Tips on V-carving metal...

[jeffreymcgrew]

Hey everyone. We're trying to mill some trophy brass and aluminum to make some small signs and whatnot. We're trying to v-carve these, and have run into a few issues, and I was hoping for some tips of how we can do this better...

First off, what bits do y'all use when v-carving metal? We've used the Amana solid carbide 60 and 90 degree bits, and it works, but the tip of them goes dull very quickly it seems, which then turns the lettering muddy. Is this just par for the course, and we'll just need to replace these bits quickly when doing metals?

We tried a nice 'Engraving' bit made for metal work from Onsrud, a 60 degree single-flute with a very very sharp tip. And that tip snapped right off on the second plunge. Ack. I've got a spare, but I don't want to break it too. We were running it at 1.333 ips cutting, with a plunge of 0.6, at 13K rpm. While it's obvious that I need to take slower and shallower passes, can anyone chime in on what they use for plunge and stepdown?

Thanks everyone!

[Brady Watson]

what bits do y'all use when v-carving metal? - A 90° Drill/Mill works well & is always exactly 0.500" in diameter. Try to get one with a coating on it...and test your zzero plate if you get the coating. Sometimes it acts as insulation & the zzero routine won't work.

As far as speeds go, I would reduce the speed to 1.0,0.4 and use a shallower stepdown. Set your safeZ height low to reduce Z travel times. V-bits do not really cut in the center of the Vee. Use air cooling to reduce the smearing effect, AND the grade of Aluminum makes a big difference on machinability. Some alloys are harder/denser and these reduce smearing/melting of the AL when it is heated up during cutting. The idea here is to keep the tool moving at all times, reduce Z position positional loss by reducing Z speed and blow 20 psi of compressed air on the bit while cutting to keep things cool. Lubricant or liquid coolant is not necessary or advised since it wicks into your spoilboard.

-B

[jeffreymcgrew]

Thanks for the tips Brady (as always!). Just two more questions:

You talk a lot about using endmills and drill/mills. So far we've just used router bits from Amana and Onsrud. What are some good suppliers for mills?

As for the air, yeah, we really need to get a better air setup. Are you using a special nozzle or cold air gun, or just an adjustable hose to direct the air into the cut?

[Brady Watson]

Jeff,
I buy all of my end mills from Oberg Brothers in Maple Shade, NJ. Just google them & give them a ring. If you can, get coated whenever possible. The coatings really help to keep the tool cool.

As far as the cooling goes...I just slapped something together using a hacked apart Husky (HD) blow gun kit, it's football inflator needle (taped off safety hole) and some brass fittings. All of which is secured via a plywood disc that fits on my spindle and a hose clamp. You can see details here: www.bradywatson.com/Aluminum.htm (http://www.bradywatson.com/Aluminum.htm) I have found that holding a blowgun on the cut is completely inadequate...and not exactly safe either. The forced air REALLY makes a big difference. If you want to get really craft, take this setup & add a reservoir filled with 50/50 water & isopropyl alky...then just have it feed into the air line. You should not see a fog when you do this...and temps get really down there! (Remember from science class - Evaportation is a cooling process)

I used 20-25 psi blowing right on the bit with great success...and the compressor cycled once every 8 minutes.

-B

[jeffreymcgrew]

Brady thanks. I was just about to go and order some fancy coolant parts from McMaster-Carr and your way looks way cheaper. Heck I think I have an old basketball inflater somewhere. We've got a fairly big compressor, so I'm thinking it should be fine.

As for the coatings, yeah, we've cut some 6160 in the past using a liquid coolant (spraybottle of water and soap) and some coated Onsrud upcut bits. Worked great. Didn't know you can order endmills coated or not, but it seems obvious now. Thanks for the tips!

(p.s. I wish you sometimes had some Revit and/or building code questions I could help out with to return the help you've send our way!)

[Brady Watson]

Jeff,
Glad it worked out. Just so you know, you'll need the football inflator to NPT thread adapter that comes in the Husky kit, as I am not certain that the fb inflator is NPT thread. It *could be*...so keep this in mind as you build your deal. If it is, it may be difficult to find fittings that small locally.

Don't ever worry about giving back 1:1...what goes around comes around, so if you help someone else out with your knowledge, the favor is returned.

-B