Hobart C-100 Tear-down and rebuild

I've done a bit of searching the web and PM'ing several members of this website looking for information on how to go about tearing apart a C-100 and putting it back together.  My machine certainly ran well enough until I, in my ignorance, made a small mistake and forced this issue.  To be honest, a teardown has been in the back of my mind since I bought it. There was dried encrusted grease/oil on the outside of the machine that defied my best efforts to clean it up without damaging the paint.  The nicks, chips, scratches, and rust here and there really bothered me.  A huge dent in the motor cover was something I wanted to fix.  And I have seen old dried out grease and wanted to remove and replace what was inside with new grease.

What did I do wrong?  Bear in mind there is precious little info out there.  I watched a few youtube videos - 200 and N-50 machines - of teardowns.  No caveats or warnings.  I began by trying to clean up the outside of the machine.  The switch had years of encrusted grime on and around the opening in the metal cover plate.  I know better than to flood a switch with simple green (or any water based liquid) so I loosened the screws to the plate.  The gear shifter would not let the plate come off, so I drove the pin out and tried to remove the handle.  No luck, the handle was stuck tight to the shaft.  While doing this I discovered that the shaft would slide outward fairly easily and there is a circlip behind the switch box cover plate.  I deduced Hobart did not want the shifter to slide out with the cover plate (there is no way to access the circlip).  This insight was too late. When I pulled the shaft out, I could not engage something inside the machine and lost the ability to shift between gears.  DO NOT EVER PULL THIS SHAFT OUT UNLESS YOU KNOW WHAT YOU ARE DOING!  In order to restore the shifting function, one needs to open up the gearbox, dig down through a pound or so of grease, find the shifter fork, and hold it in position while the shaft is pushed in, engaging the key on the shaft in the key way on the forks.  This is nigh on impossible to do without disassembling the whole gearbox.

If you are interested in rebuilding your C-100, here are a few things I have learned.  I'll be posting the whole story here as I go, probably adding to this post via the edit function, so it may not show up as new posts.  If I'm going to do something, I tend to go overboard.  In addition to oil seals and o-rings, I decided to replace the bearings.  I'll also have the entire machine powder coated and will replace some of the old wiring that cracks all the way through the insulation when it is bent.  THIS WRITEUP IS A WORK IN PROGRESS.  IT WILL SEEM INCOMPLETE BECAUSE IT IS, UNTIL I FINISH REBUILDING MY MACHINE.  PICTURES WILL BE POSTED AS I ADD TO THIS.  However, having seen more than a few threads here w/ blanks for pictures I have to assume this forum erases older pics to save memory.  PM ME AND I CAN HELP YOU DIRECTLY.

Sources of parts:  Oil seals and keys are more or less standard.  McMaster-Carr is an industrial hardware store that stocks just about everything.  mcmaster.com.  O-rings are available from a number of sources but my favorite is theoringstore.com.  Great service, cheap prices and their info on what o-ring materials resist which solvents is invaluable.  Bearings are available everywhere and all are not created equal.  There are so called Tier 1 manufacturers - well known names like SKF, Timken, FAG, NTN, etc. and there is everyone else.  I go for the big names - the difference in price is not that much.  Bearing numbers are usually found stamped or etched on the bearing.  If something is broken inside your machine, Hobart has limited parts.  As of Jan, 2022, Hobart had o-rings, bearings, a circlip, and Hobart Labels.  Try them first.

Powder Coating:  What a trip this turned out to be.  In my naivete I thought I could look a few names up in my area, send them a picture of the whole mixer and list the parts and dimensions and get estimates.  Not that easy!  Several companies' phones were disconnected, and a few had answering machines that I left messages and waited for calls.  One was too big for a small job like mine, one company simply sold the powder (in a zillion colors and several materials), and a couple are coating only.  As Caroline hinted in her thread (search for Hobart C-100 on this forum), you have to tear down the machine into the large component parts.  All bearings, electrics, everything must be removed.  The parts then have to be washed clean of grease and oil. I'll do that myself. Finally, the casings have to be media blasted to remove the paint.  Any surfaces that should not be coated need to be identified (Caroline used a red Sharpie on the bare metal).  Smaller companies may only do the powder coating - the powdered color is applied by spraying to electrostatically charged parts which are then baked in an oven at, I think, 500ºF.  I wanted one company to do the whole process - blast and paint.  I found a small company near Cleveland, Ohio that would do the whole process so that I don't have to ship these parts.  Caroline also gave the name of her vendor.  You can pick any of many many colors, I wanted something as close to the original as possible.  Note that sand blasting is out.  The casings are aluminum and sand is too abrasive.  You can easily punch a hole right through the machine's wall with sand.

Pricing:  The powder coating/blasting will likely cost me under $300, exclusive of shipping.  I'll edit these prices as I pay for them. Bearings cost 10 to $15 each and there are 6 of them.  Tooling:  This depends how creative you are.

Tools needed:  A box of disposable gloves. An allen wrench, screw drivers, hard plastic or brass hammer, wrenches, a gear puller, perhaps a bearing puller, several different sized putty knives, various wood blocks.  Hobart's service manual and instruction manual.  The latter is online on Hobart's website, the former is made of unobtanium.  There are, however, sources for this manual.  You will also need rags and paper towels.  Old newspapers are handy too.

Cleaning the inside:  As I pulled the machine apart, I cleaned pieces as I went along and put screws, keys, etc. in small plastic bags and labeled each one.  I used cheap aluminum roaster/baking pans and paint thinner for the initial wash.  I have a friend who is an auto mechanic and he lets me use his parts washer.  This is an invaluable tool.  Once the machine was opened, I scooped out as much grease and oil as I could with various spatulas.  My grease had separated into thick paste and thick gear oil (all black and yucky).  When I got down to the bottom of the gearbox (actually the top of the machine, but it was upside down on my bench) I had a thick slurry left.  I used a vacuum pump to slurp this up but you can do the same with paper towels and disposable rags.  Don't forget to wear gloves.  Mess doesn't begin to describe what you will find when you open the gearbox. 

Pictures:  Take lots of pictures.  Every time you remove something, take a photograph. It's a nice idea to take a before and after photo too.  Make notes.  Of course, if you have the HSM (Hobard Service Manual) you will need fewer pics.  This taking pictures is a bit of a pain and difficult because your gloved hands get dirty fast.  I do it every time I remove something, otherwise there is no change and I don't take the pic.

The next Parts List will be gobbledegook unless you have either the service or instruction manuals.  There are exploded drawings of the parts and reference numbers as well as the Hobart Part Numbers.  If you are not taking your machine apart, skip to the dismantling description.

Replaceable parts:  I'll add to this list below as I pull out and identify the parts...The numbers refer to the Hobart drawings in both the HSM and Instruction booklet and I've included Hobart part numbers - though they are useless since Hobart has washed their hands of these machines for proprietary parts.  ebay seems to be the only source for old gears, etc.

Planetary Assembly:  #1 Bearing - Hobart # N.D. 3201;  #12 Bearing - N.D. 99503;  #26 - Oil Seal Hobart # M72746;  #23 & #25 Bearings Hobart N.D. 99503Z.  All of these bearings measure 32mm x 12mm x 10 mm (standard nomenclature - OD, ID, Thickness). The Z indicates one side of the bearing has a metal seal, no letter means both sides are open.  #6201 and 6201Z bearings are identical to the Hobart numbers and I used these numbers.  In fact, my mixer had the 6201Z bearings in #1 position, and 6201 in #12 position (the numbers were stamped on the bearings).  The Planetary cover uses 2 Hobart #N.D. 99503Z in positions #23 & #25.  Gearbox cover has 2 0-rings - #15 Large O-ring - 5 5/8 x 1/8" NBR; #13 Small O-ring  - 1 1/2 x 1/8".  The Oil Seal is a 21x40x10 single lip oil seal.  SKF makes one.  I found an 8mm thick one on ebay, and a 7mm thick one at a local bearing/seal vendor.  SKF manufactures the original size infrequently, and I face an 8 month wait now (I'll use the ebay variant).

Sizing O-rings.  Measure the inside diameter of the ring, and the thickness of the rubber.  The ID and CS (cross section) are the two numbers you need.  I used Hobart to source these after going crazy trying to measure old rubber rings.

Disassembly:

Transmission case

1. Remove the drip cup.  The stainless steel collar is held on with two screws (mine were missing) but it was a tight fit.  I took a small punch, placed it in the hole on one side only as far as the thickness of metal and using a small block of wood between the punch and machine head, pried the drip cup down a hair.  Then the other side.  Repeat using thicker blocks of wood as needed.  My drip cup came off relatively easily.

2. Remove the planetary.  Loosen and remove the bolt in the center.  The HSM says to pull down and this disk will come off.  Mine would not so I made a clamp.  I drilled a 2" hole in a two foot long piece of 2x4, then cross drilled one hole on either side of that 2" hole.  I then ran the block of wood thru a saw, slicing through the diameter of the hole down the length of the 2x4. Threaded rod thru those cross holes finished the clamp.  I had to sand the hole a very little bit larger then it slipped over the big round boss of the planetary.  Tighten the nuts to clamp the wood to the planetary.  I then gently tapped it downward - one tap on each side of the 2x4 and the planetary disk came right off.  I held my hand underneath so I would not damage anything.  Keep an eye out for the key in the shaft and bag it.

3. Remove the head from the pedestal.  From this point on it will get very messy and there are more than a few parts you do not want to just drop out of the machine's head.  Remove the inspection/model number plate on the back of the column.  You will see two bolts up high on the right and left.  Unclip the capacitor leads, but first, use a screwdriver to short the two metal clips together.  If you recently ran the machine, the cap might have a residual charge and shock you.  Loosen the two nuts.  I blocked the head so it could not fall and when the bolts (not nuts) were loosened I lifted off the entire head.  Watch those capacitor wires.  They came right out.  An assistant might be helpful here.

Direction nomenclature:  Looking at the front of the machine (accessory port pointing at you), front is close to you, back is the motor end, right and left are your right and left.  I use this point of view throughout this discussion.  Top is the top of the machine head in its normal position.  Bottom is where you attach the dough hook.  I used disposable aluminum baking pans (like what turkeys are cooked in) for the parts major.  As they came out each was placed in a new pan for later cleaning.

4. Open the transmission - remove the cover.  I placed the head on a bench upsidedown and blocked it from moving with wood wedges.  On the underside of the machine you will see the large planetary ring gear.  Loosen and remove 4 allen head filister head screws.  Bag and label them as you have so far.  The ring gear lifts off, tho you might need a soft tap with a hammer.  Ditch your steel hammer and use a brass or plastic hammer.  This is important.  The case is aluminum and the steel parts are soft - you can peen and distort both with a steel hammer.  Plastic is best.  The transmission cover is held in place by 4 screws, one at front, one at the back and one on each side.  They are located at 12, 3, 6, and 9 oclock with 12 at the front of the machine.  These are covered with putty and painted.  I dug the hardened stuff out with an old dental tool.  An ice pick will work. They are the same allen filister screws as before.  These are different lengths, and you must not confuse them.  Bag and label them.  A long 10-24 screw (or threaded rod) is screwed into the 3 and 9 o'clock positions and a gear puller is attached to these with the center screw of the puller bearing on the center protruding shaft.  I placed a couple of washers between the puller screw and the shaft.  Tighten the screw and apply upward pressure to the threaded rods.  You are pulling up off center and the front of the cover will rise first.  You must tap this smartly with a plastic/brass hammer to jar the back loose.  It is sitting on a dowel pin and is a fairly tight fit in the machined opening of the head.  Apply more pressure, tap, continuing this procedure to remove the cover.  If one side comes up too far, stop, release the pressure, tap it back and resume.

5.  I saw a puddle of liquid gear oil that had leached out of the grease.  My grease completely packed the gearbox full and was dry and like warmed butter.  Scoop this out as best you can with a putty knife.  This gets quite messy, to say the least.  A retired Hobart service tech suggested saving the grease on your paper towels to make sure you did not pick up any loose parts.  I smeared the grease into a thin layer w/ the putty knife to look for parts.

6. Remove the planetary shaft (output).  Grasp the stack of gears and gently withdraw it from the case.  A bearing will remain behind at the top of the case in a machined recess.

7. Remove the transmission shaft.  That shifter fork that I mentioned at the beginning is now floating in the grease down there.  Dig some more grease out, and carefully grab this with needle nose pliers and pull it out.  Be careful that the two square sliders on the ends of the fork arms are not lost.  Nothing holds them in place.  Do not lose these.  I wiped them off immediately and bagged them.  Pull the transmission shaft out leaving behind a bearing and put it in its own baking pan for cleaning.

8. Clean out as much grease as you can.  If you are powder coating this you will have to pull off the power take off on the front of the machine.  There are 3 allen head fillister screws accessible inside the case that hold the outside hub (accessory hub, power take off) in place.  Remove them and gently tap the hub out.  Note the o-ring.

9. The two bearings in the machined recess (i call these bearing cups) in the top of the machine - one for planetary shaft, one for the transmission shaft did not come out readily.  I stuck my finger into the center race and tried to withdraw each one.  I asked my friends, was unable to borrow what I needed, so did an online search.  Harbor Freight has an $80 set of internal pullers with a slide hammer.  Yes I popped for it in part because I'll use it on my motorcycles, loan it to friends, and use it on my N50 later.  The bearings came out so easily w/ one or two pulls on the slide hammer that had I not tried w/ my fingers, I would have thought they were a loose slip fit.

9. I used some paint thinner to clean out as much of the goop as I could.  You will use endless paper towels here.  What I did was pour about a cup of ordinary paint thinner into the transmission case, then used a cheap paint brush - a 1" chip brush - and old tooth brush to wash the inside walls, bearing cups, and motor shaft/worm gear.  I now had a thick soup of grease and paint thinner in the casting.  I happen to have a vacuum brake bleeder that I used to suck the fluid out and into the reservoir for later disposal.  This made the job very much easier.

Motor:

10. I'd removed the motor cover long ago.  Remove the 4 nuts that hold the rear motor bearing and centrifugal/starter switch casting.  Reach inside through one of the big holes and unclip the spade terminals from the centrifugal switch.  The HSM says to pull outward and the armature with bearing and grease shield will come out together.  The rear bearing and starter switch are retained in that domed casting.  Mine would not budge.  I took two screwdrivers, wrapped some tape around them and carefully pried outward on the casting at two points.  The tape is padding - even though the casting is iron, the machine head that you are prying against is soft aluminum.  Go slowly and carefully.  I kept doing this and the assembly slowly moved outward.  When part way out, it slipped free into my hands.  I discovered there is an o-ring in the hole into which the front bearing fits.  This rubber ring was holding the bearing in place.  I wiped the grease off w/ paper towels and put the armature/bearings, rear casting in an aluminum pan for later cleaning.

11. Remove the switch from the wires, cut the splice apart (mine was crimped - white from plug to motor winding) make sure all the wires are loose and have some slack.  Loosen the 4 nuts on the threaded rods.  Reach into the center of the stator, hook your fingers around the front of the iron laminations, and pull the stator rearward.  I had to try this two or three times before it slid out.  Watch the wires where they go out through a small bushed hole.  I cut an arc out of a couple of 2x4's to form a cradle for the stator and put it in a box.  Later I'll cut off two of the wires with cracking insulation and solder on two new leads.  I used two thin pieces of wood to cushion a pair of pliers as they gripped the threaded rods to unscrew them.  Once started they came out easily.

Clean up and Powder Coating

12.  I took all pf the pieces with grease on them to a friends and used his parts wash tub.  If you have a friendly auto mechanic he might let you use his.  This made washing all the grease off easy.  I'd already cleaned most of it away because I did not want to gunk up his machine with a pound plus of old thick grease.  Once washed, I wiped them down and sprayed the steel gears and parts with WD40.  If you don't do this the steel parts will rust quickly - the solvents take all the oil off the metal.

13.  The pedestal comes apart easily.  there are 4 screws on each side of the bowl lift rails that are filled w/ hard putty and painted.  I dug the stuff out with a dental tool. and loosened the screws.  I removed the cotter pin and slipped the raising mechanism out of the back of the bowl lift.  The book says to remove the 4 right screws and loosen the left screws about 4 turns.  My rails were solidly gooped in, gentle prying with a screwdriver popped them free and the bowl lift slipped off.  I removed the rails (also from the back of the bowl lift) and wiped the area w/ a paint thinner soaked rag.  Drive out the pin, remove the cam from the lifting arm, withdraw the arm.  Loosen the 4 bolts on the bottom of the pedestal and the column comes off the base section.  I scraped and wiped all the surfaces clean.  Caroline in her post, showed her pieces with red Sharpie markings on mating parts that were NOT to be powder coated.  I used some orange and white tape that I put in places where no powder coating should be applied (oj) and wrote notes on the white tape where surfaces were to be powder coated if it was not obvious.  Everything was packaged and taken to the powder coater.  I went over everything with the gentleman I'd exchanged emails with.

After talking to him, we decided to powder coat the top and bottom of the pedestal (they sandblast this part since it is steel) even though those are mating parts.  Point out the dowels on the top, but otherwise its your decision to PC or not.  They had done several mixers before me and that is what they did on the others.  My C-100 was painted by Hobart after the base, column, and motor/transmission case were bolted together.

Gearbox Parts:

14.  Planetary shaft.  I started cleaning the planetary shaft with three large gears on it.  This is the output shaft which drives the planetary disk.  I drilled a hole in a block of wood and glued a 5/8" dowel in it.  This is my stand for disassembling the gear train.  As a gear comes off its shaft, it gets wiped with a paper towel and placed on this stand.  I'm careful to remove each part in turn and immediately place it on the shaft in the same orientation/direction that it came off the shaft.  First off is the bevel gear.  Then I drove out the pin holding the 3 gears in place.  Spacer is next, followed by 3 gears.  Don't loose the key that holds the gears to the shaft. The HSM says to use a puller to remove the flat spacer and pressed on bearing.  Since I was replacing the bearings, I used a piece of 1" black pipe to drive the bearing off.  Place the shaft on a block of wood, put the pipe on the shaft against the flat side of the large spacer, hammer down the pipe to drive the bearing and spacer off.  I cleaned the shaft with mineral spirits and a tooth brush, then scoured some hard grease stains off with fine steel wool.  A quick wash and I was ready to reassemble the shaft.  I coated each washed piece with a light oil to prevent rust.  Place the spacer with grooves on it, grooves toward the bearing, on the shaft, slip on the bearing and drive it home.  When installing a bearing, you want to drive against the part that is being opposed by a pressed fit.  In other words, if you are driving a bearing on a shaft, you can only press on the inner race.  If the bearing is going in a hole, press on the outer race.  I found a deep socket that I had from a ratchet set that matched the inner race and I used this to drive the bearing down.  A wooden block on the socket protected it.  Next I slipped the key back onto the shaft, and slipped the gears down in order with the original sides facing in the same direction as when I disassembled this.  Finish up with the washer and pin and slip on the bevel gear.

15.  Transmission shaft.  After washing this in solvent, I decided not to dismantle it.  My bronze drive gear (engaged by the motor's worm gear) showed very very little wear.  There are springs in the shock absorber mechaism and pins and I did not want to damage an otherwise functioning part.  If anything is broken here, your only source for parts will be to have a machine shop manufacture it for you, or buy used on ebay.  There are a lot of folks tearing C-100's apart and selling the parts.  One caution.  A vendor was selling the whole transmission shaft w/ all gears and parts for $200.  The pictures showed it coated heavily with old grease and the description said it came out of a working machine.  Without a thorough solvent wash, you really don't know what you are buying, so caveat emptor.  These parts may be pristine or they might show considerable wear.

Assembly:

1.  I am waiting for the powder coater to finish his work before proceeding any farther.  I now have new bearings, a new oil seal, new o-rings, and new Hobart labels.

Note to self:  need to proofread n post pics. next time.