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  • Ozzie34231
    replied
    Luv it John!
    Just got here a few days back and to Gearotica as well.
    I posted there, that maybe Art could have his program generate G-code for the lathe to cut the exact tooth form for a cutter like yours. That would eliminate the whole button making process.
    Got to get my hands on some 1 1/2" drill rod before I bust with the need to make a cutter. I'm thinking I can make a dovetail tool using your method; just need to dish down the center for mounting.
    Did you draw down the hardness; how did you control it; wife's oven?

    Thanks for sharing.
    Ozzie

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  • j king
    replied
    Ill add my compliment, Nice job John.

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  • leesr
    replied
    Originally posted by John Stevenson
    No mating part, I asked for one but it appears it weights 80 tonnes and is in Spain so took a measurement over two teeth, side to side from the pattern.

    These are not a super critical part, they have a 3/8" drive welded on one end and are used to wind a part out for inspection, they are not a drive shaft.

    JS

    Gear shops will use spline gages for a go & no go if cost permits , or a sample spline cut internal" in this case", there is a way of calculation a 2 wire check "since a spline has a truncated adddendum, " on gears a 3 wire check can be accomplished. what this does is tell you if the spline involute is correct as cut.

    spline gages are functional part which will allows for all errors on a spline.
    for example, lead (parrallel error), involute error, & index error.

    depending on the # spline teeth, DP & PA the index, lead , & involute will very.

    a good general for Hobby work these errors will work .0015" max index error
    .0005" max lead error. involute .001" max, or better yet if it fits the mating part

    Keep up the Good work JS & thanks for sharing your information.

    Cheers
    Lee Miramontes

    late night fubar my postm, re-edit to fix my poor writting. senior moment.
    Last edited by leesr; 06-14-2010, 01:17 PM.

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  • leesr
    replied
    Hobs

    Just wanted to add that a hob is basic worm it can be Threaded just like a thread. & if it has more the one start it can be calculated like a helical gear, if it a single start then it has to be calculated as a worm. just other options

    By single pointing or by thread grinding, what needs to be calculated is the
    lead angle, thus then the "helix angle" 90 deg - lead angle = helix angle, & the pitch, and so on. One way the hob can be measured is by measurement over 3 wires or 2 wires depending on the calculation. the same gear wire can be used.
    any way for mfg this one way it can be done.

    Cheers

    Lee Miramontes
    Last edited by leesr; 06-13-2010, 07:21 PM.

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  • John Stevenson
    replied
    No mating part, I asked for one but it appears it weights 80 tonnes and is in Spain so took a measurement over two teeth, side to side from the pattern.

    These are not a super critical part, they have a 3/8" drive welded on one end and are used to wind a part out for inspection, they are not a drive shaft.

    Leave a comment:


  • leesr
    replied
    JS

    Nicely done , there is always an other way to skin a cat.
    did you have a mating part to check to? & did you verify over wires?

    reiterate liked you post very much. keep up the good work.
    very impressive.

    Cheers

    Lee Miramontes

    Leave a comment:


  • oldtiffie
    replied
    Fit.

    John.

    Congratulations on a really really very nice job and demonstration of Ivan Laws book (amongst others) "button" method of making a cutter to make a gear or a spline and then showing that it works.

    As a matter of interest, did you have a chance to use the mating part ("female") to test for fit or did you just have to go ahead anyway?

    I was interested to see just how well it went as regards "fit".

    I hope you don't get paid with a Spanish Bank cheque as their banks got themselves into a bigger hole than I dug myself into.

    Leave a comment:


  • oldtiffie
    replied
    My balls-up

    Originally Posted by willmac

    I don't think that even with ganged cutters made by John's method it could be considered as hobbing. The shape of the 'hob' would not be correct.
    I sure got that 200+% wrong and should have known better - I did - but I would insist on bull-$hitting and not only painted myself in a tight corner but also dug myself into a bloody great hole - and kept digging.

    The "hob" would not only have had to have straight sides but would need to have been spiral cut as for a screw thread but with a transitional circular pitch equal to the circular pitch of John's job and cut on a relieving lathe (Eureka device??) with a pitch modified by the Cosine of the "thread" helix angle etc. The cutter in use would have needed a universal mill tilted for the cutter helix angle and with a universal dividing head geared/connected to the cutter arbor etc.

    My complete cock-up.

    Silly me.

    My apologies - as I don't want to distract further from John's excellent work.

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  • John Stevenson
    replied
    Originally posted by willmac

    I don't think that even with ganged cutters made by John's method it could be considered as hobbing. The shape of the 'hob' would not be correct.
    Correct.

    A hob has straight sides that generate the curved involute, my cutter already has the curve generated by the buttons. Ganging some up would do nothing at all.

    The offset method isn't new, as I said earlier Don Unwin used a similar method that was in ME in the 60's, 'my' method just takes a few steps out to make it easier.

    Lazlo, the relief slot were cut before hardening it was the final grinding I was mentioning, just a lick on all three faces freehand after hardening.

    Anyway, all 10 shafts done and dusted.



    And will be on their way to Spain tomorrow.

    Got to be one of the hardest seven pounds eighteen shillings and seven pence I've earn't this month so far.

    The cutter stud up to the job remarkably well and other then the initial quick lick on the grinder it did all 10 with no problems.




    Just thought this would help for any quick and dirty gear cutting jobs that may arise where you don't want / need / afford [ delete as necessary ] to get a cutter for a one off or in my case a cutter that is next to impossible to buy.

    .
    Last edited by John Stevenson; 06-08-2010, 05:16 PM.

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  • willmac
    replied
    "If the width of John's cutter was equal to the circular pitch of the gear/spline wide it might have been one of a set of ganged cutters mounted on and keyed to a common arbor"

    I don't think that even with ganged cutters made by John's method it could be considered as hobbing. The shape of the 'hob' would not be correct.

    What John has done is show a really clever (simple) way of creating a relieved form cutter with good enough accuarcy for most of us. Definitely one to keep.

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  • lazlo
    replied
    Beautiful job John! That's the first time I've seen an amateur cut an involute spline. But then again, you're hardly an amateur

    Originally posted by John Stevenson
    And the finished cutter after hardening but before grinding, sorry about the crap shot.
    Question: why not cut-out the relief slots before hardening?

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  • J Tiers
    replied
    I don't "doubt" a damn thing, Ralph. So I'm safe from "skewering".......

    It's a good idea... make fewer edges, and you need fewer reliefs..... compromise between hassle and speed of cut, and there you are. It's an extension of one of the ideas in the Goodrich book.

    One would probably top out at about 5 edges doing this, more is a hassle, might need a smaller button cutter, and likely has no real advantage Three is a good compromise.
    Last edited by J Tiers; 06-07-2010, 10:31 PM.

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  • oldtiffie
    replied
    DT

    Nicely done all round John.

    That should well and truly skewer a few Doubting Thomases.

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  • John Stevenson
    replied
    No I got dragged screaming and kicking down to Asda [ Walmart in the US ]

    Still managed to sneak two packets of fig rolls and a big bag of pork scratchings in the trolley.................

    Pub tomorrow night, and Wednesday and possibly Thursday if my new breakout boards are ready.

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  • Deja Vu
    replied
    Yes, Brilliant! But i'm not impressed. I've grown to expect as much from you, JS. I suppose you kept your local pub busy for a spell after completion?

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