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Aligning Work In The 4 Jaw Chuck, And Brief Intro.

Discussion in 'A BEGINNER'S FORUM (Learn How To Machine Here!)' started by Bill Brehm, Dec 31, 2016.

  1. Bill Brehm

    Bill Brehm United States Iron Registered Member

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    This being my first post I may as well do a short introduction.

    I'm retired and living in Columbus, Ohio. My current interest is scratch building model race cars from the 1950's. I have only two machines: an Emco 9x20 lathe I bought probably 30 years ago, and one of the small generic hobby milling machine from Micro Mark a few years ago. I have mostly used them to make useful jigs and fixtures for what ever I was interested at the time. Nothing that required a great deal of accuracy, so close was good enough. Until now.

    I have been wanting one of those metal band saws, the inexpensive ones from Harbor Freight and the like. I just don't have room in my basement for it. So I decided to make the power hacksaw I saw on YouTube. It's slow, but small and perfect for what I need. It also requires much more accuracy to build than before, which brings me to my question.

    I need to bore a small relief in both ends of a pipe for ball bearings to run in. The piece is 3.00 x 1.75 OD / 1.375 ID. The problem I'm having is aligning the piece in the 4 jaw chuck. I get within .002 close to the chuck, but it's way off at the outer end. I'll tap that around until it is also within .002, and then have to reset the other end. After doing this four or five times I just can't get both positions the same. How do you go about align this?

    I'm using the chuck that came with the machine. The jaws are held in place by a clamping nut on the back side. Naturally any attempt to tighten them after any adjustments just throws it all off again. Do I need a better chuck? If so how much better?

    Thank you.
    Bill
     
    Last edited: Dec 31, 2016
  2. epanzella

    epanzella United States Active User Active Member

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    If the piece is only 3 inches long about half of it would be in contact with the jaws. If the end is wobbling in that short span it sounds like your 4 jaw is in need repair or replacement. If you have a steady rest you can get around the problem with something like this on a smaller scale. It's just a piece of black iron pipe with two sets of bolts at 90 degree increments to act like a pair of spiders. You can adjust anything out with this setup.


    DSC_1077.JPG
     
    Last edited: Dec 31, 2016
  3. f350ca

    f350ca Canada Active User Active Member

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    Welcome Bill,
    From the way you describe your four jaw, it sounds like the light duty ones made for wood lathes, or at least thats where mine gets used. Anything would be better. It sounds like the jaws are tipping when you tighten them, so they only hold at the back.

    Greg
     
  4. mikey

    mikey Active User H-M Supporter-Premium

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    Welcome to HM, Bill.

    Emco never made a 9 X 20 lathe - do you have a Compact 8 that the Asian 9 X 20's are based on?

    Are you using a stock Emco 4 jaw chuck? If so, it should be a 5" model that bolts on with three bolts. It has a Emco-specific spindle nose taper to align the chuck. There are Asian chucks that fit the Emco spindle but the taper may not be the same so chuck alignment might be an issue if you're using a non-Emco chuck.

    I'm not sure what the capacity of your chuck is. It should be able to grab a 1.75" OD piece with the jaws in the standard orientation, which should give you some depth, but if not and you're using the chuck with the jaws reversed then your grabbing surface is considerably less. It will grab but you'll have to apply more force to do it and that can distort the pipe.

    I've tried to bore pipe a handful of times and found that grabbing a piece of pipe can be problematic because 1) pipes are not precisely round and 2) when force is applied by the jaws pipe tends to become even more not round. Moreover, the outside surface of the pipe is usually rough and not at all suitable for precisely centering in the 4 jaw with a great deal of accuracy. You can sometimes indicate the inside of the pipe unless its seamed, in which case it won't work.

    I have to admit that I haven't tried to bore a pipe for a bearing fit, though. That's a sort of precise thing if you're going for a press fit. Could you make the piece from solid rod and bore the features you need?
     
  5. 12bolts

    12bolts Global Moderator Staff Member Active Member

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    Bill,
    Not to rub your nose in it in any way whatsoever, but what you are describing is a wood lathe chuck, ( I have 1 for my wood lathe), but there is no way you are going to get the accuracy you need to dial that pipe in, with that chuck unfortunately.
    Short of buying a 4 jaw chuck to suit I think you might have more luck getting it closer by shimming a 3 jaw. Sorry I cant help more than that. Would it be at all possible to clamp it to a faceplate?

    Cheers Phil
     
  6. Chip Maker

    Chip Maker United States Active Member Active Member

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    Sorry to some above but I also have a 4 jaw that is set up the same way and it came with my Grizzly G4000 when I purchased it years ago. I have used it for odd shaped items but not very often. Things are hard to set up in it for sure. Bill, the best I can suggest is if you don't have a better real 4 jar is to maybe get one hard to do if you are already into this but maybe you can wait to build these parts. Like I said this 4 jaw is really a bear to set up but it could be done. Don't know why they ever included it with the lathe, most likely because they just figured it was better than nothing. Good Luck
     
  7. AGCB97

    AGCB97 United States H-M Supporter - Premium Content H-M Supporter-Premium

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    epanzella
    I'd like a little more info on your

    "If you have a steady rest you can get around the problem with something like this on a smaller scale. It's just a piece of black iron pipe with two sets of bolts at 90 degree increments to act like a pair of spiders"

    What's involved in setup of the jig? How do you center the work piece in the chuck end of jig?
    Thanks
    Aaron
     
  8. jim18655

    jim18655 United States Active User H-M Supporter-Premium

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    The one that came with my G4000 has the same nuts on the back and I make them as tight as I can but still able to move them to dial the piece in. May not be the proper way but it usually works pretty well.
     
  9. epanzella

    epanzella United States Active User Active Member

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    Maybe this pic will show it better. I had to machine the ends of the fuel rails on my boat. The pieces are over a foot long and have an erratic shape with bumps and holes. I made this jig from black iron pipe to old them. Take a piece of pipe big enough to enclose the part you want to machine with enough daylight between to two to center the piece on the inside. You use two rows of 4 bolts tapped every 90 degrees (not critical) to center your part. The two rows of bolts should be laid out to grab either end of your part. Put one end in the steady and one end in your chuck. (3 or 4 jaw, but 3 jaw is faster). Sweep the OD of the black pipe with an indicator and adjust the steady and chuck until it's running fairly true along it's length. Doesn't have to be perfect. Now insert your part that you want to machine, grabbing it on both ends with the two sets of bolts. Indicate the outer end that you can see by turning the 4 bolts in or out on that end like a mini 4 jaw. (mark it so you can put it back in the same place relative to the chuck) Open the steady and flip the whole pipe withing a pipe around and reclamp it in chuck and steady. Indicate that end until true. Flip it around and do the first end again. Every cycle will get this part running truer and truer until it's as perfect as you want it. As you may have gathered, a decent 3 jaw would be faster as you wouldn't have to keep redialing in the 4 jaw over and over. I usually get a part where I want it in 2 or 3 flips.
    DSC_1075 (2).JPG
     
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  10. RJSakowski

    RJSakowski H-M Supporter - Premium Content H-M Supporter-Premium

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    Hi Bill, Welcome to the group. Here is an excellent video by Keith Fenner on Centering s long workpiece in as four jaw chuck.
     
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  11. Bill Brehm

    Bill Brehm United States Iron Registered Member

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    Thanks every one for the information.

    Mike, I get that name wrong every time. It's an Enco not an Emco. I knew that clamping pipe would distort it, but read that it only takes a light force for a 4 jaw chuck to hold the work. Didn't say how light though. I'll watch out for that condition. Maybe I could make a plug for the chuck end, but I imagine that would have to be a really nice fit.

    Having the wrong chuck would explain a lot. After I posted yesterday I looked into a new chuck. I'm sure you get what you pay for, but some were surprisingly affordable. I'll wait until I get the right tool, and try again.
    Love the pipe within a pipe solution.

    Thanks again,
    Bill
     
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  12. Bill Brehm

    Bill Brehm United States Iron Registered Member

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    Just a quick follow up. I bought a small chuck, made the back plate for it, and the alignment was so much easier. I couldn't find anything on what tolerance was acceptable, but I got both ends within .0015. This was only the second time I had to bore anything, and I'm happy to say I got a nice snug fit for the bearings. It did bring up another question I'll put in a new thread.
     

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