Give Your Chain A ‘Hand’

While drive roller chain may be a mature form of mechanical-power transmission, it’s still well-suited to many applications.

Among other things, roller chain is economical; resistant to shock loads; easy to install; relatively efficient; available in a variety of shapes, forms, and materials; and capable of operating successfully in hostile environments. It also can be used for conveyance.

A drive-chain system consists of the chain, sprockets (at least one pair), guards, and some form of lubrication. According to Richard Knotek of Motion Industries, Birmingham, AL (motionindustries.com), it’s imperative that these systems be installed and maintained properly to deliver safe operation and maximum service life. Using the five fingers of the human hand as a mnemonic, he offered the following reminders.

Make sure your drive roller chains are neither too loose nor too tight. Information in this chart courtesy of Diamond Chain.

THUMB: TENSION

Drive roller chain has a recommended total mid-span movement of 0.5 in./10 in. of shaft-center-line distance, for horizontal applications, and half of that for vertical orientation (see chart). If a chain is too loose, it will jump. If it’s too tight, bearing loads increase dramatically, leading to failure

FOREFINGER: SAFETY

First and foremost, the system must be electrically locked-out, tagged-out, verified, and mechanically load-leveled prior to performing work on it. Avoid pinch points. Use proper guards.

MIDDLE FINGER: CHAIN AND SPROCKET CONDITION

“Stretch” is actually caused by the wearing away of chain components. Maximum recommended stretch should not exceed 3% of original installed length. Half links are weak links. Worn chain will jump, whip about, and accelerate sprocket wear. Sprocket teeth should not look like shark fins or be worn to the nub. These conditions contribute to system vibration, leading to rapid failure. Clean chain and sprockets last longer.

RING FINGER: LUBRICATION

Since drive roller chain is essentially a series of interconnected bearings revolving around an axis, it requires lubrication. (Note: polymer types do not.) Featuring additives for sliding friction, roller-chain lubricants are formulated to prevent centrifugal forces from flinging the lubricant off the chain. There are three major categories.

• Manual or drip: Oil is applied periodically with a brush, spout, or dripped on chain.

• Bath: Oil covers the lowest portion of a chain enclosed in a leak-proof guard.

• Circulating stream: In this type of closed system (similar to the bath system above), oil is sprayed on to chain, circulated, and filtered.

LITTLE FINGER: ALIGNMENT

Sprocket shafts should be parallel. The offset of sprocket faces should be < 0.0625 in./ft. of shaft-center-line distance. Angularity should be < 0.5 deg. Axial run-out (wobble) of sprockets should be < 0.001 in./in. of sprocket diameter (see chart). EP

Richard R. Knotek is a technical-training specialist with the Motion Institute, a division of Motion Industries (MotionIndustries.com). Learn more about extending roller-chain life through the company’s “MiHow2” videos at this link.