Good bit for 3D work

[itamarj]

Hey guys,
I'm doing some 3d work lately that is pretty deep (around 3"-4" thick).
So far I was using the 1/8" tapered ball nose that came with the starter kit and it did a good job. but I think I should get something longer. I do have a 6" long 1/4" ball nose, but I wasn't sure how detail i'm going to use.
Do anyone know where I can get 1/8" that is 4"-6" long?
Or what do you think about 1/8" vs. 1/4" when it comes to 3d?
I read here in one of the thread that actually 1/4" will give better result, but I find it hard to believe.
Anyways, would love to hear your thought!
David

[Brady Watson]

David,
This is a difficult question to answer. No diameter bit is 'better' than any other. It boils down to how much detail needs to be picked up from a given diameter ball end tool.

You will most likely not find an off the shelf 1/8" bit over 4" overall length OR a 1/4" over 4 or 5" OAL. The bit simply has too much flex and deflection to be useful at that length. If you do, they will be very expensive & only be marginally useful in low density foam.

The best way to answer this question would be for you to use PartWorks3D or Aspire & run a cut preview using different diameter tools to see the result of different diameters.

Also - You should ALWAYS do a 3D roughing toolpath with a straight or spiral bit BEFORE you run your 3D finishing toolpath. This gives a better finish, drastically increases tool life.

-B

[dlcw]

David,

When doing large carvings, I do my rough path with a 1/2" ballnose. This removes a LOT of material very quickly. I then come back and use a 1/8" ballnose for the finish path. For small carvings I use a 1/4" ballnose for roughing and a 1/8" for finishing.

These combinations have always worked for me very well. The deepest I've carved is about 2", not the depths you're talking about.

[itamarj]

Thank you guys for your replay!
I learn by breaking my bit, that roughing is an essential part of the milling work, and I shouldn't skip it. At my first jobs I thought it will take more time and effort to change bit but now I notice that the finish wasn't perfect and i broke several bits.

Brandy, where can I find 4" long 1/8" ball nose? I looked through many website and could not find it anywhere.

[ssflyer]

David,

Something you might want to consider is slicing your model. That way you avoid the many issues with a really long bit, and works well.

Ron

[itamarj]

Hey Ron,
I was thinking to do that, but since I'm milling wood, and it's a delicate piece I'm not sure how well i'll be able to attach the two pieces together.
Also, I will have to surface the table and the wood itself to get an good finish. It's a lot of work, but that definitely a way to avoid using a long bit...

[itamarj]

I wanted to share my results, and hear some feedback about the work.
These are two reliefs that I just made. The first one is 1.5" thick and about 24"x14" and the second one is 3" thick.
With the second relief I worked with a dremel and added a lot of details in the undercuts and many other places (hands faces ect.)
I used 1/2" bit for the roughing and 1/8" taper bit for the finishing.
I have several question that came from this job:

1. The models are much more detailed than the result, maybe I can use a smaller bit after the 1/8" to get more details. Which bit would you recommend? should I use a 1/16" ball nose or a different engraving bit.

2. The second relief posed a problem because it was deep. I was concerned that my basic 1/8" taper ball nose is not long enough and the collet will hit parts of the relief while trying to reach into the lowest point. Luckily, it went well, but I was looking for a longer 1/8" bit and could not find any. I bought a 4-1/5" 1/8" bit from MSC but it's for 1/2" collet and I am not sure if the 3 degree angle will work well with this kind of job (3D milling). What do you think?

3. I saw that there are tool extenders out there, but they are pretty expensive ($170 and up). Does anyone have experience with that? is that a good way to solve it?

4. This is very basic question, where can I find 1/8" collet for my Porter Cable router? Should I buy one of those Sleeve adapters to convert 1/4" collet to 1/8" bit?

Many thanks for all your help guys!

[Brady Watson]

You need a stubby collet chuck for your PC router. It will let you use 1/8" and smaller bits without adding runout like the cheap sleeve reducers. I did a write up on this in the ShopBot web column area on the SB main site.

The tapered tools are expensive, but very robust. A popular bit is a 1/4" shank, 2.5" CL, 4" OAL 1.5 deg taper. They are not cheap, but they work well, are very forgiving and last a long time. You don't want to go too much deeper on an 1/8" tool since deflection becomes a major issue.

A picture is worth a thousand words. Post up what you are doing/have done...the comments and suggestions you receive will be worth much more to you.

-B

[itamarj]

Brandy,
Thank you so much for your reply. Your post on stubby collet chuck was exactly what I was looking for. It hit two birds with one stone - both extends the bit and also allows different size shank tools. Perfect!!

I posted the pictures of my work through Talkshopbot forum album, but I guess they didn't got approved yet. Here they are again:

pic 1
pic 2

What kind of bit would you recommend for getting the little details on the relief (for the face and hands ect.)? would 1/16" ball nose do the job, or should I better go with an engraving bit?

Thanks again!

[dana_swift]

Did you do the 3D artwork for the carvings? That looks like you are doing very well for just getting started-

Congratulations and well done!

D