Why do indexable insert holders use a shim?
Close
Login to Your Account
Results 1 to 16 of 16
  1. #1
    Join Date
    Oct 2016
    Country
    UNITED STATES
    State/Province
    Wisconsin
    Posts
    73
    Post Thanks / Like
    Likes (Given)
    12
    Likes (Received)
    19

    Default Why do indexable insert holders use a shim?

    Why do indexable insert tool holders have a shim, what is it made of, etc?

    I will post an even dumber question as soon as I think of one.

  2. #2
    Join Date
    Feb 2005
    Location
    Hatch, NM Chile capital of the WORLD
    Posts
    9,541
    Post Thanks / Like
    Likes (Given)
    15978
    Likes (Received)
    11570

    Default

    You mean a seat? A carbide seat?

    Its so when you have an *OOPS*, you rotate or replace a $10 carbide seat instead of
    spending $75 on a new tool holder..

    Very nice feature on face mills.. $50 for new seats instead of $300 for a new cutter body.

  3. #3
    Join Date
    Jan 2005
    Country
    CANADA
    State/Province
    Saskatchewan
    Posts
    10,282
    Post Thanks / Like
    Likes (Given)
    1407
    Likes (Received)
    3739

    Default

    Even without an OOPS, the vibration of the insert during cutting will wear into a steel seat. When using a double sided negative insert with chip breaker geometry, there isn't a lot of surface area in contact with the seat, so a lot of small pressure points exist, and these can etch into the steel. I've got a few well used boring bars that have gotten this way, due to the fact that there isn't room for a carbide seat.

  4. #4
    Join Date
    Jun 2013
    Country
    UNITED STATES
    State/Province
    Oregon
    Posts
    1,729
    Post Thanks / Like
    Likes (Given)
    618
    Likes (Received)
    1042

    Default

    The carbide seat used under a lay down type of threading insert on a lathe is actually tapered. The taper is different according to the diameter of the part you are threading.

  5. Likes Jashley73 liked this post
  6. #5
    Join Date
    Apr 2017
    Country
    ZIMBABWE
    Posts
    128
    Post Thanks / Like
    Likes (Given)
    13
    Likes (Received)
    35

    Default

    I have always wondered why...but never gave it much thought.
    Thank you

  7. #6
    Join Date
    Dec 2008
    Country
    UNITED STATES
    State/Province
    New York
    Posts
    10,398
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    2711

    Default

    Quote Originally Posted by rabtrfld View Post
    Why do indexable insert tool holders have a shim, what is it made of, etc?

    I will post an even dumber question as soon as I think of one.
    .
    amazing is the cost for screw and shim is often over $20.

  8. #7
    Join Date
    Nov 2004
    Location
    Birmingham, AL
    Posts
    13,327
    Post Thanks / Like
    Likes (Given)
    6617
    Likes (Received)
    2620

    Default

    What Hu said. The carbide seat is to prevent the insert digging itself into the floor of the holder.

  9. #8
    Join Date
    May 2011
    Location
    Sandy Hook, MB Canada
    Posts
    890
    Post Thanks / Like
    Likes (Given)
    1
    Likes (Received)
    179

    Default

    Quote Originally Posted by Gobo View Post
    The carbide seat used under a lay down type of threading insert on a lathe is actually tapered. The taper is different according to the diameter of the part you are threading.
    Hello Gobo
    Might I add that if you want to cut external/internal left hand threads & only have an external/internal right hand tool holder & insert, you can install a negative angle anvil to cut those left hand threads.
    Last edited by Ciszewski; 11-25-2017 at 02:09 AM. Reason: Typo: Forgot the "n" in an.

  10. #9
    Join Date
    Jan 2007
    Location
    Flushing/Flint, Michigan
    Posts
    9,890
    Post Thanks / Like
    Likes (Given)
    549
    Likes (Received)
    8142

    Default

    Crash protection being the number one reason by far.
    Break a tip and that shim seat will still cut a little, hopefully you notice soon enough as it cuts very badly.
    Brinelling of the floor # 2.

    Both talked about above but there is a third reason.
    When using a negative insert your unused sharp cutting edge is down.
    You can't make a pocket with absolute sharp corners so without a shim seat you have to add the cost of undercutting the floor/wall intersection to prevent chipping the downside of the insert.
    This undercut is sometimes called a "dirt relief" but it's real purpose is that no endmill makes zero corners.
    Shim seats have a 45 on their bottom so you do not need to add this operation that is done with very short lived and fragile tooling.
    ( and yes shim seats are low cost C-2 carbide with a top and bottom grind. Expensive only because of the volume they are bought in, in quantity they are much cheaper)

    Threading shim seats are a different story being one sided tools and this relates to helix angle and maintaining the needed heel clearance which is why they are tapered.

    Somewhat weird the terminology or correctness of "shim", "seat" or "carbide seat". Not really a shim or maybe it is.
    Anyhoo, if you make toolholders you will know what the customer is talking about instantly and that is all that matters.
    For a user.... they make your holders last longer and that is what really matters.
    Bob

  11. Likes Bobw, Mike C., digger doug liked this post
  12. #10
    Join Date
    Oct 2016
    Country
    UNITED STATES
    State/Province
    Wisconsin
    Posts
    73
    Post Thanks / Like
    Likes (Given)
    12
    Likes (Received)
    19

    Default

    Glad I asked! I bet there's people on here write Wikipedia articles and I hope they do cuz you don't find this stuff anywhere else.

  13. #11
    Join Date
    Nov 2020
    Country
    UNITED STATES
    State/Province
    Ohio
    Posts
    1
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    0

    Default

    Rabtrfld and Bob,

    The number one reason for a Shim in the pocket of a lay down thread bar is to control the Helix of the thread. The other reasons listed are reasonable but have nothing to do with the actual reason the shim/seat is in the pocket. The reason smaller bars do not have a shim/seat is because the smaller the thread diameter the less of an issue the Helix becomes.
    Sr. Apps. Eng. Kennametal

  14. #12
    Join Date
    Jan 2007
    Location
    Norfolk, UK
    Posts
    21,016
    Post Thanks / Like
    Likes (Given)
    16443
    Likes (Received)
    16937

    Default

    Quote Originally Posted by Sr_Applications View Post
    Rabtrfld and Bob,

    The number one reason for a Shim in the pocket of a lay down thread bar is to control the Helix of the thread. The other reasons listed are reasonable but have nothing to do with the actual reason the shim/seat is in the pocket. The reason smaller bars do not have a shim/seat is because the smaller the thread diameter the less of an issue the Helix becomes.
    Sr. Apps. Eng. Kennametal

    Should that statement not be the finer the pitch the helix is less of an issue, .........cos it sure is on sub 1/2'' Acme and the like.

  15. Likes eKretz, gregormarwick liked this post
  16. #13
    Join Date
    Jan 2007
    Location
    wales.uk
    Posts
    1,517
    Post Thanks / Like
    Likes (Given)
    295
    Likes (Received)
    316

    Default

    I thought it was so you could loose the bloody thing in the chip pan making you clean it out, sort of machine hygiene accessory thing, like the little torx screw,
    Ok jokingly, who hasn’t lost one
    Mark

  17. Likes Mark Rand, Limy Sami, mjk liked this post
  18. #14
    Join Date
    Mar 2005
    Country
    UNITED STATES
    State/Province
    Indiana
    Posts
    5,700
    Post Thanks / Like
    Likes (Given)
    1891
    Likes (Received)
    1844

    Default

    Quote Originally Posted by Limy Sami View Post
    Should that statement not be the finer the pitch the helix is less of an issue, .........cos it sure is on sub 1/2'' Acme and the like.
    Absolutely. That guy wasn't thinking very clearly when he wrote what he did. For a given pitch, the larger the diameter the less the helix angle. For a given diameter, the greater the pitch the more the helix angle.

  19. Likes Limy Sami liked this post
  20. #15
    Join Date
    Jul 2006
    Location
    Cumberland, Maine
    Posts
    515
    Post Thanks / Like
    Likes (Given)
    84
    Likes (Received)
    127

    Default

    Quote Originally Posted by eKretz View Post
    Absolutely. That guy wasn't thinking very clearly when he wrote what he did. For a given pitch, the larger the diameter the less the helix angle. For a given diameter, the greater the pitch the more the helix angle.
    The Kennametal engineer’s choice of words was poor. The angle of the insert in no way “controls” the helix angle of the thread. The helix angle is “controlled” by the parameters of the thread itself - pitch and thread diameter.

    The insert just goes along for the ride.

  21. #16
    Join Date
    Jan 2007
    Location
    Flushing/Flint, Michigan
    Posts
    9,890
    Post Thanks / Like
    Likes (Given)
    549
    Likes (Received)
    8142

    Default

    Maybe we are mixing lay down threaders and a CNMG pin lock toolholder?
    Shim seats holders were around long before this type threading tool came to market.
    Where is the angled shim seat on a top-notch threading tool?
    Who made the lay down threader popular as the go to we all know? Hint, starts whit a C and on 8 mile in Detroit.

    Standard pin lock/ top clamp holders have a flat shim seat and guess who started that now standard design.


    I would be remiss If I did not do a big ass welcome to Sr_Applications to the board.
    Any input is welcome, you may get hit a bit but do not take it personal when some talk back.
    I am sure you know things we do not.
    Bob

  22. Likes digger doug, eKretz liked this post

Tags for this Thread

Bookmarks

Posting Permissions

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