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  1. #1
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    Default Need a cross feed gear...

    I picked up an old Seneca Falls Star lathe, in cleaning and looking at it, I found a gear missing in the apron, it is the gear that drives the cross feed screw. I thought I had identified it, 2" OD, 16 DP, 14.5 PA, a forum member sent me one, and while it is close, it is not right, the teeth don't mesh, they are bigger on the drive gear, I'm not sure if they are 20 pa or something unique, how do you measure them? Below is a picture, the drive gear in the apron is the lower of the two,
    the upper is 2" OD, 16 DP, 14.5 PA. Any help at all would be appreciated, thanks in advance.

    img_20171204_204858410.jpg

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    measure the OD of the gear, count the teeth.

    Tooth count + 2 divided by the OD

    Take your 16DP gear for example, it is 30 tooth with an OD of 2.00"

    30+2=32
    32 divided by 2.00"=16DP

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    i'd guess and say you need an 18 dp, 14.5 pressure angle gear, and your post is hard to read, no offense.

    find a gear generator on the internet and print out a copy, cut the paper out and see if it meshes.

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    that looks more like you need 15 DP here- something custom maybe. Can you measure the OD and tooth count of the drive gear?

    allan

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    My bet it is a 14DP 26 tooth gear that is needed if that 2" requirement is in fact correct...however if that 16DP gear shown in the pic is actually mounted on the stud the 2" is clearly too small...
    14 DP is the red headed step child of the gear world but not impossible to find, many older machines used them.

    but can't tell anything without proper measurements...
    Last edited by iwananew10K; 12-07-2017 at 05:39 PM.

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    Quote Originally Posted by iwananew10K View Post
    My bet it is a 14DP 26 tooth gear that is needed if that 2" requirement is in fact correct...however if that 16DP gear shown in the pic is actually mounted on the stud the 2" is clearly too small...
    14 DP is the red headed step child of the gear world but not impossible to find, many older machines used them.

    but can't tell anything without proper measurements...
    Oh, they are around - usually found hiding in a piece of stock waiting on a No. 4 cutter and a dividing head
    but seriously - not a hard gear to make if one is set up to make gears. The 27 tooth ones on the 13 tumbler are a bit more of a challenge. (27 being a large prime number)

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    Quote Originally Posted by Rudd View Post
    but seriously - not a hard gear to make if one is set up to make gears. The 27 tooth ones on the 13 tumbler are a bit more of a challenge. (27 being a large prime number)
    Since when was 27 a prime?

    WRT 14DP yeah they're hard to find, that's why I've a full set of gear cutters. Been there myself.

    PDW

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    Quote Originally Posted by iwananew10K View Post
    My bet it is a 14DP 26 tooth gear that is needed if that 2" requirement is in fact correct...however if that 16DP gear shown in the pic is actually mounted on the stud the 2" is clearly too small...
    14 DP is the red headed step child of the gear world but not impossible to find, many older machines used them.

    but can't tell anything without proper measurements...
    The 2" OD I believe is correct, I had to remove the stud to get the teeth to engage for the picture, with the stud in place, I cannot quite get the two gears to mesh, I suspect I could with a hammer. but obviously they don't match. I'll do a proper pitch measurement tomorrow when I get home.

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    search this forum archive for : HOW TO IDENTIFY GEAR PRESSURE ANGLE

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    Quote Originally Posted by PDW View Post
    Since when was 27 a prime?


    PDW
    Name me some numbers other than 27 and 1 you can multiply to get 27 as the result.

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    how about 3 and 9

    allan

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    ouch...........

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    OK, not posting till after the second cup of coffee from now on.
    I can tell you though that you aren't going to find a 27 tooth gear premade anywhere but the used market.

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    Quote Originally Posted by Rudd View Post
    OK, not posting till after the second cup of coffee from now on.
    I can tell you though that you aren't going to find a 27 tooth gear premade anywhere but the used market.
    You were probably thinking of 29 which is a prime (AFAIK).

    Agree the gear isn't likely to be found in a commercial catalog. Easy to cut though with a basic DH & appropriate involute cutter.

    PDW

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    Okay, the gear the missing gear meshes with in the apron measures 2.565" diameter, 34 teeth. 34+2=36, 36/2.565=14.035. So, 2*14=28, 28-2=26. That would confirm the 14DP, 26 tooth.

  22. #16
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    ok, you have confirmed 14DP and the machines age pretty much guarantees 14.5 pressure angle.

    But befor you commit to 26 tooth I suggest a little more confirmation...a tooth or so does not make a big difference in outside diameter.

    To that end a center to center distance across the studs would confirm the tooth count, once confirmed a WTB in the tooling and parts for sale section will get you a gear I'm sure.

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    Ahhhh. Good call, I'll get that measurement tomorrow.

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    Quote Originally Posted by wilsonsk View Post
    Ahhhh. Good call, I'll get that measurement tomorrow.

    For 26 and 34, center distance for pair should be close to 2.143"

    Arrived by:

    34/14 + 26/14 / 2

  25. #19
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    Yup..just add the teeth up(60) and divide by 2x the DP(28)

    clearly a method to the madness.

  26. #20
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    Have the #4 cutter if you decide its a 26 - you would have to grind it or get it ground like the thumbnail so it cuts without any fooling around

    No charge if you are good at returning stuff
    Attached Thumbnails Attached Thumbnails grind-gear-cutter.jpg  


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