Speedy-cut ST-2 Tapper Gears
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  1. #1
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    Default Speedy-cut ST-2 Tapper Gears

    I've been looking to find common gear sets for a speedy-cut tapper ST-2. Found new ones at a higher price than the machine. As these machines were made across the pond I presume they are metric gears. Can standard 20 degree PA spur gear be made to work on these machines and have the proper leads? Any info about these would be helpful.
    spaeth

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    its hard to help you with the information in your post above. Are these on fixed center distances, etc. Your reference to "proper leads" is confusing if they are spur gears, as spur gears have infinite lead. Give us more information!!

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    Quote Originally Posted by Dan from Oakland View Post
    its hard to help you with the information in your post above. Are these on fixed center distances, etc. Your reference to "proper leads" is confusing if they are spur gears, as spur gears have infinite lead. Give us more information!!
    They are indeed upon Fixed Centers. They use regular, old Spurs to affect the ratios that drive the lead screw that drives the quill out and back in, while turning and reversing.

    Quote Originally Posted by spaeth View Post
    As these machines were made across the pond I presume they are metric gears.
    Likely, but why guess when determining the reality of it is so simple? Just measure. Z+2/OD = your answer.

    Z = Number of Teeth
    OD = Outside Diameter

    Example -

    65 Tooth Spur Gear has an OD of 3.350".
    Z+2 / OD =
    ( 65+2 ) / 3.350 =
    67 / 3.350 =
    20

    The example gear is 20 Diametral Pitch.

    Or....

    Let's say the gear has an OD of 3.2972".

    67 / 3.2972 = 20.32

    Since it is possible but highly unlikely that the gears are 20.32 Diametral Pitch, we can try to see if they are Module Pitch.

    25.4 / 20.32 = 1.25

    1.25 is a very common Module Pitch size. So that gear would be 1.25M.

    Or, to put it another way -

    1.25 x 67 = 83.75
    83.75mm / 25.4 = 3.2972"

    Clear as mud?


    Quote Originally Posted by spaeth View Post
    Can standard 20 degree PA spur gear be made to work on these machines and have the proper leads? Any info about these would be helpful.
    Possible. But if it is Metric based, it won't likely be so simple. Why not just determine what they actually are and then purchase some commodity gears that might need minor adaptions to fit?

    Good luck.

    EDIT
    If you do not have ANY gears, then simply measure the center distance of the two shafts and work backward from there. If you do not know how to do that and your Google is broken, report back and one of us can walk you through that, as well.
    /EDIT

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    Default speedy-cut gears

    Zahnrad,
    Exactly the kind of info I need. The machine came with a really worn gear set. 62 teeth and 29 teeth. Difficult to measure the OD's close to 4.995 and 2.403 and I've not measured Center distance yet. Machine is in a different location. So....

    64/4.995=12.81
    25.4/12.81=1.982

    31/2.403=12.90
    25.4/12.90=1.968

    Does this make the module pitch 2.0 ? And how does that translate into standard thread pitch?
    Thank You
    spaeth




    Quote Originally Posted by Zahnrad Kopf View Post
    They are indeed upon Fixed Centers. They use regular, old Spurs to affect the ratios that drive the lead screw that drives the quill out and back in, while turning and reversing.



    Likely, but why guess when determining the reality of it is so simple? Just measure. Z+2/OD = your answer.

    Z = Number of Teeth
    OD = Outside Diameter

    Example -

    65 Tooth Spur Gear has an OD of 3.350".
    Z+2 / OD =
    ( 65+2 ) / 3.350 =
    67 / 3.350 =
    20

    The example gear is 20 Diametral Pitch.

    Or....

    Let's say the gear has an OD of 3.2972".

    67 / 3.2972 = 20.32

    Since it is possible but highly unlikely that the gears are 20.32 Diametral Pitch, we can try to see if they are Module Pitch.

    25.4 / 20.32 = 1.25

    1.25 is a very common Module Pitch size. So that gear would be 1.25M.

    Or, to put it another way -

    1.25 x 67 = 83.75
    83.75mm / 25.4 = 3.2972"

    Clear as mud?




    Possible. But if it is Metric based, it won't likely be so simple. Why not just determine what they actually are and then purchase some commodity gears that might need minor adaptions to fit?

    Good luck.

    EDIT
    If you do not have ANY gears, then simply measure the center distance of the two shafts and work backward from there. If you do not know how to do that and your Google is broken, report back and one of us can walk you through that, as well.
    /EDIT

  5. #5
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    When doing the reverse engineering calculations like this, beware that gears are nearly always made slightly undersize on the OD.
    My solution is to make a set in mild steel and try them for fit, in this case going for 2 module.
    As a general rule if there are no other constraints, like housing size, difficult centres etc, most oems will use standard DP or mods


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