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Thread: Good bit for 3D work

  1. #1
    Join Date
    Jul 2008
    Location
    , NY
    Posts
    27

    Default Good bit for 3D work

    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

  2. #2
    Join Date
    Jan 2004
    Location
    iBILD Solutions - Southern NJ
    Posts
    7,961

    Default

    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
    High Definition 3D Laser Scanning Services - Advanced ShopBot CNC Training and Consultation - Vectric Custom Video Training IBILD.com

  3. #3
    Join Date
    Dec 2008
    Location
    Diamond Lake, WA
    Posts
    1,616

    Default

    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.
    Don
    Diamond Lake Custom Woodworks, LLC
    www.dlwoodworks.com
    ***********************************
    Life is not a journey to the grave with the intention of arriving safely in one pretty and well preserved piece; But to skid in broadside, thoroughly used up, worn out, bank accounts empty, credit cards maxed out, defiantly shouting "Geronimo"!

    If you make something idiot proof, all they do is create a better idiot.

  4. #4
    Join Date
    Jul 2008
    Location
    , NY
    Posts
    27

    Default

    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.

  5. #5
    Join Date
    Mar 2009
    Location
    Pope Valley CA
    Posts
    689

    Default

    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
    Ron Sloan

  6. #6
    Join Date
    Jul 2008
    Location
    , NY
    Posts
    27

    Default

    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...

  7. #7
    Join Date
    Jul 2008
    Location
    , NY
    Posts
    27

    Default

    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!




  8. #8
    Join Date
    Jan 2004
    Location
    iBILD Solutions - Southern NJ
    Posts
    7,961

    Default

    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
    High Definition 3D Laser Scanning Services - Advanced ShopBot CNC Training and Consultation - Vectric Custom Video Training IBILD.com

  9. #9
    Join Date
    Jul 2008
    Location
    , NY
    Posts
    27

    Default

    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!

  10. #10
    Join Date
    Mar 2008
    Location
    Tulsa Oklahoma
    Posts
    1,237

    Default

    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

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