Mill collets by 1/8ths or 1/16ths?


Results 1 to 9 of 9

Thread: Mill collets by 1/8ths or 1/16ths?

  1. #1
    Member
    Join Date
    Aug 2012
    Location
    USA
    Posts
    278
    Downloads
    0
    Uploads
    0

    Default Mill collets by 1/8ths or 1/16ths?

    Have a decent size benchtop mill. Not sure who made it but looks significantly more powerful and rigid than an X2 and slightly more table travel. Most of my stuff with be with small cutters but will do some bigger stuff. At the point of buying tooling and wondering if I should get a R8 collet set by 1/8 or 1/16ths. I can see the 1/16th being useful in the smaller sizes like 3/16 and 5/16 but seems like the bigger sizes not so much - maybe I am wrong. Another thing is most sets go to 3/4 or 7/8 and I can't see me using anything that big. Then again, if I get one by 1/8 and fill in a couple smaller 1/16 sizes I could have gotten the whole 1/16 set.

    Similar Threads:


  2. #2
    Community Moderator Jim Dawson's Avatar
    Join Date
    Dec 2013
    Posts
    5717
    Downloads
    0
    Uploads
    0

    Default Re: Mill collets by 1/8ths or 1/16ths?

    I guess it depends on the price of the set, it is sometimes nice to have the full range. End mill shanks are normally in 1/8'' increments when > 1/2 '' The most common sizes are 1/8, 3/16, 1/4, 5/16, 3/8, and 1/2. On a smaller mill like yours, 3./8 is about the largest I would use. With the exception of the occasional use of a face mill, I rarely use larger than 1/2'' on my machine, which is a 3500lb knee mill.

    I would seriously look at ER tool holders. We have several full sets of ER collets in all the ER sizes we use, by 1/16's and then buy single collets for when we need multiples of a given size. This allows setting multiple cutters and changing them quickly.

    Jim Dawson
    Sandy, Oregon, USA


  3. #3
    Member
    Join Date
    Aug 2012
    Location
    USA
    Posts
    278
    Downloads
    0
    Uploads
    0

    Default Re: Mill collets by 1/8ths or 1/16ths?

    What's the advantage of the ER tool holders? I must be missing something. Guess that would be with a power drawbar? Doesn't seem like a easy path from R8 to easily changed ER system. Can you post some links?



  4. #4
    Community Moderator Jim Dawson's Avatar
    Join Date
    Dec 2013
    Posts
    5717
    Downloads
    0
    Uploads
    0

    Default Re: Mill collets by 1/8ths or 1/16ths?

    We probably have 40 or 50 of these in the shop in different ER sizes. And have at a minimum of a set of collets in each ER size range. The ER collets have a 1mm clamping range.so you can also put any size drill bit in them.

    Allows you to keep tools set up in the holder for quick changes without resetting the tools.

    https://www.shars.com/products/toolh...?shank_size=R8 Looks like they are missing the ER-20 size holders.

    Jim Dawson
    Sandy, Oregon, USA


  5. #5
    Member
    Join Date
    Aug 2012
    Location
    USA
    Posts
    278
    Downloads
    0
    Uploads
    0

    Default Re: Mill collets by 1/8ths or 1/16ths?

    So they have a wider range of use - I get that. And perhaps better concentricity. But you still have to switch the whole thing for different tools. I guess I see that it could be slightly faster with not having to put in the R8 collet and then insert the tool but that doesn't seem like that big of deal. Once you have a set of tools mounted does that eliminated having to do tool length when putting them back on the machine? At the start of a job you would need to set Z height for one but the relative length of them all would stay the same? By "without resetting the tools" do you mean putting them in the collet, setting the length, or both? I am guessing both...

    Then there is cost. For the cost of two ER holders I could buy a better R8 collet set and I would still need to buy the ER collets. Although it's not hugely expensive. If I was doing this for income it would be a different story but it's just a hobby shop.

    Just trying to understand the tradeoffs as I have limited experience.



  6. #6
    Community Moderator Jim Dawson's Avatar
    Join Date
    Dec 2013
    Posts
    5717
    Downloads
    0
    Uploads
    0

    Default Re: Mill collets by 1/8ths or 1/16ths?

    That is correct, you need to set the Z offsets for each tool at the start of the job. But once set, the position is repeatable. Just a bit faster than changing a collet and setting a tool for each tool change. On a manual machine this is not very important, but a bit of a time saving if you need to set up a few tools for a job, especially if you are going to be making multiples of a part. On a CNC machine with manual tool changes it makes life easier. On a CNC machine with an ATC, it's pretty much mandatory. I ran manual BP type machines for 40 years with R-8 collets, so am very familiar with the drawbacks.

    On my knee mill, I normally just leave cutters set up in the tool holders for convenience. That way I can just grab one and make chips. I should note here that none of my machines have a R-8 spindle, but rather have #20, #30, or #40 spindles depending on the machine, so the only option I have is various style tool holders. I also use ER tool holders for some of the tooling on my CNC lathe, for drill bits, taps, and boring bars.

    I agree the cost is higher for the ER tool holders compared to a simple R-8 collet. There would be no real advantage to having a single ER tool holder and changing cutters as required. It takes just as long to change a tool that way as it does with a R-8 collet, it's only an advantage if you have multiple tool holders.

    So back to your original question: The most used R-8 sizes are 1/8, 3/16, 1/4, 5/16, 3/8, and 1/2. Having the 5/8 and 3/4 might be useful for some jobs, but endmills in this size are too large for your machine to do any serious cutting.

    Jim Dawson
    Sandy, Oregon, USA


  7. #7
    Member
    Join Date
    Aug 2012
    Location
    USA
    Posts
    278
    Downloads
    0
    Uploads
    0

    Default Re: Mill collets by 1/8ths or 1/16ths?

    Thanks for the explanation. I am taking a class intro to CNC and we are just at tooling length offsets. Machines have ATC and use #30 or #40 spindles (not sure which off hand) with ER collets. Pondering the R8 or ER collets for home use and think I understand the trade offs now.



  8. #8
    Member
    Join Date
    Nov 2013
    Posts
    4281
    Downloads
    0
    Uploads
    0

    Default Re: Mill collets by 1/8ths or 1/16ths?

    Hi,
    R8 refers to the spindle interface, that is the taper, and the short cylindrical section that mates with the internal socket formed by the rotating shaft.
    R8 tool holders have a number of ways of clamping the tool.

    One of the oldest is a Weldon Flat. There is a flat ground into the shank of the cutter and a screw in the R8 toolholder clamps down on that flat. Simple and works OK.

    There are various collet arrangements, including one that has a threaded end on the tool. It works OK but there is a somewhat restricted range of tools with the required threaded
    end. The tool is threaded into the collet and result in very positive tool length clamping and not likely to change at all, a definite plus.

    Another are ER collets. They are very common and work well. The collets have interleaved splits from top and bottom and consequently clamp along the full length of the shank,
    which gives best concentricity and greater clamping force. If the tool works loose for any reason the tool can 'pull out' burying itself into the work and wrecking it, so you have to be
    careful and observant. Cleanliness of the tool and collet is vital, and a very regular and repeatable fitting procedure is required. To this end a fixed R8 spindle socket is best, you can drop
    the R8 toolholder into the socket with the ER clamping nut facing upwards and then you can torque the ER nut down properly and repeatably. Try to do it with the R8 toolholder in
    the machine and you risk not getting the clamping that you intended...and the tool pulls out...$#@!@#%^^%@uck!!!!

    Craig



  9. #9
    Member
    Join Date
    Aug 2012
    Location
    USA
    Posts
    278
    Downloads
    0
    Uploads
    0

    Default Re: Mill collets by 1/8ths or 1/16ths?

    Familiar with ER and R8 collets but somewhat limited experience with both.

    A few observations/comments. Correct me if I am wrong on these...

    R8 collets are only slotted from one end and far less slots (typically 3) so very limited size range and not quite as uniform of pressure along the grip compared to ER collets.

    Weldon flat prevents rotation well but have poor concentricity compared to other types. This means one cutting edge is doing more work than the others. I also work a lot in small sizes (1/4" and under) and think the flats are only common on bigger sizes. I did a quick search to see what sizes but didn't find that.



Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  


About CNCzone.com

    We are the largest and most active discussion forum for manufacturing industry. The site is 100% free to join and use, so join today!

Follow us on


Our Brands

Mill collets by 1/8ths or 1/16ths?

Mill collets by 1/8ths or 1/16ths?