The Lagler Hummel is one of the most trusted belt sanders in the hardwood flooring industry, but like any hardworking machine, it needs regular maintenance to perform its best. One important wear part to keep an eye on is the top roller.
The top roller plays a major role in how your sanding belt tracks on the machine. If it becomes worn, uneven, dirty, or out of adjustment, you may notice the paper tracking too far in or out, rubbing against the cover, or causing unnecessary wear on the machine. In some cases, a worn top roller can also affect sanding performance and dust control.
Below, we’ll walk through the general process of replacing the top roller on your Lagler Hummel, along with a few maintenance tips to keep in mind while you have the machine opened up.
When Should You Replace the Top Roller?
One of the clearest signs that your top roller may need to be replaced is uneven wear. If one side of the roller shows more wear than the other, that can be an indicator that the roller is no longer tracking properly.
You may also need to remove the top roller unit to clean the mechanism, inspect the linkage, or check related parts such as the guide rollers, bearings, cams, and compression spring. Since you already have the unit out of the machine, it makes sense to inspect the surrounding components at the same time.
Tools You’ll Need
If you purchased a new Lagler Hummel, your machine should have come with a repair kit that includes the proper wrench sizes for many common repairs.
For this top roller replacement, the key tools are:
* 10 mm wrench
* 5 mm Allen wrench
The 10 mm wrench is used with the mounting hardware, while the 5 mm Allen wrench helps access the screws through the opening near the belt cover. Removing the paper from the machine before beginning will make the process easier and give you more room to work.
Step 1: Remove the Side Cover and Access the Top Roller Unit
Start by removing the side cover so you can access the top roller mechanism. Open the belt cover as well, since there is an access point that allows you to insert the Allen wrench.
Before removing the unit, compress the top roller and remove the lever. Compressing the roller helps create enough clearance to remove the unit more easily. If paper is still on the machine, or if the roller is not compressed, the unit can be much harder to remove.
Step 2: Remove and Inspect the Top Roller
Once the unit is out, inspect the top roller closely. Look for heavy wear, uneven wear from one side to the other, buildup, or damage.
This is also a good time to clean the top roller assembly and inspect the linkage. Make sure the linkage is not bent or spread too far apart. Check that the machine surfaces where the unit mounts are clean and flat so the replacement roller can be reinstalled properly.
Step 3: Check the Compression Spring and Guide Rollers
The compression spring helps level the top roller unit and plays an important role in belt tracking. If the spring is compressed or worn, it may affect how the paper rides on the machine.
You should also inspect the guide rollers and bearings. Frozen bearings are a common issue, often caused by wood dust, debris, adhesive, carpet pad residue, or other jobsite contaminants. If a bearing is frozen, the guide roller may not function properly and should be replaced.
Even if the main repair is the top roller, checking these parts while the assembly is already removed can help prevent future problems.
Step 4: Install the New Top Roller
When installing the new top roller, make sure the flat side of the shaft faces up. The roller can be installed from either side because both sides have a milled flat, but the flat side should be oriented upward.
There is no top or bottom to the compression spring, so it can be installed either way. Before reinstalling the unit, check that the side supports are clean and clear. If the supports are clogged or packed with debris, clean or file them as needed so the top roller can move up and down properly on the spring.
Step 5: Set the Initial Gap Before Reinstalling
Before putting the unit back into the machine, try to make the air gap or light gap as even as possible from side to side. This helps prevent the paper from immediately tracking too far in or out when the machine is started.
At this stage, leave the lock nut loose because final tracking adjustments will be made after the unit is mounted back in the machine.
Step 6: Adjust Belt Tracking
After reinstalling the top roller unit, reconnect the machine and test the belt tracking. If the paper tracks outward, you’ll need to adjust the compression spring.
To bring the paper back in, loosen the bolt counterclockwise. This allows the spring to expand, lifting the outside edge of the top roller and helping the paper track inward.
The goal is for the paper to sit properly on the outside edge of the drum. The sanding belt is slightly wider than the drum, so you want the paper positioned cleanly without tracking too far inward or rubbing against the cover.
Once the tracking is set, tighten the lock nut to hold the adjustment in place.
Don’t Forget the Cover
Some contractors remove the cover to get closer to the wall, but keeping the cover on provides the best dust control. If you see discoloration or rubbing on the cover, that may be a sign of a tracking issue. In that case, check the top roller unit and make sure the belt is adjusted properly.
Need Parts for Your Lagler Hummel?
All of the parts for the Lagler Hummel are available at City Floor Supply. You can look up your machine on cityfloorsupply.com, use the dropdown menu, and find the PDF diagram to identify the exact part numbers you need.
Have questions about replacing your top roller or troubleshooting your Hummel? Give City Floor Supply a call at 800-737-1786, or shop hardwood floor parts online.
