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  1. #1
    Join Date
    Jan 2004
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    Mackay North Qld
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    Default Workholding in 4 jaw chuck

    A question for those that routinely use 4 jaw chucks.
    My experience is deficient in this area.

    I have pinched the drawing from the metalworking plans site for the soft faced hammer.I have changed the specs a tad to suit metric materials.It appealed to me as we can use the 3 jaws for the handle and the 4 jaws for the head and milling machine for the name plate.The lathe shown is a 350mm x 1.5 meter lathe

    The pic attached below is that of a 75 L x 40 diam bright steel mounted in a 4 jaw.I am seeking advice if this is the correct method and is it safest way to do this operation.

    The operation is to drill for a 16mm tap size and open the face of the hole to accommodate a collar for the hammer handle.The tapping is done staticly, using a tap in the lathe just to gain axial alignment

    I do know from the label on the lathe headstock not to run in excess of 600 RPM.If you see anything glaringly unsafe please speak up.
    Thanks
    Grahame

  2. #2
    Join Date
    Oct 2008
    Location
    Mid North Coast NSW
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    45
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    Default

    I don't have any problems with the way you have done that. I would have had the jaws the other way around though - the more you can hold the job by the better - especially on the curved portions of a job. Is there a flat milled on the hidden side of the head too?

  3. #3
    Join Date
    Jun 2010
    Location
    Bundaberg
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    54
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    100

    Default

    G'day Grahame,

    No major dramas with your set up; I have done similar many times. However, I don't turn my jaws around because I don't like jaws sticking out further than the material, especially if they're at the periphary of the chuck!

    What I do is insert temporary packing behind the material (1/2" HSS tools steel blanks are good) so that the material is poking out of the front of the chuck jaws in the traditional way. Slide the packing out from behind the workpiece and finish tightening the jaws.

    As for speed, if the material is central in the jaws then you can pretty much run the speed up to whatever the cutting tool will take. If the material is offset then knock the speed down to remove vibration.

  4. #4
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    Default

    I agree with Ben, the jaws definitely need to be reversed. The other way to do this job is to use a vee block to support the workpiece on a drill press.

  5. #5
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    Feb 2007
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    Katherine ,Northern Territory
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    Default

    Certainly acceptable .
    But I agree with Ben and Gavin.

    Kev.
    "Outside of a dog a book is man's best friend ,inside a dog it's too dark to read"
    Groucho Marx

  6. #6
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    Default

    Thanks fellas,

    This is the school lathe and the project is a School Cert 1 engineering project designed around the use of the lathe.The point is to expose them to the 4 jaw chuck as they are Cert 1 engineering students.


    I am wary of using The machined CI vee blocks as we have some cherubs that will drill clear through the bright steel into the vee blocks.Not kidding here, some don't give a rats.

    In general the ones that can't walk and chew gum at the same time will probably avoid the 4 jaw work. For them I'll probably have them use a fabbed steel vee block.

    They will not receive the compententcy as they religiously avoid anything that requires thought and effort.

    The committed kids are right into this one already.One guy has machined out the solid 20mm handle which has really changed the heft of the hammer.

    In addition he is doing a threaded knob for the handle end.He reckons that will be a good tool to tap in re ringed pistons on the chook chaser he rides.

    I am chasing any expertise on UMHW plastic as it is allegedly the stuff for high impact. I am led to believe it is susceptible to problems with tapping.

    Otherwise I am inclined to a press fit for the inserts.

    Thanks

  7. #7
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    Oct 2008
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    Mid North Coast NSW
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    Default

    Can you tap the head to take standard inserts? Still machine the threads on some UHMW but not tap it? I go through a set of soft caps every couple of months, Need to stop hitting the sharp end of sheetmetal!

    Just thinking that it would be easier for the kids to replace the ends in the future if they can buy them from JBS, if they are unable to make them.

  8. #8
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    Jan 2004
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    Default

    Ok, I can reverse the jaws .

    A question here though.On the 3 jaws they are number matched. Having had a cherub screw them out at another school I had some fun getting them back in until shown how.

    Any tricks I should know with the 4 jaws in this regard.

    I have already had fun with it,trying to get it to run true.

    One one the cherubs had removed the cap head screw that retained the pins and it was unscrewed a fraction.

    Why a student would do that is beyond me,some really don't deserve the opportunity being offered.

    Here a pic of the mill as well just for kicks.

    Grahame

  9. #9
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    Jan 2004
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    Default

    Quote Originally Posted by BenM78 View Post
    Can you tap the head to take standard inserts? Still machine the threads on some UHMW but not tap it? I go through a set of soft caps every couple of months, Need to stop hitting the sharp end of sheetmetal!

    Just thinking that it would be easier for the kids to replace the ends in the future if they can buy them from JBS, if they are unable to make them.
    hi Ben,
    I thought about that and purchased a set on inserts to copy.Its around 20mm and non std pitch.I can't say if they were JBS ,I got them from the local eng supplies.

    The basturds make the thread non standard as it is nothing a could match on my Fuji pitch gauge.I took it to my toolmaker mate and he confirmed it.

    I thought about ali too but reckon the thread would shear from the hammering it would get

    Grahame

  10. #10
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    Default

    Quote Originally Posted by BenM78 View Post
    I don't have any problems with the way you have done that. I would have had the jaws the other way around though - the more you can hold the job by the better - especially on the curved portions of a job. Is there a flat milled on the hidden side of the head too?
    No Ben,
    The flat is just a machined recessed panel on one side they can hard stamp their name in.

    cheers
    Grahame

  11. #11
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    Default

    Can you ask the supplier of the lathe to ask why there is a speed reccomendation in regards to the use of the 4 jaw?

    Is there also a speed limitation engraving or some other warning on the chuck?

  12. #12
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    Default

    Quote Originally Posted by pipeclay View Post
    Can you ask the supplier of the lathe to ask why there is a speed reccomendation in regards to the use of the 4 jaw?

    Is there also a speed limitation engraving or some other warning on the chuck?
    Click on the Gear box spindle speed dial picture you will see the recommendation.

    Nothing on the chuck.
    Grahame

  13. #13
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    Jun 2010
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    With regard to the jaws on a 4 jaw chuck, there usually is no strict position for the jaws to sit. Unlike a self-centering chuck (3 or 4 jaw) where the jaws have to sit on a scroll plate, a normal 4 jaw has 4 individually adjustable jaws that are identical to each other. So, when one of the little angels investigates the chuck's inner workings and hands you a selection of jaws and a sheepish look on his face you can pretty much put them back any old how. It is good engineering practice however to always use them in the same position though.

    In my earlier post I may have been slightly confusing WRT to jaw reversal; my recommendation was also to have the jaws positioned in the opposite manner to which you photographed. By placing temporary packing between the workpiece and the chuck you can still use the chuck face as a flat reference while placing the material in a position where it located slightly proud of the jaws and utilising as much of the jaw face as possible.

  14. #14
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    Default

    The idea with those hammers is to bore out the handle and thread the end to take the same heads as the end of the hammer. The gives you somewhere to store a spare head. When we make them locally we make 3 heads one from aluminium,, one from plastic and one from copper.

    The 4-jaw jaws can go back anywhere, in theory, but generally I remove and swap each jaw in turn so they stay in the same slot. It just seems more logical that way.

    I thought about ali too but reckon the thread would shear from the hammering it would get
    The threads on the heads should not be taking the hammering force, the heads should sit on a land which takes the force.

  15. #15
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    Default

    All is going well and I have got most of the 2 classes rotated through the lathe fitted with the 4 jaw chuck. So far most have had no problems other than the 2 turkeys who decided to remove the block after tapping to allow the next guy to use the same tooling.

    They were told to complete the hammer head until it was drilled,tapped and the collar recess socket cut.

    Why do 16year olds always think they know more about the job than you do? They did not know how to re centre the block and I have to acknowledge I had a lot of trouble get it close..

    ( I must admit to thoughts of the first use of the soft faced hammer to be to beat 2 students with --AAAAAGGGGHHH!!! )

    The best idea I could could come up with - among the assorted calls for various assistance from other kids - was to turn a 16mm stub which I threaded and stuck the other end in the Jacobs chuck.

    For the kids that do think,its really got them into the correct spindle speeds, feeds ,depth of cut, etc.

    Some are a little afraid of using the alox wheel to grind their lathe tools.
    The school text has the tolerance standards of half a millimetre which even with my boiler spoiler background I knew it had to be better than that .I have got most of my kids turning down to .1mm.

    What specs are students at other high school systems turning to?

    Cheers
    Grahame

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