drilling holes - expert advise needed

[duck_arse]

back before it was lost in the great battery swap of '13, there was a thread on drilling, holes in particular, which was just starting to get interesting. I don't know if it covered stainless steel, and it's gone anyway, so here's a new thread, on drilling.

shown upper below is a pair of panels I've cut from the sheet detailed lower below, which used to be a water distiller circuit box. the panels are cleaned, dressed, measured, marked and centre punched, ready to be drilled with the standard complement of holes needed for an ordinary pedal enclosure. the panels are stainless steel. cutting the sheet with a you-call-it-sabre-we-call-it-jig saw with a metal cutting blade and some light machine oil, or a frame hacksaw, was less a problem than I was expecting. drilling the holes, however, is making up for that.





I had tried drilling pilots with a TiN 1.5mm bit, but that only made the punch-marks angry. so I went and bought a 2.5mm and a 6.0mm Cobalt bit, thinking drilling would be a breeze, at least for those size holes. I even mixed some machine oil and turpentine for cutting fluid. being limited to a hand-held power drill, I was expecting to have to do some work, but again gave up as the small drill made next to no progress, and the big drill .... wandered .... somewhat. it seemed more to "grind" than cut the 2 holes shown, at least until the outer edges of the drill made contact with the work piece.

the above pic shows how far the large bit moved from its punch-mark, and the inset shows how the smaller bit has scratched itself to a standstill, hole-making wise. I have the drill set on the lowest speed-clik on the trigger wheel, everything is clamped, I'm pushing on the bits and dipping in the oil, nothing is getting hot or glowing red and still I can't make any progress. and I need 13mm holes before I'm finished.

so, any experts with any suggestions? what am I doing wrong, or is it supposed to be this hard? did the dove company choose some special mix of stainless for their product? I had planned on making 4 or 5 of these (1590a-ish sized) boxes, but I really don't have the time or the shoulders for it at his rate. and I haven't gotten to the bending, yet. say the word and I'll hack up some aluminium instead.

does anyone here work with stainless?

[italianguy63]

I'll give you a short version of a story.  I relocated a gear on a transmission shaft once (tool steel).  Try drilling into a round shaft sometime without the bit skating!  Anyway, tried dimpling the metal.  Drilling with bits, titanium bits, cobalt bits.. NOTHING.  Bought a "carbide" drill bit-- it was about $10 for a small bit.  Cut the tool steel like butter.

MC

[duck_arse]

they had no carbides, I gots no money.

[italianguy63]

Pistol rounds make large holes, and you can use some rifle rounds for the smaller ones.

[italianguy63]

Seriously, invest in a carbide, even if it is just a pilot size to get your holes started and centered.  I had to mail-order mine.  Could not find any local.  It is specialty industrial grade tooling stuff.

[thelonious]

^ +1 on the carbide pilot hole idea. But I understand having no money. What you've described makes it sound like this steel has eaten your bits for breakfast. I mean, your drill bits. If you were in the US, I'd say go get a pack of stepped or stepless drill bits like http://www.harborfreight.com/3-piece-stepless-drill-bits-66463.html. They certainly won't be as good as the carbide drill bit MC describes, but sacrificing one of them to drill your box would only cost $2.50 or so. Do you have anything like Harbor Freight in your area? (the store that sells every tool imaginable at half the cost, most of it kind of crappy, but some of it surprisingly durable for what it is)

[R.G.]

Stainless steel work hardens FAST. You can cut it with either high carbon tools or high speed steel (HSS) bits, but you simply must feed it hard enough that you do not let the cutting deformation harden the stainless under the tool edge. If this happens, the stainless gets as hard as the tool bit, and then the hardening begins in earnest. So it takes some machining skill to drill and cut stainless with steel tools. You have to get the feed rate and cutting edge speed right or else. You can lose a lot of tools this way, as the hardened stainless under the bit eats up the tool edge.

Carbide is harder than the hardened stainless, and cuts through anyway. But it has its own problems, not least of which is brittleness or cost.

The places you've tried to drill are probably now too hard to drill with even new, sharp steel bits. You'll need carbide bits on those spots, or to star over with a new bit of stainless.

I've broken a lot of bits. 

[Mark Hammer]

My late father was a machinist, and I spent many a weekend as a youth, toiling away for him in "the shop", instead of being out enjoying the daylight.  When I was a little older, he arranged for me to have summer jobs in other machine shops where I'd work high-speed punch presses and such.

One of the things you will routinely see in any metal shop where high-speed drilling, milling, or other machining of steel takes place is a steady drip over the target of cooling fluid, which is usually a sort of milky white.  I gather it also lubricates the point of contact, so as to both reduce unproductive friction and extend the life of whatever bit or cutting implement is in use.

[Gus]

Do you have a center drill?

[R.G.]

One of the things you will routinely see in any metal shop where high-speed drilling, milling, or other machining of steel takes place is a steady drip over the target of cooling fluid, which is usually a sort of milky white.  I gather it also lubricates the point of contact, so as to both reduce unproductive friction and extend the life of whatever bit or cutting implement is in use.

Soluble oils. A lot of chemistry has gone into these. They are a solution of the soluble oil in water; oil for lubricating the process and water for conducting away heat.

There are mist cooling systems that use what amounts to a small paint sprayer, but spraying oil/water mix. Uses less stuff and splashes less.

[newperson]

If you plan on drilling more in the future, I would vote you get a small drill press.  Look on what ever your craigslist equivalent is and get something cheap.  In the US if you live close enough to a harbor freight you can pick up a new small press for around $45 with coupons.  I see them on CL used from time to time for $25-30. 

[digi2t]

The problem with stainless is the chromium content, which is the principal ingredient that causes all the machining headaches. Chromium, by nature, is VERY hard. When drilling stainless, the squeaking sound that your bit starts making (as it's dying!) is the friction of the bit against the work hardened chromium. Different grades of stainless have different levels of chromium, all dependant on the degree of corrosion resistance desired.

In the old days, I mean THE old days, when hi beam switches were still on the floorboard, and bumpers actually sported real chrome, drilling a bumper to install, say, fog lights, could be a major undertaking. My Dad had a 67 Chevelle, and later on, a 64 Belair, to both of which he mounted fog lights on the front bumper. Drilling the bumpers was a beyotch, and a several hours of work proposition, but hey, like gas, drill bits were cheap back then too.

I worked in a machine shop for a short time, and we often had to work with stainless. For drilling the key points are;

- Sharp bits. HSS is fine, but they must be sharp. One of the problems is that off the shelf bits are sharpened to a 118 degree angle. This is fine for general work, but for harder material, concentrates too much heat on the point. We would often resharpen bits to 125 or 135 degrees for hard materials.
- Speed. Different materials machine at different speeds. In general, SS is slow speed/high feed work. The slower the better, with higher than average feed pressure, but beware of grab when you start to break through. Hand drilling SS can be done, but more often than not ends badly. Either you end up chipping/burning the ends of the cutting edge of the bit face, or it'll grab, and you're icing a wrist, which bring me to...
- SECURE YOUR PIECE! Use a drill press, if possible. As some can attest, hands and drills are mortal enemies. Clamp your work securely, and KEEP YOUR HANDS CLEAR!!! I cannot stress this enough. And contrary to popular belief, wearing gloves while working the metal IS NOT ideal. Yes, if you're not careful, you will injure yourself, but wearing gloves while the machine is working only offers the piece/tool/rotating whatever, a purchase to grab onto if ever it comes in contact with your glove. Use gloves to handle the work before, and after, machining it, but gloves on hands around rotating equipment only opens up the possibility of a cut becoming a broken wrist, arm, or worst after your "ride" is over. Lastly...
- Lubrication. SS needs copious amounts of lub/coolant when being worked. More than other softer materials. There are lots of very efficient cutting oils available on the market, take your pick, but you'll need lots of flow over the work for good results. Put a bucket under the work, and rig up a small circulating pump and hose to provide a constant flow to the drill point.

If you don't have the proper tools, or can't get the desired results, then I recommend seeking out a local machine shop, and letting them do the job. Sometimes, the money saved on drill bits, blood, and swearing, are best spent having a job well done... by someone else.

[duck_arse]

well, bugger!

I spent the money on the cobalts, because the sutton's website said "for stainless steel" and the hardware doesn't have the carbides."135 degree split point to minimise wandering", it says on the packet. the big holes didn't "wander" like normal drills, with the big skidmark/smear/oval shaped hole, they just drilled somewhere else.

no centre drill, that was the intent of the smaller drill. no drill-press in sight, not in the forseeable future. no shoulders for feed, either, I'm too weedy.

I didn't hear any squeeking, maybe the earmuffs hid it. more chrome = harder? as this material is cut from a water distiller, would it be on the higher end of the chrome scale?

maybe like I said to the bloke, "I'm starting to think of using a hammer instead". another project backburnering.

[Mark Hammer]

maybe like I said to the bloke, "I'm starting to think of using a hammer instead".

My dad's long gone, I'm too busy, and my boys didn't pursue "the knowledge", so you'll have to look beyond Hammers for this one, I'm afraid. 

[thelonious]

Sounds like maybe one of these is called for. Np, shipping is only $1.5k.

[duck_arse]

I have myself a couple of red and a green, like this ....



.... might take me longer than with the drill. maybe if I cross the streams ....