Hello and the first of many questions

Hi, I am in the process of setting up my 1951 ML7 lathe. One thing I would like to do is increase the inner diameter of the spindle bore by a couple of mm. First question is this possible or is there an alternative spindle with a bigger bore, it is currently 17.3mm.

Hello Dave,

Welcome to the forum.

II know this is a bugbear for the ML7, I'm not sure I a have ever hear of anyone doing this, the downside being that you could end up reducing the value of the lathe and/or end up without a usable MT taper in it.

Neil

You will find the spindle metal is quite hard and merely being able to clear 3/4" rather than 5/8" as designed is hardly worth the effort. There was not a larger bore spindle available for the ML7 and you will need to move up to a much bigger/later lathe to get an increase in size.

I still have my original ML7 but have moved on to larger lathes as the need arose.

If you did succeed in reaming out the mandrel to a larger size, (won't be much anyway) you will find that 2MT equipment then goes in deeper (You won't make it to 3MT, even if you can cut the mandrel) and this could cause you problems with some tooling.

You will have gathered that the general advice is "Don't do it".

I was equally, if not more, frustrated, by the small size of bar that would pas through the mandrel, so sold my ML7 and bought a larger lathe.

If you want to stick with a Myford, you need one of the later models, Super 7 Sigma, with a 4MT mandrel

Going from the sublime to the gorblimey, my current lathe has a 5MT mandrel!

Howard

I thought the answer might be dont do it, easiest solution is to farm the job out to a local company with the right machine.

Or buy a fixed steady....

Or swap it for a BOXFORD AUD - in my opinion a stronger and more useful lathe (cat among the pigeons !!)
BobH

I started with a minilathe (MT3 headstock bore) then got a ML7. I much preferred the ML7 but was worried about the smaller bore. So I kept the minilathe around for those occasions when I needed it.

.... and it (minilathe) sat there, essentially unused for a couple of years until I decided it was taking up much needed space (and money) for nothing. So I sold it. haven't missed it.

It depends what you are using the lathe for, of course, but I can't remember the last time the headstock bore on the ML7 has been an issue - let alone a serious one. Usually I can come up with something. A steady rest helps. It's also true that most of what I machine I design myself and you tend to design for the limitations of the equipment you have.

From memory standard bore size 14.2mm?

Dead easy run a masonry drill down but about the max limit due to strength at threaded nose would be 5/8". Looks like already exceeded that and may run in to spindle flexing.

Best thing ever done was scrap mine 16 years ago, cut your losses and get something more substantial you wont regret it. Jobs take 1/10th as long or less.