Author Topic: An anxious afternoon  (Read 1049 times)

Offline Charles Lamont

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An anxious afternoon
« on: March 09, 2023, 09:49:47 PM »
It is mid afternoon today and I reversed my usual sequence. While fitting the chuck and an end mill, I reminded myself, twice, not to forget to tighten the vice before switching on. So the job grabbed as soon as I touched it with the cutter, badly enough to stop the heavy old milling machine dead.

The job, a jig, is not pretty but probably salvageable. The 9/16" HSS cutter needs a couple of tiny patches of welded-on mild steel removing, otherwise it appears to be fine. The Autolock chuck is fine. The vice is a little Myford one and not enormously robust, but at a cursory inspection I think it is undamaged.

Unfortunately however, over about 5 or 10 degrees of rotation of the mill spindle, there is a tight spot and the sound of some kind of metal-to-metal contact. Bugger. Get a large mug of tea.

The machine is a venerable Beaver Model A http://www.lathes.co.uk/beaver/page2.html, nearly as old as me. There is a drawing on that page of the spindle assembly, which will help with what follows.

Having remembered how to get the quill out, and put back the bits I didn't need to take off, it was clear there was something wrong inside. I have had the machine for about ten years now, and I have never inspected the spindle bearings, so now is the time. It is a simple but very well made assembly, and it came apart without much difficulty, other than the top inner race being a well-nigh perfect fit on the spindle, certainly no looser than I would wish.

Well, after some grease removal and head scratching (with a wiped hand) the only thing I can find is right at the bottom, outside the labyrinth seal, the largest diameter of the spindle has picked up in its non-functional bore, or something foreign has got in there. I had to use a slip stone and fine wet-or-dry to polish out the tiny lumps - too hard to have much effect with a fine file. I have not put the spindle back together yet, as I want to give the bearings a thorough clean and greasing, which I did not have time to do this afternoon, but I am 97.5% sure that is the extent of the problem. Phew!     

Offline Brian Rupnow

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Re: An anxious afternoon
« Reply #1 on: March 09, 2023, 10:57:46 PM »
Charles--I hope that your mill hasn't received any damage that you can't fix. At least you didn't get hurt. It gets scary very quickly when something like that happens. By the time you've hit the emergence stop button, whatever was happening has happened!!!----Brian

Online Kim

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Re: An anxious afternoon
« Reply #2 on: March 10, 2023, 12:51:44 AM »
Owch... doesn't sound like any fun :(

Glad you're OK and that it looks like the machine is OK too!  That's a good outcome :)

Kim

Online Jo

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Re: An anxious afternoon
« Reply #3 on: March 10, 2023, 07:27:42 AM »
Keeping my fingers crossed that was all it was.  :)

Those Beavers are very robust old machines. I wonder how many of these modern machines will still be going strong after 80 years  :old:

Jo
Enjoyment is more important than achievement.

Offline Chipswitheverything

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Re: An anxious afternoon
« Reply #4 on: March 10, 2023, 09:14:17 AM »
Hoping you can sort this out and be back in action...   Remember, years ago, hearing a great bang from a workshop in my place of work as I approached the door. A colleague using a massive and old Richmond mill, a real slogger, had had a job shift on the table, and had split in half! a 1 1/2" diameter milling cutter, on a 1"shank, and completely kippered a new Autolock chuck in the incident.  The mill had main bearings in a quill of about 8" dia., hadn't done much to that..
I kept the cutter in two halves for years on a toolbox near the mill, the perpetrator was very lucky to be uninjured.  Dave

Offline simplyloco

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Re: An anxious afternoon
« Reply #5 on: March 10, 2023, 09:15:51 AM »
Good job you are OK, you are not alone!
I was a youngster setting up a 1" end miil in a large universal vertical milling head,  and didn't realise I was at the wrong end of the cut. When I started the cut the cutter caught, dug in, and such was the force applied that it rotated the milling head out of the cutting path and I was showered with shards of HSS from the shattered cutter!!
Good job I was wearing safety glasses, but I was picking bits of HSS out of my forehead for days afterwards...

Offline vtsteam

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Re: An anxious afternoon
« Reply #6 on: March 10, 2023, 02:35:15 PM »
I once mentioned using a hole saw to Lester, my old time machine shop owner friend, and he said "I'll never use one in my mill again." I asked why, and he said he'd broken his spindle using a hole saw on a Bridgeport clone. He said he'd forgotten to lock the table. A replacement spindle had been very difficult to find.
Steve

Offline Charles Lamont

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Re: An anxious afternoon
« Reply #7 on: March 10, 2023, 09:00:21 PM »
The mill is reassembled and running. The tight spot and nasty noise have gone. Indeed it is perhaps running a bit quieter than before. A DTI in the taper bore shows 0.0001" movement, at least some of which seems to be due to vibration from the belt drives. It is a relief to confirm no permanent damage done.

However, the bottom end of the quill is getting warm quite quickly with a few minutes running at moderately high speed. I don't think I have the bearings too tight as the top end is not affected. Perhaps I should not have grease packed the labyrinth seal at the bottom of the spindle. Grease is being pushed out round the spindle nose. 

Offline Admiral_dk

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Re: An anxious afternoon
« Reply #8 on: March 11, 2023, 12:36:30 PM »
First congratulations to you solving the main problem - that must be quite a relieve, to have it back running, with a very small runout and normal noises  :cheers:

All Bearings have a table from the Manufactor where you can see maximum speed (RPM) and this is always very dependent on the kind of lubrication. Here Oil-Mist allows the highest RPM, Oil the medium and Grease the lowest RPM - all related to 'Displacement of Lubrication during Rotation' ...!
So having a Bearing tightly packed with Grease will be a problem over a not particularly high RPM in many cases ....

I would have a look on one of those Manufactors who make a Bearing of the same size (or better same model) as is in the Mill and look at the Table - but the fact that Grease is already being pushed out, suggests (as you wonder) that there is way too much Grease in there now.

Optimum would be a service manual for the Old Girl .... but that is probably not likely ....

Per

Offline steamer

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Re: An anxious afternoon
« Reply #9 on: March 11, 2023, 01:30:33 PM »
It's happened to all of us at least once.    As long as your not hurt....the rest is fixable.

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline Charles Lamont

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Re: An anxious afternoon
« Reply #10 on: March 11, 2023, 06:36:02 PM »
I do have a reproduction manual, from www.lathes.co.uk. Everything is as original, so the bearing speeds and lubrication method are fine. The originally specified Shell Alvania 2 is nothing special, and I am using the Morris's equivalent. I have had the spindle assembly apart again this morning and removed the grease from the labyrinth seal and its vicinity. I also cleaned and re-greased the top bearing more thoroughly than before, as it had darkened some of the grease.  The bearings are Timken taper rollers, and, as far as I know, the cage and rollers do not disassemble from the inner race, so it is not easy to clean. This time it got blown through (but not spun) with the air jet as well as paraffin washes.

On reassembly I ran it until it got pretty warm and then let it cool down. After lunch, I was able to run it for half an hour at 1400 rpm. The temperature of the quill stabilised at about bathwater temperature, cooler than the normal running temperature of the motor.

The machine is now back in use. Thanks, people, for your support.


 

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