How To Convert An Edger Into A Low-Cost Stump Grinder

If you have a stump that needs chopping down to ground level, then a stump grinder is an excellent tool for the job. However, stump grinders are expensive to buy or rent. The good news is that you can make your own stump grinder using an ordinary walk-behind edger and saw blades. Below is what you need and how to go about making your own:

Tools and materials needed

  • Walk-behind gasoline powered edger
  • Circular saw blades (quantity of 2)
  • Washers
  • Adjustable wrenches
  • Clamping pliers
  • Penetrating oil spray
  • Clean cloth

The procedure

1. Don't injure yourself or others – removing the edger blade and replacing it with circular saw blades is safe as long you take the proper precautions. However, it's important to understand that you should undertake this project only if you are confident with your ability to make the necessary alterations. If you have any doubts, contact a tree removal or stump grinding service for assistance.

2. Purchase the circular saw blades – the do-it-yourself stump grinder uses two circular saw blades, and it is important for you to attach the correct blades for the grinder to work properly and to prevent damaging your machine. Below are some specifications that should be kept in mind when choosing blades:

  • Blade diameter – the blade is limited to the size that will fit beneath the edger's guard, but keep in mind that you can also choose a smaller size, as well. In most circumstances, a 7-inch blade should be suitable for the task of grinding stumps.
  • Arbor size – this references the diameter of the shaft used on the edger; many blades come in variable arbor sizes to permit them to fit on different sized shafts. Be sure to choose a blade with an arbor size that closely matches the size of the edger's shaft, or the lack of a close fit may cause excessive vibration during use.
  • Blade material – ordinary steel is sufficient for cutting softwood stumps, such as pine. However, if you are grinding hardwood stumps, then choose high-speed or carbide-tipped steel blades to prevent premature wear.
  • Number of teeth – for grinding stumps, a coarse cut is desirable, and a blade with between 17 and 24 teeth will provide excellent action.
  • Gullets – blade gullets are the channels cut into blades between each tooth and are designed to carry away material from the cutting surface. A deeper gullet is preferable since it can carry more material and help prevent blade jamming.

3. Remove the edger blade – edger blades are usually held in place with a nut and compression washer. To remove the blade, first attach a pair of clamping pliers to the blade shaft and firmly grip it. Next, apply clockwise force to the blade nut with an adjustable wrench in order to remove it. Keep in mind your edger likely uses reverse threaded shafts, so be sure you are applying force to the nut in the correct direction.

If the nut still refuses to budge, apply penetrating oil to the nut and threads in order to loosen the connection. Allow the oil to soak for about ten minutes, then try again. Once the nut comes free, remove it, the compression washer and any other washers or spacers remaining on the shaft.

4. Install the circular saw blades – after removing the blade, wipe own the shaft with a dry cloth to remove any debris or excess oil. Insert the first circular saw blade on the shaft and push it to the back. Next, slide 3 washers onto the shaft until they abut the blade you just placed. Add the second circular saw blade, compression washer and nut to finish the assembly. Tighten the nut completely so it applies firm pressure to the blades and washers.

5. Test the stump grinder - start up the edger as normal, and slowly lower the cutting blades onto the top of the stump. Do not allow the blades to dig in to the wood too deeply, and avoid making sudden movements; slow, even strokes of the blade will work best. Once you are finished, wipe down the blades to remove chips and lightly spray them with a penetrating oil to prevent rust. If you don't feel comfortable making your own stump gringer, see for professional advice or help.