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Thread: Grinding Jacobs chuck jaws bigger

  1. #21
    Boolit Master

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    When we ground lathe chucks we used a needle bearing inner race first in the back jaws then in the front and reached thru it to relieve the inner jaws, this kept the scroll play in the same direction as when using it. We had d series splindles and when installed 0-0 on spindle and the zero key socket was used they would repeat around .0005 unless damaged or abused by overtightening them. ( This sprung the scroll)
    We had soft jaws that were bored when installed for special or thin parts. Again the load was done in the same direction as use to maintain accuracy.

  2. #22
    Boolit Master Traffer's Avatar
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    Quote Originally Posted by KCSO View Post
    If you want to get a 3 jaw chuck accurate you grind it. You will use a ring on the outside of the jaws to keep them stable and then grind the inside of the jaws to true with a grinder on the lathe. This will give you a jaw that with care alnd luck will be true to 3 thousnads of an inch.

    This works with lathe chucks as they are inside outside and have a nice flat for the tension ring. A drill chuck has tapered jaws outside so I don't know how you will hold the jaws in tension. If you just back the all the way out the chuck will only be as true as the body and most cheaper Jacobs chucks won't hold 10 thou or so. Now add in the tolerance of the machine itself and it looks like you are trying to make a donkey do a horses work. I don't use bolts for die stock as they are not cut with very accurate threads. I prefer to thread the die after setting it to run true with the bore.

    All that said you can give it a try as I have seen some very good work done with some very rough tools. Just depends on how much care you put into the job.
    I am going to load the chuck by chucking a little stub cylinder deep in. Then grind the tip of the jaws. Then pull the chuck off and tighten it on some kind of rod that will be chucked in another drill press, horizontally mounted. Then I will go through the back hole of the chuck with a longer diamond burr on a dremel and finish grinding the deep part of the jaws. What could possibly go wrong
    AKA hans.pcguy

  3. #23
    Boolit Master
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    I think that by the time you cobble your contraption together, you will be out more money and be greatly disappointed in the results vs buying a small used quality bench lathe such as a southbend10" , or hell even a small grizzly or atlas would work.

    Your in Wisconsin, you should be able to find a small used lathe no problem.
    NRA High Master XTC
    DR# 2125

  4. #24
    Boolit Master Traffer's Avatar
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    Quote Originally Posted by akajun View Post
    I think that by the time you cobble your contraption together, you will be out more money and be greatly disappointed in the results vs buying a small used quality bench lathe such as a southbend10" , or hell even a small grizzly or atlas would work.

    Your in Wisconsin, you should be able to find a small used lathe no problem.
    I have been looking for a lathe in my price range for over 3 years. I have had four deals fall through. So far I have invested under $100 in this contraption.
    Drill press head-----------------------------------$8
    2 1/2" pipe for mount rail------------------------$19
    1/2 HP motor--------------------------------------$30
    3/4" Jacobs Chuck--------------------------------$19
    Pulley----------------------------------------------$5
    Still needed: V belt, fabricate tail stock.
    Estimated cost for these about------------------ $20\
    The easiest way to make this tail stock would be with a drill press table with a 2 1/2" post hole, but since I don't have one I will have to fabricate something that will attach to the post (2 1/2" pipe) which will hold a chuck.
    I have already set one of these up with a smaller drill press and use it. The problem with it is that it has a B16 chuck holder. NO BUENO! The largest chuck it will support is a 5/8" which is smaller than 7/8" dies that I will be making. But it DOES WORK. The run out is not critical. Since it holds center, excessive run out just makes the hole bigger. I compensate for that by using slightly smaller bits to start with. Once the pilot hole is established the tool itself tends to hold the run out in tolerance. But you are correct in saying that it would be much better to have a proper lathe. While doing this I keep looking for something that I can afford. But alas, my wife and I live on a budget of $16k gross income. So while most can just go to the store and buy a lathe, this is not an option for me.
    AKA hans.pcguy

  5. #25
    Boolit Master

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    A drill press is as accurate as the set up is. drilling round stock can be done acuratly if the set up is accurate. A vee block with the round stock clamped in place is strap clamped lightly to the table and set close to center thru lay out or even by eye. An indicator is the set in the spindle and the part indicated in tapping the vee block to move it, this takes some time patience and practice. Once close straps are tightened and the part is brought into zero on the indicator. Now center drill and pilot drill to desired depth clearing chips every .1 or so to avoid chip binding. use oil and work slow. Then drill to size.

  6. #26
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    Quote Originally Posted by country gent View Post
    A drill press is as accurate as the set up is. drilling round stock can be done acuratly if the set up is accurate. A vee block with the round stock clamped in place is strap clamped lightly to the table and set close to center thru lay out or even by eye. An indicator is the set in the spindle and the part indicated in tapping the vee block to move it, this takes some time patience and practice. Once close straps are tightened and the part is brought into zero on the indicator. Now center drill and pilot drill to desired depth clearing chips every .1 or so to avoid chip binding. use oil and work slow. Then drill to size.
    I am not quite sure I am seeing this correctly. Are you talking about boring round stock that is held stationary? For me there are too many variables to get it to be perfectly centered and stay centered all the way through. The idea of having a dial indicator is something that I do really need now that I think of it. And I have seen used ones go very cheaply.
    AKA hans.pcguy

  7. #27
    Boolit Master

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    Yes with a vee block that's square and true stationary stock can be set up and drilled accurately. We did some casting repairs in drill presses with a fixture to hold them. Indicated them into alighnment and ran the repairs thru instead of a repeat thru the production equipment. A drill press is as accurate as the set up is.

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check