Common practice to mill a bit off the bottom of the tool holder. My ML7 was made to take 3/8" tool bits or smaller so I had to knock 20 thou or so off it when i converted to modern 10mm insert tooling. Did it in situ with an end mill cutter held in the lathe chuck and suitable packing under the toolpost.

If you are getting the carriage and cross slides reground, you may drop the tool holder sufficiently in the process anyway and not have to bother.

Why not just make an extra toolpost or even clamp the tool with packing straight onto the topslide like Myford owners did before they got a 4-way or QC toolpost.

the bigger tooling is stiffer when you get a situation where you need a lot of tool overhang such as working with tailstock support or around the edge of  a large diameter such as a flywheel not just when you want to take a heavy cut.

Edited By JasonB on 25/09/2018 12:09:02

Or just mount the new ballscrew nut to take into account any loss of height.

Wow. £3300 plus painting and a lot of fitting. Pigs and lipstick come to mind. For that cost plus the cost of a Myford you could probably pick up a proper CNC machine and spend your time bringing it back to life, with some likelihood of ending up with a decent machine.

Murray

No, that'll be Murray from Lancashire (currently) – Lytham St Annes (posh name for Blackpool).

Murray

By top and bottom slides I suppose you mean the cross and top (or compound) slide? For CNC you have no need of a topslide any more. You can then make a properly rigid tool post that fits the cross slide. This makes it possible to used indexed tool holders and properly apply tool offsets.

The cross slide screw is best replaced with a ballscrew, it is very hard to get rid of backlash with a normal nut, and backlash on the X slide is a real pain – for example when cutting tapers. Depending which S7 you have you may need to find a small diameter ballscrew for the X slide to fit the available hole – my conversion was of a power X feed 9pxf) machine that uses a larger feedscrew so I was able to use a 12mm screw supported only at the outboard end. It isn't essential to have a ballscrew on the main Z feed ("leadscrew&quot and I haven't fitted one (it's on the to-do-one-day list). If you do use standard nut, the Myford non-pxf nuts are made of mazak alloy as standard and you'd need to make or have made a bronze one – even then you'd be lucky to get a low enough level of backlash. My ballscrew gives about 0.02 mm IIRC. The Myford pxf nuts are hardened steel, but even with those the as-new backlash is ~0.2 mm.

Why are you fitting a servo to the spindle? Normal practice is to have a spindle sensor, either 1 per rev for Mach 3 or a multi-slot sensor for better systems such as LinuxCNC, but to use a standard drive system. As long as the controller knows where the spindle is it can control the tool position to suit at least for screw cutting. If you are thinking of using this for dividing, I think you're better off having a separate digital division head. Most readily available CNC controllers expect a standard drive spindle, not a servo positioned one.

These days it is recommended to have a separate motion controller between the controlling PC and the servos/steppers (by the way please note that you DON'T use an apostrophe when an "s" is indicating a plural). This interfaces to the PC using USB or Ethernet, and actually generates the real-time control signals – I can't recall exactly but I assume that's what cncyourmyford does. With this approach you can use a laptop because all the real-time stuff happens in the controller.

Hope this helps – I first converted my S7 nearly 10 years ago and have made a number of improvements since and it works very well.

Have to agree with Martin, it looks like they have left the corners 'sharp' as well, they will wear poorly. You'll probably have to relieve the internal corners of the saddle and tailstock casting as well.

If you look at a factory fresh bed the chamfer is considerable.