When you first purchased your lawn mower, you probably had a look over the user manual. You may have noticed that it instructed you to leave the blades slightly loose and this could be confusing if you aren’t familiar with the machine. It probably left you wondering; should lawn mower blades be tight or loose?
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How Tight Should A Lawn Mower Blade Be?
While you may think that your lawn mower blade needs to be extremely tight in order for it to be secure, this is a common misconception. You will need to make sure that the blades don’t move around a lot so it needs to be tight enough for this. But on the flip side, it shouldn’t be that the lawn mower blade is hard to turn by hand, using a little force.
In your user manual, the ideal tightness of the blade will be detailed and this information is given in foot-pounds. Yes, this sounds confusing and without the right equipment, you would have no way of knowing the correct foot-poundage when adjusting the blades. However, purchasing a torque wrench can be extremely useful in getting this right.
The ideal tightness of the blades will vary by brand. Some manufacturers will suggest having the blades tightened as much as possible whereas others will suggest a little slack. The reason for this is that various brands make their mowers in different ways.
For example, some mowers are designed to give the blade some room for movement even when it has been tightly secured. Furthermore, you need to consider the durability of the blades and how they will react in the event that they impact with a solid object while mowing.
Can You Over Tighten A Lawn Mower Blade?
It is important to follow the instructions in your user manual because if you don’t, there is a risk of over tightening the blade and this will ultimately lead to damage. There are several ways that this can be detrimental to the health of the blades:
- Over tightening the bolt could cause it to break and this can be a nightmare situation when it comes to removing the bolt. While tightening the bolt too much can cause breakage, there are other things that could do this including putting on too much pressure when tightening and repeated tightening.
- If the blade is too tight, this can affect how it reacts when impacting with a solid object. When it is tight, there may not be as much give and this could result in the blade breaking.
Replacing blades or the entire mower can be a time-consuming and costly affair so it is important to avoid over tightening the blades as much as possible.
What To Do If A Lawn Mower Won’t Tighten?
In contrast to our previous point, you want to make sure that the blade is tight enough. Finding that balance may take a little practice but in some cases, it can be downright frustrating. At times, you might find that the lawn mower blade is loose and won’t tighten at all.
The solution to this is not normally to do with the blade but more to do with the bolt that holds the blade in place. Over time, as this is tightened, the threads will wear away. This is completely normal and not something that can be prevented. However, upon attempting to tighten the blade, the bolt will simply turn rather than tighten.
The only thing you can do in this situation is to purchase a new bolt. However, we would advise you to source one from the manufacturer otherwise it may not fit the mower.
Is It Normal For A Lawn Mower Blade To Be Spinning Freely?
If you notice that the lawn mower blade spins freely then this is a signal that there is a problem. This is not normal and should be addressed as soon as possible. Typically, this is as a result of the blade bolt coming loose.
Whether you are using a push mower or you have a loose blade on a riding lawn mower, the fix should be the same; tightening the bolt. However, if the blade remains loose, this could signal another issue.
What Causes A Lawn Mower Blade To Keep Coming Loose?
Aside from a loose bolt, there are problems that could be coming from the blade itself. If you want to make sure that your lawn mower continues to operate safely and effectively, you may need to do a little detective work. As a general rule, the following things are usually to blame.
The Bolt Is Too Tight
We have already discussed the fact that a bolt can be overtightened and while it may seem counteractive, this could cause the blade to come loose. Despite being tight, the bolt may not be able to keep the blade in place and you will typically have to purchase a new bolt to solve the problem.
The Bolt Is Too Loose
If you have tried to loosen a lawn mower blade, you may have gone a little too far and not tightened the bolt enough. Many lawn mower owners become too cautious when tightening the bolt and this can result in it not being secure enough. One of the best ways to tighten it to exactly the right level is to use the torque wrench that we discussed earlier and by following the foot-poundage described in your user manual.
The Blade Is Deformed
Blades are shaped in a specific way to keep them balanced and at the correct angle for cutting. When this is knocked out, the overall performance can be affected. Furthermore, you may notice that, no matter how many times you tighten the blade, you end up having to do it again because it just keeps coming loose.
This is normally a result of a deformed blade which can easily happen if it hits a hard object while mowing. This is why it is important that you clear the mowing area and avoid allowing the blades to make contact with walkways and other solid garden structures.
Since mower blades are normally made from steel which is incredibly robust, it is highly unlikely that you will be able to manipulate the blade back to its original shape. In this case, you will likely have to purchase a new blade.
The Blade Is Not Balanced
As we have mentioned, your mower blades must be perfectly balanced to perform correctly. If they are not, then this can cause them to come loose. A lot of home gardeners find that the blade starts to come loose once they have sharpened it and this can be as a result of over-sharpening the blade. Although, there does have to be a significant amount of over-sharpening for it to make a difference.
You can even things out by sharpening the heavier side and if you aren’t sure how much to take off, you could try using a blade balancing tool to assist you.
The Blade Is Not Centered
If you want your mower to perform at its best, you should replace any parts with those that come from the same manufacturer as these will be designed to fit your machine perfectly. However, all too often, people go for parts from other manufacturers because they may be easier to come by or cost less. But this could come at a heavier price; loose blades!
When the blade doesn’t fit in the mower correctly, this can cause excessive vibrations and these will loosen the mower blade significantly. For this reason, we would always advise using the correct parts for your mower.
How To Tighten Or Loosen A Lawn Mower Blade
Part of your mower maintenance is going to involve making sure that the mower blades are at the optimal tightness. When you check them, you may find that they are too tight or too loose and it is important to know how to loosen lawn mower blades or tighten them when necessary.
Tightening the blade is typically very easy and involves turning the bolt with a gentle pressure to the right until you reach the desired tightness. However, when it comes to loosening your lawn mower blade, it can be more tricky, especially if it is stuck.
A too-tight blade bolt is normally a result of being over tightened or because of a build up of rust. It can be hugely frustrating but it is also relatively easy when you have the right tools.
If you have an impact driver, this can make removing even the most stubborn bolts as easy as shelling peas. However, if you do not have access to one then there are some other effective options.
- Using products like WD40 can go a long way in loosening the bolt but if there is a lot of rust build-up then you may need something more specific such as Nut Buster which will break down the rust and allow you to unscrew the bolt.
- If the bolt is just a little tight, then you can lock the blade by placing a piece of wood in the deck to keep the blade in place. This can make loosening the bolt significantly easier.
- For rounded bolts, you can use a vice grip to get a tight grasp on the bolt and then use a hammer to hit the wrench from the left, hopefully applying enough force to loosen the bolt. However, you should be careful only to strike the wrench to avoid damaging your mower.
How To Take Off A Lawn Mower Blade
When it comes to taking off a lawn mower blade, there are some specific steps you will need to follow if you want the job to be quick and easy. Furthermore, you should always consider your safety above everything else which is why we would always suggest wearing the appropriate protective gear including a thick pair of work gloves. If the bolt is stuck, this could mean that the tools slip and there is a significant potential for injury.
- Before you begin any work, be sure to shut off the engine and give it time to cool. You will also need to drain any remaining fuel from the system. You can either allow the tank to drain naturally or siphon the gas out. Furthermore, the wire should be removed from the spark plug.
- Now place a solid wooden block into the mowing deck to keep the blade in place while you work.
- It is now time to remove the blade. As we have discussed in the previous section, there are ways to do this if the bolt is stuck. Otherwise, you can simply use the correct size wrench. There will be information on what size you need in the user manual.
- Before you remove the blade, be sure to mark the bottom side so you know which way to reinstall it. You can then take it out.
- You are now free to sharpen the blade or perform other maintenance on it before installing it by following these steps in the reverse order.
While your lawn mower blades do need a certain amount of movement, they should be tightened sufficiently. Although, this will vary by manufacturer and the best way to know how tight they should be is to look in the user manual. If the blade keeps coming loose, this could be a result of several issues, however, most of these are usually easy to rectify.