The Overflow from Bats' Lubricated Spindle

...although actually the overflow is from somewhere in the middle of the thread Escape from (VFD) noise.

The rest of the overflow is grease. Which is sort of central to the problem.

(alternate title The Grease Must Flow!)

For anyone else wandering in here, this is picking up from a tangential discussion @Rob Taylor and I were having about some trouble with lubricating the bearings in the spindle of a little vintage Rambaudi Frankenmill that I've been fighting to restore (or at least restore to functionality) for a year or two now. The spindle bearings at the top & bottom are (theoretically) lubricated with grease from a zerk in the front of the casting that flows up & down a liner around the spindle shaft and is forced into the bearings at the top and bottom. The problem is... well... down below.

No, in the post below, not down... ew. You're sick, you know that?

Well, technically it's grease not oil, so it's not really falling anywhere... but that's neither here nor there nor on a floor suddenly covered with suddenly uncovered oil. Or grease. The problem is that (aside from the entire open backside of the spindle casting leading into the head casting leading into the body) the grease doesn't do any good sitting between the casting and liner. The only place it's doing any good is in the bearings at the top and bottom - so the less available volume there is between those two, the better.

I'm starting to think we've gone so far off-topic that even Amazon's creepy Ring network couldn't spot it, so, (while it would be more in-character of me to continue a lifetime spent doubling down on my missteps and plow ahead), I'm going to split this off into a new thread over in General. [ which you're now reading! hello! ]

This is more or less what things look like:

The cyan post (which I just now shoved in somewhere vaguely around the right place on the model) represents the zerk. It's mounted in the casting (yellow...ish... goldenrod?), but only the casting. It doesn't continue into the spindle liner (the Linda Blair-vomit pea-soup greenish thing), where the grease must flow - there's just a hole leading in. This wouldn't be a problem if the casting & liner were completely flush there... but, of course, they aren't. There's a machined collar inside the casting which mates nicely with the liner, but unfortunately, when he installed his zerk, Bubba Wrenchwacker McSledgehammer only got it half through that machined and mostly-flush collar... the rest goes through the raw and not-even-vaguely-flush casting surface:

(we're talking about the upper hole, not the lower one by the threading)

Grease still mostly flows into the liner, but when it's under pressure (as it has to be to get into the bearings at top & bottom) the remainder squishes out and fills the gap between casting & liner, and eventually, as could be guessed from the lower right render, out the back of the casting into the ram in long, luscious, waves of grease-curtains.

Something like this:


So, the original idea was to build up the raw casting around the hole with epoxy paste to match the machined collar. The epoxy doesn't have to fill a lot of space (which is why flooding the whole thing or filling the open back with epoxy seemed excessive), but it does have to be reasonably flush with the liner, otherwise I've got the same problem all over again - thus the idea of using an appropriately-sized half-cylinder of waxed wood or MDF as a form (since shoving in the spindle itself as a form just smears the epoxy away from where it needs to be).

I've done it on occasion - when it's something I couldn't, for whatever reason, do on the wood lathe - but even if you cover the ways, it's still a royal pain to make sure there's nothing left behind from it.

That's not a bad idea...

That would be the easiest to turn, but hardest - or most expensive - to come by. My bandsaw's also not up to slicing steel, so it'd have to be thick enough to turn down, but thin enough to dremel or hacksaw in half afterwards.

Allowing for a little experimentation with release agents, I'm not overly concerned with the likelihood of that sort of catastrophic failure. While it's entirely possible if I was using the liner as a form (just because it would tighten the already tight fit), we're talking about a couple square inches of epoxy on a half-round chunk of something that, at very worst, can be chiseled away from the adhesive, cut out, or even burned out, should everything else fail.


And then there are two other associated problems (regardless of the form):

One is getting the epoxy to actually bond with the inner surface of the casting (something the generous coating of grease probably didn't help) - degreasing with acetone & mineral spirits didn't seem to do nearly enough, so I'm thinking I may be forced to just grind away the primer & surface of the iron with a dremel until I can get to clean metal (or at least flatten the metal enough that I'm not trying to degrease a Thomas' English muffin's worth of nooks and crannies).

Two is the possibility that, even with the gap plugged, the grease just might not be able to get into the races of the top bearing - either because the end of the liner where it sits blocks too much of the balls, or because the funky cage on the SKF Explorer bearing does - or, more likely, the combination of the two.

The bearing cage looks like this:


And the interface at the top of the liner looks (approximately) like this:

...although, not having an accurate model of an actual SKF Explorer, it's hard to know exactly where the two come together.

My thoughts had been either making some thoroughly inelegant notches on the inside edge of the liner lip with a dremel - to allow multiple low resistance paths where the grease can flow - or sticking the liner on the lathe and turning down the entirely inner edge of the lip (theoretically weakening the bearing's seat, but there shouldn't be much downward force anyhow, and the liner design is all Bubba's engineering - not anything factory spec - so I'm not too worried about that), and exposing the whole ball & cage portion of the bearings to lubricant.

The second idea has far more appeal... the problem is, I don't have a steady rest for the lathe and the headstock through-hole is under an inch, making it difficult to turn the inside of something like that (basically a 2x8" tube with a 3.8" base).

So, Rob (or anyone else who had the misfortune to stumble in here and is now wandering around lost, vaguely confused, and wondering why they're stepping in piles of grease) - that's approximately the situation, and what I'm looking at trying to figure out while I'm temporarily CNCless.

I'm open to suggestions for better ways (or any ways) to approach any of the above.


-Bats
(wow... and to think I was going to try cramming all that in as a side-note in an already long post...)

 

I'd offer to share the model of the whole mess (well, minus the mess), but I seem to remember you using something other than Fusion, and I don't know how well it would export. I also feel like that might be imposing even more on your time than simply pummeling you with a barrage of novel-length posts.

I'm not quite sure I understand what's being suggested here (in either case). Are we talking about cutting notches with a dremel abrasive (grinding?) disc? I thought that was what you meant, but got lost when you threw in the Bondo. Is this something to be done on your lathe bed surface grinder - maybe after it's modified to double as a centerless grinder? Or am I (as I strongly suspect) missing something really, really, obvious.

The winning answer is.... C! Bats is missing something really, really obvious!

This is actually sort of what I'm leaning towards right now - although I'm undecided on applicators (and fillers). I don't really want to ruin the grease gun with epoxy. I don't know how well a cartridge for the bazooka would seal up again (I suspect not very well) and that's quite a lot to waste, otherwise that would be the obvious choice. Or if I went for a thinner formulation (more like a generic 5 minute-ish viscosity), I could probably just load up a squeeze bottle with it.

And, yeah, after packing the filler in I'd almost certainly have to re-drill the channel - although that shouldn't be a big deal.

I'm curious about this one... I assume you're talking about copper lines running from the zerk, which is doable (there's lots of space inside the liner)... but I'm not sure how I'd go about terminating them at the bearing end, such that they'd actually be able to force grease into the races, rather than just squishing it out vaguely at the bearings. Mounting it to the inner surface of the liner somehow?

Easier said than done, unfortunately. The top face of the top bearing & bottom face of the bottom bearing are both flush (or close enough to flush) up against the flat caps that hold everything together, so the only real access is from inside the liner. The cap covering the lower bearing is where the spindle/taper protrudes, so it could be either drilled through or periodically removed without too much hassle. But the top one requires pulling off the belt, the cone pulley, and a couple smaller parts to get access - that's the only reason only reason I didn't just go ahead with the "I'll open it up & squirt it whenever I remember" school of lubrication.

Unless by "direct injection into the bearings" you mean drilling through the outer race, which sounds like it must be a terrible idea (and awfully hard on the balls), but otherwise might be a more logistically/locationally practical idea.

That's a whoooole lotta oil. It's also a whoooole lotta oil that would be covering the table (and floor, and my feet, and probably the dog) before I was even able to finish filling it. The bottom cap has about a 1/8" gap where the spindle exits, and I tend to doubt a felt wiper is going to hold up a liter or so of oil (or a couple, if I flood the whole casting).

I did wonder initially about a possibility lying somewhere between 3, 5, and a one-shot oiler, which was plumbing lines from the zerk (or similar fixtures) to below & above the upper & lower bearings respectively & just spraying oil on the balls (err...). It would still eventually drip out, but hopefully in smallish amounts (at which point I could claim it was way oil? or cutting fluid?). It seems to me there was some reason the idea got shot down at the time, though - that for some reason oil wasn't considered as suitable for the bearings as grease.

It would certainly get around the "grease has a tough time flowing into the top bearing" issue, though. Well, probably. Maybe.

No wood on the lathe, but that's a fairly pricey chunk of aluminum, it would be of limited use for future projects after being cut in half (sliding in a full cylinder shoves the epoxy away from where it needs to be, as I discovered when I initially tried it with the spindle liner), and I don't have any good way to cut it in half.

My guess is the solution is going to turn out to be very, very close to whatever it was that I first tried a year or so back... which I probably won't remember having tried until then.


-Bats
(the solution is always the last thing you try... which can also be said for the thing that causes catastrophic machine-destroying failure)

 

I'm a little surprised Autodesk hasn't pushed out a VR interface for Fusion yet - that would make things so much more pokeable.

Not that I could actually afford the hardware to go with it. Or at least not afford the hardware and my other absolutely essential toy tool purchases.

Interesting idea...although it would probably be a lot less refillable afterwards. Mixing up a batch of epoxy & then getting it into the caulk tube to squirt into the hole sounds like an all around messy operation, too (although I suppose it would depend a lot on the particular viscosity)

Based on this shot, it does look like the carts for the bazooka may be resealable (assuming the design is the same for the big ones that it takes) - if I could find one at a reasonable price. And if I was sure how to tell exactly what I was looking for.

This is a pretty similar design (and I'll admit, I was wrong... on closer examination it looks a little more light a light antitank weapon - or maybe a sawed off Stinger - than a bazooka), but the sizes given in the brochure don't seem to correlate with the sizes I'm seeing for sale on Amazon or McMaster.

I don't think out-&-back-in is likely to be viable (or make much sense), but something like a little U-bolt to the inside of the liner might be possible. I'm a little concerned by just how close it would have to get, though - and how to position it that closely without running the risk of the tubing actually bouncing off the cage.

I suspect it could be made to work on the lower bearing, but the upper one (which is the primary reason for going through all these headaches in the first place) has those funky cages that keep the balls mostly covered. It doesn't impede hand-packing the bearing, but trying to re-pack it through a small tube while it's spinning could be another matter entirely.

Probably more realistic than trying to plumb pressurized grease lines to both bearings from one zerk... but that's still a fair bit of very location-sensitive plumbing in a confined space.

Also, that bit where I mentioned there being lots of space inside the liner? Well... I just took another look at the model, and there is lots of space... technically... but most of it's taken up by a terribly inconveniently placed spindle, around which there's only about 2.5mm.

So... it looks like plumbing is probably out of the question for grease, and likely to be a challenge even for oil. 2mm OD is getting down into the realm of hypodermic tubing, and that was something I could only source in hardened steel last time I needed it.

Flattened, gritty, or gouged & scarred - none of which are indicative of the proper handling of balls.

You mean that it lets the oil drip out around the spindle? Or that it sprays lubricant upwards onto a bearing?

I'm not worried about it dripping out (although spraying when the spindle is turned on could be another matter entirely - ugh), but getting reliable coverage of the top bearing from below has me a little worried - especially since it's a double-row, meaning the oil it would have to make it past the low-hanging balls and their obstructive cage against gravity.

Well, that takes care of the theoretical, then. Now if only the practical would be as cooperative...

Isn't that usually called a shielded bearing?

Although, I'll be honest - I'm tempted to just eat the loss on the upper bearing, buy a shielded or sealed one instead, just use the zerk for the lower bearing, and hope that I've sold off the mill before it needs to be replaced.

If that would work, then I would've just used the spindle itself. But I tried that, and the spindle just smeared the epoxy around when it was slid into position - and I don't think the difference in surface finish alone is going to be enough to do the trick. Believe me, I wouldn't be fixating on the semi-circular shape if I hadn't already tried the full cylinder several times without success. Of course, only some of those failures were because of the shape... but enough to see that it called for something different.

I do like your no-cut cut technique, though.

While it's probably not relevant, I'm curious as to what exactly was going on with this part of the process and the internal bar you mention.

And here I thought the whole point of the exercise was to obviate the need for a metal-cutting bandsaw

I'm not entirely sure what it could be reused for aside from the same thing. I don't usually have a lot of applications for half-cylindrical stock.

Maybe mill it down to 2x1" bars?


-Bats
(I know there was a reason not to use a sealed bearing right from the start. There must've been a reason. Great holy , please tell me there was a reason!)

 

Are you sure? It looked to me a lot like the over-engineered locking caps on the little 5min epoxy syringes, that plug both holes before twisting into place:

It's that "downward at the top bearing" that's a problem:


The top bearing (yellow) backs up against a screw-on cap (orange) and nut (red...ish), with the pulley cone sitting more or less right on top of the nut.To make access even more fun, if you look at the collar at the top of the casting (below the orange cap, more or less where the bearing sits inside), well, that's another casting - a flared pulley guard - the lefternmost part of this monster below - gets slid on.


(please don't tell OSHA about my toes)

So any plumbing from outside is going to have to thread through an assortment of parts that not only make things cramped, but also need to be able to slide, screw, spin, or otherwise move relative to each other - meaning things like hard plumbing are probably out (as it'd have to be destroyed to take things apart again), and soft plumbing would have to be removable (maybe not easily, but practically and non-destructively).

It doesn't seem like it until you're looking at all the moving (and non-moving) parts, and where they come together. For instance the nut (which holds the inner race to the spindle) overlaps half the ball cage, limiting (although not completely eliminating) access to the part of the cap the plumbing would have to go through.

This is why forcing grease into the bearing from inside had always seemed like the most practical option (at least for ongoing lubrication).

Exactly. And yet trying to oil it from above is an entirely separate raft of problems. The pressurized mister - with a soft-plumbed line from the compressor (I've usually got a hose with a blowgun lying somewhere around the CNC anyhow) - almost sounds like an easier option, except that the nozzle would have to fit in a 2.5mm space next to a rapidly spindling spindle.

Oh, right. Of course.

Probably... although I'm not thrilled with leaving that grease leakage, if I'm still using the zerk for the lower bearing.

And filling the whole liner with grease just to pack the bottom bearing seems... if not wasteful, terribly inelegant. Although I think the mill passed beyond elegance long before I ever got my hands on it.

I guess I still don't see how it's any better to risk getting a $40 chuck of aluminum stuck in the casting than getting the liner stuck in the spindle. Using a form makes sense with an epoxy paste - pile up a small amount around the hole, shove the semi-circular form on top to mash it into shape, wait for it to set, remove the form, insert the liner... but if I'm squirting in a whole batload of lower-viscosity epoxy, then I might as well (as I think you even pointed out at one point) accidentally gluing the liner in place than accidentally gluing anything else where the liner is supposed to go.

Right now what I'm tentatively leaning towards is falling back on turning & cut a wood/MDF half-cylinder form (maybe rough it on the wood lathe & just do the final sizing on the South Bend) and take another shot at it with the paste, since that's the only option I already have all the supplies for, and cleaning up a bunch of sawdust, while annoying, is still going to be quicker than any of the alternatives. Having the gap plugged would also be preferable even with a shielded bearing on top.

If that still doesn't work, I've got some feelers out to makers of similar-looking pneumatic guns about what to look for when sourcing cartridges, so we'll see what that means for the "squish it full of goop" path.

Otherwise, I just found a $55 FAG double-shielded P6 (so ABEC3-equivalent) marked down to $12 on Amazon, so I'm grabbing that as a fallback if/when the others fail and/or I get disgusted with the whole process.

Nice work - but I hope you've got a license for that blaster.

I'd actually considered the idea of trying for a career in gunsmithing, if the country continues its slide into insanity... I bet I'd have an even easier time of it if I made those guns out of aluminum.

I wonder why no one else ever thought of that before...

True... but I could have an even bigger (and more usefully shaped) piece on the scrap shelf if I just bought the chunk of aluminum and then used an MDF form for my epoxy.

Y'know... it occurs to me I don't actually have the slightest clue what speed it's likely to be running at. I don't think I ever did the math on all the pulleys.

Speaking of speed, they're apparently running a 25% off we're-all-dying-of-the-plague special (any excuse for a sale, I guess?) on the G-Wizard feed & speed calc that I've managed to put off picking up for about three years now... have to see if I can finally fit it into the budget this time.


-Bats
(of course, if I remembered to buy everything I meant to get, I'd be broke)
(of course, I'm broke anyhow)

 

The only problem now is that that was a stock image, and I'm probably going to have some trouble ordering one off the German Wikipedia.

I did get a reply back from one of the pneumatic gun manufacturers, saying it probably wasn't one of theirs, but to try calling them anyhow. But then I spent all day being reckless and irresponsible and braving the plague to go buy a toy I really shouldn't have, so calling didn't happen. I've also still one more possible manufacturer to hear from, although the lack of markings makes me suspect something Chinese.

It's definitely not definitely not possible... but it's not definitely possible - I'm still playing with the idea. I was thinking maybe a short copper piece running through the cap, with a soft-plumbed line running to it (to allow for later unscrewing), but I haven't tried fitting all the pieces back together to check.

The thing I like most is that the only component it risks destroying is rather crudely made and strictly aftermarket (apparently from Bubba's Careless Customs), so no big loss if I had to make a similarly sloppy replacement.

One concern, though, is that squirting a bunch of oil in the top bearing is going to make a mess of any grease in the bottom bearing (and the whole spindle above it), so I'd likely have to make sure the zerk was as effective as a drip oiler as it is a pressurized greaser.

I know there were a few reasons I settled on grease rather than oil, but I really don't remember why, and have yet to find whatever notes might've covered it. I'm not sure how much had to do with the bearings, and how much just had to do with the (apparent) practicality, before discovering the zerk leaked.

Trying to keep a delicate arrangement like that aligned when putting the spindle assembly together sounds more than a little challenging.

While I'm not at all sure it'd be any easier (and probably the opposite), could it be turned into a single nozzle - with the pressurized air flowing straight through, and the oil line entering slightly back from the tip, working venturi-style, like an airbrush?

Of course, that requires welding or brazing on a tiny scale without any debris inside the tubes, which I'm not at all sure I'm capable of, and have a number of reasons to suspect I'm not.

On at least one end of things, apparently... although I'm still kinda fuzzy on the stuff in the middle.

The only reason this isn't #1 is that I couldn't find a similar deal on the (larger, more expensive) lower bearing, meaning I'd still be left either epoxifying the casting or setting up setting up alternate lubrication anyhow, whereas if I can successfully get that damned gap plugged, it solves for both bearings.

I'm actually ok with that part. I've been friends with several different persuasions of... enthusiasts (including one mad russian who moved out west so he could pursue his favorite hobby of building assault rifles from kits and storing them in an ever-growing series of cabinets - presumably in preparation for the eventual zombie apocalypse). What I have more trouble with is the politics that tend to go along with it, but I have enough to hate about most of the major factions that I can usually find some common ground with just about any of them. Besides, someone's gotta be ready to outfit the left-anarcho-libertarians when the balloon goes up

The bigger stumbling block is that I don't have a large enough through hole on my spindle for serious barrel work.

Well, that, and maybe the fact that know just about nothing about firearms.

Funny you should mention that. I actually spent a long time seeding the Defense Distributed printable plans, before eventually losing them on a bad hard drive & finding myself uninspired to re-acquire them...

...but I'm not sure I ever got around to looking at them.

So now we agree.

I'm wondering if I could turn it on the new "CNC" lathe (or "new" "CNC" "lathe"?)... it looks it's got a whopping 4.5" swing over the bed - although the chuck won't hold much over an inch.

I think I'd assumed that I did know the speeds, since they were printed on the nameplate. Two nameplates, even.

Of course, the nameplates were both different, including two entirely different motor speeds... and neither one showed a pulley configuration quite like what the mill actually had...


But I guess by the time I realized they were both essentially useless, I'd moved onto bigger and better further and further from thinking about actually running it.

So, yeah, I probably should try doing some pulley math.

But until then I suppose I can guess the range is somewhere between 965 to 9020 and 1400 to 4500.

Well, I could always try dropping it off something tall...

Keep in mind, they've got their wacky spindle-based pricing. Going for the $200 option means either you're overpaying or you've got a much bigger spindle than I'd realized. $60 will get you a year of full functionality and then limits itself to 2HP spindle power for life. The $105 "3 year" option is three years unlimited, then 5HP for life.

Otherwise, as impressive a tool as it is, it'd probably still end up sitting indefinitely on the "yeah, maybe someday..." list... but if dropping $60 once will cover me until I find space & power for something bigger? Then, yeah, I can afford that.

Another $75-225 for the g-code editor, though? Unfortunately I've gotta take a pass on that one.

Two other things I need (I've had a 3D tester on my drool list for years) - also throw in a surface gauge to go with the height gauge. But then I'll still need a surface plate before I can make much use of either of them, and I have yet to figure out quite where that can live.

Oh, and a larger machinist square... and angle blocks... some 2"+ micrometers... maybe a different vernier protractor that doesn't leave me scratching my head every time I look at it... gauge blocks... a sine bar ... .....


-Bats
(and I suppose it might not hurt to grab an R8 collet set for the mill, so that if I ever get it running I can actually chuck a tool in it)

 

Just a long overdue update, since I had a chance to make some long overdue progress while waiting for epoxy to set on another project and thinking "Hey, what better to do while waiting for epoxy but... wait for MORE epoxy!"



I did indeed go ahead with the MDF cylinder route, and hopefully the pictures show why I wanted to try this method - at least as a first attempt - in favor of the "flood the whole damned thing with epoxy" route. Lower materials cost, less mess, less chance of catastrophic disastrous failure, and less work to rip it all back out again when I discover it was actually a terrible idea (which should be due to happen any time now...)

So a couple weeks back I stacked up a few thicknesses of 3/4" MDF shelf board, turned it roughly round on the wood lathe (which was a miserable experience I hope never to repeat), turned to size on the South Bend (the cleanup wasn't nearly as bad as expected because I got closer than expected with the roughing), slit it down the middle on the bandsaw, and coated it (repeatedly) with paste wax (should've sealed it with poly first, but forgot until it was too late, so the only option was more paste wax).

Things might've been cleaner (in more ways than one) if I CNC'd the cylinder, but the machine was still offline at that point, and even the High Z wouldn't have let me make an 8" tall cylinder (and trying to do a half cylinder as a ball-nose contour path would've given me a scalloped surface I was trying to avoid).

Then last night I slopped some JB Weld in the casting, hit a half-cylinder with silicone spray & dropped it in on top, clamped in place, waited overnight, then declamped and gave it a light rap with a hammer to pop loose. Not to be confused with a light rap by MC Hammer, although that may also have been effective.

It's an ugly finish on top - between the wax and unsealed MDF fuzz that got trapped by the epoxy - but it seems solid... although I'll admit, I've been afraid to jam a punch in there & hammer on it to check just how solid. I think I'm going to hope that being sandwiched in by the spindle sleeve and the relatively small surface area for the grease to press on will keep it from going anywhere.

It also didn't cover quite the whole area I had prepped - I think I lost more down the hole than I expected - but the bit around the hole (ie, the only part that actually matters) seems to have filled in nicely.

Putting the sleeve back in is an awfully tight fit - I may try hitting the epoxy with some sandpaper or a wire brush to take it down a little, but I'll probably just shove it that much harder & hope I don't have to take it out again any time soon.

Now the next step is to decide whether to notch the top of the sleeve (to give the grease easier access to the balls), or just to say " it", toss in the sealed bearing, and try not to think about the fact that I'm packing the entire sleeve full of grease just for the bottom bearing - which seems both wasteful and terribly inelegant.


-Bats
(or cut notches and then use a sealed bearing, so that it can use the access to taunt the grease)

 

It's partially for my own reference, partially a continuation of a conversation Rob & I have been going back and forth on for the past year or so (largely in private, except when, like grease, it accidentally spills out messily for all the world to see), and partially something I did a lousy job of describing.

The short version (and you may have noticed I'm not very good at short versions) is that I have a little Rambaudi knee mill (~600lb little, not benchtop mini mill little) that's a bit of a Frankenstein job (ok, it's a complete frankenstein job - starting with the fact that no one's ever heard of Rambaudi ever making such a small mill):


Among the assorted problems (mostly attributed to Bubba Wrenchwacker McSledgehammer - at least three owners back, and presumably the mad doctor Frankie himself) was the lubrication method for the spindle bearings. There's a zerk on the front - shown in blu... teal cyan in the render of the spindle casting below:

...where grease is fed into to bearings at the top and bottom via a sleeve or liner (radioactive post-salad baby puke green).

All that would be fine, except that, because of where/how it was drilled, the hole in the casting for the zerk only half mated with the hole in the liner, as can (sort of) be seen here:

(that's the inside of the casting with the liner present (left) and removed (right, with hole visible))

...making it possible for pressurized grease to squeeze out.

Like this:

(gross, right?)

So this particular thread was addressing ways to address the problem - a number of methods of potentially packing the area around the hole with epoxy, or of various approaches to ditching the grease system completely.

The update was covering the final (*fingers & stuff crossed*) results. Basically:

1) Make an MDF form in the shape of the liner:

2) Cut it in half (for ease of getting it in/out without smearing the epoxy out of the way):


3) Coat it with wax & silicone spray (as mold release)
4) Slop a bunch of JB Weld around the hole
5) Slide in half of the cylinder form in where the liner would go & clamp in place:

6) Wait.
7) Remove.
8) Hope to hell it worked.

If you compare the interior shots:

...you can see the area around the hole that's now filled in with epoxy. Whether or not it holds up under pressure remains to be seen.

There's more to the problem, of course (there's always more to problems)... One of my concerns was that part of the reason the grease wasn't making it into/through the top bearing is because of the design of the fancy ball cage and/or the way it mates with the top of the liner. I was worried that, even with the hole patched, the grease still wouldn't have access. There's some discussion earlier in the thread about that too, but I basically took the easy/hacky path and cut some notches around the inner rim with a dremel, hoping those would provide a sufficient path for the grease to the top bearing (the bottom one already seemed to be fine):



So... that's basically the story (or the story of this particular problem) up til now. If not short, hopefully this was at least a little more enlightening.


-Bats
(and if not enlightening, hopefully it was at least... erm... something else)

 

Exactly. Or, well, lower in the portion that bears on the liner, rather than the portion of the liner that bears on the bearing. Or the bear that regularly tears down the bird feeder on the porch.

I did consider it, but I generally prefer to exhaust the non-destructive approaches first (one of the reasons I went for the approach I did before Rob's suggestion of flooding the whole thing with epoxy). It's also complicated a bit by the fact that the hole goes through a boss on the front of the casting (that & the screws didn't make it into the models):


Short of maybe brazing or welding, I think anything I filled the original hole with would make the bit drift if I tried to drill an overlapping hole (as I would have to if I wanted to keep it on the face of the boss), drilling on the side of the boss would be awkward at best, and shifting it below the boss gets pretty cramped (although not impossible).

I suppose drilling down & a little to the side (between the screws) might've been an option - even if it throws off the symmetry - but the workholding would've been a little more challenging (and the thought of punching through that much mixed iron & steel with a hand drill has just about zero appeal. maybe less).

I'm still waiting on more grease to test the whole assembly under pressure, but I'm curious to know why you think so - or where exactly you think the failure is likely to happen.

From one angle, I'm not sure it would've even been possible (at least without more drastic approaches) to completely seal the gap - after all, even if the hole were in a better position, the grease would still have to flow past the gap between casting and liner (and the two vary somewhere between a loose sliding fit and a loose press fit, depending on temperature). The main goal - both of the epoxy and cutting the grooves supporting the top bearing - was to make sure there the grease had to face higher resistance around the hole than packing itself into the bearings where it belongs. If I can get the vast majority of the grease to go where it belongs - rather than flowing out in waves from the back end - I'm not going to begrudge a little leakage.

The original problem was less that grease was escaping (although I'll admit I'm not exactly thrilled by the idea of wasting - or buying - enough grease to fill the entirety of a 600lb mill body, nor the fact that it would eventually come out and pile on the floor underneath), but that I wasn't able to pressurize it enough to pack the upper bearing, and that it was taking the leakage route as the path of least resistance.

Hopefully on Monday (if NAPA doesn't change their hours on my again) I'll be able to pick up another grease cartridge and we'll be able to see how well the repairs work. Or don't work.


-Bats
( err...leakage? back end? I didn't really say... eww. )