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Senior S Type Vert' mill repair

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Simon Williams 326/09/2016 20:02:32
412 forum posts
67 photos

Having watched Damian Noble's thread re-building his newly acquired Tom Senior mill, I have been spurred into action to tackle a project I've been ignoring for several years. The pulley driving the quill is supported by a plain bronze bush, and the steel inner drive piece has worn where it runs in this bush. I had diagnosed this as the cause of an annoying rattle/knock coming from the head - but more of this later! The bush inner diameter was scored, but still true to size, but the steel was worn as shown below.

drive spindle inner.jpg

Simon Williams 326/09/2016 20:09:04
412 forum posts
67 photos

So I decided to go for needle roller bearings, as there was not enough meat in the casting to accommodate ball races. I toyed with making like for like replacements, but using needle roller bearings was actually easier as it meant I could keep the worn inner, and not have to remake this bit with its captive key.

So onto a faceplate with the top casting, and bore the bearing recess to 1.624ins to take two standard needle rollers. There was room for a 0.250 thick spacer between the two bearings. I liked the idea of two bearings, as the pulley runs above the bearings as a cantilever. The change wheels are there as a token counterbalance.

casting boring.jpg

Simon Williams 326/09/2016 20:11:26
412 forum posts
67 photos

Here's the top casting with the rollers in place, and the inner spindle ready to instal. The PTFE washer is a thrust bearing just to separate the alloy drive pulley from contacting the alloy housing, as the needle rollers have no axial location.

modified drive.jpg

Simon Williams 326/09/2016 20:18:08
412 forum posts
67 photos

But this didn't solve the nasty knock in the drive. So I decided (with a deferential nod to John Stevenson) to repair the drive end of the motor spindle as the pulley was running about 20 thou' out of true, thanks to the damage of the grub screw coming loose and chewing the end of the shaft. The picture of the damage to the motor shaft is out of focus, so just imagine a 14 mm dia stub with a 5 mm keyway, chewed by a dog point grubscrew which was the location, fastener and drive key. Cheap and cheerful until it came loose! So here's the repaired and lengthened motor drive shaft, with a blind key way cut in it.

motor rotor.jpg

Simon Williams 326/09/2016 20:21:24
412 forum posts
67 photos

A matching keyway in the cone pulley, throw it back together, nice and true BUT IT STILL KNOCKS!!!!!

Stripped the motor again, to find a very small mark on the outer of the rotor, and a corresponding excresence of something hard and nasty that doesn't belong in the stator slots. Clean it out, all back together and runs as sweet as a nut.

back together.jpg

Simon Williams 326/09/2016 20:24:23
412 forum posts
67 photos

So the interesting debate for me is, having agonised over modifying the internals of such a well designed machine, I've eventually decided to alter its design. In the eyes of many I'm sure this is heresy, and repairs should be carried out with as close attention to keeping it original as possible.

Comments anyone?

thaiguzzi18/12/2016 04:34:05
avatar
573 forum posts
130 photos

Nice repair job. Sod originality...

thaiguzzi18/12/2016 04:34:08
avatar
573 forum posts
130 photos

Nice repair job. Sod originality...

not done it yet18/12/2016 07:03:14
3358 forum posts
11 photos

Looks like some improvements, perhaps. I've not read (or watched?) The thread you mention.

Seems some were unnecessary, mind!

What took my immediate attention, right at the end was how you missed the frequency of this 'knock' remaining the same, wherever the belt was fitted on the variable speed pulleys!

Time may tell, whether the needle bearings are as good as the original design. I would only make a modification if there was a known design weakness with a machine, obsolescence, or clear improvement in technology. I reckon those that design these things are far more clever, than I, at that.

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