2-Start 1/2" 10 (5 TPI) acme tap?!??!

[ewest]

Hello,

I just tried to mount my nice new acme nut assemblies on this cute little CNC table I have. One of the original nuts was made of nylon or something, and shattered. I machined new nuts out (it's a weird design) and tapped away, and to my horror, they did NOT fit at all. OOps.... The screw was a 2 start and I had no idea! So now, I really feel like I ought to get a 2-start tap, but I can't find one!!!! The other, far less desirable option is to get a new single start screw and replace the one thats in there now, with which there is absolutely NOTHING wrong.
RAARARAR!!

Does anybody know where I can get a 2 start 1/2 x 10 (being 5 turns per inch) acme tap set? The nuts are Delrin, so I don't need coated cobalt or anything fancy. Mcmaster and MSC don't seem to have them.

Thanks!


Andy

[ger21]

You could buy a length of 2 start screw and use it to make you're own tap. It'll probably be cheaper, if you can even find one.

[ger21]

Or buy some of these and adapt them to your machine.
http://www.dumpstercnc.com/leadnuts_acme.html

[ewest]

I do have a nice Deckel tool grinder...hmmm... Of course I might just replace the screw too.

Unfortunately I can't use any commercial nuts. This table is set up with the screw running about 1/4" above a solid plate. Can't move either, so I had to machine my own nuts. I am only cutting Delrin, so maybe making my own tap wouldn't be so bad. Plus, I've heard other guys doing it too

Hmmm..


Thanks guys

[ewest]

OK so what about this idea..

Does anybody have any experience in milling multiple start acme threads? because I have none. I do have a CNC here that does have helical moves for doing such a thing, though I've never personally tried it, and I have NO idea what kind of cutter I would use, though one of the guys here says "Probably single tooth"

I've been looking in to just replacing the screws, and it looks like more and more of a pain, but one of the better options at this point.

Of course, saving money in this case is not the most motivating factor. This table cost an arm and a leg. Spending $75 on a cutter will not hurt my feelings. Right now it's just a very expensive boat anchor.

Your thoughts?