Question on CCMT inserts for boring bar in boring head
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  1. #1
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    Default Question on CCMT inserts for boring bar in boring head

    I have been using a Criterion boring head in my Bridgeport. The Criterion bars which came with the head don't handle interrupted cuts well.

    I have wanted to try using a bar with inserts. After reading past threads on the forum, the consensus seems to be that sclrc boring bars using ccmt inserts are a good choice in a boring head, if one is looking for a tough insert.

    Mesa tools seems to have some very reasonably priced USA made bars. I spoke with the owner about a CCMT bar w/ 3/4" shaft he sells. He indicated the a 2" hole was the smallest hole that bar would bore because the bar had an 11 degree rake.

    That's the part I don't understand. Why would a 3/4" boring bar require a 2" minimum hole to start? I'm sure there is a reason, but I can't picture the geometry in my head, as to why it can't bore a smaller hole.

    Here is a pic of the boring bar.

    3/4″ x 4 1/2″ RH Boring Bar w/CCMT-32.51 | mesatool

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    Mesa Tool is making their recommendation based on the optimum use case, most likely. Note that there is a flat on the shank of the boring bar, and the rest of the geometry is then completely fixed by the insert and insert pocket geometry. I suspect their guidance is simply based on the typical relief angles that are present on a CCMT insert, combined with the geometry of the bar. Smaller hole = more rubbing, most likely. I have a Mesa Tool LH boring bar w/TPG insert for use in the cross-hole of a boring head. Nicely made, and it has worked well for me on the rare occasion when I needed it.

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    Heel, the bottom corner of the insert inside the circle. There is no primary and secondary.
    It does not fall away fast enough and even when clear in the cad it traps chips on the side that have no where to go.
    Many (all?) of these are zero top. This leaves a triangle of top to bottom that loves to pack.
    Bob

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    Thanks for clarifying that for me.

    If you don't mind, could you guys answer one other question for me?

    Mesa has a tool which is rigid for boring large holes (i.e. more rigid than a horizontal boring bar).

    Here is the tool.

    3″ Boring Head Attachment | mesatool

    The description says, "Bore range increases by reversing head."

    What in the heck does that mean?

    One can't flip the tool around and fit in the head to increase the bore range. The head only advances one direction, as far as I know.

    Here is a pic of what I'm trying to describe. The head moves from left to right. The bottom of the head is not made to go left, according the the paper which came with it.

    kimg1030.jpg

    Any ideas what Mesa means by saying the range of their tool increases by "reversing head"?

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    So cute, what kind of material are cutting and at what speed and feed? What type of machine are using and how ridged is it, and ridged is your set up.
    An ECGT type inert has worked for me, pressed and ground is best for interrupted cuts if remember correctly.

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    Quote Originally Posted by doug8cat View Post
    .
    An ECGT type inert has worked for me,y.
    Is ECCT a typo?
    Problem with C on smaller bores is the clear area below even it the cutting tip is all fine.
    This is why drills and such have a secondary. Ideally any boring tool also would or radially open but many will bore with second letter "N" inserts for the extra edges.
    Bob

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    One of my boring bars came with CPMT inserts. Don't need them for the majority of work, so I save them for when I'm pushing it to the limit on bore size.


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