Stupid question time for drilling stainless

[phill d]

Hi guys, to some of you this is probably silly questions that anyone should know, but I don't
so I am asking those that do know....YOU folks.

I know the slower the better when drilling stainless and been told to put on lots of pressure.

But what is considered lots of pressure ??? I have an Elliott progress 1bench drill and will be
drilling stainless propeller hubs.
these are around 6mm thick and will eventually be needing 3/8th and 1/2 inch holes for prop venting.

So what I need to know is, just how much pressure should I put on the levers to pull down the chuck etc.
is it a case of a bit of pressure or a case of pull it as hard as I can ?
I don't want to bust the drill etc.
ive never used bench drill before this weekend, so this is all new to me. especially the stainless drilling.

ive have a few good drill bits and keep them very sharp.

I will be drilling at around 320 rpm with 1/4 bit after I get through with a 1/8 pilot hole, then 6mm and finnish with a 10mm before
testing to see if I need to go to 12 or 13 mm .

picture below
this shows vent holes already drilled on this prop, this is the same as I want to drill.

phill

 

[mechman]

You shouldn't need much pressure if your drill bits are sharp enough, Take it easy at first if it cuts then that's all you need, also use a cutting fluid.

 

[phill d]

thanks for the info, ill take it easy and see what happens.
can I use condensed milk for the cutting fluid on stainless steel ? ive used before on steel and hard alloys.


phill

 

[Paul.]

can I use condensed milk for the cutting fluid on stainless steel

Buy yourself some Rocol RTD, it comes in a paste and a fluid, I prefer the fluid, the trick with drilling stainless in to apply enough pressure too keep the tool cutting but without making it labour, there is a bit of a knack too it.

Condensed milk indeed, got to be the first time I've heard that one, put it in a sandwich much more fun.

 

[hotrodder]

Don't step up drill sizes in small increments. While we're all guilty of this (especially with hand drills) twist drills are designed to make holes, not enlarge them a little bit... http://www.fairburyfastener.com/db_warning.htm

As said the issue with stainless* is you need to keep the drill cutting, let it rub and the material work hardens very quickly and ruins your day

* the austenitic (non magnetic) grades especially but a prop could also be other flavours too

 

[phill d]

I have seen condensed milk used in lots of machine shops in the past for drilling fluid.
its nothing new that's for sure.

just noticed a thread already on this forum and exactly what I was looking for ,
http://www.mig-welding.co.uk/forum/threads/drilling-10mm-holes-in-6mm-stainless.5582/page-2

 

[phill d]

Chinese cobalt drill bits
do you mean Chinese cobalt coloured drill bits


phill

 

[ukracer]

I bought some cobalt bits from ebay from a chinese seller...very very good...and extremely cheap also...
Want the link?

Are you joking or serious. Text lacks contextual or facial expression...lol

 

[scott0031]

Well i have to say i have a feeling this will not end well for you. Call me a bit old fashioned but being a machine shop guy I have a nasty feeling about this.

Reasons:

1) ive never used bench drill before this weekend, so this is all new to me.
2) especially the stainless drilling.
3) very expensive looking prop you probably do not want to damage.( I hope it yours to damage)
4) Non flat surface you are trying to drill, The drill breaking out the back face will most likely turn it into a kite unless you have a proper vice and clamps for said vice so you have a nice ridged set up. ( Applies to the larger drills you are talking about more than the pilots)
5)Things like props are generally nasty variety of stainless and parts subject to mechanical load can toughen up considerably tougher than new stock material of the same grade, and are a son of female dog even for the experienced to machine ( A thread on here about a prop shaft a few days ago is evidence) and i can verify what they say is true about it being tough as nails to machine even compared to 316.
6) Rpm a bit to fast to be safe if you need to go to 12 or 13 mm. especially for someone who does not know stainless
7) Your Pillar is broken and you do not have the lowest rpm available to you!


This a bad thing to learn to drill stainless on, get some off cuts of 316 from someone and drill holes for a few sessions. Initial pilot to small, small drills can load up with torque on materials that are resistant to machining, that torque is then released and the process repeats(or the drill breaks) This is what gives you horrible screeching when drilling some stainless steels. If its not necessary to use a 3 mm drill then don't. Use a 4 or 5 they can resit the torque much better.

Best advice for fluid is neat cutting oil. All will work to varying degrees but operator input is the most important fact with nasty stainless steels.



Kind regards,


Scott

 

[Rocketman]

Scott if it is the curved face and he wants to do a good job he should spot face it with a slot drill first.

As for drill speeds
http://www.chipblaster.com/drilling-stainless-steel

 

[phill d]

yes I know I have broken pulley wheel and this will be rectified. but not exactly going to drill without the pulley wheel on the machine am I ?.
the prop I am drilling is not the one in picture that is an example of vent holes, (pretty obvious realy as its already drilled ).

most stainless props are made from made from 316L stainless for use in the marine environment. if its not 316l it shouldn't be on a boat.
only the real cheap crap props are made of a mish mash of stainless and are painted, not polished finnish.

This is not my first time drilling stainless steel, but first time drilling it with bench drill.

I have drilled stainless in the past with normal (heavy duty) hand held power drills with holes up to 1/2 inch. that was flat plate 1/4 inch thick.
slowest speed I had available for that was 700rpm, and to be honest was not too bad. only drilled 4 of those before drill needed to be sharpened up again.
I found that best to keep stopping and starting to let the drill bit cool down.

I know what you mean about trying to get the prop in some sort of vice, that's very difficult job with a prop, due to blades not giving much of a hub to secure.
all taken in and thought about.
340 rpms is going to be the slowest I can get my drill to use, that has to be slow enough as no other option apart from portable Ryobi drill, don't fancy that.

I will give cutting fluid a try out and see if it beats the milk on a piece of scrap stainless plate I have hanging around.


phill

 

[phill d]

if by spot face you mean a semi pilot hole, I do that already. not all the way through I use it just as a start for the main drill bit. if that makes sense

phill

 

[langy]

I drill stainless all the time and firstly don't centre punch, it hardens the surface, then you want to use Dormer A002 split point drills and either Rocol or CT90 fluid, just enough pressure to keep drill cutting and it will easy.
If you do it this way it won't be any different to drilling mild steel

 

[gordon stephenson]

Still scratching my head Re; condensed milk for cutting fluid.Anybody else, never seen this despite 50years in heavy industry?

 

[phill d]

amazing what you can learn, no matter how long you have been in a certain industry.


phill

 

[ukracer]

How does this compare to rocol RD??

http://www.lubetechshop.co.uk/product_info.php?cPath=25_52&products_id=236

Any one using it?? Rocol is like buying gold...lol

 

[Rocketman]

Still scratching my head Re; condensed milk for cutting fluid.Anybody else, never seen this despite 50years in heavy industry?

I agree. It's bad enough coolants going off in a machine shop/toolroom the last thing you want around is food stuffs that go bad over night.

 

[MattF]

amazing what you can learn, no matter how long you have been in a certain industry.


phill

I'm guessing you may be the only one who has heard that one. I've seen various food related substances, (usually cooking fat based), and other quirky stuff mentioned for cutting operations over the years, but never once has any form of milk seen mention. Are you sure you're not just seeing a white milk like fluid and assuming?

 

[Rocketman]

Well if you want to drill into something very hard you would use a solid carbide drill. You would only want to use it on a very ridge machine though with the part being drilled held by a strong vice.

 

[Rocketman]

if by spot face you mean a semi pilot hole, I do that already. not all the way through I use it just as a start for the main drill bit. if that makes sense

phill

Yeah using something like a slot drill to start on a curved/angled surface it takes away the curve surface. Plunge it a couple of mil and then change to the drill bit. You can use the same size slot drill as the drill bit. Sounds like that is what you are doing anyway.