Silvey SDM-4

The SDM-4 is an industry standard and one of the best square-chisel chain grinders on the market. For an individual timber faller, someone sharpening chains for a crew, or for production grinding in a saw shop, the Silvey SDM-4 is a good machine.  This is the grinder that set the standard for accuracy and dependability that Silvey customers now expect.


SDM-4 Chisel Grinder
Silvey SDM-4
Square Chisel Grinder

The SDM-4 Features:

  • Reversible motor that keeps chrome edges clean and the grinding burr on the cutter tooth
  • Adjustable diamond tipped wheel dressers
  • Twin chain holding and feed mechanisms
  • Patented slide design that keeps tooth angles constant throughout the life of the cutter tooth
  • Adjustable motor mount slide to compensate for wheel wear
  • Finger lock hold down pin for improved indexing
  • Sturdy flat bottom stand
  • Flex-mounted standard socket work light for easy angle viewing
  • Threaded feed crank for smooth tooth advancement
  • Adjustable tolerance gibs and neoprene bellow seals on the slide mechanisms for easy maintenance and long wear

Silvey SDM-4 History

The Silvey SDM-4 is the "Silvey" most people refer to when they speak of a Silvey grinder. This grinder has been around for over thirty years -- almost as long as square-chisel saw chain. Today, a few of these machines are older than their owners!  Not many products endure the test of time like the Silvey SDM-4. Its record of durability and reliability is unmatched.

The  SDM-4 was an early contender in the square-chisel grinder market. Not long after they were introduced, several other manufacturers produced competitive square-chisel grinders. By protecting most of the best ideas with patents, Silvey kept their competitors at bay. As a result, the SDM-4 endured, when many challengers faded away.

Overview

The SDM-4 is the standard by which most chisel grinders are judged. Few products earn such status. It is a true "classic." But today's SDM-4 is not a modern antique. Ongoing upgrades have kept this machine up-to-date. Today's SDM-4s have a new high-torque motor, a new flex mounted work light, a new base angle better suited for 3/8' chain, new indexing pawls, and more. 

The chain indexing mechanisms are one of the features that earned Silvey favor with early users. The chain stops are positive and the locking mechanisms stop each tooth accurately and hold it in position. This makes it is easy for an operator to sharpen each cutter tooth precisely.

These indexing mechanisms are mounted on sliding blocks, which utilize tolerance adjusting gibs on the moving parts. Neoprene seals isolate the sliding mechanism from grit.  These slides typically give years of service with minimal maintenance. Occasional cleaning and lubrication, is all a user has to do. Since the gibs are adjustable, when the slides finally need service, repair and setup is inexpensive. 

The sliding blocks are what move a cutter tooth into the grinding wheel. They advance with the turn of a crank. They move straight into the wheel keeping the angles ground into the cutters the same no matter what the length of the cutter tooth is. On both the Swing Arm and Razur Sharp II grinders, the chain is mounted on an arc-shaped block. These cause the orientation of the cutter tooth to change as the tooth is ground shorter. 

Another superior feed feature of the SDM-4 is the way the cutter tooth meets the grinding wheel. The corner of the grinding wheel only cuts the corner of the tooth. Compared to a machine like the Swing Arm or the Razur Sharp II, this helps preserve the corner of the grinding wheel. This is a big plus for the SDM-4, because having a crisp corner is essential for peak performance from square-chisel saw chain. This also helps grinding wheels last longer because frequent dressing is not as necessary with an SDM-4 as it is on either the Swing Arm or Razur Sharp II. 

The wheel dressing mechanisms on the SDM-4 are also superior to the Swing Arm and Razur Sharp II. These dressers are very accurate. This is important because the shape and finish of the grinding wheel is a mirror image of the shape and finish of a sharpened cutter tooth.

An Interesting Observation

The SDM-4 is a good machine, but lacks many features found on the Pro Sharp. In spite of this, new SDM-4s continue to sell. Even Silvey is a little surprised by this.  We believe one reason the SDM-4 remains  popular is because of familiarity. Many pro saw users have owned one or been around one at some point in their career. Some have worked at camps in Alaska and used the "company's" SDM-4 grinder. After moving to a different job, they now need their own machine. Learning how a new machine works takes time. No one likes learning curves, especially when it affects the performance of a pro saw. Familiarity has value.  

A related thought. If you are learning to grind square-chisel saw chain, find a mentor. Locate an experienced (and willing) grinder operator who makes really good chains and find out what grinder they sharpen with. If they are using an SDM-4, give it serious consideration. Having someone to help you that has experience with a  machine exactly like yours invaluable. The SDM-4 has been around for decades. It is often the machine an "old hand" will have. 

Our Advice

The SDM-4 is a good choice for both experienced grinder operators who want to move up or beginners looking for their first square-chisel grinder. It's a good choice for production grinding in a saw shop or for a big crew, because it easily takes both .3/8" and .404" pitch chain with minimal setup. It's a durable and time-tested  machine. 

Click here for an illustrated parts list of the SDM-4 grinder.