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when you have to cut an odd numbered gear

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madjackghengis:
While cutting the old valve seats out of a set of heads, the portable power unit for my portable valve re-seating machine stripped out its worm gear, the first gear in the train that gives me fifty rpm, and about two hundred foot pounds of torque to turn the spindle.  A quick check with Boston gear showed they don't carry a fifty one tooth gear, checking with the company that took over, when K.O. Lee went out of business gave me the answer they could give me an estimate on the cost of having the gear made, however they did not have one and would job it out to a machine shop.  Looking at my dividing head, I quickly discover I don't have differential indexing either, so I'm out of luck there too.  Since I've been using my DRO on my mill for lots of holes, it suddenly occurs to me, I can make an index plate for my dividing head using the DRO, and by drilling fifty one holes in it, I can make it possible to use my simple index head provide fifty one holes for the cost of making a plate, and with this and a twenty dollar gear cutter, or a fifty cent tool bit and my shaper, I can cut that gear and make that motor just as good as it was when I bought it, twenty years ago.  The next step is deciding whether to grind a cutter to fit the shaper, and save the money and shipping, or do the gear cutting on the mill, and wait till a proper #3 cutter arrives, and then set the angle and cut the gear.  Unfortunately, this "worm gear" was not cut as a worm gear at all, but as a spur gear, cut with the angle of the worm matched by the teeth of the "worm gear", which gives strictly line contact between the worm and the gear, while a true "worm wheel" cut with a "worm hob" would give a plane of contact, and thus a place for lubrication to interact with the worm and gear, and not just get pushed out of the way.  The index plate has been drilled, I just have to fit it to the dividing head, and find some material suitable for a "worm gear" or better named bevel spur gear.  Pictures are forthcoming, the repair will be shown and joy and happiness restored after weeks of muted anger and hostility.  I thought the machine was supposed to last a lifetime, and I'm only half dead yet!!! :bang: Mad Jack

madjackghengis:
This gear has presented about three different ways to make a replacement, and I have finally settled on using a dividing head, even having made tooling for another method.  Having already turned an index plate, and drilled the fifty one holes using my DRO function, here is the plate in the lathe, being turned to size

Taking a cut, this is a piece of scrap, and its hard cast iron, part of a lathe scrapped out almost thirty years ago, the feed clutch plate for the apron.  It has cost lots of time getting to this point.  This is recycling at its most efficient :thumbup:

The center hole was too large, so I bored it to put on a stub arbor to turn the o.d., with a tight press fit and locktite, and now am boring the arbor to fit the arbor on the dividing head, as the "stub" will end up part of the index plate when it is finished.  After this, three mount holes, drilled and counterbored, and it is done.

index plate mounted and tested on the dividing head, now I just need to make a blank and an arbor to hold it on, and buy a cutter.  Mad Jack :beer:

Darren:
Excellent, I like the way you used the dro on the mill  :clap:

Bernd:
Mad jack,

I have to say the light bulb went on after you said use the DRO on the mill to make an index plate. Can't believe the answer to making index plates was sitting right there in front of of me.  :clap:

Seems like I'm forgetting stuff I learned years ago. :scratch:

Bernd

Rob.Wilson:
hi Mad Jack

if you have 51 holes in the index plate , and are using the 40:1 reduction on the dividing head , how will you get 51,  am i missing some thing ? ( i probably am )

would it have not been better to make the index plate fit the front of the dividing head ,were you can do direct indexing, just a thought .


cheers Rob

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