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  • Bridgeport type M Help

    thank you to everyone for helping with their replies to my last thread about inspecting a BP before buying.

    It just so happens that I was actually offered a free Bridgeport Type M today I just have to go get it. However, i love a bargain but if this machine will not suit my needs I wont take it. I couldnt take it for the sake of a free machine then sell it or get rid of it again because I dont want it If i dont want it, id rather see it go to good use.

    Can I work one of these as hard as a regualr bridgeport? Ive done a bit of reading and see that these heads were 1/2hp 110v and have a max collet capacity of 1/2" they do not take r8s which is ok, however 1/2" collet size is a little small as i use a lot of 3/4" endmills and all my fly cutters and tpu cutters have a 3/4" shank. Making a 3/4" collet/adapter is easy enough but I am afraid to go out of the limits of the spindle. I know the motor might not have the guts to drive a 2" tpu cutter through a chunk of A2 but I could always replace the motor later. But what will happen to the spindle? I know that a BP is supposed to be a light milling and profiling machine but face it everyone uses fly cutters on them.

    Basically will I destroy a Mtype head using 3/4" endmills and fly cutters?

    Thank you

  • #2
    Originally posted by TDmaker01
    Basically will I destroy a Mtype head using 3/4" endmills and fly cutters?

    Thank you
    Short answer no,but as with any machine you most observe it's limits.

    I had an M head and sold it.There are times I wish I had it back.It's not as robust as a J-head,but it is still a capable machine,better than a bench mill by far and more convenient than say a round column mill drill.

    Simplest way to use 3/4 endmills is buy reduced shank endmills.As for fly cutters HP is more of a limiting factor than rigidity.A 2" fly cut is doable so long as the DOC is kept realistic,something like .030" in MS.

    If your tight on shop space the M-head is a good fit,it's about half the footprint of a J-head factoring the table travel.The 1/2hp motor isn't all bad,you can get a VFD for that for $120.

    Last thing to consider and the deal breaker is what sized work do you need to do?If you need to plunge and rough out 1" deep 3/4" wide slots in toolsteel,well the M is out and even the J would have a time with it.

    OTOH,if you want to do modeling,car restoration or light tool making it would be a good machine.
    I just need one more tool,just one!

    Comment


    • #3
      I have a rare high speed M head(just head) that I need to think about mounting on the other end of my Bridgy ram,or as a vertical head for my Harrison horizontal mill. It will do 12,000 RPM,and has a flat rubber belt drive.

      To lubricate these M heads is something that might not be well known. there is a slotted setscrew on the top of the M head's housing. You get a tube of lithium grease like a toothpaste tube. Take out this screw,and screw in the lithium grease tube,squeeze about 1/2 teaspoon,IIRC.

      I was very lucky to get to talk with an official Bridgeport mechanic about this. A search on the PM site would turn up my info. from him,as it was several years ago. I'd look it up,and double check for the EXACT grease,but I'm pretty sure it was lithium.

      These M heads are much lighter than J heads. They use a #2 MT spindle,or a B&S taper about the same size,so they aren't very heavy duty. I think you can put in a max. 1/2" shank end mill in one.
      Last edited by gwilson; 09-28-2011, 12:38 AM.

      Comment


      • #4
        Originally posted by gwilson
        I have a rare high speed M head(just head) that I need to think about mounting on the other end of my Bridgy ram,or as a vertical head for my Harrison horizontal mill. It will do 12,000 RPM,and has a flat rubber belt drive.

        To lubricate these M heads is something that might not be well known. there is a slotted setscrew on the top of the M head's housing. You get a tube of lithium grease like a toothpaste tube. Take out this screw,and screw in the lithium grease tube,squeeze about 1/2 teaspoon,IIRC.

        I was very lucky to get to talk with an official Bridgeport mechanic about this. A search on the PM site would turn up my info. from him,as it was several years ago. I'd look it up,and double check for the EXACT grease,but I'm pretty sure it was lithium.

        These M heads are much lighter than J heads. They use a #2 MT spindle,or a B&S taper about the same size,so they aren't very heavy duty. I think you can put in a max. 1/2" shank end mill in one.
        You are probably thinking of lubrizol, think they come in 4oz tubes(like toothpaste)

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        • #5
          There are several things you should know to make an informed decision. First the M head is just that the head only. The M head or J head for that matter can be installed on either an early vintage (1956 or earlier) "round ram" or on the later "v ram" machine. The v ram machines could have two knees. The early 9" travel and the later 12" travel. Table widths varied and could be 32", 36", 42" and 48". Early round ram machines are typically 32 and 36 inch models. Round rams are a little shorter and weigh a touch less than a v ram machine but not much.

          The M head itself could have three different tapers. The Morse #2, Brown & Sharpe #7 or the more rare B-3. The motor was typically a 1/2 HP but most in my experience are 3 phase not 110 volt. Not much to a M head you can break one down in no time at all. The J head is much larger and heavier and would have a 1 HP 3 phase motor and an R8 spindle and the addition of the power down feed.

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          • #6
            Thank for all replying. The reason for wanting to use 3/4 endmills is because I won an auction lot of about 75 new ones for real cheap so id like to be able to use them, rather than make an adapter for a 3/4 shank, ill just buy or make a er32 collet holder with a morse #2 taper!, thanks for all the help

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            • #7
              Thanks for the lube reminder. Mine is a #7 B&S taper. Came with all the tapers,fortunately. I need to some day mount it up as I do lots of small work.

              Comment


              • #8
                Jeff at Tools4Cheap sells both B&S No 7 and MT2 end mill holders up to 3/4" capacity. You'd loose a little day light between the spindle and the table (compared to a collet setup) but on a Bridgeport that's not as big of concern in my opinion as many lighter mills.

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