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  1. #1
    Join Date
    Apr 2009
    Location
    Kingswood
    Posts
    930

    Default 16 DP Gear Cutting Tool

    Hi all,
    I am attending a class at TAFE for Fitting & Machining and currently plodding though a module on gear cutting. (The next exercise is a 3 Module 28 tooth 20 degrees helical gear).

    My lathe, a Colchester (Imperial) Bantam, is missing one gear from the standard set of screw threading change gears - 49 T.

    Now, I may never have to use a 49T in earnest, but it would be 'nice' if I could use the TAFE facilities to make the gear and so complete the set.
    But, the TAFE does not have a 16 DP No. 3 cutter.

    Does anyone have such a cutter that they are prepared to loan ?

    I would gladly accept a worn cutter (capable of being sharpened) as the TAFE have a Tool & Cutter Grinder and this would be a great opportunity to learn how to operate that machine.

    I am near Penrith, west of Sydney.
    Please PM if able to help.
    John.

  2. #2
    Dave J Guest

    Default

    Hi John,
    Check CTC tools, he has just got a hole new range of cheap gear cutters.
    Results for New Products
    Dave

  3. #3
    Join Date
    Aug 2008
    Location
    Charlestown NSW
    Age
    65
    Posts
    1,669

    Default

    No cutter, but I know where there is a gear planer, sitting in storage with a couple of pallets of assorted cutters and fixtures that will probably never be used again.

    bollie7

  4. #4
    Join Date
    Apr 2008
    Location
    Canberra
    Posts
    805

    Default

    Hi Electro, I have a small, eclectic selection of gear cutters at home. I have a feeling one of them is a 16dp 14.5 pressure angle cutter. Im not sure what number it is though. Ill check it out for you and get back to you in a couple of hours.

  5. #5
    Join Date
    Apr 2009
    Location
    Kingswood
    Posts
    930

    Default

    Thanks Brendan,
    I have already got a loan of a cutter from a forum member.
    This forum is really something, great comradeship.

    Thanks also to Dave and Bollie7 for their inputs.

    I plan to cut the gear on Monday night at the TAFE using a horizontal mill.

    The next task is to cut the 8-spline in the bore.
    My plan is to bore the ID accurately, then cut the splines in the lathe using a HSS tool with the carriage acting like a shaper.
    The tool will be sized for the full width of the spline notch.
    The final depth will be a little more than necessary as the critical fit appears to be the ID.
    Should not be too hard in the cast iron with the cut (say 0.05 mm) per stroke put on with the cross slide.

    Only difficulty is the bore size, the TAFE have a 20 mm tapered mandrel, but the gear is something like ~21 mm ID for the lathe fitting.
    I will bore the blank to the correct size and make a mandrel to fit over the weekend.

    John.

  6. #6
    Join Date
    Apr 2008
    Location
    Canberra
    Posts
    805

    Default

    No probs John. Turns out mine was an 18DP no 2 anyway.

    Sounds like a great course your doing there.

    Brendan

  7. #7
    Join Date
    Apr 2009
    Location
    Kingswood
    Posts
    930

    Default

    So much for assumptions, the critical fit is the OD !

    A close examination with a strong light showed an air gap on the ID fit, no gap on the OD fit.
    A sample of gears measured (vernier) 20.6 to 21.1 on the ID, and 22.26 to 22.28 on the OD.
    The OD on two gear shafts were 22.23 mm.
    Imperial 0.875 inch is 22.25 mm, nuff sed.

    So, back to 20 mm bore to fit the TAFE mandrel, cut the teeth on the horizontal, and then on to the 4-jaw at home.
    I will dial-in off the 20 mm bore with the part-gear square and machine the bore to, say, 20.8 mm.
    I will use aluminium protectors on the chuck jaws, and increase the stiffness against the thrust of the tool by using a spacer between the gear and the chuck body.

    Then shape the slots to give, say, OD 22.27 mm.
    The banjo gear shaft is removeable from the lathe, so I will have a shaft at hand to test the fit before removing the gear from the chuck.

    This gear also prompts me into putting a simple divider on the lathe spindle - something a was going to 'get around to' one day.

    John.

  8. #8
    Join Date
    Jul 2010
    Location
    Melbourne
    Posts
    9,088

    Default

    electrosteam I can't rememeber what lathe you have but you might get sick of winding the carriage back and forth. You might like to make something like this.
    SLOTTER
    There are ones that fit a four way tool post better but I cant find one online ATM.
    Stuart

  9. #9
    Join Date
    Mar 2010
    Location
    Nth Qld
    Posts
    687

    Default

    Quote Originally Posted by bollie7 View Post
    No cutter, but I know where there is a gear planer, sitting in storage with a couple of pallets of assorted cutters and fixtures that will probably never be used again.

    bollie7
    Hmmm sounds like an in interesting bit of gear

  10. #10
    Join Date
    Apr 2009
    Location
    Kingswood
    Posts
    930

    Default

    Stuart,
    That slotter is a nifty bit of gear - something else on the 'to do' list.

    Following is a photo of the gear I cut at TAFE.
    The cutter borrowed from Pipeclay worked a treat.

    Full depth design is 3.41 mm and the job was done in two passes.
    First pass by hand at 3.3 mm depth, second pass at 3.41 under power at 120 mm/min.

    Two teachers at TAFE agreed the gear matched very well with a sample genuine Colchester one.

    Now for a spindle divider and the slotting.
    For the divider, I will make a 48-hole plate to be clamped on the end of the spindle.

    Happy machining,
    John.

  11. #11
    Join Date
    Jul 2010
    Location
    Melbourne
    Posts
    9,088

    Default

    My "to do list" is about 4 pages hehe

    That's a nice looking gear. That's on my to do list as well once I can spend some more money on the cutters. Hey wait a minute, I have a shaper! although I think milling would be easier on the dividing head.

    Why 48 for your divider gear? What other gear do you have in your change gear set? Why not use them for dividing on the spindle? It's going to make loud noises if you try to divide and power feed at the same time

    Stuart

  12. #12
    Join Date
    Apr 2009
    Location
    Kingswood
    Posts
    930

    Default

    Stuart,
    I have elected not to use change gears for a dividing plate on the lathe spindle because:
    - a pain to make a splined fitting,
    - it would obstruct the spindle bore.

    The 48 hole plate will be clamped to the OD of the end of the spindle, nothing in the bore.
    In two pieces, a clamp and a separate plate, so that I could make a different plate in the future if the need arose.

    48 holes gives divisions of: 2, 3, 4, 6, 8, 12, 16 and 24.
    This covers all the normal engineering requirements for fittings off the lathe.
    The assumption is that a toolpost/cross-slide fitting like a small milling attachment will be used to make spanner flats, hex nuts etc.

    My initial requirement, of course, is for an 8-way indexer for the change gear bore slotting.

    I plan to make a backstop clamped at the end of the spindle and adjusted from that end (see Model Engineers Workshop issue 165).
    I can see the need to have both the backstop and divider in use at the same time for small brass fittings for model locomotive boilers.

    John.

  13. #13
    Join Date
    Jul 2010
    Location
    Melbourne
    Posts
    9,088

    Default

    John
    I some how missed the part about 8 splines in the bore, I just have the one keyway.

    I've be designing an indexer for my lathe, your idea of fixing the gear to the outside of the spindle has given me something else to think about. Although from memory the bore of my change gears is 16mm so I should be able to make a backstop that passes through the piece that holds the gear to the spindle.

    Stuart

  14. #14
    Join Date
    Apr 2009
    Location
    Kingswood
    Posts
    930

    Default

    Well, I made the divider plate, one circle of 48 holes and another of 20 holes.
    This gives me 2, 3, 4, 5, 6, 8, 10, 12, 16, 20, 24 and 48 divisions.
    Room for another circle if I need it.

    The circles are just off centre because the bare plate was clamped to an MDF mounting plate on the rotary table for drilling the holes - it was checked and re-checked to be on centre, but not quite so.
    The error does not affect the dividing at all.

    I used a lathe tool ground to the width of the slot and planed each slot to depth using the carriage hand wheel with the spindle clamped on the divider plate.
    A bit if de-burring and general fettling and it fits fine.

    The new gear was fitted to the leadscrew gearbox and the lathe run to prove it.

    The slotted shape is not quite the same as the original due to the straight tool tip, but the fit is the same at the critical points on the diameter and slot sides.

    John

  15. #15
    Join Date
    Jul 2010
    Location
    Melbourne
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    Default

    Looks like is came up great John
    How many cuts did the splines take?
    Stuart

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