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04-23-2009, 04:56 PM #1
L-Series L-00 Spindle Nose question
Do L series chuck plates bottom out on the square face of the spindle nose or do they seat entirely on the taper? Maybe both? I'm not sure. I have acquired a couple of pieces of cast iron to turn some back plates out of and I was just wondering how critical the the diameter of the taper is relative to the back of the plate.
I am confident I can get it extremely close in the CNC lathe, but I don't have a good way to gage the taper.
04-23-2009, 05:04 PM #2
L series spindles/chucks locate on the taper only.
04-23-2009, 05:09 PM #3
Correction, they locate tight in the tapers but are designed to have 0.001" to 0.003" draw to make bring the faces up tight withe the cam locks (or bolts in the case of the A1 series). Skinner used to have a nice tutorial covering this topic and others. Interesting read.
Damn me for an idiot. Ignore the above. This is NOT a D series or an A series spindle nose. It's an L-0 long taper. L-0.
Yes, tight on the taper. The lock nut holds it together and the fitted taper under the load of the nut provides a rigid connection between spindle tooling and spindle nose. .
04-23-2009, 05:53 PM #4
I had the the chuck loosen up on my Regal 17 in the middle of a cut a week ago. It was the first time I'd ever had that happen. It's an L0 spindle, and I had a 10" Buck 3-jaw on there. Fortunately, I caught it in time! I was in the middle of a cut on a piece of 1018, running at 180 rpm, when it started to vibrate and dig. Then I heard a nasty scraping sound coming from the headstock. I shut it down quick. My first thought of terror was that somehow the front spindle bearing had catastrophically failed (on a LeBlond???). Then I noticed that the spindle locking nut had backed off and was scraping against the front face of the headstock casting. It was still holding the chuck, but the chuck was loose and wobbling. If I'd kept it running much longer, it would have let go. I wasn't going real fast, but it still could have caused some serious damage or injury.
I still don't understand why it loosened up. I'm always careful (so I thought) in seating and tightening the locking nut. I snug it down with the spanner to maybe 20 ft-lbs, then put a light rap on the wrench handle with a plastic mallet. The previous job I had done on there had been an interrupted cut, but it wasn't anything heavy and only took a few minutes.
Anyway, it was a wake-up for me, and I offer it here as a caution. Since then, I've been checking the tightness of the locking nut as part of the "daily pre-start" routine on that lathe. No other signs of it loosening again, but I'm going to keep checking.
04-23-2009, 06:09 PM #5
L series related drawing scans from B5.9 Spindle Noses are available for emailing. PM me with address if interested.
04-23-2009, 07:57 PM #6
A good many years ago, I was running a 25" Heavy Duty lathe in the shop at RK LeBlond. I was turning a tailstock spindle for an NK or NQ lathe, don't remember which. It was a sizeable log of steel, though...perhaps Ø10 inch by 60~70 inch OAL.
Anyway, it was chucked in soft jaws and supported by the tailstock center. I was watching one of several long OD turns when the spindle/workpiece instantly stopped rotating!
No slow down or coast one-half revoltion, just BAM...stopped dead, broke the tool, etc.
I pushed the spindle control lever down to the stop/brake position immediately. I called the leadman over and we bumped the spindle jog button, tried the spindle control lever, shut off and restarted the electrics, nothing worked.
After a bit of study, we found the same situation as you did, the L3 spindle nut had backed off and was wedged against the front spindle bearing cap. The big tailstock on the Heavy Duty was taking all the thrust generated by the threads in the spindle nut and had stalled the spindle!
We worked on the spindle nut with a spanner wrench, BIG babbitt hammer and a pipe for a while (maybe we should have just backed off the tailstock spindle a bit ) and I was back in business!
That was an experience I've never forgotten!
From the "older & wiser" perspective, I'm really glad that happened on a chuck and tailstock process, rather than on a chucker job!
04-23-2009, 08:08 PM #7
I think sometimes you can get a chatter or vibration at just the right frequency to make otherwise firm connections come unglued. In the case of an L-series spindle nut, maybe the nut "rings" in just the right way so as to allow it to unload .
04-23-2009, 08:19 PM #8
wow. I suppose this is why the L series spindle nose style went by the wayside. I guess it went by the wayside anyway, but I don't think any machines have been made with that spindle for 25-30 years???
I figure the clearance in the bore of L00 tapered is to help it seat properly? or does it do anything at all? I find it strange that the clearance is not centered in the taper.
04-23-2009, 08:25 PM #9
Yes, you need a bit of clearance for the key, and the face can't interfere with the spindle flange before the taper seats, but no clearance in the bore.
04-23-2009, 08:33 PM #10
There is clearance in all my backplates...a ring maybe .030" deep about 3/4" wide all the way around.
04-23-2009, 08:42 PM #11
Oh, you mean a relief cut out of the middle of the tapered bore . OK, yes, that's there to make sure the front and the back of the taper seat firmly.
04-23-2009, 09:06 PM #12
I made a back plate for my little Rockwell 11" on the Rockwell. I cut all the rough straight dimensions, threaded the shoulder for the lock nut, then indicated the compound to track the same as the l-oo nose and started chewing the taper into the slug. I scraped the id taper to give good bearing to the spindle. Then i mounted it on the spindle and cut the od of the flange that fit my new chuck. Wish I hadnt used 8620 for the material.
There is clearance to the end of the spindle, about a half inch.
04-23-2009, 09:55 PM #13
Is it possible a previous owner has replaced the original spanner with something inadequate to the task?
Failing that, I'd take out the key and blue up the male taper and check the fit. There may be a bruise you're not aware of. I'd be suspicious about fits any time an L series chuck did not have to be forced off the taper by hyper-loosening the nut, even after a heavy session.
04-23-2009, 10:40 PM #14
BTW John, this may be a stupid question, but what is the document/book B5.9?
04-23-2009, 11:04 PM #15but what is the document/book B5.9?
All these A, D and L type spindle noses fall in to the general category of standardized, and there is a Standards organization that administers all this data.
04-24-2009, 03:28 AM #16
My incident of the lock ring loosening was also on a chuck and tailstock job. It was a piece of 2" dia 1018 x 24" long, with a live center in the tailstock. Hmmm....maybe there's something to that? Maybe the combination of the axial pressure from the tailstock, plus hitting some frequency while turning the long shaft, got the lock nut vibrating.
The spanner I'm using is about 12" long from the spindle c/l. As a guess, after I snug it and give it a little rap with the plastic hammer, it's probably tightened to 40-50 ft-lbs. Normally, loosening it requires the same little hammer rap. That is, it's tight enough that I can't just push on the 12" arm to break it loose. That would seem to be about right, by my mechanical knowledge. The Running A Regal manual doesn't seem to say anything about how tight the lock ring should be, unless I missed it somewhere.
04-24-2009, 04:04 AM #17
If the C spanner is massively proportioned, I'd be hitting one that short with something just about as heavy as I was comfortable to wield, preferably faced with endgrain timber, aluminium or similar. (Not plastic - too absorbent)
With a heavy slugging implement, you don't have to swing it hard, just let the weight bring itself to bear. The ponderous application of a something massive is much less traumatic for machinery (and less likely to be mis-struck) than swinging something lighter, more vigorously.
As my mentor used to say, in all seriousness "If it doesn't fit, don't force it; get a bigger hammer"
That's my take, anyway. My L0 spindle nut and thread are still in perfect nick, FWIW