Helical Gears

Just wondering if there is anyone here that wouldn't mind sharing some information on cutting helical gears. I will be taking 2 originals with
worn out bores and reverse engineering them. I will be using a 4th axis vf4 haas mill. I have also been looking around the internet for an endmill style cutter to do the teeth but haven't found anything yet.
Aproximate dimensions would be: 8.080"OD X 2.08 THICK (84 TEETH) 5.465"OD X 2.08 THICK (56) TEETH)
Any information provided would be greatly appreciated.
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Dave wrote:

Dave, No help with your making new gears, but if it were me I'd think about restoring the bores to the old gears if that was all that was wrong.
Just a thought.
Best, Steve
--


Regards,
Steve Saling
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On Fri, 18 Sep 2009 19:16:02 GMT, "Dave"

======As indicated by another poster it will most likely be a *LOT* less work to rework the bores, possibly by sleeving.
For one off gears, including helical, Ivan Law's book "Gears and Gear Cutting" is hard to beat. It is written for the home shop machinist for one-off production using minimum special equipment. (Amazon.com product link shortened) other US home shop suppliers such as Blueridge also stock. http://www.blueridgeshoponline.com/product.sc?productId $3&categoryId=3
All of the mill type gear cutters that I am aware of are like Woodruff cutters, that is they cut from the side and not the end. As these are form relieved cutters this allows resharpening without changing the profile.
When you get Law's book, use the formulas to determine if you have DP [generally inch based] or Module [generally metric] gears, the pressure angle [14_1/2 and 20 are common] and the helix angle.
You will need both the cutter and an arbor to hold the cutter. With 84 and 56 tooth gears you will only need the #2 cutter.
For some PD gear cutters see http://www1.mscdirect.com/CGI/GSDRVSM?PMTYPE=KEY&SISMNO293484&SISHNO983321&SIPCNO00000575&SIZZNOD288332&SIS0NO42644&SISRC=KG&SISRCH=1&SIT4NO=&SILEVL=3&SILSEQ=1&SIORhttp://www1.mscdirect.com/CGI/NNPDFF?PMPAGEH8&PARTPG=GSDRVSM&PMT4NO=0&PMITEM191228&PMCTLG&PMT4TP=*LTIP
Metric/module cutters are somewhat more difficult to locate. See http://www.newmantools.com/cutters/gear.htm http://www.tap-die.com/index1.html http://www.ecvv.com/product/1568754.html
{be setting down when you check prices}
One trick to minimize wear of the expensive gear cutter is to use a slotting saw or possibly an end mill to remove most of the material in the spaces before finishing with the gear cutter.
What other machines do you have? If you have a cnc lathe with c-axis spindle control I have written a program to generate a program to use this as a [very slow] light duty low volume gear hobber. This allows you to grind a straight sided form tool which (with a "knee" type holder) will generate the involute curve by a combination of x axis feed and blank rotation. To download click on http://mcduffee-associates.us/PE/HOB03C.ZIP Use winzip to unpack. Runs under any version of windows, no need for a DOS box. This is currently set up for straight cut gears but can be modified for helical, however setup would be a right b***h.
Unka' George [George McDuffee] ------------------------------------------- He that will not apply new remedies, must expect new evils: for Time is the greatest innovator: and if Time, of course, alter things to the worse, and wisdom and counsel shall not alter them to the better, what shall be the end?
Francis Bacon (1561-1626), English philosopher, essayist, statesman. Essays, "Of Innovations" (1597-1625).
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Take a look at the chapter where they build the steering rack from scratch, and mill the gear with a 1/16" ball mill.
http://www.kirkhammotorsports.com/book_aoe/aoe_13.pdf
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