Product Details

The definition of a deep hole is one where the depth is more than 10 times the diameter. Thus a ¼” diameter hole becomes “deep” when it exceeds 2 ½” in depth. Deep holes are unavoidable in many engineered metal parts but producing them is a machining challenge. Impro specializes in deep hole drilling to accurately and consistently make these features.

Deep hole drilling is sometimes referred to as “gun drilling.” That’s because one of the first engineered components needing a long, deep, and straight hole was the gun barrel. Today many machined parts rely on deep holes to function. For example:

Crankshafts and camshafts, where drilled holes deliver lubrication
Fuel injectors
Perforating dies (used in the food industry and elsewhere)
Cooling channels for gas or liquid
Surgical instruments
Hydraulic valve bodies and similar parts

Four Main Challenges of Deep Hole Drilling

Tool runout
Chip evacuation

Runout refers to the tendency of the drill tip to orbit around the axis of rotation. The amount of runout grows as the drill gets longer and will increase the diameter of the hole.

“Walking” occurs at the point the drill tip contacts the workpiece. If the surface isn’t completely perpendicular, a sideways force will push the drill in that direction (and a long, thin drill can bend slightly.) This results in the hole being misplaced and drilled at an angle. It may also break the drill. The same can happen if the surface has an as-cast or rough milled finish.

Material cut away at the bottom of the hole has to be removed to make space for the drill to advance. In deep holes, these chips tend to wrap around the drill flutes and build up to where they rub against the sides of the hole. This raises the temperature and will eventually cause the drill to seize and/or break.

In most precision machining operations cutting fluid keeps the cutting interface cool. In a deep hole, it’s very difficult to get fluid down to the bottom. As a result, the drill tip temperature rises to where it may damage the workpiece or even weld to it.

If your product requires deep holes and you want to find an expert in this field, don't hesitate to contact us to discuss your machining needs.

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