What is this Myford thread? Approx 4.5x0.8.

I messed up the internal thread in my cross slide lead screw (pressing off a seized/rusty dial... very soft steel). I wanted to put a tap down there but none seem to fit.

It seems like metric 4.5 with 0.8 pitch.

https://www.myford.co.uk/acatalog/18.-CHROME-BALL-HANDLE-SECURING-SCREW--A1541-1-4551.html

Myfrod is more likely to be either BA or BSF than Metric. The ML7 uses 1/4" BSF to hold the dials on, but is a slightly different set up to what yours appears to be, possibly Super 7?

It is 2 BA, I've just checked my S7 topslide.

Tony

Thanks. It is a Super 7. My 2ba taper tap didn't want to go down there so I must have really squashed the threads. And, of course, the taper for the handle.

Youch sounds nasty. Proceed with caution. The feedscrew is possibly made from relatively soft leaded steel for the sake of faster/cheaper mass production. I know the ends of both top and cross slide screws on my ML7 have been bent over the years by previous owner/butcher so they are not particularly stout. Certainly not high tensile or the like.

You may have to very carefully open up the hole with a tapping sized drill if it has been squeezed shut. Taper can be remachined in the lathe if you lock the cross slide in place using the gib screws or slide lock screws and machine using the top slide and carriage traverse. No idea what the angle would be.

A similar point:

The cross slide end bracket screws are 2BA as well (and not 3/16BSF).

If its all squished then retap with a 5mm or 6mm and put in a metric screw

easy peasy

I've retapped a bunch of stuff on my old imperial gear with zero failures so far

y

Edited By Ady1 on 30/01/2022 11:25:18

I got it bodged back together but yes- very soft stuff. My cross slide screw had also had a knock on the handle making it out of true so went stiff-loose as it turned through 360. A friend who knows told me to put a clock on it and bash it back straight with a mallet. I just wouldn't have thought of it without being told. It's much better now!

Edited By jaCK Hobson on 30/01/2022 14:04:55

Edited By jaCK Hobson on 30/01/2022 14:05:24

Tubal Cain's Model Engineers Handbook quotes 2 BA as having a top diameter of 4.7 mm and a pitch of 0.81 mm.

And a gib adjuster on a Myford Cross Slide is what i would expect to be 2 BA unless it is a very recent machine.

Howard