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Subject line says it all, really.

What's the consensus on the usefulness of coated bits for machining wood? I was pondering getting at least one big mill (3" cut, 1/2" or 5/8" diameter) with a coating (TiN or TiCN) for milling full depth MDF building molds, but I can't really find any data on whether it's worth the additional expense. Anyone have some words of wisdom to share? Are coated mills worth the upcharge for carving the woods I'll likely be using most (maples, mahogany, some walnut, rosewoods and spruce)? Or should I just get simple, uncoated bits?

I use HSS without any issue. I know some guys are believers in carbide...I just cant bring myself to fork out that much money.. (c:

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http://www.PeakeGuitars.com

Carbide's cheap if you shop in the right places and consider the added life. $16-20 for a 1/2" cutter is really too much?

I wouldn't bother with coatings for woodwork unless you were doing something really serious like only doing production milling in ebony or some other abrasive wood with that cutter. I don't use coatings on any of my wood-cutting mills unless it so happens that the mill I want to use has a coating because I'd bought it for something else. Bright cutters can be a bit sharper, as well.

So far as the long flute length goes, just don't do it. I wouldn't have a 3" flute length on anything under a 3/4" cutter, and a 4" flute length on anything under 1". Those are minimums, in carbide...the long-flute-length 1/2" cutters I've used have been money in the fire! Get a long cutter with a short flute length (I've used 1.5" x 6" 1/2" cutters) and only leave as much shank outside the collet as you need.

(Note: you might be able to get by in soft materials, like MDF and some plastics, with more flute than I suggest but IMO you'd be better off using two passes with less flute and you'll get a better finish. >4x diameter flute length is something for foam cutting only in my book)

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

My experience with TiN coatings has only been on drill bits. I didn't notice any improvement.

I toured a Hitachi plant recently and they were talking about their carbide costs being $50/hr for this particular work cell which was two machines (one with four heads). Their cutters were not coated that I could see.

My point being that the coatings probably only make sense if you're doing huge volumes in metal where getting a few extra minutes of service life makes a big difference.

I've had no luck with HSS and MDF, they seem to dull and burn really fast. What's your secret Parser?

Thanks for the info, plenty of food for thought there.

the biggest diameter shank I"ll be able to run is 5/8", so I think I'll stick to 1-2" of cut length, max (knowing I'll probably only use half that at any one pass).

Where do you get your carbide Bob (if you don't mind my asking!)?

I don't run production off of my machine...just onesies and twosies for my own builds mainly...so I don't spend much at all on tooling. I wouldn't mind trying some carbide cutters though.

Thanks,
Trev

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http://www.PeakeGuitars.com

See my previous 'favourite tool suppliers' thread from a couple days ago - plenty of interesting links and the like. And there's always eBay.

I can vouch for the coated bits as long as it is going to be in material that is real abrasive. I used to cut a laminated gunstock material with a waterproof glue that was death on tool steel. In my opinion the tool steel gave a much better cut while it lasted, but it only lasted about 20% the life of the coated bits.

In natural woods I stick with tool steel when I have them lying around.

Mike

Depending on what they're cutting, it's believable. Big cuts in stainless will eat up inserts fast, titanium eats cutters like it's got a hollow leg, and glass-filled composites (G10...grr!) really cook cutters fast. Running 5+ heads it doesn't need to be much of a performance increase to justify spending $XX extra on carbide in exchange for speed.



The cheapest place is USA Carbide. Best prices and worst service I know of, but it's an online shop so if you can get their order form to work you're golden. They tend to grind sharp, which is good for wood. I think there's a quality difference between their stuff and someplace like OSG, but I don't think it would ever show unless you were really stressing the cutters (milling fast in aluminum, doing full-on production work on industrial machines).

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Bob have you ever notice some of the less expensive, (and I use it) tooling sometimes have one flute just a little different that then other and you get a somwhat cupped cut? If so, do you have a solution for that?

Mike

I haven't experienced that. I'm talking about fine cutting edge geometry differences when I talk 'quality', something like being out of cylinder is a whole other level of craptitude

IME, there's definitely a price point where the amount you save at the till costs you more at the mill.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services