Member postings for Chris Pearson 1

I am puzzled by the operation of this chuck and I can find nothing on line. It appears to have been made by Pfander. This is what I have been doing:

- load collet (163E)

- fit closer loosely

- place workpiece in collet

- tighten closer so that the lever has about about 1/4" of slack

- push lever to right - this locks the collet

To remove the turned article:

- push lever to left

- undo closer with spanner

My expectation was that a collet would be mounted and closed to a sliding fit over the workpiece. The lever would then lock it in place and subsequent operation of the lever in the opposite direct would release the article.

Am I doing something wrong, or am I expecting the chuck to do something for which it was not designed?

Edited By Chris Pearson 1 on 20/09/2019 10:29:20

Edited By Chris Pearson 1 on 20/09/2019 10:29:51

Well, it's now in pieces and I shall be off to my usual bearing supplier tomorrow.

There is quite a bit of fine, and not so fine, swarf in the bottom of the headstock. It is mostly below the right hand bearing, which shows signs of wear, but it doesn't seem to be enough to account for the muck. There is no obvious damage or wear elsewhere.

Photos to follow.

I take the point. If one calculates module = 4/9 x tooth depth, the result is 1.46.

In theory, as Duncan points out, the reference diameter is 24 mm with a tip diameter of 27 mm and a root diameter of 20.25 mm so the scale of the pinion has been reduced by a factor of about 5%.

I found out today that this pinion was routinely replaced during refurbishment, which probably explains why they are in short supply as well as being, perhaps, a weak point.

OD = (N+2)*1.5 is only an approximation, which may be better for larger gears.

The pinion meshes with a 48 tooth gear which drives an 18 tooth pinion which meshes with the rack.

Funnily enough, the imperial rack measures 25.4 mm over 6 teeth. So one turn of the hand wheel turns the big wheel 1/3 of a turn, which equates to 6 teeth of the rack pinion.

It has been interesting fettling my 254. In many ways, they are very basic lathes, but they do seem to be well made. One exception may be poor lubrication of the handwheel shaft, but in the absence of oil, no lubrication system will work.

Just in case anybody else has this problem ...

In my case the pinion is acceptable, but the shaft is a little worn..

The tip diameter is 25.6 mm. The root diameter is 19.05 mm. It is module 1.5 with a 20 degree pressure angle.

Some of the other gears in the apron seem to be 20 DP and 14.5 degrees or at least they mesh with standard change wheels, but this one is clearly not.

I have replaced a fair few bearings in my time. The worst one came out of a Jaguar's rear hub - the rollers looked more like gallstones.

Thank you for suggesting the drive belt - even though it looks fine, replacing it won't break the bank.

Yes, thank you, I know about that, but why does the leadscrew nut have what looks like a reservoir? It cannot be one because the oil would simply run out. Odd!

Ifoggy, thank you for the response. Yes it is present in direct drive and absent with the belt removed - I have replaced the motor's bearings. Yes, pulley is tight.

Yes the manual has the exploded diagrams. There is no obvious means of adjustment.

I'd be most grateful for advice on a couple of matters in connexion with servicing a Myford 254 please. FWIW, mine is a 254+ Varispeed.

(1) I wish to remove and inspect the spindle - there is a hint of vibration and the oil in the headstock was not entirely clean. I cannot detect any play in it. Removal of the spindle may be fairly easy, but putting it back may be more difficult. Can anybody advise on, for example, whether any preload is required for the taper bearings.

(2) There is what looks like a small oil reservoir on top of the leadscrew nut. I don't think that it can be a reservoir because (a) there is no obvious way of filling it save for removing the apron, and (b) any oil would flow straight out.

If have a copy of the owner's manual, but was there ever such a thing as a service manual?

Many thanks in anticipation.