Bridgeport M Head Pull Gear Pulley...
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  1. #1
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    Default Bridgeport M Head Pull Gear Pulley...

    I just ran across something for the first time today. A guy and I were having a discussion on another forum about going to fast for cutting holes with hole saws and he dropped this little nugget. He said, one of his drill presses came with a Pull Gear pulley and I thought to myself, that is exactly what I was looking for for my M Head. I wonder if anyone else has thought of building one of these for an M Head. Would it even be plausible?

    I do know this guy built one for his drill press. Maybe a little bit of reverse engineering could make one work for the little M Head...

    YouTube

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    You mis-understood the comment.

    It's a Bull Gear pulley. Some drill presses have a shaft that mounts between the motor and the spindle pulley, and use
    two belts. This allows a greater speed reduction.

    Bridgeport J heads come with an actual low speed bull gear. The M head however really does not have room for that.
    Your best bet is to slow the motor using a VFD.

    Hope things are good with you, did you get that head set up OK?

    Jim

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    I've seen those attachments. It's just that I have never needed to find one or build one because my drill press stable covers all the ranges I need, as of right now. When they do come up, they are usually ridiculously overpriced and not worth it to me.

    I am currently just thinking about the Pull Gear thing. Of course, I'd have to design it from scratch, since the Pull Gear works with a motor that is mounted underneath. If I were to do something like that, I'd want it on the driver end and of course, it would have to have an adapter to lift the motor about 2" out of the head to fit the extra pieces. I looked at some calculations and it looks like belt slippage wouldn't be an issue, but it was only rough and fast math.

    Oh, I got the head mounted and have used it more than a few times. In fact, it was used to help put replaceable rails in a DeWalt GR Radial Arm Saw. Anyways, I messed up my adapter a little, it's off front to back by .0003". I'll shim it in eventually or scrape it in sometime, but with that measurement, it's not that critical. I included a few pictures of it on my mill, so you can see how it attaches and where it plugs in. Oh, don't judge the plywood, I just needed a way to hold that arm up that was quick.

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    I bought this guy 25 years or so ago. It is a planetary gear speed reducer called....Pull Gear. It reduces the speed by 4-1/2 to 1 when the key is pulled out and runs 1 to 1 when the key is locked in. 3 step pulley gives you 6 speeds. I have it mounted to the head stock of a Ribon Rur 7000 Cylindrical Grinder. I use it often and it has never failed. You need to attach the threaded stop rod when in slow mode. I have no idea where I bought it.
    spaeth
    dscn2957.jpgdscn2958.jpgdscn2959.jpg

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    Quote Originally Posted by spaeth View Post
    I bought this guy 25 years or so ago. It is a planetary gear speed reducer called....Pull Gear. It reduces the speed by 4-1/2 to 1 when the key is pulled out and runs 1 to 1 when the key is locked in. 3 step pulley gives you 6 speeds. I have it mounted to the head stock of a Ribon Rur 7000 Cylindrical Grinder. I use it often and it has never failed. You need to attach the threaded stop rod when in slow mode. I have no idea where I bought it.
    spaeth
    dscn2957.jpgdscn2958.jpgdscn2959.jpg
    I don't know why they stopped making those things. I still think there would be a market for them.

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    Thanks for the photos, makes me feel good it is being put to use!

    Jim

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    I'd worry about how well those tiny gears would hold up under load or interrupted cut on a mill. They might give you the desired speed, but it's a little deceptive IMO as I don't see the torque really coming through. Consider how many people have broken teeth on full size back gear mechanisms on lathes and such.

    It might work though. Your hole saw scenario could warrant giving it a shot. I'm always a fan of keeping little round ram M-head BP's cutting, but if I needed the the low speed high torque of a back gear on one, I'd rather adapt an old worn J-head to my machine. They're at least easier to get parts for and they have a track record of what they actually can and can't do.

    The biggest down-side I see is that it's a permanent solution to an occasional issue. It'll change all your speeds and you can't turn it off like an actual back gear.

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  13. #8
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    How about a really rough sketch? I'm thinking all of this could be fit inside a newly manufactured pulley and only requires the lifting of the motor by a few inches to get the adapter player in. I do not want to ruin the little M Head in any way now that I have one that is in beyond amazing condition. I think there would be room to get at the pull knob through the top of the motor. Who knows. Honestly, this is just a bunch of hypothesizing and I'm a little bit, lot a bit aways from moving on this.

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