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Thread: home made worm drives - clever
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22nd Feb 2014, 10:42 PM #1Golden Member
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home made worm drives - clever
Thought this was clever - there are a few different versions of it on youtube and other web pages.
http://www.youtube.com/watch?v=J0o3W4_LRBw
http://www.astronomyasylum.com/gears.html
What puzzles me is that neither of these people seem overly concerned about the diameter of the wheel - one actually says that you just keep cutting until it works.
Will have a go.
Bill
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22nd Feb 2014, 11:04 PM #2
Bill I was shown this on MEM forum some months ago and tried it on a scrap piece of aluminium that I had and yep works well.
PeteBoycott Shampoo!!
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22nd Feb 2014, 11:20 PM #3Most Valued Member
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Thanks for this Bill, very interesting and would never have thought of using a tap.
Kryn
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22nd Feb 2014, 11:39 PM #4Member: Blue and white apron brigade
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Very clever. It would probably be worth turning a concave groove close to the radius of curvature of the tap drill size first and then taking if from there. It should reduce the amount of metal that needs to be removed.
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23rd Feb 2014, 07:24 AM #5Philomath in training
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In this case they are only using the worm as a reduction gear and don't care about the ratio. For something like a rotary table where the ratio is important because that is how you keep track of where you are for fractions of a degree you would have to hob things properly. For a bit of hobbing action, try this -
http://www.woodworkforums.com/showth...78#post1661078
Michael
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23rd Feb 2014, 10:41 AM #6
When this was discussed it was suggested to gash it first then the ratio is correct. The guy was making a gear for a specific uzd
Pete
Sent from my GT-P5110 using TapatalkBoycott Shampoo!!
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23rd Feb 2014, 11:22 AM #7
I did a lot of research into hobbing gears for worm screw drives, a couple of years ago. My intention is to build a rotary table. Some of the best information came from Telescope sites. If you cut your own hob you can make it identical to the worm shaft.
Here is a nice rotary table build from MadModder. Worm gear cutting starts at Reply #19.
http://file:///L:/Documents/Workshop...le%20Build.htm
Dean
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23rd Feb 2014, 12:18 PM #81915 17"x50" LeBlond heavy duty Lathe, 24" Queen city shaper, 1970's G Vernier FV.3.TO Universal Mill, 1958 Blohm HFS 6 surface grinder, 1942 Rivett 715 Lathe, 14"x40" Antrac Lathe, Startrite H225 Bandsaw, 1949 Hercus Camelback Drill press, 1947 Holbrook C10 Lathe.
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23rd Feb 2014, 12:55 PM #9Golden Member
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matching up again after 360 degrees
Its not the ratio that bothers me, although I can see that is important, its the fact that one of them implies that the cuts will be in exact synchronisation after going 360 degrees around the wheel, ie once you have hobbed the teeth to 359ish degrees around the wheel then the next "cut" " will line up exactly into the very first cut.
Isnt this going to be a bit like knurling, where if you are not careful you can just make a mess if things dont line up right after you have gone around 360 degrees ? (have only read about it not done any knurling yet)
Have to test it in shed.
Bill
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23rd Feb 2014, 01:07 PM #10Philomath in training
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That would be a concern if you only had a small number of teeth on the worm gear, but given the pitch of the tap and the number of teeth on the gear it is probably not going to be a problem in reality - as the guy said you go a bit deeper (that is make the PCD smaller) until it works.
Michael
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23rd Feb 2014, 01:21 PM #11
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23rd Feb 2014, 01:21 PM #12
Did anyone pick up on the lathe spindle speed? It increased speed from the initial cutting through to the finish full depth cut. I did not notice adjustments made for speed change ,but it may have been edited out.
The spindle speed change was not to be confused with the frequency of the noise from the turning tap lobes. The duration of noise from each lobe strike increased as it cut thread ever deeper, in the wheel as thread became deeper.
The material chipped like brass but I don't recall any mention being made of the material, but as a worm wheel, I imagine it had to be softer than the worm shaft.
Grahame
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23rd Feb 2014, 02:15 PM #13Senior Member
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Im thinking that the cutter / wheel should be positioned at full depth and then the wheel fed in along the x axis, otherwise the tooth count around the perimiter of the wheel wont divide properly. That said, does anyone know how to calculate the pitch circle of a worm wheel? Is it just treated as a normal gear calculation at the root of the gear?
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23rd Feb 2014, 02:15 PM #14
Whadja talking bout?
Are you suggesting I am missing a few links?
I wonder if links to other forums are filtered.... I seem to remember they were at some stage.
Dean
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23rd Feb 2014, 02:28 PM #15
The spindle speed changed several times up to a much faster speed than at first. I had the impression that it was a variable speed lathe and I thought I saw a hand movement towards the headstock at one stage.
Its not the ratio that bothers me, although I can see that is important, its the fact that one of them implies that the cuts will be in exact synchronisation after going 360 degrees around the wheel, ie once you have hobbed the teeth to 359ish degrees around the wheel then the next "cut" " will line up exactly into the very first cut.
Isnt this going to be a bit like knurling, where if you are not careful you can just make a mess if things dont line up right after you have gone around 360 degrees ? (have only read about it not done any knurling yet)
Have to test it in shed.
Bill
I have ideas to produce a 72 tooth gear so I get 5 degrees per rotation of the handwheel on a rotary table. This seems to be a nice middle point.
Dean