My First ACME Thread

I was hoping to avoid the whole "hobbing" thing. If the single point cutter cutting the wheel has the same profile as was used to cut the worm, would that not work?
 
The valleys of the driven gear are slightly wider at the sides than the middle due to the entry and exit angle of the worm gear. I single point cutter cannot perfectly create this geometry. It would not be that hard to make a hob out of O1 tool steel. Go back and look at how I modified the acme lead screw to make a simple hob. It worked for a while but is now dull.
It also depends on the accuracy you need. I'm sure you could get it to run without a perfect gear mesh.
 
I assume that if I make a hob I'll also need to make a mount on my xslide to allow the worm wheel to spin during "free hobbing"? The ultimate purpose of my worm gear adventure is to make a gearbox that will serve as the power head lift on my mill. I've already built a power head lift that uses a leadscrew. It works well but it was always in the back of my mind that if the leadscrew snaps the head will drop like a pile driver. I like the self locking feature of a worm drive. If I make a hob you're welcome to borrow it. In the meantime you may be able to set your lathe up for 4tpi. As an example, my G4003G had no 27tpi on the thread chart. My gear normal train included two 40tpi gears for imperial threading. By replacing the second one with a 60t gear the speed of the carriage was reduced by 40/60 or 2/3. Then 18tpi on the norton gear box would cut 27tpi. If you take a 6tpi setting and increase the speed by a factor of 3/2 you'll get 4tpi. An 8 tpi setting will become 4 by increasing the gear ratio by a factor of 2/1. A 12 becomes 4 with a 3/1 increase, ect. If your lathe doesn't have a gear that would work maybe you can make one. I have a 1 1/2" piece of O1 that I can make a hob from. This is why I made the worm gear 1 1/2 inches in diameter so if I absolutely had to make a hob they would have the same radius. This worm drive project is not on the front burner right now so it may be a while before I get to the rest of it. You're way ahead of me in this worm gear business so I may check in with you when I get time for the next step. Ed P
 
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It would still be nice to have some kind of safety on the head to prevent drop. Maybe a counter weight pulley system?
Yes, I mounted my blank on the cross slide on two ball bearings stacked. My lathe has a quick change gear box. It goes down to 5TPI. I suppose I could play with the gears proximal to that?
I would need a 1" hob but thank you for the offer.
I suggest you try to make your single point cutter out of carbide. An old 1/4" end mill would be ideal. If you have a tool post grinder, you can grind a 30 deg taper on the end mill shank and then form that into your cutter. I would offer you mine, but I will need it for more gears yet to be made.
 
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