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Craftsman 42in Tractor uneven cut


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05-07-07, 10:06 AM   #1  
Craftsman 42in Tractor uneven cut

I have a 42in 16HP 2 blade Craftsmans Lawn Tractor. I have just put new blades on it but it does not seem to cut the grass right in the middle under the tractor. I had this problem with the old blades so I put new ones on it. When you look at where I have cut there is a 2 inch area that is uncut. Everything seems fine under the mower and the blade deck is even on both sides. Any ideas why the middle of the cutting area is getting missed? The replacement blades are the correct size and style for the 42in deck.

 
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05-07-07, 06:31 PM   #2  
Are you certain that you have the corect blades??? Excessive grass buildup under the deck can cause this problem particularly directly in front of the area being missed by the blades. Post back with the chassis' ID numbers as well as the part numbers you have bought for the blades and I can confirm if you, indeed, have the correct blades.

 
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05-07-07, 08:57 PM   #3  
Do the blades nearly touch together in the center under the deck? If not, the blades aren't right. Otherwise, the grass buidup can cause this, if the blades are upside down, or if the front of the deck is much higher or lower than the back it aan cause this.


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05-08-07, 07:48 AM   #4  
Correct Blades

Thank you for the reply. The blades are correct and match the owners manual and the Sears recommened blade replacement. I also compared them to the original blades I tool off and they are exactly the same.

They are installed correctly (which side is facing up). The one question is can the blades move apart and if so how do I adjust? Also can the blades be out of alignment somehow? They just bolt on but can the area the bolt onto be messed up. This tractor was only used for two seasons and is in great shape. The mower deck is perfectly even and aligned to the ground, it is the very center that is not getting cut.

I will check the space between the two blades tonight.

Thank you.

 
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05-08-07, 07:57 AM   #5  
Azis
Not sure about missing the middle but, just for giggles check your tires to make sure one is not nearly flat. I have found low or near flat tires cause some interesting cutting patterns.

 
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05-08-07, 09:23 AM   #6  
Check your tire pressures in all 4 tires. Check the distance from the center of each axle end to the ground to be sure that the tractor itself is level. Check that the tires on the left side of the tractor are the same diameter as the ones on the right side. DON'T check the edge of the mower deck, but DO check the distance from the blade tip to the ground with the blades located pointed out to the side. Left side should match right side. Now spin the blades so they now point front to back. The front tip should be 1/8" t0 1/4" LOWER than the rear tip. You do all of this, and your deck will be set up correctly. If all of that does not fix the problem, then you might have a bent deck or a bent spindle. I'm ruling out a bent blade as the new blades did not correct the problem but you might want to check that as well.

 
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05-08-07, 12:12 PM   #7  
I know the tires are even, I check before each use (14 PSI frontm 12 PSI back) because it seems the left front tire has a very slow leak. Also the blade housing/mount is even to the ground when I check it in four places (two on each side).

What I am not sure about is if the blades them selves are level. But, can they even be adjusted? When I changed them on Sunday it was just a bolt with a washer and lock washer. There was nothing to adjust up or down, left or right.

Thanks.

 
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05-08-07, 12:21 PM   #8  
For your slow leak, put some Slime in that tire. Works great for slow leaks.

 
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05-08-07, 02:32 PM   #9  
Only time I've seen this is when the front of tractor/mower/deck/blades are higher in the front than in back.

If the shaft was bent even a little bit, I'd think you'd know it by vibration. I don't know what could cause that except everything you already checked.

 
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05-09-07, 02:32 AM   #10  
If you are leaving a strip down the middle, then you needn't worry about deck level (in either direction), you need to have a look for grass build-up under the deck. Don't assume that the manual is correct, as I asked before, what is the chassis model number as well as the part number of the blades you purchased?

 
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05-09-07, 06:54 AM   #11  
puey61,

Can you clarify that please?

I just fixed a mower deck (that didn't have build up) and was higher in the front and was leaving a strip down the middle. I lowered it to level and it cuts perfectly now.

I would write it off to inadvertantly fixing something else (knocking off grass build up, etc) while adjusting deck but I've seen it more than once and the decks weren't clogged.

I realize I'm a newbie and you're a mod but apparently I'm missing something.

 
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05-09-07, 06:59 AM   #12  
Having the housing level does not mean the blades are level. You have to adjust the deck hangers (mounts) so that the blades are level and let the housing itself be wherever necessary for the blades to be level.

 
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05-09-07, 07:34 PM   #13  
Leveling a deck does not change its radial position to the tractor, it changes its position relative to plumb. Using a two blade deck as an example, if you were to draw a straight line through the center line of the blade centers, you will see that the line is not perpendicular to the mower frame. This is necessary so that as you travel parallel to the frame (as you do), the blades have overlap. Now lets imagine, for arguments sake, that the centerline of the blades were, indeed, perpendicular to the frame. In order to keep the blades from contacting one another, they must have clearance and therefore would leave a strip in the void area. Unless the blades were timed (as a few are such as some older MTD's and some rear discharge Wheel Horse's) using a cogged belt with cogged blade spindle pulleys so that the blades never changed position relative to one another, the blades would hit one another. Now we know we can't have this happen so therefore the blades must be offset to one another relative to perpendicular with the tractor frame thereby changing it radial position. When you level the deck from front to rear, you are changing the perpendicular axis and a side to side adjustment will change the parallel axis. Neither of which will change the radial position of the deck to the frame. Now, for explanation purposes, lets exagerate a possible hypothetical situation. Using a typical configuration of mowers and since the majority of decks are a right-hand discharge and the blade rotation then is clockwise, the left hand blade is further ahead of the right hand blade. This makes the radial position a few degrees clockwise of perpendicular. And now lets say you whack the left side of the deck into a solid, immovable object where it renders the blade centerline perpendicular to the frame. You will now leave a strip down the center since you no longer have overlap because, as we know, the blades must not contact one another. Now to emphasize the radial positon theory we'll exagerate the deck position relative to the frame. Lets say you have a 40 inch cut deck and you rotate the deck clockwise 45 degrees you will now have a cutting width at or about only 30 inches in width and if you rotate the deck a full 90 degrees (blade centerline now parallel (or close enough, for arguments sake) with the frame), you will now have a 20 inch cutting width. As you see it is only radial position that determines blade overlap and not a change of either axis'. Listen, I'm not a professor or necessarily a teacher so i did my best to make my point and hope it comes across clear.

 
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05-09-07, 08:57 PM   #14  
I believe I followed your detailed explanation ... but I just attributed it to a minor wind tunnel being created towards the front and laying the grass down before it could be cut. Maybe I did inadvertantly fix the "real" problem without knowing it.

I do like these forums and I got great help so quick when I first posted, it's hard to not try and give something back by helping when I read them now.

But I guess I should let you experts handle the answers and limit my posts to just questions.

Thanks.

 
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05-10-07, 12:21 AM   #15  
No problem Ttow. I've had the same problem...blade deck too high in the front causing a ridge in the center. Levelled it and the ridge went away. Blade overlap wasn't part of the equation though. Overlap isn't what is being changed by the deck being too high in the front. The problem is that each blade cuts a circular pattern. When it's level, this is fine. Tilt that circle so that one side is lower than the other, and you will get a concave cut on the low side of the blade. Now, put two blades together and tilt both of them the same. You will have two concave spots cut next to each other, leaving a ridge in the center. The one offset to the rear will leave the deeper cut, but it will leave a ridge. It has to be off quite a bit to make a difference you can see. Usually when one is that bad, it has a broken deck hanger or something bent. When this is happening, it doesn't leave an uncut strip...just a higher strip or ridge.

Puey is right that deck level won't change the blade overlap, no matter which way it's moved, but it can be levelled to a point where it will leave a ridge.

In any case, I guess that's not whats happening in this situation though.


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05-12-07, 10:31 AM   #16  
Wow, this was my first time on the forum and I appreciate all the responses. I have checked the blades underneigth and there is about a 1/4" or less gap. I have cut a little of the lawn again and it is missing the middle. I will bring the mower in and varify again the housing and blades are level. I is hard checking the blades with such little clearance.

Thanks.

 
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05-14-07, 06:43 AM   #17  
Sorry if this sounds stupid, but have you verified that the center blade spins with the outside blades when running? The center blade shaft is usually the main drive shaft for the deck, but is the blade itself firmly attached to the shaft? Is the deck belt properly tensioned so that none of the blade shafts are slipping?

 
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05-22-07, 05:20 AM   #18  
Did you ever fix this? Mine is starting to this and I think it's because one of the spindles wobbles just a little; not even enough to cause a lot of vibration. The other spindle is perfectly solid.

 
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