Bearings on a Smithy

Well, I'm having one of those nice reverse-midas days when everything I
touch turns to dog doo.
Plan D was to finish milling out some dihedral braces for an
almost-ready-to-fly kit that I'm building. After setting everything up
and turning on the switch I find that the spindle on my Smithy 3-in-1
machine's milling head won't turn.
The spindle rides in tapered bearings in the quill, which are adjusted
by a round nut. The sheet metal retainer for the nut either never got
bent into place to prevent the nut from turning or it bent itself out of
the way. The bearings were way too tight -- to the point where there's
some bluing of the spindle on the bottom end. The grease in the
bearings has obviously overheated and left each roller bedded in it's
own little custom-made varnish pocket.
So I have two questions:
For the short term, is there anything that'll likely dissolve this
varnish? I can scrape it off the outer races with my fingernails, but
the rollers are retained onto the inner races & I can't get to it. I'd
like to soak it off if possible, although I may just leave things fairly
loose & make my dang cut to get through today.
For the longer term, how much of a chance is there that I can get these
bearings from a local bearing house? Should I just be applying to
Smithy for new ones? If I'm going to go to the trouble of pulling those
outer races I darn well want to put in decent bearings rather than
Chinese crap.
Thankee much.
Reply to
Tim Wescott
Loading thread data ...
Oh, and while I'm sure that the grease in there was of the finest possible quality, I somehow inadvertently scraped it all off and threw it away in a moment of distraction. Should I just replace it with regular old automotive bearing grease, or is there something better?
Reply to
Tim Wescott
I would bet you that good old brake cleaner will cut the old grease just fine - you can spray some into a container and soak the bearings. Automotive wheel bearing grease sees a very similar load profile - while I am not a grease expert, my inclination would be to use a high pressure type automotive bearing grease, or maybe the short fiber grease (do they still make that?)
Reply to
william_b_noble
snip
I had been eying my bucket of carb cleaner -- I dumped the bearings in for the mere 30 minutes recommended and they cleaned right up.
I think I'll use the bearing grease that I have in my grease gun -- at this point I'm kinda considering that those bearings are 1/2 way to being toast anyway, so there's probably a teardown in that mill head's future.
Reply to
Tim Wescott
Brake cleaner seems to come in at least two formulations. The one I like is 50/50 Acetone/Xylol(Xylene). This, IMHO, is a better solvent than either alone. I buy the Acetone and Xylol from a large paint store in gallon cans and mix them myself. I pour them into a ShueShot sprayer (available from KBC, Travers, ...). This sprayer is pressurised with _clean_ shop air. Besides being "environmentaly friendly" this is MUCH cheaper than buying aerosol cans of break cleaner.
An other one that I don't particularly like is perchloroetylene and Methylene Chloride.
Ted
Reply to
Ted Edwards
On Mon, 29 Aug 2005 21:14:48 -0700, the blithe spirit Tim Wescott clearly indicated:
You done did a baaaaaad thing, Tim. Those oil-based solvents leach into the metal and take forever to come out, usually with heat when the bearing is spinning, effectively neutralizing the grease. Doesn't that sound like great fun? I heard warnings about it in tech school and again when I worked for Palomar Technology, a vibration tester manufacturer for predictive maintenance firms. "Spectacular" is when a 30' steam turbine is running at top speed and a bearing seizes.
I'd heat and spray (NOT soak) those bearings with a film-free, evaporative solvent before putting them back into service if they were mine. YMMV.
-- Like they say, 99% of lawyers give the rest a bad name. ------------------------------------------------------
formatting link
Lawyer-free Website Development
Reply to
Larry Jaques
Yes, but it's hard to find. It is sometimes called "Drum brake wheel bearing grease". Plews or possibly Lubrimatic.
I'd caution that some ball bearings use a plastic separator between the individual balls. That plastic may not like strong solvents.
Reply to
Rex B
All these warnings come too late!
The separator is sheet metal -- I wouldn't have dumped the bearings into paint-stripping parts cleaner otherwise. I guess I'll spray the bearings with starting fluid (ether) to wash out what grease I can, then heat them gently and let them outgas.
Since I'm reclaiming them instead of replacing them I was planning on monitoring their health in any case -- I'll just do that ever much more so.
Reply to
Tim Wescott
I think you're being a bit alarmist here, Larry. If there is such an effect it's likely only a factor in very critical applications - I've never heard of it in over 20 years of designing and working around rolling bearings. SKF, NSK, and Klueber (mfr of fancy lubricants) all recommend rinsing bearings in hydrocarbon solvents, with no warning about avoiding any specific solvents.
The rotors of all the steam turbines I'm aware of run in hydrodynamic bearings. I'd be interested in any info you might have on medium to large turbines equipped with rolling bearings.
Re the OP, I think my biggest concern would be the bluing of the bearings indicating overheating.
Tim: If you post the part numbers from the bearings we can likely give you some idea of the cost of replacements.
Ned Simmons
Reply to
Ned Simmons
On Tue, 30 Aug 2005 11:39:03 -0400, the blithe spirit Ned Simmons clearly indicated:
Yes, perhaps for a Smithy bearing... ;)
I'm surprised since I heard about it from two vastly different user sets of bearings. Then again, designers and repairmen work in two entirely different fields/worlds. Could we know something you don't? I'm positive that you know things we don't. ;)
What are the absorptive factors in bearing race material?
You could be right there. I don't know that it was a roller bearing which seized, but a guy from SDG&E's Encina Power Plant was at PTI one day (ca. 1990) discussing the horror stories of machinery failures with the engineers and I had the opportunity to listen in. Scary!
PTI was absorbed by SKF, and the potential resultant corporate climate was what made me take my leave. They closed the Carlsbad, CA plant, moving all to the other absorbed company in Kearney Mesa (northern San Diego suburb), about 2 extra hours in gawdawful traffic each day for me. Test technicians aren't paid enough to want to go that extra mile for the company.
-- Like they say, 99% of lawyers give the rest a bad name. ------------------------------------------------------
formatting link
Lawyer-free Website Development
Reply to
Larry Jaques
That bugs the hell out of me, too. The bearings themselves aren't blue, it's the quill in the vicinity of the lower bearing -- would this be because the bearings were embedded in grease and had no air contact? I dunno.
The Smithy chart gives their own part numbers -- S20500 & S20410, but the chart also has a column of "generic" numbers, in which the bearings are listed as "D2007107" & "2007106". I have to admit to focusing so tightly on diagnosing the problem that the fact that I may have had the reference I needed didn't fully penetrate -- it was just that sort of day yesterday.
I wasn't clear on my original question, which was how likely would it be that I could waltz into a bearing place with bearings in hand but no other information and get decent replacements. If the bearing numbers mean anything, though, then I know I'm set.
My intention would be to get a set of bearings that are one or two grades better than what's indicated in the Smithy part number, unless they're already claiming to use really good bearings.
Reply to
Tim Wescott
Use 50/50 Xylol/Acetone. I have a ShureShot sprayer which is presurised with shop air and another with mineral spirits (paint thinner). The X/A is a very effective solvent.
Ted
Reply to
Ted Edwards
Ether should not be a problem. Chem-Dip or similar carb cleaner definitely gets into the pores and seeps out for a long time. Once in my mis-guided youth, I elected to use carb cleaner to reclaim a big aluminum percolator with strong carb dip cleaner. This was back in the 1970s before all that EPA and OSHA silliness. Got the pot clean, but after about a week of strange-tasting.... make that AWFUL-tasting! ...coffee, we abandoned that pot.
Reply to
Rex B
That would be my guess. But if the spindle runs true you might leave well enough alone and watch it closely. Bearing steel will tolerate relatively high temps without loss of mechanical properties, around 400F IIRC. I believe distortion is often a problem before the bearing reaches the temperature where its temper is affected.
Check for numbers on the bearings as well. I suspect the 7107 and 7106 indicate these bearings are extra-light angular contact bearings, which also fits with the application. That would make the smaller of the two, the 7106, 30 ID x 55 OD x 13 W. The 7107 would be 35 x 62 x 14. Can we assume that there is a single 7107 at the nose of the spindle, and the 7106 is at the upper end? Or does the "D" (for "duplex"?) on the 7107 indicate a pair?
If the bearings are angular contact bearings, one shoulder of the races will be higher than the other. The balls and cage may or may not be separable from the races, but, unlike normal radial bearings, there will be considerable play in the bearings when they're unmounted.
Price will be much higher for precision bearings. Probably around $20 each for standard, and around $150 for ABEC 7, which is what you'll find in Bridgeport spindles, for example. Regular ABEC 1 bearings from the big mfrs (SKF, NSK, etc.) are so good these days it may be worth trying them before spending the big bucks on the precision bearings, unless you have a matched pair of bearings at the spindle nose.
Ned Simmons
Reply to
Ned Simmons
Absolutely. I often worry that after I've designed, built, and installed a new piece of equipment that the folks who actually have to live with it every day are cursing me behind my back. I'd much rather have the feedback, even if it's negative, and a chance to improve things and avoid repeating a mistake in the future.
I wonder if rather than a matter of absorption, it's a case of contamination by solvents that don't evaporate completely?. Klueber seems to recommend some pretty aggressive and volatile solvents in preference to mineral spirits or kerosene, which they warn about leaving a residue.
I've done a bit of work for GE's medium steam turbine division over the years and have some second hand knowledge of how elaborate the oil supply systems for the bearings in turbines can be, particularly on naval vessels. It's very obvious that keeping those bearings happy is paramount.
Ned Simmons
Reply to
Ned Simmons
Without going out to the shop and looking the sizes sound right. If by "one shoulder higher" you mean the races (and rollers) are conical like a wheel bearing in a car then yes, they are. In this case the cages and inner races are married and the outer races are free (well, pressed into the quill, at the moment). I'm sure this was so they could make the bearing tension adjustable without spending big bucks on matched duplex bearings. The big bearing is _not_ a duplex, but maybe it was in some previous design.
Thanks Ned. Right now I just want to get this thing back together so I can make my cut. I've printed your post out and will keep it with the machine if & when I ever buy bearings for it.
Reply to
Tim Wescott
Tapered roller bearings? Ignore everything I said, except perhaps the stuff about how the heat may have affected the bearings. It looks like your 2007106 crosses to an SKF 32006X (30×55×17mm). D2007107 = SKF 32007X (35×62×18mm). Precision class for tapered roller bearings is very confusing, and the run of the mill bearings are generally much less accurate than ABEC 1 ball bearings.
Ned Simmons
Reply to
Ned Simmons
On Tue, 30 Aug 2005 16:01:35 -0400, the blithe spirit Ned Simmons clearly indicated:
You're a good man, Ned.
OK. How are bearing races made? Do they have any pores to catch grease/solvent at all? If so, how much?
Ayup, broken pieces of large-diameter spinny metal things might go quite a distance before something solid stopped them. I'd imagine that hydro power plant generators and turbines might be the same way. I definitely wouldn't want to be around one when it let go, whether it was a bearing or something solid hitting a turbine blade. =:-0
Reply to
Larry Jaques
In the process I've seen for high volume bearings, the races are roughed out of tubular stock on multi-spindle automatics, heat treated, then finish ground. Great care is taken with the finish and surface condition, but at some level there is obviously some roughness, so I suppose some residual solvent could be trapped. But I'm inclined to believe that contamination as a result of incomplete evaporation of the cleaning agent is more likely. I thought you might be alluding to this in your original reply to Tim when you recommended spraying them off with an "evaporative solvent."
Ned Simmons
Reply to
Ned Simmons
On Wed, 31 Aug 2005 23:55:22 -0400, the blithe spirit Ned Simmons clearly indicated:
I was, to some extent, but I thought they might be more porous than I than that. (More like a sintered metal.)
.-. Life is short. Eat dessert first! ---
formatting link
Comprehensive Website Development
Reply to
Larry Jaques

Site Timeline

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.