1012 Sensitive Drilling Attachment ( 1lb)

The sensitive drilling attachment gives you rapid feed and good control when using small drills. The brass spring support tube goes up inside the spindle and the body screws onto the external spindle nose thread. It is very easy to install and use.

About the sensitive drilling attachment...
Small drills are easily broken when using a drill press or mill because the leverage provided by quilland handwheel feeds makes it difficult to "feel" how the cut is progressing. It is easy to apply too much force. The sensitive drilling attachment allows you to hand feed the chuck by gripping a knurled ring while pulling it down against a light return spring. The ring is on a ball bearing, so it doesn't spin while the chuck turns within it. When done, the spring returns the chuck to the retracted position. Sherline uses a Jacobs chuck that can hold drills from 5/32" down to #80, although this attachment is recommended mainly for holes 1/16" or smaller where breakage is a common problem. The attachment installs quickly and easily. The brass spring tube is inserted into the spindle bore, and the body is threaded onto the 3/4-16 external spindle thread. It's ready to use in just a few seconds. To facilitate silky smooth movement, a brass key with flat sides is used in the slotted shaft rather than a simple pin. The shaft and body components are all turned from steel, while the knurled ring is aluminum with a tough red anodized finish..

Purpose of the sensitive drilling attachment

Drilling holes with small diameter drills requires a certain "touch" that is hard to achieve when using a standard drill press. Small drills are easily broken if pushed too hard, and being able to feel the cut offers better feedback, allowing you more control over the feed rate. Remember, however, that larger size drills require significant force, and that for holes larger than 1/16" or so you might be better off with the leverage of the handwheel feed when drilling hard materials.

Note that several design features enhance the operation of this attachment. For example, rather than a simple pin that will wear and eventually cause jerky movement, a brass key with flat sides was used in the shaft slot. The brass tube is simply a spacer to cover the shaft and to provide a support for the end of the spring.

Installation

The drill attachment body simply screws onto the external thread of the spindle. To insert the brass tube into the spindle, you will have to either remove the headstock or raise it almost to the top of its travel. To assure the drill attachment runs true, before installing it, check the spindle threads to make sure they are not damaged and are free of chips. Also check to see that the spindle shoulder at the end of the threads is not dented and that there are no chips present that could keep the drill body from seating squarely.

Changing return spring tension

The spring can be changed to provide more or less return pull. You can purchase other extension springs and substitute them for the one provided or you can shorten the one installed by cutting off some of its length and forming a new loop at the end if you want a more positive return. Any 2.5" overall length extension spring with an overall diameter of .25" or less can be used. To remove the spring, pry up the cap and pull it away from the body. Hold the spring and remove the hook on the cap from the end of the spring. Release the spring and slide off the brass tube. With a small drift, remove the pin that goes through the shaft. Install a new spring in the reverse order.

Lubrication

Smooth movement and proper "feel" require that the shaft remain properly lubricated. Any good lubricating oil will work. Clean the shaft when done with your job and apply fresh oil before putting it away.

Use of the drilling attachment

Spring tension holds the drill chuck up against the spindle. To drill a hole, set the speed control to zero, turn on the motor and then adjust the speed control. Grasp the red, knurled ring and pull the drill down. A bearing allows the drill to turn inside the ring while the ring does not turn.

Remember that the rules for clearing your drill of chips are even more important when drilling very small holes. Failure to properly clear the chips from the hole and/or lack of cutting fluid can result in broken drill bits. The first pass is drilled two drill diameters deep. Subsequent passes are drilled one diameter deep and then the drill is withdrawn to clear the chips

Example: To drill a 1/16" diameter hole 1/2" deep:

Pass No. Pass depth Total depth

1 2 times drill diameter or 1/8" 1/8"

2 1 times diameter or 1/16" 3/16"

3 1 times diameter or 1/16" 1/4"

4 Continue to desired depth… etc.

This means that for a .015" drill, the first pass will be only .030" deep with each subsequent pass only .015" deep.

Coolant/Lubrication

Other than brass which is cut dry, most drilling operations are best accomplished with the aid of lubrication. Apply a bit of cutting fluid to the drill before beginning the cut and replenish as necessary. Stainless steel is in a league of its own and requires slow spindle speed, constant feed pressure and sharp tools as well.

Other drilling tips

Accurate hole location requires the use a center drill to start the hole in the proper location. They do not have a tendency to "walk" on the surface when entering like standard drills. They are particularly helpful when drilling into a surface that is round or at an angle to the drill.

Use only sharp, high quality, high speed steel drills. Sharpen or replace them as needed. Dull drills can drill up to 10% oversize.

Tighten the chuck evenly and firmly with the key provided. Make sure drills are held tightly so they can’t slip and spin in the chuck jaws. This will score the shaft and ruin the drill and can also damage the chuck jaws.

It is difficult to maintain tolerances closer than +.003" -.000 with drills. If greater accuracy is required, a reamer should be employed.