Denford Software & Machines

I stripped the top of the lathe today after draining the oil overnight . It seemed the more I looked the worse it looked , Oil covered glasses on I think on first look .
There seemed to be a tight spot on the shafts when spun by hand , as I inspected it,it seemed to get worse , The gear selector lever was getting tighter ..
I removed the shafts with very little effort seems the last man in there had a 5 year old tighten everything up .. Not a hint of grabbing on the way out really easy . decent size hammer and a bit of hardwood persuasion and spindle shaft came out nicely.
Lower input shaft came out just as easy. .
On inspecting the bearings . seems that 2 of the 6204's are good with 1 having a damaged rubber seal .
The fag 1 3/8 rear spindle bearing is running rough , dry and feels like it as a little flat spotting on the balls. So i have decided replacements throughout .
This is where my question lies .. Does anyone know the preload process when replacing the 2 taper units.

The lower plastic gear is in a sorry state , , At some point some fool tried changing gear with it running and took away several teeth edges on one side .. Then someone decided to turn the gear around ,
for some unknown reason the holes didnt match , so then the holes for retaining the gear were redrilled into slots . I kid you not . this left the gear eccentric of the shaft .. Thus causing the binding . Voila .

I just hope the same previous meddler hasn't touched the Apron or anything else .

Don't be too hasty to condemn the holes as ham-fistedness. The original gear made from technyl 90 that came out of my machine also had ovalised holes and the register was also over-sized. I don't think the material is so well suited to long years of exposure to oil, or perhaps just not more modern oils than when the machine was new.
Turning the gear around should not be possible and have it fit right, the sides are not machined the same depth, though I guess it's possible to re-machine it to fit (which would go to explain the runout since the drawing shows one side a close fit and the other side a clearance).

[quote="Stucapri170"]I stripped the top of the lathe today after draining the oil overnight . It seemed the more I looked the worse it looked , Oil covered glasses on I think on first look .
There seemed to be a tight spot on the shafts when spun by hand , as I inspected it,it seemed to get worse , The gear selector lever was getting tighter ..
I removed the shafts with very little effort seems the last man in there had a 5 year old tighten everything up .. Not a hint of grabbing on the way out really easy . decent size hammer and a bit of hardwood persuasion and spindle shaft came out nicely.
Lower input shaft came out just as easy. .
On inspecting the bearings . seems that 2 of the 6204's are good with 1 having a damaged rubber seal .
The fag 1 3/8 rear spindle bearing is running rough , dry and feels like it as a little flat spotting on the balls. So i have decided replacements throughout .
This is where my question lies .. Does anyone know the preload process when replacing the 2 taper units.

The lower plastic gear is in a sorry state , , At some point some fool tried changing gear with it running and took away several teeth edges on one side .. Then someone decided to turn the gear around ,
for some unknown reason the holes didnt match , so then the holes for retaining the gear were redrilled into slots . I kid you not . this left the gear eccentric of the shaft .. Thus causing the binding . Voila .

I just hope the same previous meddler hasn't touched the Apron or anything else .[


Does yours have a transducer gear, or just the 2 locknuts? The manual expects there to be one, but mine doesn't nor is there any sign there was one. As you will already have noticed, the locknuts are left hand thread. The manual isn't terribly helpful, all it says is slacken off the lock nut, adjust preload by turning the transducer gear in small increments. After each tightening, check the pre-load is not excessive, some temperature rise when running at high speed is to be expected, the machine should run for an hour at full speed after which you should be able to put your hand on the spindle without discomfort. (if you have a means of measuring temperature, it mentions 65 deg C, so quite hot, really) Tighten the lock nut after adjustment.
Hope that helps.
My general experience is that too little preload is probably worse than too much.

In my machine, one of the locknuts IS the transducer gear. It never had a transducer but the gear is there.

Hi mine too has the transducer gear , if you mean the hall sensor pickup ?. Yes Pete the gear is really sloppy on fit , And when I say elongated holes you can see were he missed drilled it in 2 spots .. Absolute numpty who touched it . Is there a drawing relating to the plastic gears . I saw that the original size was revised on OD ? ( in another post) . I was expecting the retaining plate to fit better and at least some kind of centralised location for the gear to the shaft . On mine it's all over the place good 1.5 mm float all round . Thanks for the replys .

The Od was revised because I think of binding issues when the gear warms up. I know mine did, when it had been working hard it would bind the gearchange lever.

The drawing for the gears is attached here. The larger one on the spindle is 68t and the smaller but thicker one on the layshaft (the one which gets chewed up by changing gear in motion) is 65t. I've attached a picture of the last one I made, you can see it's a nice snug fit on the hub.

I've got a photocopy of a file note dated 15th December 1978 (must have got it off this site somewhere, just where I can't remember) which notes that the PCD of the layshaft gear is reduced from 5.417" to 5.397, and the OD from 5.583/5.579 to 5.563/5.559 'as advised by Green's of Sutton' because of the co efficient of linear expansion of Technyl 'A'90.
At the same time, the thickness of the gear was altered from a dimension of 7/8" to 0.875"/0.870." As a fractional dimension, the gear thickness could have ranged from 0.885" to 0.865", and I have read that some lathes did have issues with the gear binding in the shift fork.
The PCD and OD of the plastic spindle gear were reduced by 20 thou at the same time.
I checked the OD on my spindle gear, and it seems to be the original, larger size, but to date, I haven't had any binding issues.
Without dismantling, I can't get down to the layshaft gear to check that, but I presume thats the larger size too. I must be lucky, and mine are lower end of the tolerance range for OD and thickness.

Theres also a drawing for a Viceroy 280VS layshaft gear, dated 14/10/1977 which is 54T 10DP, different OD and different register bore. Its been scored across in pencil, so obviously superceded, but I don't know if any of the early 280s made it into production with 10DP gears or not.

You're right Richard, all that info is in the pdf I attached above.

The 10DP gear would require that the splined sections on the spindle also be 10DP. I also have no idea what machine it was meant to fit - I thought it might be a 5" lathe or it might have been a developmental one.

I don't know if you'd noticed but I believe the recess ID's are marked backwards on the drawing. The 1/8" recess has a ID of 4" +.005"/-.000" which suggests it fits onto the 4" hub OD and the 3/8" recess is marked for clearance (4 1/16"). The trouble is that the flange is 3/8" wide so fits in the 3/8" recess. The clearance should be on the 1/8" recess and the fit on the 3/8".

Silly me! I looked at your drawing, but didn't scroll down to see the other drawing and the notes!

When you had your machine apart, had the factory actually made the gears to the drawing, with the recess 1/16" larger than the flange? Did you make your replacements a better fit?

Richard

The gear was worn loose in every direction, the hub ID and the holes. I think the ID was at least 1/16" oversize. I machined the new blank for a good fit on the hub OD and the flange OD. This is the first one I made.
This is the 68T I made about 5 years ago, still looks pristine so we know that acetal is perfectly tolerant of running in hydralic oil.

Thanks RPWilson for the info on Preload . I had searched the net beforehand and found 2 posts that suggested no exacting method just nip up till no spindle play ? . I used to build heavy plant equipment and when we did a taper it was always preloaded for heat expansion at running temperature . Due to the bearings design .
A guy in the design office always provided torque figures .Easy when they have software for that .
A fitter that worked with me always used a length of bar with a suspended weight on to test drag .
I got new bearings 2 tapers the FAG 1-3/8 rear and the 3 6204's from bearing king at Rotherham which isn't far .
£52 inc vat for 2 tapers original spec
£40 inc vat for 1-3/8 RHP branded
3.60 each inc vat for SKF 6204 .

I have even managed to source all new Elesa handles ... But I dont like the plastic . I will make new metal replacements.

Check the bearing fit on the spindle when you do the new bearings. They can be a very tight fit on the ID which makes setting the pre-load very tricky. You might want to ease the fit a little with fine emery to reduce the force necessary to install the spindle.

Oddly, the slightly smaller TD1 models did have a a drag resistance of 10-15 lb inches specified after adjustment, but not so for the 280 models. What are you planning to do about the plastic gears, put them back in for the time being at least?

I am making a pair of gears for Stu. I have one spare just doing the spindle gear.

Yes and again a big thanks to pete . RP I will be very careful fitting outer tapers . To be fair I could always repack the originals and fit them back in as they were good , The inner taper was not well lubed , It looks as if there is no grease retainer for the inner bearing and it flicks inside the box at the rear .NORMAL?? The race faces and bearing faces look ok . but while they are out for the sake of £50 just over why risk it . And after Boxford bearings at £300 a pair this is cheap .

Also on the spindle bearing housing ( chuck side outer ) there is a groove in the housing . a square cut but no seal, should it have a seal ?..I have looked at the headstock arrangement drawing on my big tv . I can't tell weather its a seal shown from the housing to the spindle shaft.. part number is MVS100 124 for the housing .
I cant tell weather it represents a rear seal aswell between part number MVS100 151 and the shaft . The one i thought was missing on rear taper.
taken part numbers from drawing BVS100 100

Thanks for the help guys..

There's no seal on my rear bearings, the back of the taper rollers are visible if you loosen the clamp plate. There isn't anything on the front either on my machine, just the square recess in the back of the nose plate. I think it relies on the bearing to sling any grease towards the outside so it doesn't migrate to the front.

They do some strange things with lathes .. The bearing needs a flow through of grease as any non life sealed unit does . The large crusher gearboxes I worked on, the inner taper bearing was fitted with a shim disc that restricted the flow and stopped it flinging grease into box , thus contaminating the oil. The front Taper is ok without a seal as it retains grease but allows through movement . I was confused after seeing the seal groove .
Thanks again Pete . Did payment go through ok ..

Yep, gear blanks are ready for gluing the teeth on tonight
Soon as the glue is dry they'll be in the post

Thanks again Pete . Look great .

Gears are done.