cnc bits

Computer Numerical Control

cnc bits

Postby loyd » Sat Jun 29, 2019 11:04 am

CNC bits can be pretty pricey. Has anyone looked into bits like these? https://www.amazon.com/HQMaster-3-175mm-Cutting-2-Flute-Tungsten/dp/B074FSYYSR/ref=sr_1_6?keywords=cnc+ball+nose&qid=1561826919&s=gateway&sr=8-6

I look at the price of these and get befuddled. I spent $35 for a single 1/8" bull nose tapered bit from Think and Tinker and see other sources nearly as expensive and wonder what's going on here. Of course, these are tungsten steel and the others are solid carbide. The reviews are all over the place. Most reviews are 4 and 5 but there are a number of 1 and 2. The complaints center around tolerance ["the shank is OK but the actual cutting diameter isn't accurately as shown.]

I'm tempted to try these out since they're so cheap. I just purchased new 1/8 and 1/4 inch end mills. I have 5 or 6 old ones of each and hate to just keep retiring carbide bits like this. I wonder if I'm just using the wrong feeds and speeds for the end mills, but I hesitate to mess around with those settings.
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Re: cnc bits

Postby rgulley » Sat Jun 29, 2019 2:19 pm

I have some of the cheapo 1/8" end mills and ball nose, if you'd care to try them. I first used the end mill just the other day on the TVW keychain prototypes. They did surprisingly well.
On speeds and feeds, it's a mystery to me. But I have read several experienced guys that all said a bit shouldn't scream as it cuts. Most recommended a higher feed rate - it screamed because it was hungry. In the shark interface you can change the feed rate +/-, but not the spindle speed. Most routers will let you change speed in steps.
When my bit scream I vary the speed of the spindle up or down to the quietest setting, then adjust federate for best sound.
On 3D carving, I find I get a smoother cut (less fuzzies) with lower feed and higher spindle speed. I'm buying more Amana bits these days and they give recommended speed/feed rates. They also have tool configs you can import into Aspire/Vcarve tool database.
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Re: cnc bits

Postby loyd » Sat Jun 29, 2019 3:32 pm

I'll try Amana next. I need new ball nose bits. Mine are leaving a lot of fuzz. Of course, it may be the wood and not the bit. I cut a pocket in a tulip poplar board today and it came out really nice, but I made a 3d insert to put into the pocket and it fuzzed up on me. See photo.
Untitled.jpg


I got most of the fuzz off with a tooth brush and pumice powder.
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Re: cnc bits

Postby loyd » Wed Sep 25, 2019 7:11 am

I used the cheap bits to carve the bowl top in this photo. A 1/8" ball nose for rough which went pretty smooth. The 0.059" Ball nose [in place of 1/16"] bit left an unforgettable uprising of fuzz as it cut the finish. The fuzz came down to almost forgettable levels with a tooth brushing and a little work with fine sandpaper, but it took about a half hour to get it to the level in the photo. Don't look too close.

RBeMV0inS-WfE0kebIQoFw.jpg


I lowered the feed rate of the finishing bit and the router was full speed -- I think in excess of 18,000 rpm. The fact that this is very dry walnut may be a factor too.
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Re: cnc bits

Postby southpaw57 » Wed Sep 25, 2019 11:45 am

Still, a great looking job. :geek:
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Re: cnc bits

Postby sid_matheny » Wed Sep 25, 2019 4:23 pm

It looks as it was worth the extra effort Loyd and I look forward to seeing it finished.
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