Ball nose bit for Oak project

[dogboy]

Hello,
I am new to CNC woodworking and now have a small project to complete.
I need to carve a post cap like in the image attached, which I did using the chamfer toolpath in Vcarve Desktop.
My question is what would be the best bit to use? I think I would like to try a ball nose bit, maybe 6mm or 9mm.

As I have not yet purchased a bit for this project I thought I would ask on here first.
I intend to use Oak for this project and the overall size of the workpiece is 250 x 250 x 50 mm.
Not too sure about the bit settings either, what is the best spindle speed, feed rates etc?

I am also not sure if I should do some sort of rough cut first as it seems to take a long time in the toolpath preview.

I did think about upgrading to Vcarve Pro so I can use a gadget for this but it seemed a lot to pay just so I can use Gadgets, but maybe something I need to look at further.

Any suggestions to get the best result for this would be helpful.

Thank you

[sharkcutup]

It can be accomplished several different ways. The Moulding Toolpath, The Fluting Toolpath, or as you said upgrade to Gadget Capability. The gadget would be the easiest but you would not learn a thing in using it. I prefer the Gadget but next to that I would use the Moulding Toolpath.

Sharkcutup

[sharkcutup]

Fence Post Cap_1.png

Here are three ways of creating a Fence Post Cap Using V-Carve Pro. As you have mentioned, you would not be able to create the Gadget created Fence Post Cap in the Vectric Desktop Version of Software for it does not support Gadgets.

Fluting Created.png

Fluting Toolpath Created Above

Gadget Created.png

Gadget Created Above

Moulding Toolpath Created.png

Moulding Toolpath Created

Sharkcutup

[jimandi5000]

Hello,
I am new to CNC woodworking and now have a small project to complete.
I need to carve a post cap like in the image attached, which I did using the chamfer toolpath in Vcarve Desktop.
My question is what would be the best bit to use? I think I would like to try a ball nose bit, maybe 6mm or 9mm.

As I have not yet purchased a bit for this project I thought I would ask on here first.
I intend to use Oak for this project and the overall size of the workpiece is 250 x 250 x 50 mm.
Not too sure about the bit settings either, what is the best spindle speed, feed rates etc?

I am also not sure if I should do some sort of rough cut first as it seems to take a long time in the toolpath preview.

I did think about upgrading to Vcarve Pro so I can use a gadget for this but it seemed a lot to pay just so I can use Gadgets, but maybe something I need to look at further.

Any suggestions to get the best result for this would be helpful.

Thank you

I have used the the Easy Fence Post Cap Maker gadget with a 0.25" ball nose and after I got the step over amount correctly set I made 12 caps for my neighbor. I milled 3 caps on one board at a time. I did some sanding to cleanup the fussy bits. All in all he liked them and he used them on the deck and fence.

Making the caps takes time on a mill. I do have the time and if you are new to CNC milling it is a good learning project.
What I learn on my project:
1. Milling strategy's (any time you make numbers of parts over a single part you think of better ways to run the part)
2. Stock hold down
3. Repetitive stock setup
4. Feeds and speeds
5. Patience (CNC milling is a process of the mind and machine)

Hope this helps.
https://www.gadgets.jimandi.com/

[adze_cnc]

My question is what would be the best bit to use? I think I would like to try a ball nose bit, maybe 6mm or 9mm.

For such a shallow slope you may find that a 9mm or even 12mm ball end bit will produce a superior finish to a 6mm or smaller cutter. Plus your step-over can be larger (I might even give 1.5mm a thought—that's what the simulation is for) thus reducing time.

[FixitMike]

I would suggest using the fluting toolpath with an end mill. Here's a shower pan example that is the inverse, but it shows the principle involved.
.

shower pan.jpg

Fluting Notes:
1. Use a flat bottom end mill for the smoothest result.
2. Maximum spacing of vectors = 1/4 end mill dia. works well for me.
3. The vectors steer the center of the bit, so actual cut is larger on all sides by the bit radius.
For more information on using the fluting toolpath (and a lot more) , see Help-Help Contents.

[dogboy]

Hello,
Thank you so much for your replies, which has been very helpful.

I have already completed the design in Vcarve Desktop, using the chamfer tool path (See original image), Is that not a good idea? It seems to work just fine in the toolpath preview. I just need to decide on the bit and the various bit settings to use.
I think I will order a couple of ball nose bits today, maybe a 6mm, 9mm and a 12mm. I already have a selection of end mills so will try a few test cuts using the various bits.

I am so tempted to upgrade to the Pro version, but its a big jump in money. What I don't understand is why the chamfer tool does not seem to be the go to method to do this sort of job? Maybe I am missing something here?

The think I am still confused about is how to do a quick rough cut first? Not sure how to go about his so I need to do more reading / watching you tube!

Anyway, I really appreciate your replies and opinions, which is of course what this forum is all about.

Thanks again.
John

[adze_cnc]

In the last twenty years ir the term "best practices" has gained currency. To me, there are no best practices, only alternatives.

If your slope exactly matched the angle of a v-bit (say a 45 degree slope) then the chamfer toolpath would be ideal.

Since the slope doesn't appear to match a v-bit the chamfer toolpath needs to use another tool. If that is some sort of ball-end cutter you get cusps (a scalloped look) as the cutter steps over. We can only but lessen them (hence my suggestion for a larger cutter).

FixitMike pointed out that a fluting toolpath with a square-end cutter can be used to produce a smoother result. Its drawback, it's a bit time-consuming to set up and possibly has a longer running time.

A moulding toolpath could work but in execution with a constant slope it's probably not much more effective than a chamfer toolpath with ball-end cutter..

[sharkcutup]

Since the slope doesn't appear to match a v-bit the chamfer toolpath needs to use another tool. If that is some sort of ball-end cutter you get cusps (a scalloped look) as the cutter steps over. We can only but lessen them (hence my suggestion for a larger cutter).

There is an issue with this though the Chamfer Toolpath only allows three types of tools/bits. BallNose, V-Bits, and Engraving Bits. When Said "suggestion for a larger cutter" I was thinking along the lines of trying out a bowl cutting bit or a large Box Core Bit (.75" diameter .375 radius) but with the Tool limitation they cannot be used, Of course maybe, the software can be tricked into using a large Box Bore bit as a Ballnose bit. You won't see a change in the Preview but you will see a change in the actual project carve at the machine. It would be similar to a situation where the user chooses the wrong bit for a Toolpath!

Just Some Thoughts!

Sharkcutup

[ohiolyons]

Table saw

[dogboy]

Hi,

Ah, I didn't realise that the chamfer tool path was limited to certain bits.
I could make this cap many other ways, I have other tools that I could and could do a god job, but as I have my CNC, I thought this would be a nice real project to start with. Maybe upgrading to Vcarve Pro might be the best option, as I would have access to other gadgets and features. I need to have a hard think about this.

I think I also need to play around with this, using various bit just see the results, to get a feel for whats what.
Maybe I was expecting this to be a simple case of using the chamfer toolpath, a large ball nose bit and a couple of hours of work!
I think I was expecting too much! LOL.

Anyway, time to rev up my CNC and do some test cuts., learning by doing seems to be the only way forward.

Thanks
John

[dealguy11]

A large core box bit can (and probaby should) be set up as a ballnose bit so that is not a limitation. I use large core box bits that way all the time. So, a 1" diameter core box bit would just be set up as a 1" ballnose, for example.

[sharkcutup]

I usually set the Box Core Bits up as a Form Tools but I also have the same bits setup as a Ballnose that way I have plenty of options to work with.

Sharkcutup

[dealguy11]

Out of curiosity, what is the advantage of setting up a core box bit as a form tool?

[Will Williamson]

So, you can, cut a cove shape and have it, show up in the preview, best as I know.
But, there is always, someone else that has another opinion. that is the great thing
about this site lots of very smart members, willing to help.