What hammer to hit drawbar?
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  1. #1
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    Default What hammer to hit drawbar?

    The chuck gets stuck, but the collets with end mills do not. I need a bigger hammer. I have a plastic head hammer from Boeing surplus that weighs half a pound.

    I measured the weight of the drawbar plus the chuck is 4.5 pound.

    Should I buy a dead blow hammer?
    A brass hammer?
    A plastic hammer?
    Make a wood hammer?

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    I like a plastic faced dead blow hammer on a Bridgeport. I feel it is better to give it one good rap than to beat on it. IMO many people tend to overly tighten the drawbar. A clean R8 adapter and spindle taper should not need excessive tightening if the mill is used within the limits of a not too rigid machine.

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    You're supposed to use a hammer? Gee, for fifty years I've been using a wrench. I even have a special box end wrench that I bought at a pawn shop. 3/4 on one end and 7/8 on the other. The 7/8 end fits standard 1/2-13 flange nuts used on hold down sets.

    If you've got an R-8 shank that's sticking:
    Make sure it's clean and free of burrs.
    Make sure the spindle socket it clean and free of burrs.
    Make sure the drawbar and washer are clean and lubed (I like to change the O-ring every year).

    If you've done all that and it still sticks, replace it.
    JR

    BTW, if you get a hammer, get a Lixie like this: Lixie 56 Oz 2" Dia. Head Lixie Dead Blow Hammers - - Amazon.com

    If you want a drawbar wrench: Martin BLK8731A Forged Alloy Steel 3/4" x 7/8" Opening Double Offset 45 Degree Long Pattern Box Wrench, 12 Points, 12-9/16" Overall Length, Industrial Black Finish: Box End Wrenches: Amazon.com: Industrial & Scientific

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    I was trained as an apprentice to use the same wrench to tap the top of the drawbar that I used to loosen the drawbar. Loosen it up a little bit, use fingers to unscrew it a turn or two and then rap it with the wrench turned on it's side.

    I know there are people who will tell us that it is wrong to use anything harder than a rubber mallet on a drawbar but this was standard practice on mills that saw 2 or 3 shifts of full time running and it never caused a problem.

    If a wrench is too light to do the job, you probably have the drawbar too tight.

    If hitting the drawbar with steel concerns you, I have seen and owner a hammer that has a 3/4" socket on one end and a brass hammer opposite the socket.

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    Default

    3/4"x7/8" long box end wrench here also. Have had the same wrench for years. Sit on one of the coluum bolts when not in use, so always handy.

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    Don't buy anything.
    Get a 2 - 3 inch diamter bar of brass 3 - 4 inches long.
    Attach a wood handle through a hole and securing with a wedge.
    Works remarkably well.

    Wood mallets. Make them heavy. Drill a hole and fill with lead shot if needed.
    I avoid striking metal on metal. I use dense Eucalyptus and dense harvested oak instead.

    dsc_0826.jpg

    dsc_0823.jpg

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    We always used a lead hammer to knock the taper loose on the drawbar.

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    Sharp but solid rap is best for releasing so you need a solid metal striker with some mass. I strangle a 2 lb club holding it pretty much directly behind the head and give a sharp sideways twist of the wrist to generate the strike. Probably 50° of twist but no major effort. Just get the mass moving so the sudden stop does all the work. Mine will release if belted with the end of the wrench but the club hammer is less work.

    Deadblow is the wrong weapon as its designed for shifting / adjusting things, the damping makes the effect more of a solid push than a sharp strike. Lots more to hitting things than just swing and hope. Effectiveness depends on getting right balance of mass and speed for the job in hand. Swinging faster and harder doesn't compensate for less hammer head mass even though the total energy in the head at the end of the swing may add up to the same. Its the slowing down that does the work. Fast swing on decent length of handle is for driving nails when you need the hammer to follow the nail down pushing it in as far as it can before the energy runs out. A drawbar is free moving once the taper has released and has very little distance it can travel anyway so any sort of hammering action via a handle is less than ideal. Everything happens in the first thou or 3 after the strike. Done perfectly the drwabar drops away from the strangled club hammer leaving it held in mid air.

    A properly comprehensive scientific treatise on the dynamics of hammering and matching striker, style and effect would be interesting but probably far to big a tome to lift.

    Clive

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    I just push the in / out button. There is no B-port accessory that will pay for itself faster than a Kurt power drawbar.

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    If you are going to hit the drawbar with a wrench make sure the wrench is not chrome plated. Years ago I got a nasty cut from peeling chrome on a wrench that had been used that way for some time.

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    Quote Originally Posted by moonlight machine View Post
    There is no B-port accessory that will pay for itself faster than a Kurt power drawbar.
    Not for me. I'm so friggin' old that you can't teach me new tricks. Last place I worked at as a toolmaker, had them. I still picked up the wrench and reached to the top of the mill. Then, I had to put the wrench back, push the button take out the tool, put tool away, get next tool, get wrench, reach to top of mill, put wrench away, push button.

    It took twice as long! The owner yelled at me for taking so long. I left! Boy was that a long time ago!
    JR

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    In the shop I worked at that had bridgeport clones, they bought each machine its own wrench and cast a lead hammerhead on the open end. Quite handy.

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    I've always used the wrench, tapping it ONCE with roughly the amount of force I would use to tap the lid of a glass jar of olives. If you need more force, it needs cleaned.

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    I've been using one of these forever. Works great!

    Hammer 955561 - MSC

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    Quote Originally Posted by moonlight machine View Post
    I just push the in / out button. There is no B-port accessory that will pay for itself faster than a Kurt power drawbar.
    I have a Kurt power drawbar on my Bridgeport and it is handy but I think a much bigger time and effort saver is the attachment that I bought that goes in a drill to raise the knee. Cost about 30 bucks and saves major arm wear and tear if you have a lot of different height parts to run.

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    Quote Originally Posted by Edster View Post
    I've been using one of these forever. Works great!

    Hammer 955561 - MSC
    That's the same one that I had with my last mill. I gave it to the guy that bought the mill because my B'port has a power drawbar.

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    I'm going to jump on the use the wrench bandwagon. Bridgeport's should have that 3/4 & 7/8 combo wrench kept in arms reach, and you already have it in hand when you are loosening the drawbar. it should be more than enough to suffice ( if something else isn't already broken). Draw bars are not that expensive to replace, and I doubt the threads on the other end last as long the top, getting tapped with a wrench. Also, the slightly sharper ping of cold steel, I find, does a better job breaking tapers.

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    here's what I've been using forever...a piece of .75" x 1.5" round welded to an offset box wrench that fits the drawbar

    img_1016.jpg

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    I'm with JRIowa and BigB. The Bridgeys at the old shop were sans power drawbar, and I'm still programmed to run them.

    The Bridgey I run at the new shop has a power drawbar, but I still catch myself grabbing the wrench from the turret bolt that that it hangs on to give the drawbar a rap.

    Probably doesn't help that my own '57 J head is wrench drawbar, and I exercise her regularly. Old habits die hard (says a 31 year old LOL).

    From my Bridgeport manual:

    'Drawbar has 7/16-20 right hand thread, and should be tightened by hand with normal amount of pressure using wrench furnished with machine. To loosen collet, back off drawbar and if collet does not open immediately, give knob on top of drawbar a slight tap'.

    A person does not have to read into it very far to realize they meant the "tap" to be with the "Bridgeport wrench".

    You can interpret it how you want, but the wrench is already in your hand, in close vicinity to the end of the drawbar you just loosened it with. Thinking they would have suggested a lead or brass hammer in the literature as the alternative, but they don't.

    The wrench makes sense.

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  32. #20
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    Quote Originally Posted by Big B View Post
    I have a Kurt power drawbar on my Bridgeport and it is handy but I think a much bigger time and effort saver is the attachment that I bought that goes in a drill to raise the knee. Cost about 30 bucks and saves major arm wear and tear if you have a lot of different height parts to run.

    I made on of those but the drill was always walking away so I gave it away and bought a servo power feed for the knee. It's the second best accessory for a B-port as far as payback time.

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