ML7 spindle change

[Mick BaileyParticipant @mickbailey28509]

I like the look of the 5C chuck, especially the key operation. It seems to be more inclined towards work holding rather than as a toolholder, though the tolerance on work diameter isn’t as flexible as an ER holder. No worse than the Myford collets though.

However, something unexpected is the offer of a brand-new spindle which would restore my lathe to the original functionality. I’m back to the original question – other than fitting up the spindle to the existing shells, is there any other consideration?

[JasonBModerator @jasonb]

With 5C there is the option to fit a 5C to ER32 converter. I don’t use mine very often but it can come in handy for odd sizes. I only have imperial 5C collets in 1/32 increments not 1/64, also got metric ones which get the most use now. You can also machine the “emergency” collets if you have a particular size you want to hold but not really worth it for a one off.

5C was always designed with workholding in mind, the Hardinge spindle tapers accepts 5C not MT.

[HopperParticipant @hopper]

[JohnFParticipant @johnf59703]

[Mick BaileyParticipant @mickbailey28509]

I’m used to scraping bearings and flat surfaces, but these have all been either bronze or aluminium alloy. Perhaps more forgiving than white metal. I think before carrying out any work I’ll properly assess any wear to the existing spindle and blue it up to get a good idea of the current contact area, then do the same with the new spindle when I get it. Whilst the existing spindle bearing surface appears to be in perfect unmarked condition, it may have worn unevenly. Despite a lot of use in my 32 years of ownership I’ve never adjusted the shims and there’s no appreciable play but this may be masked to some extent by the oil film. The belts have been replaced a few times in my ownership, so spindle removal and replacement are familiar.

Out of the numerous  ‘what if…’ thoughts that always precede any job I plan to do these days (likely due to ageing), it occurs to me the possibility of the existing arrangement having excellent contact, whist a brand new spindle could show much reduced contact. At that point a decision would need to be made; how much do I want to scrape off to achieve satisfactory contact, versus how much will the overall alignment change? I suppose I have to arrive at that point, but if then I’m reluctant to proceed in changing the spindle there are then the other options already mentioned.

 

[Mick BaileyParticipant @mickbailey28509]

Here’s an update;

I blued up the spindle and bearings and was rather surprised that there’s almost 100% contact. A few days ago I had an idle afternoon and because I’d got the offer of a brand new spindle though that I had nothing to lose in trying to rehabilitate the taper by boring. I used my most rigid HSS boring tool, freshly sharpened and with tightened gibs, and took enough cuts to remove the damage, then very lightly reamed it.

The Myford collets need a workaround as they sit far too deep, but with some thought I should be able to figure out something. They will clamp up with the closer over the collet nose, rather than engaged in the groove. I did a test cut on some 3/8″ silver steel and the accuracy is perfectly fine for my own needs. The cut is uninterrupted as soon as the tool contacts the work – no sign of any runout.

Given that the bearing/spindle contact area is so good, it seems that I could well upset things and end up in a worse situation with a new spindle. My chucks and faceplate are all fitted to that spindle and its had since 1953 to bed in. Perhaps its been scraped and re-shimmed in the past.

 

[Author]

Posts