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Moving the mill

Spindle Noises

ShumaTech Digital Readout

ShumaTech DRO Continued

DRO-350 Repairs

South Bend 9" Lathe

South Bend 405 Lathe Bench

Grizzly Mill Revisited

Surface Grinder Rebuild

Surface Grinder Continued

Grinder April 6, 2008

Grinder April 20, 2008

Grinder August, 2008

Grinder September, 2008

Grinder November, 2008

Grizzly G3103 Mill

Grizzly G3103 Mill
Rebuild - Part 2

Moving the Shop

Moving the Shop 2

Bringing Home a Sheldon 12" Shaper

Sheldon 12" Shaper 2

Sheldon 12" Shaper 3

Sheldon 12" Shaper 4

Sheldon 12" Shaper 5

Sheldon 12" Shaper 6

Sheldon 12" Shaper 8

Sheldon 12" Shaper 9

Way Alignment Tool



Email Jim

DoAll D624-8 Surface Grinder Continued
Updates - November, 2008

I had been able to spend a couple days playing with the grinder, but the more I used the grinder, the more the lack of a good surface finish bothered me.  It was time to get it fixed.

I had been reading everything I could find on angular contact bearings.  What I found was a little disheartening.  It would seem that the tolerances are so tight on the bearings that the residue left by a fingerprint is about twice as thick as the clearance between the balls and the race.  A speck of dust could be enough to damage a new bearing.  The more I read, the more I began to worry about where I would be able to do the work.  There is no place in our home that comes close to being dust free.  This is not to say that we keep a messy home, we don't.  However, it's no clean room environment, either.  I needed to come up with a method of keeping the parts clean while still being able to use the hydraulic press and other tools I required

While I pondered how to keep the bearings clean, I was also looking for proper replacement bearings and maybe a new or used spindle - if one happened to show itself.  I put up some ads on a couple of bulletin boards I frequent and sent email off to a dozen or so spindle rebuilders.  I didn't have much luck finding a replacement spindle.  The rebuilders wanted to rebuild mine and the prices were a bit more than I was prepared to spend at this point. 
angular contac bearing
angular contac bearing
Angular Contact Bearing - back to back configuration
Spindle drawing - measurements and layout

Before I could look for bearings, I needed to pull the spindle apart and find out the quantity and size(s) I needed.  During my reading, I did find out that I needed to pay close attention to how the bearings came out so I would know how to reinstall them.  Angular contact bearings can be arranged in a few different configurations depending on what the manufacturer had in mind.  The configuration is first dependent on how many bearings are needed to support the spindle shaft and then dependent on how much and in which direction the forces will be applied to the spindle.  When I finally got the spindle apart, I found a total of 4 Barden 107 matched angular contact bearings (two on each end) in back to back configuration.  B
ack to back in Barden's symbols is shown as / \.  Each slash indicates the axis of the balls when viewed from the side and the ball at the top of the bearing.  Each pair of bearings have the printed sides touching as shown in the image above.  Other possible configurations are face to face ( \ / ) and face to back ( / / ). On the back end of the spindle, both the face to face and back to back configurations would have the bearings in the same configuration as on the front of the spindle. For a spindle with face to back on the front, the rear would be the opposite, or back to face.  This configuration preloads the bearings as two front against the two rear( // ----- \\ ), rather than the more common preload of 1 against 1 in the front and 1 against 1 in the rear ( / \ ----- / \ ).  From my limited experience in mills, lathes and grinders, I have seen back to back used most often.

spindle repair 1
spindle repair 2
The press tool, spindle cartridge and wheel guard.
Lots of corrosion
spindle repair 3
spindle repair 4
You can see the 2 worn areas of the taper
Checking the lapped end of the housing

Getting the spindle housing out of the grinder wasn't the easiest thing I 've ever done.  The spindle housing is 3" in diameter and the rear half of the housing is held in a bored hole of a couple thousandths larger diameter in the grinder's vertical member.  There were 4 cap bolts holding the grinding wheel guard to the vertical slide assembly.  These came out easily enough.  There's a pinch bolt and a couple cylindrical wedges that hold the spindle housing in place (see drawing above).  With the pinch bolt removed, there are threads in the first wedge to allow a larger bolt to be threaded in to give you something to grab so you can pull the wedge out.  With the first wedge removed, there's room to insert a drift and knock the second wedge out the other side.  Both wedges removed easily and that allowed the spindle housing to move fairly freely.  Using a harmonic balancer puller, the sheave on the rear of the spindle was removed.  This allowed the whole spindle housing with grinding wheel guard to pull out toward the front of the grinder.  There was nothing that was now holding the guard on to the spindle, but it wouldn't separate.  I soaked it in PB Blaster and laid the guard on top of the jaws of my 6" bench vise.  No mallet and block would budge it.  No hammer and brass drift did either.  Finally, I resorted to a hydraulic press and a press tool made from cast iron pipe fittings.  Once it had moved a fraction of an inch, I saw that it should move in either direction as there was no lip on the guard.  More PB Blaster and more pressure were applied until the spindle housing and wheel guard were separated.

I stripped the spindle, bearings, spacers, end caps and the single 0.002" shim from the housing, noting and marking the bearings and where the alignment marks were on both the spindle shaft and housing.  This is necessary information for reassembly.  The marks that denote the high spots on the inner races are matched together and set 180° from the marked high spot on the spindle shaft.  The same is done for the outer races (if marked) and the high mark on the spindle housing.  I used a soft wire wheel on my bench grinder to clean the corrosion from the first few inches of the spindle housing.  I was careful not to remove too much more than the bare minimum in order to retain a tight fit between the housing and guard.  Over the next couple of afternoons, I cleaned all parts in a succession of baths.  I started with my less than clean parts cleaner filled with mineral spirits and ended with a few baths of new lacquer thinner in an ultrasonic cleaner.  They were dried with filtered compressed air and bagged in plastic zip bags.

The spindle housing ends were lapped square and checked with a precision square and surface plate, then cleaned again and bagged.  The spindle was checked to make sure that it wasn't bent, it wasn't, and all the threads were chased.  I stoned the edges of the journals to ensure that the bearings would slide on as easily as I could manage.  Once again, the spindle was cleaned in successive baths and bagged.  I then threw it in the freezer to try to shrink it a bit to make reassembly easier.  Last, the ring nuts, spacers and end caps were cleaned and their fit checked with Prussian blue.  Burrs were knocked down and then lapped smooth and true.  One of the ring nuts was cracked, probably due to the amount of force necessary to break through the corrosion.  I grabbed a piece of 2" bar stock and made a new ring nut.  This too was checked for fit and lapped until the contact area left a blue ring against the spacer,

spindle repair 5
spindle repair 6
Cleaned and bagged - just like a small clean room
Red/blue boxes show high run out marks on old/new bearing. Set marks 180° from spindle high marks

I had been watching Ebay, among other sites, for Barden 107 bearings.  I had found a cross-reference for bearings that showed that Barden's 107 number matched a few other manufacturers 7007 numbers.  I set up automatic searches for those numbers also.  The letters and numbers after the size designators include nomenclature for a matched pair of bearings, whether they were duplexed and whether the duplexing was face to face, back to back, or whatever.  The letters and numbers also depict whether or not the bearings are marked for radial run out and how much maximum run out.  These numbers are not etched on the Barden bearing shell.  They are found only on the sticker that comes on or in the box.  On the second day I checked for Barden 107* on Ebay, I found my bearings.  The seller only had one pair listed, but when I wrote him with a ton of questions, he graciously answered my questions and said he had another pair as well.  I ended up with 2 pair of 107HDL with codes for duplex back to back, light preload,  I.R. radial run out 0.00005 max.  There's a good page with the Barden nomenclature here.  The nicest part of the purchase is that 2 pair cost me less than 1/2 pair would have cost retail.  Sometimes I get lucky.

While I waited for the bearings to arrive, I set out to find some bearing grease.  I had learned that one doesn't use unfiltered grease in a bearing with these close tolerances.  Just like the bearings, the grease is special.  The recommended grease for my application was Kluber Isoflex NBU-15.  It was a bit of a search to find it.  McMaster has something close, but not quite as good for my application and the smallest size was a lot more than I needed.  Barden recommends only 2 cc of grease per each 107 bearing and too much grease can cause the bearings to overheat.  I finally found 30cc syringes of the Kluber from Precision Spindle.  I gave them a call on a Monday and had the grease on Wednesday.  Fast service.

With all of the individual parts cleaned and bagged, I pulled the bearings out of their packaging while my freshly gloved hands, a couple of new zip-close bags, some lint-free wipes and the grease syringe were all inside a large clear plastic bag.  This was my clean room.  With the clear bag surrounding everything, I was able to inject the 2 ccs of Kluber grease in each of the bearings and work it around, then put each pair of bearings in the small zip bags.  The only dust that the bearings may have seen would have to have come in when I carefully opened it to add the bags, grease, etc.  It's still not as good as having a clean room, but it was a heck of a lot cheaper.

spindle repair 7
spindle repair 8
Making sure that the spindle wasn't bent
Shop made tool post grinder (TPG)
spindle repair 9
spindle repair 10
Checking for concentricity of the taper
Checking the temps as run-in was done on lathe

Once the bearings were greased, I removed my wrapped spindle from the freezer and tried to slide the warmed front bearings over the journal.   They were a little too tight for this to work, but I was ready for this possibility.  I moved the bag, with spindle and one pair of bearings inside, to the cleaned and waiting hydraulic press.  Everything was already set up for this press job.  With the bag still surrounding the spindle and bearings, I pressed the front bearings home with a press-tool on the inner race.  I didn't even tear the bag.  Still working in the bag,  I moved in the clean spindle housing from another bag.  Back to the press.  This time the press-tool pressed on the outer race to seat the bearing and spindle shaft into the housing.  Next, I added the front spacers and end cap and cinched them down finger tight.  The last job on the press was the one I was most concerned about.  I needed to press the pair of rear bearings on to the spindle shaft and into the housing at the same time.  Fortunately I had already made sure that the inner press tool was able to nest inside of the outer press tool, and so put equal pressure on both races.  This required using a shim on the outer race for the first bearing, then removing it for the second bearing.  These bearings are NOT an interference fit, just a very close sliding fit, so there was very little actual pressure being used.  Once the rear bearings were close to their intended location, I added the cleaned spacer, nut and end cap.  With the inside of the housing now closed off from the outside and little possibility of dust entering near the bearings, I was able to tighten down the end caps.  Tightening the end caps sets the preload.  There's no measuring torque or any computing done at this stage.  As long as the new bearings measured the same as the old ones in thickness and they had the same preload rating (both old and new were "15° - light preload"), then the preload setting machined into the bearings would automatically be correct.  I had measured everything before I began the assembly and it all looked right, but it was reassuring that when the nuts and end caps were tightened, there was no end play in the shaft and just a small amount of drag when the shaft was turned in the housing.

I chucked up the spindle in a 4-jaw on the lathe and used a steady rest with the fingers reversed to hold the housing.  Starting in back gear at the lowest RPM, I ran the spindle while checking the temperature of the housing above each pair of bearings.  When I finally got up to around 1000 RPM and let it run, the front bearings were reading about 92° and the rear about 90° at the 15 minute mark and had dropped to about 80° by the end of an hour.  I had looked for specs for bearing temperatures, but didn't find much more than "The bearings shouldn't run hot."  Since the spindle normally spins at 3000+ RPM, they might have run hot if I would have spun it up to high speed in the beginning, but by running it in slowly, I was able to avoid that issue.

I let the spindle run for another hour.  By this time, the housing temperature was just a few degrees over the ambient room temperature of 74° at 1000 RPM.  The next step was to grind the spindle taper.  I had built a quick and dirty tool post grinder as an early project to grind an inside taper on a end mill grinding jig.  I didn't use angular contact bearings, but did preload the bearings a bit to lessen the end play.  I doubt that these bearings will last too long, as they were not meant for this type of service, but it was better than using a Dremel as a TPG.

I dressed a 3" wheel, set the compound slide to a little over 7° and made a very light grind with the lathe turning the spindle at about 350 RPM.  I checked the angle with some Prussian blue and an almost new Sopko adapter.  It took a couple trys to get the angle correct, but once I had the angle right, I ground about 3 thousandths off of the taper.  The diameter of the spindle shaft is 1.0625" just inboard of the taper, so the 200 series adapter, with its 1.000" maximum inside diameter doesn't seat all the way down on the taper.  This is nice as I could regrind the taper many times without running out of real estate.

So how did it turn out?  I'm so amazed at the job this tool post grinder did, that I had to shoot a short clip of the outcome.  There is just a hint of a waver from the needle on an indicator that is graduated in 50-millionths of an inch (half-tenth).  Not too shabby.

spindle repair 9

A little out of focus at start, but almost zero run-out

The finish on the taper could have been nicer with a better grinder or maybe with a better choice of wheel, but it is so much better than the 0.0012" run out I started with, that I'm quite happy with the results.  I got so excited with the results, that I went ahead and reinstalled the spindle in the grinder that evening.  I paid for this the next day, as I didn't get to bed until almost midnight on a Sunday night with a very early alarm (4:30 AM) on Monday morning.  I told myself that I wouldn't have been able to fall asleep anyway, due to thinking about it.

For the last week or so, I have been doing lots of grinding.  On most things, the finish I'm able to get is very nice.  On others, I find that I have lots to learn.  However, any finish problems I've had can't be blamed on the spindle taper not being true - and that's a good thing!  I reground the table, the chuck, some long thin stock for practice and I am now working on some fixtures to assist me in grinding some templates so I can do a good job of scraping in a fairly "new to me" South Bend model A saddle and cross-slide I added to convert my 405 "C-type" lathe to a "B-type" lathe.  They were not very worn and the saddle checked favorably against my very slightly worn South Bend 405 bed ways, but I have been wanting to "do the job right" and scrape the saddle ways to a perfect fit.  Since I needed to remove the saddle in order to clean the grinding dust from the lathe anyway, now would be a great time to scrape it in.  Yes, I threw a towel over the lathe while grinding, but I know that the grinding dust still gets through.  The dust settles on surfaces all over the basement and gets kicked up for a while after a grinding job.  This is one of the reasons why the surface grinder lives in the garage - away from the rest of the machine tools.  Well, that and because it was too much work to move it to the basement.... but that's another story.

Here's a parting shot of a pair of parallels that I ground after the spindle repair.  Not too bad of a finish for a novice..

Grinder 1
Grinder 2 Grinder 3 Grinder 4 Grinder 5 Grinder 6 Grinder 7