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  1. #1
    Join Date
    Aug 2008
    Location
    Melbourne
    Age
    34
    Posts
    1,075

    Default Another worm wheel, but with more details

    This came in a couple of weeks ago with a minor issue...
    PXL_20210819_230821142.jpg

    Perfect opportunity to learn how to measure up for a new one. Everything comes from the worm, from the top we have: Number of starts, axial pitch, OD, pitch diameter, helix angle, addendum, tooth thickness at the pitch line, and the gear train for our thread mill. We're only making the wheel, but it only takes a minute to add it in. Once we have the pitch, we'll check to see if we've done the same pitch before because that means we can simply copy much of the information; the only thing that will change is the helix angle and number of teeth in the wheel
    PXL_20210818_224751556.jpg

    Once we have that, we can then work out everything else.
    PXL_20210818_224755576.jpg

    Then it's off to (hopefully) find an existing tool bit. We've cut this pitch before, so there's a good chance of finding one
    PXL_20210818_225029223.jpg

    Got a bit, time to set it up. All we're doing, in theory, is creating a single point of the worm that will cut the teeth to match the exact profile. As you can tell from the shifter and hammer used to actually set the thing, being a few thou or 10 minutes out isn't going to make a whole lot of difference in the real world. The tool bit is held in place by a screw in the end of the bar clamping against a stack of dowel pins.
    PXL_20210818_224503171.jpg

    Because we can't measure the size of the wheel directly, we have a simple fixture that sits on the hob slide to hold the worm in tight mesh, then we can take a measurement from that with gauge blocks and calculate the remaining depth of cut
    PXL_20210819_055854448.jpg

    Didn't get any pics of checking the fit in the gear tester due to time, but it's pretty simple; wheel sits on the pin, worm is held across it (usually between centres, but this one didn't have a centre in one end so it sat on the V-blocks on the ground bearing diameters), they're brought to the nominal centre distance and we make sure they run freely.
    PXL_20210820_030643606.jpg

    All deburred and ready to go.
    PXL_20210819_230914172.jpg
    Gear cutting specialists and general engineers www.hardmanbros.com.au
    Fine pitch gear cutting from 0.1 Module www.rigear.com.au

  2. #2
    Join Date
    May 2011
    Location
    Murray Bridge S Aust.
    Age
    71
    Posts
    5,942

    Default

    Nice to see that you're getting a bit of variety in your work.
    Kryn
    To grow old is mandatory, growing up is optional.

  3. #3
    Join Date
    Aug 2008
    Location
    Melbourne
    Age
    34
    Posts
    1,075

    Default

    Sometimes we go for months without one, sometimes we get one a week I'm glad there's lots of them now, means I can consolidate what I've learnt before the last guy who knows anything about it leaves
    Gear cutting specialists and general engineers www.hardmanbros.com.au
    Fine pitch gear cutting from 0.1 Module www.rigear.com.au

  4. #4
    Join Date
    Nov 2007
    Location
    melbourne australia
    Posts
    3,228

    Default

    Nice work. Can you tell us the cost of that part?
    Chris

  5. #5
    Join Date
    Aug 2008
    Location
    Melbourne
    Age
    34
    Posts
    1,075

    Default

    Nope, but I can have a guess...

    They ordered 2 of them, so lets say 1 hr for measure and calculations, 3 hrs to turn and slot the blanks, 6 hrs for gearcutting at $120/hr (not 100% sure on the shop hourly rate, but that sounds in the ballpark) comes to $1200, plus material, plus the "tear down the job that's already set up because we need these now" surcharge... Might be looking at $2k for the pair

    I'll try to remember to ask out of curiosity, might not get an answer though
    Gear cutting specialists and general engineers www.hardmanbros.com.au
    Fine pitch gear cutting from 0.1 Module www.rigear.com.au

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