mower mandrel rebuild

mdigby · Jun 11, 2011

Well I'm going to bite the bullet and rebuild the center mandrel(s) with new bearings for my GT-18.

I have information, from another post, that the bearings [for the center mandrel (7/8 shaft)] (top & bottom) are LM12749 and the races are LM 12711.

I have the damaged one disassembled (Bearing splitter, vice hammer and bronze punch.)

I need help removing the cast iron pulley on the "good" one. There are 3 "set" screws in the good one which clamp the pulley in place (two clamp to the shaft, and one clamps to the woodruff key.) They are recessed into the holes in the pulley.

I've tried PB blaster to soak the "rusted in place" set screws I also heated them with a torch.

How do I remove the set screws, so that I can remove the pulley?

I plan to make this thread, a "How to..." thread with photos :thThumbsU:thThumbsU:thThumbsU, BUT I need some help with this step!

Thanks:thanku::thanku::thanku:

69l46vert · Jun 11, 2011

I soak em good with 1/2 acetone-1/2 transmission fluid. Longer the better. Also might help to lock the allen wrench (perfect new one) in a vise and hold and turn the pulley by hand. This allows you to push down hard helping to keep the wrench engaged. If you can't get them then I think you can just pull it anyway as the ones I've done, the setscrews are not in pockets but just on the round shaft and on the key. They'll drag but the puller will still pull them.

Small Fry · Jun 11, 2011

Rick's idea sounds good. Some of these things are a real pain. I have one deck the guy drilled the set screws out and really made a mess of the pulleys. The one I did came a part pretty easy. Once the pulley was off I had to press the mandrel a part. Then the bottom bearing was stuck on the shaft. By the time I got that off I killed that little tin dust cup on the bottom. Not sure where you can get that part.

69l46vert · Jun 11, 2011

I had the same problem. That bearing was so hard to get off. I wound up heating it red and splitting it with a chisel after the cage and rollers were gone. There was no way to get behind it or get a puller on it.

mdigby · Jun 16, 2011

Well
The adventure continued. I soon discovered that getting the shaft out of the bearing is the EASY part of the rebuild. The 1st mandrel I had (from the PO) already had the pulley removed.

This one i bought used "frozen" on eBay.

I began by gathering the needed tools

PB Blaster

To start I removed the zerk (grease) fitting from the mandrel and shot a generous amount of PB blaster into the mandrel.

I let it soak for a couple of days, then sprayed more PB into the mandrel and was able to "free" the rusted bearings. They weren't good enough to mow with, but they did turn.

The next problem was removing the cast iron pulley. It is held in place with three socket head set screws & a woodruff key. They are (or were in the one I have) 3/8 diameter and 5/8in long.

I use more PB blaster and heat (MAPP gas) and new hex keys. I used left hand drill bits into the set screws and finally I used cobalt alloy drill bits in my drill press to remove enough to free the shaft. None of it worked.

Another member suggested that I could , probably, use a puller and slide the pulley off, without loosening the set screws and not damage the shaft too badly.

The original pulley I had, already was chipped, from when it was removed.

So when you place your puller, AVOID pulling on the belt groove.

DO NOT PLACE IT LIKE THIS

Instead I placed the puller on the THICK ring where the brake rides. I thought it would be sturdy enough.

I was wrong. The puller broke a large chip out of the brake ring.

DO NOT DO THIS EITHER!

So I decided to use the bearing splitter I had. This tool is used to "get behind" the bearing on a shaft and remove a bearing. This is what it looks like...

I bought mine at harbor freight. It is CHEAP. Here is a link. Better tools are better. YMMV

I placed this under the pulley and attached the puller to it and then applied pressure.

I thought this would work too, but again I was wrong. After I finally got the pulley off, I discovered this damaged the pulley too. It broke the lower edge of the pulley on both sides.

It did scratch the shaft, but I think the shaft is salvageable.

In Part 2, I'll explain how I got the mandrel apart, once the pulley is off

mdigby · Jun 17, 2011

Part 2

This is actually the easy (easier) process once the pulley is off of the mandrel.

For this process you need four tools.

1) More PB blaster ( or penetrant of your choice)

2 a sturdy bench vise and work bench (Not pictured)

3 & 4

A bronze or brass punch or drift and a sturdy hammer

Next position the mandrel housing on the bench vise so that the bearing housing is supported, but the mandrel shaft is free to move.

if you removed the nut from the shaft, to be able to remove the pulley...

BE SURE to thread the nut partway on to protect the threads during this process.

Position the brass or bronze punch inside the nut at the top of the shaft. Strike the punch FIRMLY with the hammer. It will (should) cause the shaft to begin moving through the upper bearing.

Continue using the hammer and punch to move the shaft until it is driven to the top of the upper bearing. Then remove the nut.

The upper bearing is covered by a "metallic seal" I have not seen where this part is still sold, so be careful to avoid losing or damaging it.

After you have removed the upper bearing, Take a break and have a cold one.

Small Fry · Jun 17, 2011

Now to remove that lower bearing with out trashing that lower dust cap. Didn't work for me, good luck.

Caish · Jun 17, 2011

Next time your at Harbor Freight pick up at least a 12 ton press.
The bigger the better.
No more fighting stuff like that.
I too got the cheap arbors/pullers from HF but I use them with the press typically unless its something like the steering wheel.

mdigby · Jun 17, 2011

Part 3 The lower bearing

The lower bearing is a bit tricky. Other have said that it can be done without the bearing splitter. I don't know. I spent the $30 at harbor freight and used the one I already owned.

For this part you will need:

hammer
bearing separator
Screwdriver (slotted)
Vise
bronze punch

Position the mandrel shaft in the vise so that you can begin to work to separate the bearing the seal and the metal "cup" grass shield from the shaft.

These are assembled using a shop press and again the metal cup and the metallic seal above it may NOT be available as replacements, so work carefully to save what you have.

I started using a screwdriver to pry around the outer edge to separate the bearing & metal cup from the bottom of the shaft.

work slowly and carefully to minimize bending the seal and cup as you do this. You want to create a small groove, where the bearing separator can fit beneath the metal cup and around the shaft.

clamp the bearing separator around the shaft taking time to ENSURE that it fits in the grove between the metal cup and the flange where the blade bolts. Clamp securely, but avoid biting into the shaft.

Position the bearing separator above the vise again, ensuring that it is supported, but the shaft is free to be driven downward.

Using hammer and bronze punch, drive shaft down out of lower bearing.

It IS LIKELY that the metal cup and seal will be distorted by the process. save them and reshape them to fit over the bearing housing as best as possible.

You now should have a bare shaft

The metal cup rests at the bottom against the mower blade flange.

Next is the "metallic seal"

Then is the lower roller bearing.

Now wasn't that simple? (compared to removing the pulley):drunkie::drunkie::drunkie:

mdigby · Jun 17, 2011

The last step step, for dis-assembly, is to remove the bearing races (or "cups") from the bearing housing.

For tools again you'll need.

hammer
vise
bronze punch

Position the bearing housing on the vise and place the punch at an angle inside the bearing housing so that it catches the edge of the lower bearing race.

Move the punch from top to bottom and left to right and strike the bearing race once at each location, before moving to the next. You will soon drive the lower bearing race out of the housing.

Then, turn the housing over, and repeat the process with the upper bearing race.

Now you have a bare bearing housing.

Congratulations, :drunkie::trink40::drunkie::trink40::drunkie::trink40::trink39:

you have disassembled your sears suburban mower deck mandrel and you have removed the bearings & races.

My center mandrel uses bearing LM12749 and bearing race LM12711

BUT you MUST check to see if you can see the numbers on your original parts OR take the old ones (both the bearing and the race) to a mower shop or auto parts store to have them matched up. Yes I said auto parts store. Many cars use the same bearings, that are in our mower deck mandrels, as wheel bearing assemblies.

Next cleanup of parts...

VWJake · Jun 17, 2011

Very detailed write up so far. Keep up the good work.

69l46vert · Jun 17, 2011

Great write up Mark. Thanks for taking the time to do it.

I rebuilt a set last winter. Had all 3 painted and reassembled with new bearings. Was carrying all 3 in my arms coming out the door of my shop and dropped an outer mandrel assy. onto the concrete floor. Broke the cast pulley. Thought i would start crying. It was for an old DB deck and those pulleys are hard to come by.

One thing I did was use new setscrews and never sieze them of course, but also used a second short setscrew over the first which really could be likened to a dust cover. Just to keep the one below it clean and protected for the next time around. Rick

Small Fry · Jun 17, 2011

Looks like your winning. :fing32: To bad we can't find some of those tin caps for the bottom.

GT_80 · Jun 17, 2011

69l46vert said:
Great write up Mark. Thanks for taking the time to do it.

:ditto: Now I guess I really need to get a bearing separator

renelson177 · Jun 26, 2012

VERY nicely done! I have a 917.25400 HydroTrac with two decks; a 42" 917.253150 that I use with my "leaf harvestor" and a 48" 917.253161 that is my regular mowing deck. Here's a shot of the whole rig in dethatcher mode. I'm maintaining ~1 acre and this is my primary piece of equipment.

I've had the tractor since 1989 and have rebuilt both decks. I just had the center unit on my 48" start making noise so I'm in the process of rebuilding it.

I was especially happy to see your photos of the metal grease seals! Mine are long gone but I'm trying to come up with something to cut down on the amount of grease under the deck belt shield. We'll see what I can come up with and if it works I'll upgrade the uppers on the two outer mandrels.

Thanks for the great photo display and write up! You did a great job of showing how to do it and how NOT to do it. Should be required reading for anyone rebuilding a 917 deck.

Tractor-Holic · Jun 26, 2012

Looked like you had "fun".....

I have tried replacing these bearings before,and was very lucky that everything came apart fairly easily,but I had to use my torches to cut the races off and get the pulley to move...those cast pulleys are like glass,especially when they get old...sometimes taking the whole shebang somewhere that has a hydraulic press that can push the shaft out of all the parts at once is money well spent...but you must trust the guy doing it,dont bring them to some monkey who doesn't have much experience!..even old machinists can have bad luck though,there is no gaurantee when your dealing with parts half a century old,unfortunately....

I have used freeze plugs to make those tin cup dust sheilds,the hard part is making a hole 3/4" in diameter thats centered perfectly in them...a lathe is the right tool for that job,but I had a guy drill them on a bridgeport for me,since I dont have a lathe..

GT_80 · Jun 26, 2012

you got your spare parts from Joe's eh? I recognize the green tag with "sc" part numbers- I have bought a few parts from him as well.

I'mnofarmer · Jun 27, 2012

Great write up! :thThumbsU

Another method to getting rusty parts that are frozen together apart is to use electrolysis. This can break the rust bond on parts that are steel without a whole lot of labor and it's great for cleaning up rusty parts for restoration. For a good description of this process, visit my FJ40 web site. I use this to de-rust a lot of stuff.

I first clean off all the loose crud by cleaning in my kerosene tank, then hot soapy water, then place into the de-rust tank. After a a day or two (depends on the amount of rust and how large the part is) it's removed and given another hot soapy bath to remove the now quite soft rust deposits then a going over with a wire brush mounted in a drill to remove any remaining crud. THEN I start making the attempts to get the item apart. It's amazing how effect it is..

Plowthesidewalk · Jul 5, 2012

You gotta great discussion here. Has anyone ever been able to figure out the name of the manufacturer of the Sears tractor mower deck mandrels they made for 42" & 48" decks back in the mid 1970's?

I have been wondering if anyone has found acceptable substitute spindles that will work. Without knowing the dimensions of each type of mandrel (center or side version) it is difficult to try to begin to match something up.

After just looking at a few spindles they currently have on the market I wondered if they would work by simply drilling the holes in the deck shell to bolt them down. An example would be a spindle for a Cub Cadet, part #618-0595A, or Universal Part #10-12972. Once again I don't have the measurements to compare them. The Cub part does not have the slot for the brake but can they be retrofitted?

I thought I saw a SS16 on eBay years ago with matched up spindles so I am figuring there is something out there that has to work. The blades would have to be checked to be the right size also. Anyone have thoughts or input to add?

69l46vert · Jul 6, 2012

Awesome setup you have there renelson177. Very nice!

mower mandrel rebuild

mdigby

69l46vert

Small Fry

69l46vert

mdigby

mdigby

Small Fry

Caish

mdigby

mdigby

VWJake

69l46vert

Small Fry

GT_80

renelson177

Tractor-Holic

GT_80

I'mnofarmer

Plowthesidewalk

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