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Thread: Boring bars

  1. #1
    Join Date
    May 2005
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    Turramurra, NSW
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    2,267

    Default Boring bars

    I'm trying to bore out a 22 mm socket to a round 24mm to use as part of a die holder for the lathe. The boring bars I have will not fit into such a small diameter (maybe min of 19mm) The support for the carbide bit rubs.

    I ground and rounded off the base of the bit support but I dare grind no more for fear of weakening it, still dont fit.

    I guess I need a small boring bar but when I look at the on-line stores I get confused.

    Some have round shanks, some need a holder etc etc. There are some sets available for circa $80 plus post.

    My lathe expects a 1/2" bar in the tool holder.

    I suspect I need a set, however I can't see any 1/2" shanks, Round, even MT2 (which would fit the tailstock taper)

    Any advice
    Bodgy
    "Is it not enough simply to be able to appreciate the beauty of the garden without it being necessary to believe that there are faeries at the bottom of it? " Douglas Adams

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  3. #2
    Join Date
    Aug 2005
    Location
    Blackrock Vic Aus
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    Default

    Suggest you try McJing tools I bought one (1/2") at the www show in Melb last year around $50.00 has a carbide insert tip and has worked well for me so far.


    Peter

  4. #3
    Join Date
    Jan 2006
    Location
    Blue Mountains NSW Australia
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    Default

    I would abandon the idea of boring out the socket.

    I have turned sockets down on the OD a few times, and that is doable with carbide tooling, but they are tough. Ordinarily I bore holes over 1/2" with carbide tooling, and under that, I make my own HSS tooling. I find ccmt carbide tips best for smaller lathes.

    The problem you will find trying to bore a socket, is that it will obviously be an intermittent cutting action which will destroy your carbide and HSS won't touch it.

  5. #4
    Join Date
    Feb 2006
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    Default

    Quote Originally Posted by Bodgy View Post
    to use as part of a die holder for the lathe.
    Quote Originally Posted by Bodgy View Post

    Any advice
    What Fossil said is very true.

    However, I must ask if you are going to use it as a die holder. How are you going to drill out and tap the holes for the screws that enable you to set the die to the diameter you require?

    Personally I would make it out of mild steel as I did on my apprenticeship.

    Cheers
    MH

  6. #5
    Join Date
    May 2003
    Location
    Perth WA
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    3,784

    Default

    I have a set of these as well as the 10mm boring bars. They have flats on them and just shim to centre height on a standard 1/2 inch toolpost.
    They work well and I quite often have quite a bit of overhang and with light cuts no problems. The small inserts help with clearance.
    http://cgi.ebay.com.au/12MM-3PCE-5-I...742.m153.l1262
    Cheers,
    Rod

  7. #6
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    May 2005
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    Turramurra, NSW
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    Default

    Thanks guys for the advice.

    Fossil, yes I suspect you're correct. The chrome flaked off easily, but when I hit the steel it did seem 'reluctant'. Never really new cause my bring bar started rubbing after the first mm or so. As you said the interupted cut didn't help

    I love McJings and wish to be buried there when I fall off the twig, but I couldn't see any boring bar suitable. They have a set, where the smallest would do but this set had a round shaft. I suspect for use in the mill? Or in the lathe tailstock??

    MH. Of course you're correct. I was just being lazy and trying to take a short cut. Re the screw, my tap and die sets are not of the highest quality, in that they dont have the slit that allows a small adjustment of internal diameter. They only have a single depression to hold the die fast into the holder/wrench whatever. I had intended to braze a small nut onto the exterior to take the grub screw.

    Anyway, I have some 30mm round and I'll use that, however I still will need a boring bar that can take over from the 13mm drill.

    Rod, I saw these on Epay, but the picture doesn't give me an idea of how small a hole they will bore. Could I ask you if yours would bore from the drilled 13mm onward? IE would the smallest fit into the 13mm hole?

    I'm sure these questions are pretty basisc and I need some hands on instruction, but with the death of manufacturing in Oz, none of the local TAFEs offer anything appropriate, nor the community colleges. Basket weaving, macrame, IT skills etc but no metal stuff. Bear with me.
    Bodgy
    "Is it not enough simply to be able to appreciate the beauty of the garden without it being necessary to believe that there are faeries at the bottom of it? " Douglas Adams

  8. #7
    Join Date
    May 2003
    Location
    Perth WA
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    Default

    Hi Bodgy,
    Don't worry there are a lot of us seft taught machinists out there. Trial and error is a good teacher.
    The 12mm boring bar will not fit in a 13mm hole. The 10mm looks like it will as it is 11.4mm across from tip to outer edge of bar. I use a 5/8 drill bit so I can't say for sure.
    All the bars have a downwards rake on the tip which allows for the bar to be mounted higher to get the tip on centre. This means the boring bar is not dragging on the bottom of the hole. The tip is also pointing forward so the cut gives the bar clearance. I hope I am making sense.
    I have attached photos of the 10mm set and an end on shot to show the negative rake. Bad photo but you can also see the flats on the boring bar so it can be mounted in a standard toolpost.
    You probably already know this but use with minimum overhang and light cuts.
    Cheers,
    Rod

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