1/2" LH Modified Square Tap for ML100-512 Cross Slide Feed Nut

[Paul Page]

I've been quoted £322 (for 2) or £277 9for 3) plus carriage of £15 for the manufacture of a 1/2" LH Modified Square Tap for ML100-512 Cross Slide Feed Nut.
Does anybody want to purchase purchase one with me please to keep the cost down?

[DavidB]

The drawing I found for ML100-512 showed the thread as 1/2" x 10TPI ACME thread so is there a reason not to use an off the shelf offering such as on ebay, both RH and LH are listed.

[Paul Page]

My copy of ML100/512 definitely calls up a modified square thread form which is what the feed screw looks like.

[LesT]

Hi,
You can change to ACME for the Cross slide feed nut if you want, you will also need an ACME threaded cross slide screw obviously, however, if you have a lathe with a powered cross feed there is a drive gear on the shaft so you will need to accommodate that if you still want the powered cross feed to work.
Les.T.

[Pete.]

The modified square section is just 5 degree flanks AFAIK. Hell would freeze over before I spent that much on a single-use tap, I would look at producing an Evanut from Delrin or even making a tap from silver steel.

[rpwilson]

I've overcome this problem a number of times, making my own tap from silver steel, hardening it and then tempering. Make the tap about 10 thou oversize in diameter, this gives clearance between the top of the crossslide screw and the nut. Rough out the screw in the nut in the lathe, then finish off with the tap.