It is important to know how to troubleshoot your hedge trimmer when they get temperamental to save you money and time on unnecessary repairs.
To speed up the process and help you get back to trimming, this article explains some common reasons why hedge trimmers blades move but don’t cut.
7 Reasons Why Your Hedge Trimmer Blades Move But Don’t Cut:
1 – The blades have grown blunt and needs sharpening
2 – The cam is obstructed, and you need to remove the jam
3 – The teeth on the blades are bent and need straightening
4 – The blades have developed rust and need restoring
5 – There’s plant sap on the blade and it needs cleaning
6 – Debris has misaligned the blades and need adjusting
7 – The blades are too worn and need replacing
From my experience, the solution to the problem is somewhere in this list. If you’ve no idea where to begin troubleshooting, start at the top and work your way through until you find the issue that’s plaguing your trimmer.
Now let’s dig deeper into each of these problems and learn how to fix them.
Why My Hedge Trimmer Is Not Cutting
This troubleshooting guide deals, specifically, with hedge trimmer blades that are moving and rotating freely but not trimming as well as they should.
If the blades aren’t moving at all, there may be a problem with the trimmer’s engine and, though fixable, the repairs are a little more complicated.
Before you begin troubleshooting, check to see if there’s any movement in the blades when the tool is switched on.
Blades Need Sharpening
All hedge trimmer blades will grow dull eventually. It doesn’t matter how expensive or sophisticated your tool is, it happens to all of them.
The more frequently you use the trimmer, the faster its blades will dull although high-quality blades will stay sharp for at least three months.
This is the easiest problem to fix because it isn’t really a problem. There’s no repair to be made. It’s standard tool maintenance and should be done after every fifty hours (approximately) of use.
The classic indicator of a dull blade is branches with frayed, ragged edges. Sharp blades cut cleanly every time. It takes longer to trim with a dull blade and more force is needed to cut through thick branches.
If you notice branches getting stuck between the teeth but not getting cut, it’s probably an alignment issue rather than a dull blade.
You will need the following items to begin resharpening your hedge trimmer’s blades:
- Flat file
- Cloth for cleaning
- Resin solvent
- Safety gloves
- Safety goggles
Step 1 – Use a soft cloth to wipe away any grime and plant sap on the blades.
Step 2 – Use a flat file to sharpen each blade taking care to always move towards the cutting edge. The file must move in one direction and never back and forth like a saw.
After every forward stroke, lift the file off and bring it back to your starting position before stroking forward again. You will dull the blade even further if you see-saw back and forth.
Apply the same number of strokes to each cutting edge. Never file off more than 5mm at one time or the blades may become structurally compromised. Remember to only sharpen the cutting edge of each tooth.
Step 3 – Use the whetstone to smooth any burrs on the underside of the blades leftover from filing. Draw the whetstone along each blade and towards the tip in a controlled motion.
Apply small amounts of water to moisten the blades and remove any residues as you work.
Step 4 – Wipe the blades with a clean cloth to remove any grinding dust and other residues. Next, spray the blades liberally with a resin solvent to replace the anti-corrosion coating that’s been filed away.
Cam Is Jammed
Gearbox and cam maintenance is another key part of keeping your hedge trimmer happy and healthy. When the lubricant around your trimmer’s components wears away, which is normal and to be expected, the blades will start to move sluggishly.
They might stick, momentarily pause in a rotation, while the tool is in use. If the tool is in desperate need of lubrication, it might judder and vibrate.
This can also be caused by an obstruction in or around the cam. When you open up the gearbox to add lubricant, take a look inside and check for debris.
You will need the following items to begin servicing your trimmer’s cam:
- White lithium grease
- Wrench (x2)
- Allen wrench
- Safety gloves
- Safety goggles
Step 1 – Use a wrench to remove all the blade nuts, bolts and the locknut on top of the blade. Depending on the model of your hedge trimmer, you might need to use two wrenches.
Step 2 – Remove the gearcase cover bolts and gearcase cover. Take care because you’ll be working close to the trimmer’s gasket.
Step 3 – Apply 35 to 50 grams of white lithium grease to the inside of the gear case. This is a messy job so you might want to swap your safety gloves for rubber gloves if you have them.
Apply until the gear case is well coated (half to three-quarters full of grease).
Step 4 – To help with realignment when you put the blades back, clean a section of the drive gear so that you can place a marker on it.
The easiest way to do this is with white paint or a white marker pen. Use whatever you have as long as you can clearly distinguish which tooth you’ve marked.
Step 5 – Lubricate and replace the upper blade gear taking care to line up its timing indicator with the mark you’ve made on the drive gear.
Step 6 – Lubricate both sides of the upper blade end. Then, replace the blade on the cam for the upper gear.
Step 7 – Lubricate both sides of the washer and replace it on the shaft. Next, lubricate both sides of the lower blade end and replace the lower blade.
Grease both sides of the lower blade gear, then replace the gear on the shaft. Line up the timing marks in the same way you did before.
Step 8 – Put the gearcase cover back on, again taking extra care when working close to the trimmer’s gasket.
It’s rare for the teeth on a high-quality hedge trimmer to bend without there being an obvious incident. Common causes include dropping the tool while it’s in use or making contact with something unexpected like a metal fence.
The teeth on a hedge trimmer are unlikely to bend due to normal wear and tear unless the blades are poorly constructed.
The best way to avoid this problem is to take care when gardening. Just one bent tooth can significantly impair a tool’s cutting ability and blade alignment, and it’s not an easy problem to repair.
Purchase a harness or take regular breaks if you struggle to hold a heavy trimmer for long periods.
If you need to trim dense bushes in an outdoor space you don’t know well, use a long pole to check for hidden obstructions first. Old metal fence posts, hidden and forgotten in thick hedgerows, are the biggest culprit.
You can try to bend a tooth back into shape, but the danger is you’ll only make the problem worse. One method is to remove the offending blade and realign the warped tooth with pliers while it’s clamped in a vice.
However, this is a very risky business. Even if you heat the metal first to soften it, there’s still a good chance the tooth or the blade will crack.
If the bend is very slight, it might be worth removing the blade and attempting to tap it back into place with a hammer. Generally, though, this problem requires a professional service or a replacement blade.
I’m happy to say this isn’t the case for a rusty hedge trimmer blade. Provided the rust isn’t severe enough to have compromised your tool’s structural integrity, it should be easy to repair.
It’s a problem that’s relatively easy to spot too. If your hedge trimmer’s blades are rotating slower than usual or sticking at intervals, switch the tool off and inspect the surface of the blades.
While wearing safety gloves, you might want to manually move the blades through a rotation so that you can see all of the surfaces and/or identify where the ‘sticky’ patch is.
Rust is fairly easy to remove and even easier to avoid in the first place. To prevent corrosion, always store your hedge trimmer in a dry area.
If the blades get wet for any reason, maybe it starts raining while you’re gardening, they must be wiped dry before the tool is put away.
Ideally, you should be wiping your trimmer blades clean with mild soap and water after every use and drying them thoroughly. Some natural materials like tree sap are mildly corrosive.
Cleaning the blades prevents a build-up of acidic substances that will slowly corrode the metal.
You will need the following items to remove rust from a trimmer blade:
- Steel wool pad
- Mineral oil
- Soft cloth
- Lemon juice
- Table salt
- Paper towels
- Safety gloves
Step 1 – Remove lightly ingrained rust by rubbing the hedge trimmer blades with a steel wool pad in a back-and-forth motion. This should be enough to dislodge small amounts of rust.
Step 2 – For thicker, deeply ingrained patches, apply mineral oil to the blade to soften the corroded areas. Wait ten to twenty minutes. Then, rub the blade with your steel wool pad.
Step 3 – If the rust still won’t budge, make an abrasive paste using two parts table salt and one part lemon juice. Apply to a paper towel and rub on the blade. Allow it to rest for at least two hours.
Then, scrub the trimmer blade with a steel wool pad. This should dislodge the corroded materials. Don’t forget to wipe away all traces of the paste and dry the blade when finished.
Sap build-up is another thing you can’t avoid if you’re using your hedge trimmer frequently. If you’re cutting through branches, you’re going to get plant goop on your blades.
There’s no way to prevent it but you can remove it and stop it from corroding the metal.
Plant sap is tacky and too much of it can gum up a trimmer blade and cause it to stick during use. Wiping the blades clean after every single use, regardless of whether you can see rust spots or sap patches, is a great way to prevent this.
It’s worth noting that, while plant sap poses no risk to your health, it sometimes contains bacteria that can cause harm to plants of different species. Clean the blades after every use to prevent cross-contamination.
You will need the following items to remove sap from a trimmer blade:
- Old rags
- Soft cloth/sponge
- Stiff bristled brush
- Machine oil
- Safety gloves
Step 1 – Use a stiff-bristled brush to rub the trimmer blades and dislodge stubborn dirt and debris.
Step 2 – Dip a soft cloth or sponge in a mild soap and water solution. Then, use it to clean away the debris.
Step 3 – Wipe the trimmer blades with a rag dipped in turpentine. This will loosen sticky sap patches and other plant residues.
Step 4 – Dry the blades thoroughly with a clean cloth or rag to prevent corrosion.
Step 5 – Apply a light coating of machine oil to the blades to keep them well lubricated and protected from rust.
Trimmer Blades Need Adjustment
Hedge trimmers contain two sets of independent blades stacked neatly on top of one another, an upper and a lower.
Over time, the two sets can become misaligned due to the forces involved in cutting and slicing through thick branches. The good news is, it’s another easy problem to solve.
Your hedge trimmer’s blades may be misaligned if twigs frequently get caught up in the module or the blades make rough, uneven cuts.
Provided the upper and lower blades haven’t become so separated they’re on the verge of coming apart, a problem that requires a professional repair, you should be able to gently pry them back together.
Make sure the blades are aligned before you start any extensive sharpening of the teeth because properly aligned blades will make the process much easier.
You will need the following items to realign your trimmer blades:
- Thread locker
- Safety gloves
Step 1 – Start by using your hands to press the upper and lower sets of blades together. Don’t forget to wear safety gloves while you do this. By applying small amounts of pressure, you should be able to complete the realignment mostly by hand.
Step 2 – To make sure the blades are as perfectly aligned as possible, use the handle of an old screwdriver as a pry bar. Place the handle between the blades to protect the metal while you apply more pressure in the direction of alignment.
Step 3 – Once the hedge trimmer blades are aligned, apply a thread locker to the adjustment nuts and fasten tightly.
Trimmer Blades Need Replacing
There are various reasons you might need to remove a trimmer blade and replace it with a brand new one:
- Heavily corroded (rust has eaten through the metal)
- Teeth are too bent to reshape
- Old blade with teeth that blunt too quickly
- Not powerful enough to cut thick branches
- Blades have become severely misaligned and loose
Older hedge trimmers can be tricky to handle but newer models have features that make blade removal and replacement very simple.
These days, it’s common to see hedge trimmers with quick-release buttons though not all tools will have one.
Before you start, consult the manufacturer’s guide for information on the most suitable replacement blade. You can always jot down the model and brand number and take it to the hardware store with you.
If your model does have a quick-release button, hold it down with one hand and wiggle the blade out of the tool with the other. Remember to always wear thick safety gloves when handling trimmer blades.
There should be information in the manufacturer’s manual about how to safely remove and replace the blade on your specific model so read it carefully.
It will also tell you if there’s any type of blade replacement service included with ownership of the hedge trimmer.
Some brands have a warranty that allows you to take the trimmer into a store and have an expert replace the blade for free.
Helpful Tips to Know About Fixing Trimmer Blades That Move But Don’t Cut
If your hedge trimmer blades move but don’t cut, here are some things to do to diagnose the problem:
- Inspect the blade for rust patches
- Check whether the blades are clean
- Check whether the blades are aligned
- Tap SLIGHT bends in the teeth with a hammer
Like a lot of gardening tools, hedge trimmers are designed to be tinkered with and repaired at home. So, you don’t need to panic and buy a new tool every time the blade vibrates or gets a little sticky.
While there are some scenarios in which a replacement trimmer is the best option, it’s worth troubleshooting and trying all of the repairs listed here first.