Drilling stainless steel

[raro3]

I took advice from my previous posting on the forum and decided to upgrade the bolts securing my chainplates from 6mm to 10mm. This requires me to drill out a total of 18 10mm holes through the chainplate and backing plate which have a combined width of around 8mm. Can anyone recommend a suitable drill bit? I've already got through half a dozen titanium ones from B&Q, and am not yet half-way there.

 

[Talbot]

I suspect you are drilling too quickly. For good quality drill bits I would not purchase from B&Q. Suggest you buy a pack of Irwin 10mm bits from http://www.screwfix.com/app/sfd/cat/cat.jsp?ts=66556&id=100181

 

[ccscott49]

Slow speed, cutting oil/grease, higher weight, best in a drill press, agree with the other poster, not B&Q drills and they are not titanium! You relly need good tool steel drills, HSS or similar, wheres Cliff when you need him!!

 

[boatbuilder]

Use a pillar drill anything else is too fast and the metal wokhardenc. Slow speed even pressure sharp bit and plenty of cutting fluid.

 

[boatbuilder]

Snap!!

 

[AIDY]

also are you cooling the tip down while you are cutting using oil, or even a squirt of WD40 helps as you cut, if you dont have any cutting fluid.

If you are cutting a big hole how about a few pilot holes to start with. Pillar drill will be ideal if you can use one varing the pressure and depth of cut.

best of luck

 

[tcm]

But re HSS on s/s

You should try to avoid leaving carbon deposits on stainless whcih will happen if you use HSS . or if absolutely must use Hss best the grind/ream hole with non-carbon tool aftrwards.

You often see bits of s/s which have been hacksawed - and rust appearing at the cut - it is due to the contamination of the s/s by the high carbon steel tool being left behind raher thanbeing ground off.

 

[savageseadog]

use a cobalt tipped drill and drill dead slow use a synthetic motor oil as a cheap cutting fluid

 

[ccscott49]

Re: But re HSS on s/s

Do they make stainless drills?

 

[Sinbad2222]

It's easy if you:
1 Punch a dent first
2 Use a cobalt steel drill
3 Use lots of pressure
4 Use a very slow speed - never high as you will harden the piece and never be able to drill there again
5 Get someone to spray cutting fluid as youu drill
(Cobalt bits and cutting aerosol fom Screwfix)

 

[spynappels]

Will agree with the use of HSCo (Cobalt) drill bits rather than HSS. If you cannot get the work into a drill press, consider using a stepped dril or else drilling out to 8mm first and then to 10mm. And use plenty of cutting oil and very slow drill speed.

Stefan

 

[sailorman]

Sharp and Slow + coolant

 

[Norman_E]

Re: But re HSS on s/s

No. Stainless steel is tough, rather than hard, so you drill it with ordinary HSS drills. The first problem is most power drills are simply far too fast, and if they have electronic speed control they lose power at slow speeds. The second problem is that if the drill is allowed to rub rather than cut they stainless will quickly work harden, so sharp drills and plenty of pressure are required. An old fashioned "gut buster" hand drill will do the job if you cannot get the part under a nice slow pillar drill. You can even use a carpenters brace if you grind the drill shank square to fit it. For hand drilling try to get a paste cutting lubricant like Trefolex. So called "Titanium" drills are more accurately called "TiN coated drills", as they have a thin gold coloured coating of Titanium Nitride, which is hard, but is soon worn off the cutting edge, and lost completely when you re-grind the drill to sharpen it.

 

[Strathglass]

As Spynapples has said. With a few extra comments.

Cobalt drills, very low speed, do it in steps ( even 7,8,9 then 10 ).

You are working at quite a disadvantaged position.
I have managed to use my bench vertical drill on it's side in similar situations.

If your hand drill will only run too fast then trigger it manually off and on. Don't let it get anywhere near it's normal running speed.

Plenty of lubrication, But watch the mess you can make of your decks. Cover them well.

If any smoke starts coming from a drill bit then stop immediately. Let the job cool down and also change to a new drill bit.

It's not too dificult with sharp drill bits and some preparation.

Iain

 

[reeac]

A man with lots of experience with S/S told me to make sure that swarf was coming off all the time that you're drilling - if it's not then you will blunt the drill almost instantly.

 

[Avocet]

Agree - Keep it cutting at all costs. He who hesitates is lost! (well, stuck with a blunt drill bit anyway!)

I've had good results with Screwfix Cobalt drills. Getting the speed down and the torque up is the key though. Almost impossible with an electric hand drill.

 

[William_H]

Yes you would be better off investing in a cheap drill press (pillar drill) than buying more drill bits. Yes if you are not getting swarf cut out then press harder or sharpen the drill. Stop often to let it cool. Use any oil for lubrication when the oil smokes it is time to stop cos it is too hot. No I am not a fan of cutting pilot holes first.

You can sharpen your drill bits quite easily. Especially big bits like 10mm. Just look hard at a reasonable bit You will see the cutting angle and the edge that has worn round. Use a powered stone or even aknife sharfening stone. Don't take too much material off and don't let it get hot if using a powered stone. A little grind then look try not to lose the shape of the tip. Give it a try.

 

[cliff]

[ QUOTE ]
You really need good tool steel drills, HSS or similar, where's Cliff when you need him!!

[/ QUOTE ]
Here!

Well having read the posts above I am shocked at some of the replies, I expected better from such esteemed forumites, guess it must be the weather.

O.K. here we go... Drilling Stainless steel....
Sharp good quality drills NOT "B&Q" specials and stay away from the TiN (the gold coloured ones)drills - waste of money. Go for a good HHS or Co drill. Better yet BC drills if you can get them, failing that WC.

As for cutting oils do not use "any old oil" and wait until it smokes - the damage is done by then - use a proper EP cutting/tapping oil/emulsion and keep the drill bit flooded with the solution.

A press drill is advantageous if you can get the piece into one but failing that a slow speed hand drill and lots of pressure. The main things are relatively slow speed and comparitively high pressure and sharp drill bit(s) oh yes and proper cutting oil/coolant.

Unless you are very skilled do not try regrinding a drill by hand or even using one of these £9.99 drill guides - you might get away with it on carbon steel but not on stainless steel. The cutting and clearance angles are critical for obtaining a good cut on stainless.

As a point of interest, if you have access to a sharpening machine, increasing the standard 118° angle to 138° or 140° helps but not worth the trouble if only drilling a few holes.
--------------------

"Artificial intelligence is no match for natural stupidity"
sailroom <span style="color:red">The place to auction your previously loved boatie bits</span>

 

[john_morris_uk]

[ QUOTE ]
Unless you are very skilled do not try regrinding a drill by hand or even using one of these £9.99 drill guides - you might get away with it on carbon steel but not on stainless steel. The cutting and clearance angles are critical for obtaining a good cut on stainless.

As a point of interest, if you have access to a sharpening machine, increasing the standard 118° angle to 138° or 140° helps but not worth the trouble if only drilling a few holes.


[/ QUOTE ] I did read William's thoughts with a slight foreboding as to what he was suggesting as 'easy'. I remember reading a whole book on the subject of drill bit shapes, angles and sharpening over thirty years ago which made me realise how critical the whole business is. I also remember trying to rescue some of my own
fathers attempts at drill bit sharpening. I also decided that one book thirty years ago was not an excuse to question William's normally sound advice. I am also aware that lots of people read these forums and apply the advice to their situation, so there is a moral imperative to be accurate in what you say.

FWIW I use Cobalt drills and a drill press, and oil as necessary and have never had a problem drilling stainless. However I also admit that if I have lots of holes, I take it into a friendly machine shop where the holes are punched rather than drilled.

 

[cliff]

[ QUOTE ]
FWIW I use Cobalt drills and a drill press, and <u>oil</u> as necessary and have never had a problem drilling stainless. However I also admit that if I have lots of holes, I take it into a friendly machine shop where the holes are punched rather than drilled.

[/ QUOTE ]But not "any old oil" I hope /forums/images/graemlins/grin.gif
As a point of interest, for any who are interested, one technically does not need cutting oil with properly sharpened Cobalt drill bits but a little of the correct oil/coolant does not hurt. (SBC bits can run red hot without loosing their edge although running them that hot is not recommended)
--------------------

"Artificial intelligence is no match for natural stupidity"
sailroom <span style="color:red">The place to auction your previously loved boatie bits</span>