Technologic Design Engineering

Drill Press for dummies

Technologic Design Engineering; Drill press for dummies

Drill press overview

"A drill press is preferable to a hand drill when the location and orientation of the hole must be controlled accurately."

A drill press has a number of advantages over a hand-held drill:

Less effort is required to apply the drill to the workpiece. The movement of the chuck and spindle is by a lever working on a rack and pinion, which gives the operator considerable mechanical advantage
The table allows a vise or clamp to be used to position and restrain the work, making the operation much more secure
The angle of the spindle is fixed relative to the table, allowing holes to be drilled accurately and consistently
Drill presses are almost always equipped with more powerful motors compared to hand-held drills. This enables larger drill bits to be used and also speeds up drilling with smaller bits.

(Wikipedia)

Topic's about a drill press that will be discussed on this blog

The Body + induction motor
The V-belt transmission + pulley
The spindle & quill
The chuck
The work table, column & base

The Body + Engine

A Drill press is usually powered by an electric motor, an induction motor. In this case the motor produces 350W and spins at 1300rpm.

The body of the dill press is made through steel casting, in 2 parts that are welded together. The top, where the belt and pulleys are, is made out of sheet metal. All the metal parts of the drill are connected to the body and the body is connected to the ground earthing system. This is necessary for the safety of the product (safety class 1).

The top case covers the pulleys and belt. The case has to be closed when using the machine for safety reasons. But it can easily be opened by unscrewing a screw which holds the 2 half together.

This is a close up of the safety switch installed on the top of the machine. The switch prevents the machine from functioning when the top case is open. On the picture you can also see the the hinges are welded to the case. (Probably to lower cost and reduce production time)

The engine is connected to the body of the press drill in a special way. It's hung an a hinge that is situated on one side of the body. It's designed that way so the V-belt van be tightened and discharched in (dis)assembly or use.

The regulate the distance between the 2 centers of the pulley (is necessary when the belt becomes deformed over time), the engine can be rotated a little bit. By tightening the bolt (in red) the distance between the engine (circle) and the body (square) will enlarge and the tension the the belt will increase.

V-belt + Transmission

V-belt

The v-belt is a transmission belt developed to solve alignment and slippage/traction problems.

The v-belt tracks in a pulley with mating grooves . And as the loading increases the traction increases (because of the shape), improving torque transmission.

V-belt
Type: K-660
Hight: 6,4mm
Width: 8mm
Length: 658mm
Material: enforced rubber

Pulley's
Material: Steel
spec's: in the slideshare presentation

Transmission

Technologic Design Engineering; Transmission on a drill press

View more presentations from xhuyghe.

Excell spreadsheet;

The Spindle

The spindle is the axis which is connected to the chuck and is driven through the pulley. The pulley is connected to the spindle through an axis with slots for the torque transmission.

The quill is assembled over the spindle, connected through bearings.

Bearings

Bearings: 6203Z 17x40x12 (Single Shielded)

Ball Bearings; because they can handle radial and axial force. Most the bearings need to handle radial forces caused by the movement of the chuck.

Material spindle and quill: Steel

The spindle, and therefor the drill, can move up and down if the user moves the operating leverages. The leverage is connected to an rack and pinion and a flat torsion spring. the rack and pinion converts a rotation into a translation. The flat torsion spring makes sure when the leverages are not in the hands of the user, that the drill returns to it's original position (to avoid accidents).

Calculations to determine the gear inside the body of the machine.

Three Jaw Self Centering Chuck

The chuck is used to hold the drill fixated in place.

The chuck is held in place by a friction fit in the spindle. The interference fit only has to overcome gravity forces on the chuck and when the drill is used to drill in a material it pushes itself in the spindle increasing the friction fit.

The chuck is used to hold the drill fixated in place.

The chuck has 3 jaws wich can open and close, the opening, at it's maximum, is big enough to hold a drill or bit with a 13mm diameter.

It works kinda like a rack and pinion because the chuck translates a rotation into an translation. Using a speciaal tool you can let 2 parts of the chuck move (turn in opposite direction). This wil rotate a disc inside the chuck which is threaded. The rotation of the disk will move the jaws (which are also threaded) in the chuck.

The material of the jaws has to be very hard, harder than the material of the drill, especially with a "cheap" drill for home use. Because the cost of a new drill is way less than the cost of a new pair of jaws or a new chuck. That is why they make the jaws out of steel which they case harden.

Wikipedia about case hardening;

http://en.wikipedia.org/wiki/Case_hardening