Carving Edges. Need Bit

[dirk martin]

I just purchased the X-Carve 4x4 Pro, and should be taking delivery this next week.
One of my projects will be to hopefully carve/cut some creative/natural edges on some 2 and 3" slabs.
Is there such a bit out there I can use to do such work?

The XCarve has a z-travel of 4", but it's the length of the bit cutting edge that will be the limiting factor.

[Jim Becker]

For the LOC you need that will also not chatter, you'll want to source .5" tooling. The reason for using the long LOC is so that you can do your profile cutting with a small allowance on all the passes until the last one and the final pass is on the line so it cleans the entire edge. I use a .375 tool for guitar bodies, but I only need a 1.75" LOC for that job.

[dirk martin]

...For the LOC you need that will also not chatter, you'll want to source .5" tooling. ...

Being brand new to the CNC realm, can you point me somewhere?
And, are you saying I should look for 1/2" shanks?

[Jim Becker]

Being brand new to the CNC realm, can you point me somewhere?
And, are you saying I should look for 1/2" shanks?

Well, the shanks will be .5" but so will the tool. You need that much metal to not get a huge amount of chatter. The challenge is going to be with speeds and feeds on the type of CNC you opted for with big tooling like that. Vortex has longer LOC tooling in .5", but I've never bought anything that long as it would be a bear for my Camaster Stinger II to handle at anything but reasonable feed speed despite it being a heavy machine for its size. You have to be realistic about the actual cutting capabilities of your machine.

An alternative for you to consider is to partially cut through the thick stuff; remove the stuff proud of the kerf and then use a pattern routing bit to clean the entire edge. Many folks use this method for things like heavy furniture parts.

[Michael Burnside]

The process Jim mentions is a good one. I recommend and use it often. It’s just sometimes easier. I will say that the larger tooling is far more forgiving if you’re not taking too deep of a cut and not feeding fast enough as they can dissipate heat better. That way your machine isnt taxed, just the tool.

By the way, Whiteside/Bits-n-Bits have a 1/4 down cut with 2” LOC so you could get quite a ways through.

[stephen thomas]

One of my projects will be to hopefully carve/cut some creative/natural edges on some 2 and 3" slabs.

Can you clarify what the intention is?
Are you intending to carve what would look like a random live edge on a piece that does not currently have such?

Or, as has been adequately answered by others, are you intending to make smooth, but contoured edges?
With or without undercuts/re-entrant shapes?

[Jim Becker]

By the way, Whiteside/Bits-n-Bits have a 1/4 down cut with 2” LOC so you could get quite a ways through.

Using a down cut for these deep, um, cuts...can be an issue because the chips will not get cleared which raises the heat significantly. It can actually be a fire hazard in some cases.

[Kevin Jenness]

You might do better with handtools (drawknife, spokeshave, gouges) or handheld power tools (angle grinder with carving disc, die grinder with burrs) than trying to model the contours on a screen and cut them with a long bit on a less than robust router.

[dirk martin]

Can you clarify what the intention is?
Are you intending to carve what would look like a random live edge on a piece that does not currently have such?
[/COLOR]

This, exactly.
And in order to "make" a live edge like that, I'm willing to go as slow as I need to, with as many passes as necessary.

[dirk martin]

Being new to the CNC arena, please point out my ignorance with the following....

I have a pine slab, 2.75" thick. Dry.
It has straight sides.
I'd like to cut/carve a "fake" natural edge, on one side.

I see this bit, on BitsBits:

AstraHP Coated* Bits&Bits 560-CM500 – 1/2″ Extra Long Compresion End Mill – 6″ OAL x 3″ LOC.


It reads that it's also available as an UpCut bit.
I fully understand my CNC has limits, but aren't those limits mitigated by simply slowing down the feed rate, and taking many shallow cuts?

[stephen thomas]

This, exactly.
And in order to "make" a live edge like that, I'm willing to go as slow as I need to, with as many passes as necessary.

AstraHP Coated* Bits&Bits 560-CM500 – 1/2″ Extra Long Compresion End Mill – 6″ OAL x 3″ LOC.

So you are going to make a 3D contoured edge with random striations, inclusions, typical bark defects, etc?

How many axes on the spindle does your mill have? I'm kind of assuming only 3?
So realistically, you need a tool that can do the undercutting and in-cutting without the ability to swivel the tool itself to effect that.

The tool you choose will be a compromise, but probably look like a very small, thick saw on a stick.
E.G, a woodruff cutter, or a keyseat cutter. I have a rack in the shop with maybe 1/2 dozen that have shanks up to 4" or so.
You will probably have to free-hand grind the cutters so they cut a rounded or spearpoint shape, to make the work come out looking mostly realistic.
It's easy to do so long as you pay attention to the fact that all cutters need clearance at every point along the edge. But beyond that, for the work you propose, the shape is not critical.

PS: it's also easy to make extended shanks to take common router wing cutters. Use the smallest diameter cutter, and probably one that is only 1/8" or max 3/16" thick, if you want to have it do small detail striations and such. The smaller the cutter diameter, the easier it will be for you to use it to carve small details. Also, the smaller the diameter, the safer. For safety, don't make the shank any longer than absolutely necessary, so you don't have it fail and create mayhem with a whipping action. I use 4140 prehard for that type shaft, but there is a lot to pay attention to when building and using an extended shaft tool.

You need to understand your tool paths and infeeds. Jam the tool in accidently, and it is going to either fail suddenly, or it will bend, whip and cause brown pants syndrome if you somehow find a way to get down on the deck and scrooch over to pull the plug before the whole machine schrapnels. Worst case you impact valuable body parts or die.

Keep guards between you and the cutter, even if it is a 2 x 6 on edge, or 4 x 4 clamped to the table somewhere so a broken tool cannot fly across the shop.

Play safe!

[dirk martin]

So you are going to make a 3D contoured edge with random striations, inclusions, typical bark defects, etc?

No.
I'm looking to achieve something more like this:

1130_Pine.jpg

[Jim Becker]

Being new to the CNC arena, please point out my ignorance with the following....

I have a pine slab, 2.75" thick. Dry.
It has straight sides.
I'd like to cut/carve a "fake" natural edge, on one side.

I see this bit, on BitsBits:

AstraHP Coated* Bits&Bits 560-CM500 – 1/2″ Extra Long Compresion End Mill – 6″ OAL x 3″ LOC.


It reads that it's also available as an UpCut bit.
I fully understand my CNC has limits, but aren't those limits mitigated by simply slowing down the feed rate, and taking many shallow cuts?

A compression bit will work, but they are generally designed for situations where one needs to have pristine cut lines on both top and bottom. There is a small up cut portion at the end of the tool and the rest is down cut. The issue for your application is the thickness of the material and the fact that a substantial portion of the cutting in the kerf is on the downcut side, which forces chips down into the wood. For your specified application, you don't really need to worry about a perfect edge on the wood because you are going to have to return to the workpiece with hand tools, sanders/grinders, etc., to make the faux natural edge actually look like a natural edge. Natural edge slabs never have perfectly vertical surfaces...they are always at various angles relative to the faces because logs are rounded. So I'd go with a normal up cut endmill so that you are clearing chips as best as possible for each pass as you make your cuts. The up cut version of the tool you are looking at is likely less expensive, too, because it's less complicated to make.

FYI, the cherry desktop I'm sitting in front of has faux natural edges...because the sapwood was punky and not salvageable. I did not use the CNC for this, but the principle is the same. The edges are angled as shown in the photo you attached to post #12. You are not going to get that edge just with the CNC unless you do some serious 3D modeling with final shaping and refining by hand.

[stephen thomas]

No.
I'm looking to achieve something more like this:

1130_Pine.jpg

That you can do with a round nose bit or cove type bit; however most carving type apps use a lollipop bit.

(having been censored for linking to my own content, i'm still not clear what i can link directly so just google lollipop bit tons will come up)

While the shape you intend to carve is essentially a blend of OD forms, the radii are all changing everywhere. If you use a flat-nose bit, there will be a lot of ridges.
Lollipops still leave a somewhat scalloped effect depending on the level of resolution for your final pass. Obviously hog at low resolution for speed, then dial the steps down for smoothing.
Then you will still have some finish work with scrapers or sanding implements but it should go fast.

A lollipop allows undercut and gradual re-entrant shapes, which you don't intend, however that type of tool is common for carving, so ends up being one of the less expensive options for the volume of material removed even if the underside edges get little wear.

good luck!
smt

[Jim Becker]

stephen, most CAD/CAM software that "regular people" use with their consumer grade CNCs doesn't support undercut or at least doesn't support it without jumping through hoops and careful toolpathing.