Author Topic: Chucks Helical Gear Cutting fixture  (Read 12740 times)

Offline donrecardo

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Re: Chucks Helical Gear Cutting fixture
« Reply #15 on: October 26, 2014, 12:20:41 PM »
. If I'm thinking right, a bit of equal diameter to the gear should yield a 45 degree cut.

That should be fun then if you want a 16DP gear with 80 teeth , can you get 5.125" drill bits in LH and RH 
and if so , wont they be rather expensive

Even a 32DP gear with only 30 teeth would be 1" in diameter and thats not a large gear , but is still an expensive drill bit

Offline tangler

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Re: Chucks Helical Gear Cutting fixture
« Reply #16 on: October 26, 2014, 02:13:43 PM »
Nice idea but.....

The lead required to cut a specific gear depends on the Number of Teeth, the Diametrical Pitch and the Helix Angle.  Only a pair of 45 degree gears running at right angles with the same number of teeth (1:1) will need the same lead.  All other situations will need a different lead for each gear.  I've just a had a look at my set of of 1/16"-1/2"  x 1/64" drill set;  The lead for the 1/2" drill is 3" as is  31/64, 15/32, 29/64, and 7/16.  I didn't measure them all but the lead on 3/8" is 2.3" and 1/4" is 1.8".  There does not appear to be systematic progression of lead with drill diameter.  I imagine the manufacturer sets up his machine to give a certain lead and then flutes a series of drill blanks of similar diameters at this setting. For a pair of 45 degree crossed helical gears to give a 2:1 ratio as is often used for cam shaft drives, the lead of one gear will be precisely half of the other gear.  If you can fiddle the design of one gear to fit in with the lead available from a drill, it is seems unlikely that you will find a drill to give exactly half this lead.

Slow and fast spiral drills are available apart from the standard jobbers but I think one would need a very large selection from which to choose a drill with the correct lead.

Shame really :(

Rod

Offline tinman13kup

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Re: Chucks Helical Gear Cutting fixture
« Reply #17 on: October 26, 2014, 02:45:30 PM »
Well dang, you had to go and mess up a perfectly crazy idea.  That lets me get back to thinking about a cold fusion reactor ;).
Tom

Offline donrecardo

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Re: Chucks Helical Gear Cutting fixture
« Reply #18 on: October 26, 2014, 07:23:51 PM »
Never give up on thinking up new ways to do things ,
now and again they actually work quite well   :ThumbsUp:

Don

Offline stefan-k

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Re: Chucks Helical Gear Cutting fixture - Question about the math
« Reply #19 on: May 14, 2020, 11:54:06 AM »
Hi all

I´m just building the fixture to make Helical gears and i have a question about the math in the excel sheet that Donrecardo createt.
If i look to the numbers of a Helical gear with lets say: 24 DP , 12 teeth and 60 degree angle, how can it be that the Pitch diameter is 1 inch in that case and the Blank diameter is only 0,583 inch.???
I don`t understand that. Afaik shouldn`t the Blank diameter always be a little bigger than the Pitch diameter?

If someone is still out there, please enlighten me.

Stefan


Online Jo

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Re: Chucks Helical Gear Cutting fixture
« Reply #20 on: May 14, 2020, 12:04:13 PM »
Welcome to the forum Stefan, Would you like to introduce yourself over here: https://www.modelenginemaker.com/index.php/board,3.0.html

I seem to recall seeing the calculations in Model Engineer in about 1946  :thinking: If no one else can find the answer for you I will have to see if I can find it  :noidea:

Jo
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Offline gbritnell

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Re: Chucks Helical Gear Cutting fixture
« Reply #21 on: May 14, 2020, 01:24:42 PM »
One of our members and contributors, Don1966, who had responded to this thread earlier on has made spread sheets for both helical and spur gears. I opened his program and put the numbers in that you stated and the O.D. came out as 1.083. The O.D. is very easy to calculate. 1\24=.04166 x 2= .0833. Add this to the P.D. of 1.00 and you get 1.083. This is the same calculation for spur gears.
I don't know if Don's spread sheet is in the files section or not but I used it in making all my helical gears and the numbers were fine.
gbritnell
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Offline gbritnell

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Re: Chucks Helical Gear Cutting fixture
« Reply #22 on: May 14, 2020, 01:31:36 PM »
I just did a search in the plans and drawings section and here's Don's spread sheet and fixture information.
http://www.modelenginemaker.com/index.php/topic,4871.msg92744.html#msg92744
gbritnell
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Offline gbritnell

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Re: Chucks Helical Gear Cutting fixture
« Reply #23 on: May 14, 2020, 02:35:53 PM »
I built Chuck's fixture but rather than setting it up in the lathe I used it on my milling machine. Here is a video of me using it to cut a helical gear.
gbritnell
<a href="https://www.youtube.com/watch?v=blaZ5tz0_6E" target="_blank">http://www.youtube.com/watch?v=blaZ5tz0_6E</a>
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Offline Don1966

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Re: Chucks Helical Gear Cutting fixture
« Reply #24 on: May 14, 2020, 04:35:01 PM »
The file is in plans a drawings but it’s not the correct one As George has pointed out. I had tried to upload the file with revisions and it was too large for the forum. So the one there is not the complete spread sheet. If anyone wants the spreadsheet PM me with your email address and I will gladly forward it to you. And your email address is safe with me it will not be shared.


Regards Don

Offline stefan-k

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Re: Chucks Helical Gear Cutting fixture
« Reply #25 on: May 14, 2020, 06:35:56 PM »
Hello Jo , gbritnell and Don

Thanks Jo for welcoming me..!
I´m surprised about the short response time.  :) Thanks for helping me out of this Problem. I guess i found the mistake by comparing the Spreadsheet from Don to the one from donrecardo. There was a wrong formula in the cell that calculates the blank diameter. I corrected the formula after gbrittnell pointed me in the right direction and now both sheets produce the same numbers. I already finished building the fixture and the next challenge will be making the template. I plan to use my fixture in the mill, like gbrittnell in his videos, because i don`t have a height adjustable milling attachment for the lathe. I like to try both ways to make them, the one by cutting a piece of sheet metal and the other one by milling a pipe to the desired shape. I´m curious how the first pair of Helical gear will come out.  I will post some pictures. For now Thanks very much, i´ll keep you updatet.

Stefan

Offline awake

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Re: Chucks Helical Gear Cutting fixture
« Reply #26 on: May 14, 2020, 08:09:31 PM »
Stefan, welcome to the forum. We love to see pictures - looking forward to seeing your fixture and your first gears!
Andy

Offline crueby

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Re: Chucks Helical Gear Cutting fixture
« Reply #27 on: May 14, 2020, 08:26:31 PM »
I built Chuck's fixture but rather than setting it up in the lathe I used it on my milling machine. Here is a video of me using it to cut a helical gear.
gbritnell
[youtube1]https://youtu.be/blaZ5tz0_6E[/youtube1]
Fascinating to see it in action - thanks for sharing that video. For different helix angles, would the angled piece at the bottom of the fixture that the wheel rides on be changed out, or is there some other adjustment for that?

Offline Craig DeShong

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Re: Chucks Helical Gear Cutting fixture
« Reply #28 on: May 14, 2020, 08:33:51 PM »
Yes you need to make a new ‘angle piece’ for the fixture for about every gear you make.  You also need to make a different ‘indexing wheel’ for each gear with a different number of teeth.
Craig
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Offline crueby

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Re: Chucks Helical Gear Cutting fixture
« Reply #29 on: May 14, 2020, 08:39:50 PM »
Yes you need to make a new ‘angle piece’ for the fixture for about every gear you make.  You also need to make a different ‘indexing wheel’ for each gear with a different number of teeth.
Thanks!

 

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