Craftsman 42" mower deck - questions about blade bolt

[KirklandMike]

Hi. I messed up my mower deck by hitting a stump at my new house. My goal is to see if I can do a workaround repair because I can't find a used riding mower that looks worth buying and new lawn tractors are not available any time soon. If can get through a month or two - I'm not worried about getting good quality mowing - I'll be be OK.

The longer blade got bent and the deck was damaged at the mulching / discharge port. I've been able to bash the deck some, and I think that if I can put new blades on the tractor might sort of work. But I want to take the bent blade off to see if I can straighten it to check, and of course I'll need to take the old blade off to put new ones on.

Question 1. Are the bolts for the blades standard thread or reverse thread? From the Sears PartsDirect site, it seems pretty clear that there is only one type of bolt, and that it's normal thread. I've been able to loosen the bolt on the shorter blade.and it's normal thread. So I'm really just asking for confirmation.

Question 2. How can I get the bolt for the longer blade off? I probably need to take it off to straighten it (it's still mounted, and under pressure from a car scissors jack right now), but I'll need to do more than that. And need to take off the blade anyway. I can't undo it. I'm using a pry bar to stop the blade rotating. I've tried a socket with extra leverage from a pipe, WD-40, heat from a small propane flame, a plumbers wrench (the type that tightens up as you try to turn). Nothing is working. I thought about unbolting the mandrell so I can work at a bench, but a pulley on the other end of the mandrell is in the way, and I haven't been able to remove the nut.

I'm out of ideas, so any suggestions would be appreciated.

Thanks

 

[bertsmobile1]

I regularly cut the heads off
The bolt is not stuck in the hole, it has just overtightened
I cut slots across the head, point to point with a narrow cut off wheel then give each cut a healthy whack from a cold chisel
Usually the head breaks off and then you can undo the bolt with your fingers.
Blades can never be straitened and running with a bent blade will destroy the spindle bearings in no time flat and if you are really lucky will cause the spindle housing to crack through at the mounting arms then the belt will jump off when the deck is under load .

 

[StarTech]

Model of the mower helps as normally the deck usually has the same length blades. In this case 21" blades. There are a few that rear discharge decks where the blade on one side rotates CW and the other side rotates CCW.

And Bert, it is a bunch of bull that blades can never be straighten as I has straighten near new blades where customers including myself have hit tree roots. I even had to straight new out of the box blades that weren't fully bent on one end. It does take a hydraulic press to do it. Its just that most used blades are too worn out and really should be replaced. Although these spindles of the Sears AYP and MTD decks uses 3/4" spindle shafts they can still get bent on occasion. But most damage if the blade is meeting the same place height wise but are not level inside that deck it usually the mounting points of the spindle assembly that got bent.

If you haven't destroyed the hex yet then a good impact usually works but as said you need to know if it is CW or CCW threaded. Most of these screws and nuts are RH threaded due the use of the star on the spindle shaft blade mount ends. Now I have seen a few spindle screws and nuts rusted in place or cross threaded to a point that the spindle shaft has to be replaced.

 

[Cusser]

The blade bolts on my 2005 LT1000 42 inch lawn tractor are right-hand thread, and fine thread as well, specially hardened bolts. I use a 1/2 ratchet and 6-sided 9/16" socket for these.

 

[slomo]

Use propane heat, candle wax or penetrating spray like PB Blaster. Don't use WD-40. Spray it down a couple times a day for several days. Numerous youtube videos about removing broken bolts.

One you get the bolt out, use anti-seize on the threads prior to installing. Makes it so much easier to remove.

I wouldn't use a hardened bolt at all. If it breaks off, pain in the ear to remove. Grade 5 is plenty OR get the OEM bolt.

Definitely use an impact gun with a 6 point IMPACT socket. Those cheap electric ones from Harbor Freight are great for seldom use guys like me.

Why straighten blades? Weren't not talking about replacing the wife's shoes or her daily casino trips LOL. Get some new blades and an OEM bolt or two. Slamming stumps is tough on them.

Might want to walk the property again a couple times PRIOR to mowing.

slomo

 

[KirklandMike]

Thanks for the comments and suggestions. Written before the last couple.

Sorry for leaving out the model. It's 917.289253. The blades are - in fact - the same length. I guess I was losing it (optical illusion from the damage and the way the different sides look).

Impact device seems like a good idea. I think I'll need an adapter for my impact screwdriver - hex shaft to 1/2" socket. No, not needed because the impact driver has a 1/2" end. I feel more comfortable trying that than my pretty new cordless impact driver (which would also need an adapter) because I think it might get over stressed. Perhaps impact would work on the pulley bolt; it's not easy to prevent the mandrell spinning.

I don't have high hopes for success beyond just proving that a new blade is worth trying (i.e. the deck can be made good enough). I think Bert is right - the bolt has just become stuck due to hitting the stump. [It would be good if I could use this mower in the scrub that's about 1/3 of the "grass" so I wouldn't have to use the new one in that area when I get it.]

Yes, the bolt head is getting smoothed out. I'm doubtful that cutting the head of the bolt off will allow it to be unscrewed - certainly by fingers. The blade is only contributing to the bolt being stuck when it hits the deck. Still, removing the bolt head should allow the blade to be removed, and then I can work on the bench.

I don't have a hydraulic press, and it does feel like something I'd get much use from. I wonder about rigging up a jig for my floor jack instead. Or just buying new blades, although I'm not certain if the spindle on this side is damaged.

Some of this is about tradeoffs - time as well as money.

 

[KirklandMike]

@Cusser. I was able to confirm that the blade bolts are right hand thread - but not by removing.

@slomo. The point of reusing the blade was to see if it's worth doing anything at all. Since I'm mentally committed to a new lawn tractor, I don't think it's worth doing much - although depending on how I deal with scrub it might be worth keeping the old one as well. The stump I hit was in the better part of the yard - although right on the edge. But yes, walking around more is a good idea. When we moved into the last house we had an arborist check things out. At that time the neighbor was doing most of the mowing. The arborist called the damage to the base of the trees "mower blight".

UPDATE. I was able to remove the pulley at the top of the mandrel. The impact screwdriver did the trick for the bolt, and I used a gear puller to get the pulley off. Then I sheared all four of the bolts holding the mandrel to the deck without even using the impact screwdriver. But I was able to bring the mandrel and the blade to the workbench. Still wasn't able to get the bolt to shift. I take the points about stuck bolts - different approaches and time. But I decided that enough was enough. Ordered mandrel assembly, blade bolt, and blades from SearsPartsDirect. Fingers crossed for June 10.

Since I still have the blade attached to the mandrel with the stuck bolt, it's probably a good idea to get adapters for the cordless impact driver and see if it's able to move the bolt when the manual impact screwdriver couldn't. I like the manual tool, but I'm only 100% certain that I've rotated the innards properly is if the stuck bolt gets unstuck.

Thanks all!

 

[StarTech]

With model number given I can comfirm the both screws (bolts) with captive washers are RH. They are also 7/16"-20

 

[slomo]

New machines are not necessarily better. They keep adding more circuit boards and fuses. Think everything needs a wiring harness connected to it. $$$$ when it fails on you. I would keep the oldest one you have running. Way cheaper anyway than a new machine.

slomo

 

[bertsmobile1]

Model of the mower helps as normally the deck usually has the same length blades. In this case 21" blades. There are a few that rear discharge decks where the blade on one side rotates CW and the other side rotates CCW.

And Bert, it is a bunch of bull that blades can never be straighten as I has straighten near new blades where customers including myself have hit tree roots. I even had to straight new out of the box blades that weren't fully bent on one end. It does take a hydraulic press to do it. Its just that most used blades are too worn out and really should be replaced. Although these spindles of the Sears AYP and MTD decks uses 3/4" spindle shafts they can still get bent on occasion. But most damage if the blade is meeting the same place height wise but are not level inside that deck it usually the mounting points of the spindle assembly that got bent.

If you haven't destroyed the hex yet then a good impact usually works but as said you need to know if it is CW or CCW threaded. Most of these screws and nuts are RH threaded due the use of the star on the spindle shaft blade mount ends. Now I have seen a few spindle screws and nuts rusted in place or cross threaded to a point that the spindle shaft has to be replaced

Well we are going to disagree on this point
The blades are hot forged then tempered or the cheap imported ones are hot forged then case hardened
When the blade strikes something it usually will both bend & twist
A bend can be straitened in a press but the twist requires special jigs to return it to the original profile.
Once you have done this then the blade will be stressed differently left to right so will try to relieve that stress by twisting & bending again.
If the twist is not taken out then the airflow will be different each side which from the perspective of the spindle & bearings is the same as being unbalanced weight wise .
I have ben guilty of trying to save a bent blade that was almost new and got it back to within 0.002".
Thought I was pretty smart doing it only to have the spindle bearings fail on that side the following season.
Being a curious type of person, and because I do have access to the testing gear, I mounted the straitened blade in the big lathe on an old spindle with the hex ripped off and spun it.
It was so far out of balance it was not funny although I had checked the weight balance and the blade was spot on.
Double checked the weight balance and found it out by .0015" front back so rebalanced the blade again then spun it up again
Fine up to 2200 rpm but from there to 4000 it became very out of balance.
Good enough for me tossed the blade , not worth the effort of filling in a public liability claim form.
I don't believe in luck, don't gamble, don't buy lottery tickets & don't accept any risk with customers mowers.
What we do not know is what structural damage is done to the blade in the first impact.
Typically it comes under the mantle of a high energy rate deformation in which condition the metal can actually flow .
The high energy rate deformation that most are familiar with is metal spinning and drop forging.

Considering the cost of replacing the blade is less than the taxi fare to an A & E ward , let alone an ambulance ride , it is a fools errand to my mind.
And yes I have had blades supplied to me that were not properly made and they went strait back to the supplier.
Not a big problem as I always order at least 2 sets on the assumption that the customer will be happy with my work & come back latter in which case I will have their blades in stock ready to fit so it is easer to convince them to replace the blades if deemed necessary