Preventing tear out

[MDHunt]

I completed a project that used a 1/32" Tapered Ball Nose bit as well as a 45degree V-bit for some of the cutting. The cuts were not clean as there was significant (what I'll call tear-out for lack of a better term).
The pass depth for the Ball Nose bit was .0313 inches with a spindle speed of 18000 and a feed rate of 10 inches/min.
The V bit also left the same splintery aftermath.
I am not able to clean it up with a light sanding because of the detail in the project, so I will have to redo it.
Any suggestions?
Thanks

[sharkcutup]

Question: What is the board material wood type? ex: pine, hickory, walnut, mahogany, etc... (Sometimes it helps to know the wood type for it makes a difference in feed/speed rates)

I have seen this feathery, fuzzy looking condition too but not as bad as what you are showing/experiencing! On my carving it was on a softwood (premium pine) and I just used a Dremel tool to clean it up. Of course with your project that would be rather tedious and time consuming. As little of it as I had I did not take the time to investigate/brainstorm for cause and effect. Maybe someone else here on this forum has experienced this and can provide insight as to solving this feathery, fuzzy mess!

Good Luck with your Project!

Have a GREAT DAY!!!

Be SAFE around those AWESOME machines!!!

Sharkcutup

[Rando]

MDHunt:

From your F&S, it looks like you're probably going much too slow. You need the material to be CUT from the stock, not eased out with a million tiny cuts. A better feed rate for that kind of work should be in the 40-70 IPM range,....IF you have a sharp bit. I'd start with 50, and if they still happen, go slowly UP. And easy way to test is on the backside of that same board, make a small and simple design (a set of straight-line vectors cut to depth), set the feed rate to 80IPM, but set the feedrate overide (slider?) to 50% for effectively 40 IPM. Adjust that slider up and down and see precisely what feedrate that type of wood, and your bits, want.

However, your biggest problem looks like probably a dull bit, or too many flutes. Is it a 2- or a 4-flute bit? When the bit moves that slowly (10 IPM), it's really more rubbing against the material and not cutting it, which generates heat, which kills the hardening on the bit, which dulls it even faster. Gotta keep the chip-load where the heat of the cut is carried away by the chip, not left on the bit. Chip load is the amount of material cut per flute per revolution, typically in thousandths of an inch. Moving to HSS instead of carbide can also help, as HSS bits start out sharper. If you run them at the right rates, they can also last longer. Use the same IPM, but cut the RPMs to like 60% of what you normally would. But either way, wood is abrasive. It has silica particles in it, and gummy resins that both act to coat the bit producing more heat, and dull the cutting edges. Unlike in metals where a proper cut can leave the bit essentially unchanged, cutting wood and plastics like HDPE, just in and of itself, dulls bits. Don't expect bits in wood to last months of cutting. I did a bunch of HDPE a while back, and the bits were clearly dulled with less than 20 hours of cutting in them. Clean, sharp bits are the way to go to prevent burrs and fuzz.

To save this one carving, you might have the tools around: an old toothbrush, and a medium-stiff wire brush. Depending on how thick those hanging chads are, they could pull off the delicate top surface, so brush DOWN into the grooves, not so much along them. My guess is most of them will come right off. Depending on how deep the design is, since you're already considering it wasted material, I'd see if shaving off 0.010" from the top of the whole thing might whack those off but not impact the lines of the design too much. Worth a try, right? I'd use a flat end-mill, or a facing bit, sometimes called a fly-cutter, if you have one. Like what you'd use to flatificate a spoil board.

In future, adding a finishing pass with 0.010" margin left in the first, might help prevent it by giving that second pass a chance to cut those burrs off. That finishing pass should be run faster than the first pass, or with lower RPMs. But either way, use a brand-new shiny sharp bit for the finishing pass, and reserve that bit (and its on-hand spare....you do keep an on-hand spare, right?) for only finishing passes.

Anyway, those are my ideas. Hope they help, or at least don't just make more wasted wood.

Regards,

Thom

[sharkcutup]

Depending on how deep the design is, since you're already considering it wasted material, I'd see if shaving off 0.010" from the top of the whole thing might whack those off but not impact the lines of the design too much. Worth a try, right? I'd use a flat end-mill, or a facing bit, sometimes called a fly-cutter, if you have one. Like what you'd use to flatificate a spoil board.

GREAT IDEA!

I believe Thom has an interesting idea here. A very light skim surface cut just might be the ticket to save your project.

But I am sure you are looking for the cause so that this fuzzy, feathery mess does not occur in your future projects --- Thom has some interesting information that you may want to delve into.

Good Luck in Solving your Dilemma!

Have a GREAT DAY!!!

Be SAFE around those AWESOME machines!!!

Sharkcutup

[TAW]

I use a soft wire brush used from work and thrown out when not doing the job anymore. But you may save this carve with a brush of sorts to just scrub the fuzzys off...worth a try. I stay with grain as much as possible because this brush will scratch oak even but then light palm sanding cleans those up

[MDHunt]

Thanks for the info fellas. I am going back and revisiting my F&S info first.
Precisebits.com has some excellent tutorials that I am going through right now on it, including cutting the parallel slots like you suggested Thom.
I also ordered two steel wire brushes online that I will use to 'clean up' some of what was left behind.
I appreciate the feedback.