Drills Help Determine Ice Thickness

Wednesday, December 31st, 2008 at 7:09 am

Several factors affect the relative safety of ice, like temperature, snow cover and currents. According to the Minnesota Department of Natural Resources (DNR), a cordless, rechargeable electric drill is a new way to check ice conditions and the actual thickness.

“If you keep an eye on the bit as it bores into the ice, you can estimate how thick the ice is when it finally breaks through,” said Tim Smalley, Minnesota DNR water safety specialist. “To double check, you can use a tape measure to be sure the ice is thick enough for your planned activity.”

With a cordless drill and a long, five-eighths inch wood auger bit, people can drill through eight inches of ice in less than 30 seconds. Most cordless drills that are at least 7.2 volts will work, but the bit needs to be a wood auger bit with a metal spiral called a “flute” around the shaft. The flutes pull the ice chips out of the hole and help keep it from getting stuck.

“It’s important to dry the bit and give it a quick spray of silicone lubricant after each use,” Smalley said. “Otherwise, the next time you open your toolkit, you’ll find your once shiny drill bit looking like a rusty nail.”

Smalley said people who don’t have access to a cordless drill may use an ice chisel or auger to check ice conditions, but they should also contact a local bait shop before venturing out on the ice.

According to the DNR, here are recommended minimum thicknesses for new clear ice:

* 4 inches for ice fishing and small group activities
* 5 inches for snowmobiles and ATVs
* 8- to 10-inches for small to medium cars and pickups.

The above thicknesses are for new clear ice. Old white ice – sometimes called “snow ice” – is only about one-half as strong, so the above numbers should be doubled. Vehicles weighing one ton should be parked at least 50 feet apart and moved every two hours to prevent sinking.

Ice safety pamphlets, posters and videos, are available online or by contacting the DNR Information Center at 651-296-6157 or toll free 1-888-646-6367.

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