Cobalt drills

[Andi]

Anyone know if 8% cobalt drills would be over-the-top for pedalmaking? Too over-the-top?

Ta!

[ampman50]

Definitely over-the-top. I run an automatic screw machine and use cobalt drills in one position. I run about 15,000 parts before I have to change it. Over course it's a high speed production machine not you basement drill press. Price wise you better off using either bright or black oxide coated drill, there much cheaper. I've been building boxes for several years and use a Unibit (1/2" max dia), it works fine. I use a drop or two of oil to lubricate the drill so it last longer.

[Andi]

Ah - ta.

I have some TiN coated drills at the mo which are pretty good but still get aluminium stuck to them. I gave up on Unibits because they didn't offer the precise sizes I wanted - 2mm for LEDs, 2.5mm for switch locator tabs, 3mm for pot locator tabs and so on and so forth...

The 7mm bit is already clogging. I s'pose with the TiN ones I can just replace one at a time as I need to.

[R.G.]

Black oxide -> good for ferrous and brass related alloys
polished -> good for aluminum with tapping/cutting oil; the polished surface does not allow aluminum "gum" to stick like the oxide does
TiN -> good for hard materials like hard-ish steels, but less life than cobalt containing tool steels. Ti-N is a low temperature way of adding a hard surface layer on a tool. When the TiN layer wears off the cutting edge, you're back at where you started with the base metal of the drill. Can't be sharpened back to good as new because this grinds the TiN off the cutting edge
Cobalt -> actually, cobalt-alloy tool steels; very good for high speed work, and the original "high speed steel"; cobalt alloys were the original high speed steel and are actually softer than high-carbon tool steels, but they retain this hardness to quite high temperatures during cutting, so can be used for high speed (Doh!) production work. No advantage at low speeds.
Carbon steel tools: hardened and tempered steel with 1 to 1.5% carbon, which means they're a composite of iron and iron carbide. They are as hard as steels get, from the carbide; slightly harder than cobalt steels. But cutting friction can heat them and "temper" or soften the edges so they're soft and wear quickly. As good as anything else for low speed drilling in softer stuff (like aluminum). Black oxide and polished bits are often high carbon steel. If it's High Speed Steel, it will say "HSS", "Alloy", "cobalt steel" etc. Otherwise, it's high carbon steel. No serious maker of tools sells high carbon for industrial use anymore. They're only available for cheapest cost in drill sets for uneducated consumers.

[Andi]

Thanks RG - so polished with some cutting fluid is the way to go for Hammonds and such. That'll save me a chunk!

[R.G.]

Tap-A-Matic fluid is the standard.

[Andi]

Cheers. I shall have to have a look for that - is there a more generic name? I'm in the UK and we rarely get the fun stuff...

[R.G.]

Cheers. I shall have to have a look for that - is there a more generic name? I'm in the UK and we rarely get the fun stuff...

Oh, sorry. Yes, that's the USA trade name. Look in your telephone directory for a supplier of machine tool accessories and call them. Tell them you want aluminum (aluminium in the UK?) cutting fluid. That will get you the right stuff regardless of trade names. If it's horribly expensive, you've called the wrong place. We buy it in smalll containers with perhaps 4 to 8 fluid ounces in them, that being 120 to 240ml in metric places; should be the same in UK fluid ounces.

In a pinch, WD-40 will work, as will light machine oil. Both are much better than nothing, but not as good as the right stuff.

[Andi]

Fantastic - thanks again.

[Andi]

I found me some from RS (where I buy most of my enclosures). I think it was about £5 for half a litre which I'd think should last me quite a while.

[smallbearelec]

I had wanted to offer this material ever since I tried it based on R. G.'s suggestion. I have a bulk source for it, but the smallest available bottle was a pint. This is fine for a boutique, but too much for most hobbyists. So I started to research packaging, tested a bottle and various caps and seals, and cobbled together a filling station:



You can find it in the Stock List with the drills, SKU 2802 and 2802B.