might plasma cut it anyway. Who would choose to use a drill over a plasma cutter?

 

[fusa]

Yes, sorry forgot to mention, its a stainless steel keg. I just looked over Home Depot's return policy and might stop by to try to return the drill for for better one with torque control. Its only been used for this, and less than a month old, so hopefully I will have no problems.

 

[ArtVandelay]

if you heated the metal up until it is red hot and let it cool slowly it would relaxed back into a less hard phase.

 

[fusa]

Just returned the corded drill to get a better model, tried that, and no lucky, just heated way too fast. I tried the cordless drill, and at least had some flakes, but battery is still too weak. Not sure why the cordless is working better, maybe the corded is just too fast and heats the metal too quick. If the fully charged cordless drill still doesn't work, I'll try heating it with a blow torch.

 

[Catt22]

He actually recommended using a hole saw for this. He said they used to cut a few holes in some work for a customer's stainless product and that was what they used. I said ok as long as I can use the company's bits! But I might plasma cut it anyway. Who would choose to use a drill over a plasma cutter?

I would choose to use a hole saw over a plasma cutter for this job. It will give you a much more accurate hole, no splatter and just about as fast.

 

[JuanMoore]

The drill needs to be turning very slowly while you apply a lot of pressure. Most corded drills spin at ~1,000-3,000 rpm at full speed, and you want to be somewhere closer to 400-500 rpm. Your corded drill should work fine, just don't go full speed! Now that you've work hardened the spot you want to drill, try using a hammer and center punch to create some irregularities in the divot to give the bit something to grab on to.

The bit has only been used once before to drill a 13/16 hole for the bulkhead. The steps on the bit feel the same and look the same from each step to the other.

The steps of the step bit may still be sharp, but If you ran a corded drill on full speed against stainless, then the very point of your bit has probably been dulled considerably. What does the very tip of the point look like? If it's dull, you might be able to use a regular twist bit to drill a small pilot hole, and then use the step bit to drill it out to size.

 

[fusa]

The point looks fine, its the 3/4" to 13/16" step that is having the problems, I'm only about 1/16" away for the final size I need.

 

[jfkriege]

Stainless will work harden if it gets too hot, and it is a bear to get through. I was machining stainless parts just yesterday. Slow feed rates, cooling if you have it, a little cutting oil if you dont, and take as much material as you can in one pass. For what you want, slow rpm and put a lot of pressure on it. If it starts getting hot, let it cool.

 

[Bobby_M]

It sounds to me like the corded drill just doesn't have enough torque when you try to run it slow. My Dewalt XRP cordless has geared 3 speed so the low speed is also high torque which is better for drilling stainless than my larger corded drill.

Now that you're 1/16" away, I'd just get a round file and go to work.

 

[AnOldUR]

So you have the pilot portion of the step drill through?

Open up the hole to size with a Dremel.





Edit:
Oops, didn't read all of Bobby's post. A file is cheaper if you don't have a Dremel.
I just like power tools. SPARKS Errrrrrrr!

 

[fusa]

Yeah I was considering using my dremel to at least make some irregularities so the bit can catch on something. Might just use a file, to finish it, my hands aren't steady enough to make a very good circle. What material should the file be made of? Are there stainless steel files?

 

[lincoln]

if you heated the metal up until it is red hot and let it cool slowly it would relaxed back into a less hard phase.

This not true for stainless!!!

"Annealing
The austenitic stainless steels cannot be hardened by thermal treatments (but they do harden rapidly by cold work). Annealing (often referred to as solution treatment) not only recrystallises the work hardened grains but also takes chromium carbides (precipitated at grain boundaries in sensitised steels) back into solution in the austenite. The treatment also homogenises dendritic weld metal structures, and relieves all remnant stresses from cold working. Annealing temperatures usually are above 1040°C, although some types may be annealed at closely controlled temperatures as low as 1010°C when fine grain size is important. Time at temperature is often kept short to hold surface scaling to a minimum or to control grain growth, which can lead to "orange peel" in forming.

Quench Annealing
Annealing of austenitic stainless steel is occasionally called quench annealing because the metal must be cooled rapidly, usually by water quenching, to prevent sensitisation (except for stabilised and extra-low carbon grades)."

best thing to do is get a "cobalt" stub or screw machine length drill bit from mcmaster or msc direct to punch through you pilot hole then finish with you step bit.

as for a file there is no specific material but i would get a medium or fine half round. also find something round to trace you finished hole with and file to the line.

 

[AnOldUR]

Yeah I was considering using my dremel . . . my hands aren't steady enough to make a very good circle.

If you use a barrel sander in the Dremel it's pretty easy to control and doesn't remove material too quickly. I've done several of these and always drill a little small and open up the hole with the Dremel. It's a good way to guarantee a snug fit because drills run in nominal sizes and it’s hard to get an exact match. The tighter the fit, the less chance you’ll have of a bad seal.

 

[fusa]

Finally was able to get the hole large enough to fit the stainless steel nipple through. The dremel and grinding wheel did a good job of removing some of the outer-edge, then using the step bit was easier. Still a slight leak, but I should be able to fix it after adjusting it some. Next I'll be sure to not run the drill at full speed.

 

[dogtailale]

Did you get that bit at HF? If so those are one shot bits for SS. You get one shot only. (I drill holes for a living)

SS likes a water oil mix better than strait cutting oil. Just boil oil water mix it, pour and use a windex type spray bottle.

Youre lucky get out the dremal

 

[fusa]

No the bit isn't from Harbor Freight. I used Mibro cutting fluid, from Lowes. I'll remember next time to try that with the spray bottle. I was hoping to find cutting oil in a spray canister, but a spray bottle would be just as good.