Acme Tap

[Techbuilder]

Hey everyone
maybe someone can help me out with this problem
I have.

I am looking for a 1/4" 20 acme tap

I can't find it anywhere

I found this one but it is left handed not right handed

https://www.travers.com/scripts/cgii...ge=&webpageIn=

I tried mcmaster carr and I searched a couple other places that I do not know the name of.

If anyone has any information it would be greatly appreciated

[Mcgyver]

thats a small acme thread.....at that size, what advantage would an acme hold over a 20 tpi UNC? maybe you dont have a choice because its to mate with some existing part, but if at all possible i'd be thinking design change. acme vs unc wouldn't be much different engineering wise. you could even make the argument that a two start unf would be a superior solution strength wise and have a faster lead than a 1/4 20 acme

if i had to make the thread i'd make the tap. that would be a very easy tap to break, so make several that cut the finished thread in stages....or you could try to single point it, (not as unbelievalbe as it might sound)

[mc-motorsports]

http://www.ncweb.com/biz/leesmachine...e/Page_1x.html
Call Lee or Mike, they sell them NOS and used, good prices too.

[Techbuilder]

Originally Posted by Mcgyver thats a small acme thread.....at that size, what advantage would an acme hold over a 20 tpi UNC? maybe you dont have a choice because its to mate with some existing part, but if at all possible i'd be thinking design change. acme vs unc wouldn't be much different engineering wise. you could even make the argument that a two start unf would be a superior solution strength wise and have a faster lead than a 1/4 20 acme if i had to make the thread i'd make the tap. that would be a very easy tap to break, so make several that cut the finished thread in stages....or you could try to single point it, (not as unbelievalbe as it might sound)

The biggest I could go is 3/8 but I want 20 and I can only find 16
and I still can't find a tap for that either.

What is UNC?

[mc-motorsports]

Unified Course,
American standard nuts and bolts (UNC - Unified Course Threads) have less threads per inch than machine nuts and bolts (UNF Unified Fine threads). For example, given a 3/8" bolt, the UNC version has 16 threads per inch (TPI). Where a machine style thread for 3/8 bolt has 24 threads per inch - (TPI).

1/4"-20 UNC?

[Mcgyver]

What is UNC?

Unified National Coarse, the most common thread form and series in North America. my point was, what reasons do you have for wanting it to be ACME and would a UN thread from (considering 1/4 20 is the UNC standard and one of the most common out there so taps and dies are readily available) work just as well?

maybe you really do need that tap; I have no idea because there is no context....however that you're not familiar with UNC suggests maybe you're new at this.......why not describe what you're trying to do and other options might present themselves? Just saying I need such and such a tap solicits responses like my 'make one' which probably isn't much help if you're just getting your feet wet.....with a little more context other solutions might appear

[Techbuilder]

Well the reason I wanted an acme screw is because I wanted no backlash on my mill. Now I know there is some but not as much as standard screws.

The reason for the 1/4" size is because I was just going to couple the shaft from the stepper which is a 1/4"

Now I know I can go bigger but I only want to go about 3/8" max

[CountZero]

you could always turn the end of the screw down to 1/4 from say 1/2....

[Mcgyver]

whether its acme or V doesn’t determine backlash. backlash results from clearance which all screws have, the better the class of fit, the less clearance but you still have to devise an anti backlash mechanism to remove it altogether (a screw with zero clearance wouldn’t move). The motor shaft doesn’t have much to do with determining screw size - imo you'd be better to come at the design with different criteria, but if you're fixed on 1/4" going with a unc V thread would be my approach......just because as i said there seems little engineering advantage in an acme thread and the unc screw cutting tackle is so readily available

[Metal1cutter]

Originally Posted by Techbuilder Well the reason I wanted an acme screw is because I wanted no backlash on my mill. Now I know there is some but not as much as standard screws. The reason for the 1/4" size is because I was just going to couple the shaft from the stepper which is a 1/4" Now I know I can go bigger but I only want to go about 3/8" max

Widell makes acme taps.

Regards,

Stan-