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Working with Stainless Steel

nz Offline Syncop8r

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Working with Stainless Steel
on: June 15, 2018, 09:11:57 AM
My first question regarding working with stainless steel is what do you use to drill holes into it?  :think:
Some of you have mentioned carbide bits in other threads. The only ones I could find at my local hardware store was a 3-pack of 5,6 and 8mm diameter bits.
Is anyone able to elaborate more on what exactly they use? Perhaps post a link? :pok:


wales Offline hiraethus

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Re: Working with Stainless Steel
Reply #1 on: June 15, 2018, 09:38:21 AM
There are two issues when drilling stainless - first is that it work hardens, so if you just tickle the surface you'll soon find that the drill no longer bites, you get a lot of smoke then you blunt your tools.  The second is that when modding you're often drilling material that's already been hardened - and the same thing happens.

You can get away with good quality HSS bits, the correct speed, lubrication and a firm hand (oo-er :o) but cobalt or carbide bits make things easier.  The ones at the hardware store are probably masonry bits.  I can't remember where I got mine, but they're something like this: https://www.amazon.co.uk/12692530-Quality-Carbide-Milling-Tools/dp/B00K1ZFD06.  I've also used Dremel tile bits: https://www.amazon.co.uk/Dremel-Tile-Spiral-Cutting-Bit/dp/B0002SMMZQ  I've also seen that PTRSAK uses PCB drills - PCBs are very abrasive, so carbide tools last longer.  These can be had cheaply on eBay.

They're very brittle, so any side load or if the bit gets stuck they'll snap.  A pillar drill and proper workholding makes this less likely, but you should still expect to break some.


nz Offline Syncop8r

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Re: Working with Stainless Steel
Reply #2 on: June 15, 2018, 10:05:05 AM
Thanks!  :salute:

I shall look for something similar closer to home....


no Offline Vidar

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Re: Working with Stainless Steel
Reply #3 on: June 15, 2018, 10:06:37 AM
What hiraethus said :)

I think the most common issue is that people tend to use too little pressure and or use too high drill rotation speed. The mechanical action will work harden the steel so you basically need to make sure every new rotation cuts deep enough to go below what was work hardened from the last round. Too little pressure or too high rotation speed will make that hard to achieve.

A drill press or mill really helps a lot - and will give you much more life from your drill bits. (I once tried making some holes in regular 10mm mild steel plate. Handheld I was able to do 11 holes before the drill bit was uselessly sharp. A milling center did several hundred holes with an identical drill bit in comparison. Steady direction, speed and good pressure does help).

Edit: As for the drill bits I've used both normal HSS and massive tungsten carbide ones. The latter makes short work of stainless and makes very precise round holes. But the prices are high, and I don't imagine them working all that well with hand held. The HSS ones with tungsten tips brazed on might be worth a try - I haven't tried :)
« Last Edit: June 15, 2018, 10:13:05 AM by Vidar »
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mc Offline Gerhard Gerber

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Re: Working with Stainless Steel
Reply #4 on: June 15, 2018, 10:34:34 AM
We destroyed a very expensive HSS end mill on my buddy's milling machine trying to drill a Spydie hole on AUS8A Cold steel blade.....

I drove to the hardware store, bought a masonry bit for next to nothing, quick tweak of the cutting edge on a bench grinder  and it went through that blade like butter....



mc Offline Gerhard Gerber

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Re: Working with Stainless Steel
Reply #5 on: June 15, 2018, 10:40:34 AM




no Offline Vidar

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Re: Working with Stainless Steel
Reply #8 on: June 15, 2018, 12:21:49 PM
If you are handheld I'd be sceptical about massive carbide bits, especially at those sizes. They are prone to breaking, and thus you might just end up placing some even harder material where you actually want a hole :D

135 angle tip is better for hard stuff than the standard 118. That is supposedly a quick rule of thumb, and pretty much all I remember about that. :facepalm: (The reasons being something to do with edge cutting lengths, relief angles, swarf thickness, reduced pressure requirements and what not).

If you don't have a drill press I will press that it does indeed make wonders when it comes to drilling in metal. If you can find it I think a good option might be carbide tipped HSS drill bits made for steel. They should the right geometry, be hard where it counts and tough where that counts. (Some of these might be straight fluted instead of spiraling).

Not sure if you are just doing stainless (and if so what kind) and if it has been hardened already. Given a mystery piece that might be hardened I would go along the lines of (something) carbide in a drill press, and something HSS carbide tipped if handheld. If specially made for steel then all the better.'

Edit: There are plenty of drill bits for these purposes, so if you happen to have some industrial tool supplier nearby they should be able to get you the right stuff. As opposed to say the general hardware store around the corner.
« Last Edit: June 15, 2018, 12:25:48 PM by Vidar »
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us Offline chrono

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Re: Working with Stainless Steel
Reply #9 on: June 15, 2018, 01:19:22 PM
If you use standard 118-degree drill bits, you need to center drill first, regardless of materials. This keeps the drill from walking. Those 135-, 140, 150-degree drills are self-centered by design, and do not need a spotted hole. Carbide drills tends to hold size better. Solid carbide drills are expensive though. If I need some drills for personal use, I will look up eBay first.

Yeah, I hate drilling stainless  :twak:


us Offline SteveC

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Re: Working with Stainless Steel
Reply #10 on: June 15, 2018, 01:28:44 PM
Tile/Glass drill bits work very well.


nz Offline Syncop8r

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Re: Working with Stainless Steel
Reply #11 on: June 15, 2018, 01:39:08 PM
The tile/glass ones I have seen only go down to Ø3mm - I may need to do some smaller holes.

Any comment on the cobalt ones I linked to earlier? https://www.georgehenry.co.nz/shop/Cutting+Tools/Drills/Evacut+Cobalt+Drill+Prepack+Metric.html

"The Evacut Cobalt Jobber Drill bits are an industrial quality accessory for drilling stainless steel and other tough materials.

Features include:
    Made with high speed steel
    Cobalt alloyed to improve abrasive and heat resistance, for increased strength at higher drilling temperatures
    135° split point enables accurate positioning and less drilling pressure"


no Offline Vidar

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Re: Working with Stainless Steel
Reply #12 on: June 15, 2018, 02:02:36 PM
Any comment on the cobalt ones I linked to earlier? https://www.georgehenry.co.nz/shop/Cutting+Tools/Drills/Evacut+Cobalt+Drill+Prepack+Metric.html
"The Evacut Cobalt Jobber Drill bits are an industrial quality accessory for drilling stainless steel and other tough materials.

WIth a drill press and not hardened steel I believe that would work just fine. Likely even hand held with good pressure and slow speed. If it is hardened material though I would have doubts. Anything you can do to check that?

If you use standard 118-degree drill bits, you need to center drill first, regardless of materials. This keeps the drill from walking.

A bit of a blanket statement as there is much more to that than just the drill angle. The point is certainly fair enough though.

If the holes intended by the OP are to be made in thin material it does bring up the possibility of finding a carbide spot or center drill that happens to have the right diameter. Those are very tough and rigid by design, but often comes with somewhat off diameters.




« Last Edit: June 15, 2018, 02:09:46 PM by Vidar »
"Simple is hard"
"Hard is hard too"
(Partial disclosure: I design tools for a living).


nz Offline Syncop8r

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Re: Working with Stainless Steel
Reply #13 on: June 15, 2018, 02:30:36 PM
If it is hardened material though I would have doubts. Anything you can do to check that?
I guess any multitool I drill into will be hardened?  :think:


no Offline Vidar

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Re: Working with Stainless Steel
Reply #14 on: June 15, 2018, 02:58:59 PM
If it is hardened material though I would have doubts. Anything you can do to check that?
I guess any multitool I drill into will be hardened?  :think:

Looking at some Chinese ones I'm pretty sure not :D

Some seem to use 3xx series stainless which basically cannot be hardened except for work hardening. (If it isn't magnetic, and becomes slightly magnetic if you hammer it a bit, that might be what you have). With proper pressure and speed to avoid the work hardening issue 3xx is fairly agreeable. (If you make swarfs instead of tiny bits or grit you're probably doing ok).

I believe others like Leatherman uses 4xx series which is most likely hardened. But there are various degress of that. A file will likely be made very hard (but on the brittle side), a knife will aim for the hard side but still tough enough to not break, while things like handles and bottle openers likely leans to the tough rather than the hard side. Screwdrivers might be hardened just at the tip, cutters mostly at the edge, and so on. Do the things you want to make holes in functionally prioritize being hard or tough?

If you are not drilling into a file then carbide in a rigid setup should do the job - it might even then. With HSS I usually try to avoid real hard stuff, but if handheld I would avoid carbide so I might just try sacrifice a drill bit in an possibly vain effort anyway. HSS with carbide tips seem to make sense for that but I haven't tried myself.

If nothing else works buy some small grinding drill bits and plenty of speed and patience - they work hard or not. (Edit: Not really for handheld).

« Last Edit: June 15, 2018, 03:32:59 PM by Vidar »
"Simple is hard"
"Hard is hard too"
(Partial disclosure: I design tools for a living).


nz Offline Syncop8r

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Re: Working with Stainless Steel
Reply #15 on: June 15, 2018, 10:15:28 PM
I appreciate all the replies.  :cheers:

So, in summary the choices are:
- Carbide-tipped bits (used for masonry)
- Cobalt-alloyed bits (used for SS)
- Tile/glass bits

I want to use them on a variety of things...
I guess I should get imperial sizes for any Leatherman pivots.
« Last Edit: June 15, 2018, 10:17:45 PM by Syncop8r »


no Offline Vidar

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Re: Working with Stainless Steel
Reply #16 on: June 16, 2018, 12:54:01 AM
Chances are the cobalt ones will work just fine. Use plenty of cooling so they keep their edge longer.

A drill press or similar contraption to add controlled direction and pressure will make it a lot easier.

"Simple is hard"
"Hard is hard too"
(Partial disclosure: I design tools for a living).


 

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