- Thread starter brendan h
- Start date
Bear in mind this is M3 tap with 2.5mm hole. Yep it was with my cheap and nasty cordless on lowest torque.
M5 and above no problem but would then use the Dewalt.
If in either of the millers i would drill then tap before moving the job, quick release chuck handy.
M5 and above no problem but would then use the Dewalt.
If in either of the millers i would drill then tap before moving the job, quick release chuck handy.
Late in on this one - only just joined ...
I find the secret when drilling big holes in stainless is to work up with increasing size drills - say, 4, 8 then 10mm. If you sharpen your own HSS drills, then increase the rake angle slightly, to help the drill dig-in to the soft metal. Start the drill with the bit in contact with the work-piece, press down reasonably hard at the slowest possible speed - and finally, use condensed milk as a lubricant. Grease would do the same job, but c/milk can be washed off afterwards so is nice and clean to use. A thick lube helps to prevent the formation of chromium oxides which form a bl##dy hard skin on the surface.
Was given the condensed milk tip when I worked in a Kodak factory, where lots of stainless fabrication took place.
Colin
I find the secret when drilling big holes in stainless is to work up with increasing size drills - say, 4, 8 then 10mm. If you sharpen your own HSS drills, then increase the rake angle slightly, to help the drill dig-in to the soft metal. Start the drill with the bit in contact with the work-piece, press down reasonably hard at the slowest possible speed - and finally, use condensed milk as a lubricant. Grease would do the same job, but c/milk can be washed off afterwards so is nice and clean to use. A thick lube helps to prevent the formation of chromium oxides which form a bl##dy hard skin on the surface.
Was given the condensed milk tip when I worked in a Kodak factory, where lots of stainless fabrication took place.
Colin
Weldingartisan
Aiming for retirement
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Condensed milk!!! What do use for tapping lubricant - Marmite? I bet the bugs and beasties love your workshop!
Don't you find increasing the rake tends to make the drill snatch? I use a water based cutting fluid which is much better for disapating the heat with stainless being such a poor conductor. W/A
Don't you find increasing the rake tends to make the drill snatch? I use a water based cutting fluid which is much better for disapating the heat with stainless being such a poor conductor. W/A
I was equally skeptical until I watched a guy using it. Then I reckoned if it was good enough for guys who worked with stainless every day at Kodak - then it was good enough for me.
That was 20 years ago, and I still use condensed milk for drilling (and tapping) stainless.
When drilling big holes in mild steel with a puny 250W pillar drill (which is all I own) I usually drill a pilot hole, then smear grease into the bottom of that hole then fill the hole up with oil - so from then on I'm drilling into a micro oil bath. HSS bits last for ages that way. If I had a kosher workshop with a proper lube pump, then I'd probably do what you do - but with my primitive setup, it's necessary to be inventive. <G>
Re: the increased rake - no snatch as such - when working up through drill sizes, I find the drill cuts into the s/s like a knife through butter, producing a continuous helix of swarf - with very modest amounts of heat. Bit like you'd expect from cutting in a lathe ...
Certainly no 'bluing' of the work-piece (and drill bit !), which is what I was experiencing when trying to drill stainless with HSS bits before.
Colin
Just done a quick Google - seems that the condensed milk trick has been around for a while ...
http://www.chaski.org/homemachinist/viewtopic.php?t=61064&sid=c7a64ead5ceca876900ab0a45cad6aa8
"get some condensed milk. it works wonders on drilling stainless. trust me you will be amazed."
http://www.plowsite.com/archive/index.php/t-32249.html
"You do not need a plasma torch to cut this thickness of stainless, use a new (or nearly so), brand name, bi-metal hole-saw, use the SLOWEST drill speed you can get away with, and use sweetened condensed milk (Carnation, in a can) as a lubricant and cooling aide, (spray bottle)"
"My dad taught me that one, I always thought he learned it in the Navy, he was a welder, he passed away in June, so he took many tricks I hadn't learned yet with him."
Can't say I understand the reference to using a "spray bottle" with condensed milk though ... !
http://www.chaski.org/homemachinist/viewtopic.php?t=61064&sid=c7a64ead5ceca876900ab0a45cad6aa8
"get some condensed milk. it works wonders on drilling stainless. trust me you will be amazed."
http://www.plowsite.com/archive/index.php/t-32249.html
"You do not need a plasma torch to cut this thickness of stainless, use a new (or nearly so), brand name, bi-metal hole-saw, use the SLOWEST drill speed you can get away with, and use sweetened condensed milk (Carnation, in a can) as a lubricant and cooling aide, (spray bottle)"
"My dad taught me that one, I always thought he learned it in the Navy, he was a welder, he passed away in June, so he took many tricks I hadn't learned yet with him."
Can't say I understand the reference to using a "spray bottle" with condensed milk though ... !
