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  1. #1
    mtbr member
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    for the machinists: knee mill crank arm

    I know this isn't a machinists forum, but some of you may have some words of wisdom for me on this. Excuse my lack of knowing the correct terminology...

    I picked up an old Diamond M20 horizontal mill the other day and it's missing the knee crank arm. The only ones I can find online are at ebay and are for much bigger square drives (mostly for Bridgeports). This guy's square drive is only 1/4", and even though I *can* use the table's quill feed handle it's not idea (pretty difficult to get the table up but not down). I'm pretty sure I'll never find a replacement arm for this actual machine, so I could buy a larger handle and tap one or two set screws for the arm to fit against the smaller square drive but that's not ideal obviously.

    So the questions
    - If i were to make my own arm, how would I create a 1/4" square opening for the mill's knee drive?
    - Does anybody know another source of miscellaneous mill parts (other than ebay) that I could search online or call?
    - The mill has little grease ports for the ways, and there's a buildup of grease from the previous owner. Table runs really smooth but I've read it's better to use 'way oil' for these fittings. What do you use and/or recommend? Grease or oil? What type of gun?

    thanks!

  2. #2
    RCP Fabrication
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    3 ways I would do it, I'm sure there are more

    You can broach a square hole
    Get a piece of square tube with the right ID and use it as a "hub"

    Or

    Drill a 1/4" hole then open it up with a small end mill, as small as you feel safe using, it will leave a small radius on the corners, break the corners on the square shaft to match.

  3. #3
    Nemophilist
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    Hey;

    Saw your post over on Practical. That's a sweet little rig. Should work pretty well for bike bits, as long as you don't try and run too heavy a cut. Lagging it into the floor will help a lot. Actually, it looks like a horizontal mill with a vertical cutting attachment, but no matter.

    There is a lot of debate about lube, but I am in the oil camp. Grease has too much drag and also retains chips, dirt, and debris much more than oil. It's also harder to clean regularly.

    Yes, 1/4" hand wheels are not common, but I bet they are out there. You'll find one somewhere. I made a handle for my Palmgren 6" mill vice. It has a 7/8 shaft which is an oddball. I had 3/4 and 1", of course. I took a couple scraps of angle iron, shimmed and clamped them against the shaft, then welded them into a square tube. I then welded that square inside a scrap piece of round. The rest of the handle is made from McPherson strut shaft. Really good grade steel. That may give you some ideas. It works like a champ.
    Attached Thumbnails Attached Thumbnails for the machinists: knee mill crank arm-millvisehandle.jpg  

    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
    - John Hajny, a.k.a. TrailMaker

  4. #4
    RCP Fabrication
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    I just had another idea. Use a 1/4" drive socket.

  5. #5
    mtbr member
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    Those are all great ideas! I'm almost glad i have to fabricate something. almost.

    I'm considering using a very old square taper bike crank and rigging that up somehow like RCP suggested -- by bonding it to a steel square 1/4" I.D bar that fits on the drive or...? At least until I can find a 1/4" arm on ebay. I'd love to find an original...but unlikely.
    That angle iron strut combo is very cool TM, looks pro!

    Good to know that info on oil vs. grease. Oil it is, makes more sense to me and easier to clean up. This thing has years of cutting oil and grease baked on.

    I've already taken off the vertical head and am going to use it as a horizontal for coping tubes - chainstays, smaller cyclocross unicrown blades, and seatstays. Slotting stays too. It's got a small table, but has a solid cast iron base and weighs around 800lbs.
    I'm psyched. It feels better than my 1-2 year old Grizzly and it's decades old!

  6. #6
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    that is by far the simplest solution, i like. i can do that today too. thanks!
    I feel dumb for not thinking of that myself.

  7. #7
    Shamisen Appreciator
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    I had to do the same thing for the quill on my Deckel. Found of piece of scrap round, cut it in half lengthwise, milled a notch (.25 x .125 deep for you), welded them together and then welded a handle on it. Took about half an hour and I had all the scrap I needed on hand.
    Sean Chaney :: Owner/Builder :: Vertigo Cycles LLC
    flickr :: www.vertigocycles.com

  8. #8
    Eric the Red
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    Quote Originally Posted by RCP FAB View Post
    I just had another idea. Use a 1/4" drive socket.
    That's what I did for the handle on my horizontal mill, which luckily is 1/2". I used some 7/8" chro-mo tubing for the handle and laid some nice fillets brazes on it. Perfect for a frame shop

  9. #9
    Nemophilist
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    Humph...

    I was gonna suggest the socket thing, but I figured that was too easy!

    I did the socket thing for the tailstock locks on my 102 year old lathe. Works like a charm!
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
    - John Hajny, a.k.a. TrailMaker

  10. #10
    mtbr member
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    The square drive is actually 3/8" not 1/4", so there are some handles one could buy but nothing close to the original arm.

    Here's my temporary fix. It's embarrassingly ugly but works great. I'll make a nicer one later. The dropout/chainstay was leftover from a mistake frame and the handle I found lying at the bottom of a drawer of crap. The stainless socket nut extension is silver brazed into the dropout so I can salvage the dropout if/when I want it back.
    for the machinists: knee mill crank arm-imageuploadedbytapatalk1356316522.038052.jpg

    Once I cleaned the old grease and sawdust off the ways and draw bars and added oil the knee moves up much easier. I can actually use the wheel fine now. But I'll fab something combining parts of Sean's, RCP's and TM's ideas in the long term.

    Thanks again for the great ideas!

  11. #11
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    Version 2.0

    Took a bit more time for this version of the Z-axis crank arm. A bit overkill but looks much nicer than the last. The other part of that botched chainstay brazed to a 3/4" tube with the socket nut extension brazed inside. The handle was $5 on eBay, made for a Bridgeport.
    for the machinists: knee mill crank arm-handle-onmill.jpg

  12. #12
    Nemophilist
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    Hey;

    How much fun is that? Repurposing things is more fun than using the right stuff, every time! That machine is like mine with the Y & Z feeds parallel and near each other. Not the most efficient handle layout, but I guess I'm not really in a hurry anyways.
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
    - John Hajny, a.k.a. TrailMaker

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