Alloys used in tooling

[scar]

Hello all,

I was wondering if the most-experienced in metalwork on the forum could sort out the jargon that's always running around in my head about the kind of alloys used to make the tools we use - from the simple hacksaw blade to the most expensive milling cutter. Please note - all tooling refers to metalwork.

General purpose hacksaw blades are made from high carbon steel - now I've come across molybdenum blades.

Drill bits are mostly high speed steel - I also came across titanium coated high speed steel and now it's high speed steel alloyed with cobalt.

Hole cutters are mostly bi-metal. Now there are tungsten carbide ones.

HSS, molybdenum, bi-metal, bi-metal+cobalt, carbide, tungsten-carbide, titanium, ----the list is endless. The cutters of super alloys are becoming more and more expensive and you'd have to know what you're talking about to keep up with the times.

As a simple example, I bought titanium-coated drill bits for experimenting. The coating does make then a retain their sharpness slightly longer ...but in the long run I guess the initial cost isn't worthed cos they will dull up in the end and when you sharpen them, you also remove the titanium coating, --which leaves you with a regular HSS drill bit.

What do you normally use? What works best for you? Is what you buy really worthed the initial cost of the alloy? Of all the alloys above, which is the most cost effective one for a cutting tool? Do you understand the advantages (and dis-) of using an alloy compared to another? If you know, then please explain and share with me so I won't keep scratching me head at shops.

 

[fingers99]

Really depends on what you're doing.

For work in mild steel there's no reason to use anything better than HSS. Generally, the better the alloy you're working with/on, the better the alloy of the cutting tool needs to be.

 

[hotrodder]

Very generally, as hardness goes up so does brittleness i.e. a 'harder' tool will retain it's edge for longer/withstand more heat but it may be easier to break/chip teeth. Take hacksaw blades for example, a HSS blade is easier to snap than a bi-metal blade which retains the hard teeth while the back of the blade is a softer, tougher alloy. Another (potential) advantage of harder tooling is that cutting speeds can be increased. If the machinery isn't man enough (stiffness and power) then harder cutting tools can be a waste of time as you can't take advantage of the higher speeds/feeds possible

Drilling stainless is a common one that'll get a wide range of suggested tooling. Plain 'ol HSS works fine if technique is correct but they can be destroyed pretty easily if it isn't and the stainless is allowed to work harden. Cobalt drills give a larger margin for error or allow higher drilling speeds with the correct technique

Ti nitride coatings i don't really get myself. It's used to lower friction (and thus heat) but as you say it wears off/is lost when resharpening

Drill bits, hole saws, lathe tooling... a mix of HSS and cobalt for me but a decent brand makes a bigger difference than alloy imo. If my lathe was big/stiff enough i would have some carbide tooling

 

[snowcat]

theres no rights and wrongs on tooling just tooling that works, generally the top end expensive materials will give durability and faster work rates.....

Ti coated tooling TiN, Ticn, Tialn, or firex are cost affective ways of increasing work rates and increasing work rates, theres a paragraph in each, for there apps, but basically these can push work rates up to 100% above standard HSS.....most coated tooling is single use, ideal for milling cutters which are rarely re sharpened these days..

Don't get proper Ti, coated tooling mixed with rubbish often found at motor factors, you would be unlikely to get one drill for the cost of a set of a 100, found lurking at the counter, these offer poor performance/ value for money and IMHO are dangerous as they have a tendency to shatter......

HSS is fairly versatile and forgiving and fine for most free machining (jobber type work), its also easy to regrind and to change rake angles.... It will however soon mishape overheat and not chip cleanly if used on higher carbon content materials, Its also a PITA when used with work hardening materials as a slight loss of an edge makes the hole harden before its worked..

Cobalt is much more durable and can cope with higher speeds 10%+, Its far more cost affective when working with Harder than LCMS materials, as it holds its edges for much longer.....

Solid carbide is top end tooling, £150+ can be paid for a 1/2" drill, the biggest advantage is its ability to hold a constant shape, holes drilled with expensive carbide tooling rarely need reaming, but it will shatter if abused......

generally if your a lay person working at the weekends, the some good branded HSS tools will be the best investment, Dormer, Hertel Guhring etc.......

This is very general the subject has whole books written on it, and whatever tooling you use it should be used with the correct rake for the material, fed at the right speed and be driven at the correct RPM, £100s of tooling can become scrap in seconds with a bad operator.......

I personally favour indexable tooling (replaceable tipped) on and abusive apps, ie machining weld on the lathe, these will withstand far more abuse than any other tooling on the market

 

[Drains]

Always worth remembering that different tool materials like to work at different work rates - eg, don't use carbide tip tools on a lathe at the same speed as HSS (as I've seen people do), as carbide PREFERS a higher tip speed, and gives a better finish at at the higher speeds that burn out HSS. Run carbide slow, it's crap.

 

[Jay]

I can't be as technical as these guys but I drill holes on a bench drill or with a pistol/ twist drill from 3mm to 24mm in stainless and mild steel upto 25mm in thickness day in/ day out.
It started when the cheaper HSS drills were brought in instead of the Dormer etc ones, and the suppliers favoured the cheaper ones despite knowing that as the steel was bad in comparison most of the 'buyers' in steel shops don't understand that you largely 'get what you pay for'
I prefer to use cobalt drills where possible, hss-c, which our firm originally brought in for stainless work, as I find the tips stay sharper for at least twice as long as with a normal hss, the drill bit stays cooler, can run faster and is less prone to work harden the stainless steel.