Is stainless steel hard to drill?

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jamesdestin

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I'm trying to drill some 3 mil stainless strip I bought yesterday. I've broken one drill bit and totally knackered another two! I'm trying to drill a series of 3 mil holes in it but didn't expect it to be this difficult. The description stencilled on the strip is

ICC WNR 14301 TYPE 304 HEAT

From a quick search on the web I can see that type 304 stainless is sometimes used for heat resistant vessels (as in containers not ships /forums/images/graemlins/grin.gif ) but that doesn't mean it's hardened does it?
 
Now that explains something, It did seem to get progressively more difficult. Will try again in the morning, neighbours strangely averse to the sound of my metal torturing. Thank you.
 
You have to drill at slow speed and dont forget the cutting oil - it will help to keep the drill bit going for a bit longer.

As you drill slowly you will pick up the tic tic tic sound as the drill begins to bite stay at this speed until you are through. Once you get this sound you will always remember it for the future.
/forums/images/graemlins/smile.gif
 
[ QUOTE ]
s/s "work hardens"

[/ QUOTE ] And one thing that will harden it is centre punching it. If you can avoid centre punching do so but otherwise do it as lightly as possible.


I drilled hundreds of 6mm diameter holes in 304 plate some years ago to collect swarf for chemical analysis. I had a decent bench drilling machine (Bought specially for the job) did not use any coolant/ lubricant did not centre punch just whacked the holes through as fast as I could. Got through a few drill bits though.
 
If it is anything like here a bench drill press is surprisingly cheap (about 30 squid) They really are the answer with the ability to run slowly with lots of pressure. You will use the drill press a lot for all sorts of things.
One trick I use is to lubricate with oil (old engine oil or WD type spray.) It lubricates a bit but starts to smoke as soon as it gets hot.
It is time to stop if it smokes. So if you are using a hand held drill go for short bursts of high pressure.

Of course high pressure in a hand drill can lead to breaking the bit.

Sharpening drill bits is not hard. However the trick is to start with a large drill bit like 1/2 inch. Look closely at the cutting angle (if it hasn't been sharpened before by an amateur) You need to sharpen the bit while maintaining the cutting angle. Think of the cutting edge like a wood plane. It can be too shallow or too steep. After fiddling with large bits you can proceed to your 3mm bits but you will find a grinder wll take too much metal off too easily so even an oil stone can be enough. And if you are like me you will need a magnifying glass to look closely at the cutting edge.

good luck olewill
 
Under NO circumstances would I use old engine oil or even WD40 spray - too much lubrication is the last thing one wants for cutting/machining stainless steel - use proper cutting fluid to keep the drill bit and material cool, cobalt drills with positive rake angle, a press (pillar) drill, slow speed and lots of pressure (constant feed speed). The trick is to maintain the chip and not allow the drill bit to slide in the stainless without cutting.
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just a quick note about stainless grades; 316 (aka A4) is more corrosion resistant than 304 (aka A2), which shouldn't be used below the water line, and I would avoid using outside, but that is probably slight overkill.
 
Most of the above is sound advice. Just a word about drill bits, HSS (High Speed Steel) bits are perfectly adequate as long as you go for good quality. Dormer, Presto, Intal are some examples, buy them from a specialist stockholder or beg at your local engineering shop. A quality cutting compound also helps, buy or scronge from the same source.
 
I had to do this over the winter and used Bosch Titanium drills that I bought from B&Q.

I was removing winches that required drilling out the 5 s/s fixings each. The first winch using regular metal drills took 3-4 hours and a lot of swearing. The second winch took 20 mins using the Titanium drills. Well worth the extra cost.
 
Thanks all - result

I got some silicon cutting lube in a spray can, a cobalt drill bit and (for another 14mil hole) a HSS blacksmith bit. Used my dad's old bench drill on a slow speed and managed quite easily. Even the HSS drill went through ok by doing it in short hard bursts. Got lovely spiral cuts of swarf off it. Very satisfying, thanks for the advice
 
[ QUOTE ]

One trick I use is to lubricate with oil (old engine oil or WD type spray.) It lubricates a bit but starts to smoke as soon as it gets hot.
It is time to stop if it smokes. So if you are using a hand held drill go for short bursts of high pressure.


[/ QUOTE ]

The secret for drilling stainless steel is to use a sharp drill at slow speed, and use *condensed milk* as a lubricant. Being thick, the milk sticks well to the drill, as well as coating the cutting area, thus preventing the formation of hard oxides.

Another tip when drilling progressively larger holes in any kind of steel: once a small lead drill has been used, it's nearly impossible to keep the cutting oil where you need it. So - smear a plug of grease into the hole, which will then keep the cutting oil in situ - there's nothing kinder to drill bits than cutting in an oil bath ....

Colin
 
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