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    Red face cutting gears

    hi all i need to make a missing gear for my smith barker and willson lathe project but don't know where to start as i do not have a sample to copy so i need someone to tell me how to go about this. the missing gear mates up to a 2nd gear which is there but that does not help..any clues???

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    the missing gear mates up to a 2nd gear which is there but that does not help.
    It does help - the teeth have to mate with the one you need to make

    There is an easy way to find out Diametral Pitch (assumes an "Imperial" make)

    Measure outside diameter of the mate that you have - and record that

    Count teeth and add TWO to that count

    Divide the O.D. into the count plus TWO

    Example - 32 teeth, and 2.125" O.D.

    34 / 2.125 = 16 Diametral Pitch - or "DP"

    Now.....how MANY teeth (on the one to be made) is a bit more work if you have no idea

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    Default smith barker and willson lathe

    thank you john it all helps.i will do the sums you suggest which is more than i knew.this is very hard with no sample

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    hi again john , out in the shed today i measured the existing gear=6 1/4 inch=6.250and tooth count 38 plus 2 makes40 so far so good.divide outside diameter into tooth count (40)and we have6.4 diametral pitch.i now need to buy a set of diametral cutters and then somehow do the job ..if not for your help it maybe would never happen, cheers for the help.it is appreciated.

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    6.35 DP is 4 Module which is metric gearing. You will still need to determine pressure angle. 14.5 and 20 degree are the most common. You can compare your tooth profile with one online to note the difference.
    Center to center distance between gears will help calculate number of teeth on missing gear.
    Good luck with your project.

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    If you scroll down here enough, you can see that Kevin is correct

    Gear Diametral Pitch, Module Conversion Table Chart | Gear Diametral Pitch | Circular Pitch | Module - Engineers Edge

    have fun

    Here is a comparison 14 1/2 to 20 PA - one can see the 20 is a bit more "pointy" - with more tooth "beef" at the bottom

    20200828_190223.jpg

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    Can't offer much more than above, save for encouragement. The first time you cut a gear it's a bit mysterious and scary. After you've done one or two, it's easy and by the time you reach one or two dozen teeth (by hand with a dividing head) it actually gets boring. That's the point where you don't want to lose concentration and mess up! There are fewer and fewer decently priced involute gear cutters available, but they do exist if you do a good search.

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    Let's see pictures of the lathe and the gears.

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    Page HERE covering that manufacturer. Must be a hefty machine to have a MOD 4 gear in the train.

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    Just that the Op's title and great information are ideal for a future search of this question and solution.

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    Probably makes sense to NOT just assume mod 4 gear goes there. Any following mod 4 gears there? Like on end of lead screw? Maybe all the gears were missing and a PO thought the "found" mod 4 was as good as place to start as any in gearing it up. As suggested in a post above, mod 4 is way overkill unless the lathe is a "bigun"

    As a for instance, my 9900 lb 24 X 80" Lodge & Shipley only had 8 DP (mod 3.175) gears back there

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    Quote Originally Posted by Conrad Hoffman View Post
    Can't offer much more than above, save for encouragement. The first time you cut a gear it's a bit mysterious and scary. After you've done one or two, it's easy and by the time you reach one or two dozen teeth (by hand with a dividing head) it actually gets boring. That's the point where you don't want to lose concentration and mess up! There are fewer and fewer decently priced involute gear cutters available, but they do exist if you do a good search.


    img_20210719_140948.jpg

    error on 1 tooth, missed a turn on the rotary table, or one too many...

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    Yeah, sucks when that happens. I throw mine out so nobody saw nuttin! FWIW, I make many gears for my small Logan out of Delrin. They hold up great and are much easier to cut, plus the cutters last forever.

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    This one 6061, for my father to cut the threads he wants using his SB 9". i wanted to scrap it and start over, but it was a rush job, so we filed the error down a bit and it works ok-ish. gives him something to tease me about when i make fun of how dirty he leaves his lathe 😁

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    Borrowed from another of your threads......

    Where is the 38 T going?

    What's on this end of lead screw?

    001.jpg

    Hard to believe you are running that direct off a cone pulley equipped motor - does it not go way way too fast?

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    Quote Originally Posted by kevin johnson View Post
    6.35 DP is 4 Module which is metric gearing. You will still need to determine pressure angle.
    I've never seen a 14.5* metric gear. Not going to say they don't exist, cuz there's probably one (1) somewhere, but definitely not the norm.

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    Quote Originally Posted by EmanuelGoldstein View Post
    I've never seen a 14.5* metric gear. Not going to say they don't exist, cuz there's probably one (1) somewhere, but definitely not the norm.
    I think the Deckel FP 1 machines are 14.5. 20 for all later developed machines FP2 etc.

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    Quote Originally Posted by EmanuelGoldstein View Post
    I've never seen a 14.5* metric gear. Not going to say they don't exist, cuz there's probably one (1) somewhere, but definitely not the norm.
    I would agree, I've never seen one either yet I do have a 0.5mod 14.5PA hob.

    I would also agree with John about not going on the MOD4 gear assumption without careful checking because Willson lathes are apparently specified in inches in every other way.

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    Quote Originally Posted by Screwmachine View Post
    I think the Deckel FP 1 machines are 14.5.
    That's what makes it dangerous to say "never" ... with gears, someone, somewhere has done it at least once.

    Good to know tho, I'll put that in the 'little-known facts' section of the brain

    4 mod does seem pretty huge for a little thing like that. But you never know who knocked together what to keep the thing running, some time in the past.

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    Yeah, gears are *easy*, right?


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