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DP350 Variable Speed Bench Drill Press
on February 7, 2003
The DP350 is a [mostly] well-designed tool of good quality, and a terrific bargain. This is the only reasonably priced variable-speed bench drill press I could find, so for the time being, Delta appears to have a unique product.
Delta says to tighten the head using the two supplied Allen screws to prevent the drill head from moving on the column. I wanted to be able to move it occasionally, so I installed handles attached to 5/16" x 18 threaded bolts. Now, I can loosen the head, and swing it in place, and re-tighten it, in seconds.
There was no obvious place to store the chuck. I fixed it to a small chain and connected one end to the lower column tightener, so it's handy.
The base is held down to the bench with lag screws or machine bolts. The four corners of the base touch the bench, with the middle of the base 1/8" off the bench. Install spacers directly under the hold-down bolts to keep from flexing the middle of the cast iron base.
I've owned multi-speed drill presses for 35 years and rarely changed speeds, as it was too much trouble to move the belts. So, I selected a middle speed and left it there, sometimes for years on end. With the DP350, I adjust speed based on the drilling to be done for each job - controlling speed is as easy as turning a handle and can be done in seconds. The drive belt never has to be moved.
Spindle RPMs are controlled by turning a control with two handles on the top front of the unit. As the control is turned, the motor and spindle pulley's effective diameter changes, altering spindle speed. Each pulley has an upper and lower half. When together, they look like any other pulley. They separate vertically as you change speed. As one pulley's effective diameter increases, the other decreases, and vice versa. The diameter of the pulleys doesn't actually change, but the place within the pulley that the belt rides, does. At the lowest speed, the motor pulley is at its smallest diameter (pulley sections apart), and the spindle pulley is at its largest diameter (pulley sections together). As the control is turned clockwise for more RPMs, the bottom of the spindle pulley moves down. This results in a smaller diameter spindle pulley and a larger motor pulley, thus increasing speed. It's a clever design that has worked reliably on my machine. In observing speed changes with the top cover off looking down at the belt and pulleys, speed seems to change at a linear rate, and with the motor always turning the same speed. (Click on customer images above for pulley photos at high and low speed.)
Warning: Don't force the speed control handle, as doing so can bend the inner part that separates the spindle's pulley halves. Only move the handle with the machine ON.
The press comes with a metalworking table (oil troughs in the table). However, it's easy to find a flat spot on the table bottom to clamp a wood piece down.
The adjustable-position locking depth stop (for repetitive hole depths) has a button for release for quick adjustments. Release the button - then screw the stop down or up for fine-tuning. It works fine.
The speed dial decal on my press inexplicably had only the lowest and highest speeds: 500 RPM and 3100 RPM. I calculated approximate RPMs at the beginning and end of each range, and made a new speed decal. (See customer photo of decal.)
Range 1: 500 to 760
Range 2: 800 to 1235
Range 3: 1305 to 1950
Range 4: 2060 to 3100
1. The table angle scale is practically useless. It's ?" below the table's scribe line so you have to swing the drill head to one side to get your eye in position to read it. That ?" gap makes accurate alignment of the scribe line to the scale imperfect, since any side-to-side eye movement changes the apparent reading.
2. Needed felt between the sheet metal case and cast iron to eliminate a rattle.
3. The top cover plate is held on with six machine screws, instead of a piano hinge. Install your own hinge, or drill two perfectly aligned holes in the plate, in order to oil the pulleys without removing the top plate.
4. The pinion handle seam needed sanding to smooth it out.
5. The lower head locking screw (5/16" x 18) is in cast iron only ?" thick. Over-tightening or repeated loosening/tightening could strip those threads.
It's simple and quick to set the proper speed for each drilling task - the major feature of this tool, compared to other bench drill presses. Tool improvements are needed, but it's still a good bench drill press and an excellent bargain.
At least one reviewer had the drill chuck "fall off". Suggestion: thoroughly clean (e.g., with alcohol) the tapered chuck spindle and the chuck's mating surface, open the chuck all the way, and, using a wooden mallet, give it a good whack to reseat the chuck onto the spindle. Mine has stayed put for 2 years.
September 2005 update:
My DP-350 recently failed. The rear upper (belt) pulley connected directly to the motor, started wobbling, and the machine was making noises. This is the same problem reported by many others, but theirs died much sooner. A design flaw allows the upper pulley to slide off its inner sleeve, which renders the rear belt pulley, and the drill press, useless.
I repaired the drill in about 30 minutes using $2.00 worth of standard hardware. Here's how: Unscrew the top cover to access the motor pulley assembly; lift off the retaining ring with a removal tool, then remove the spring retainer cup, spring, upper pulley half and its inner sleeve. Once the upper rear pulley half is off the machine, drill two holes using drill size No. 3 in opposite sides of the thick part of the pulley base. Thread the holes with a ?" x 24 tap. Insert ?" long, ?" x 24, Allen screws, coated in Locktite, slip the pulley onto the sleeve, and tighten the screws. This will solidly hold the upper pulley onto its inner sleeve.
Similar-sized Allen screws are OK in lieu of ?" x 24. Click on customer images above for photos of screw location. If the old ring was stretched (& weakened) when you removed it, reassemble using a NEW retaining ring. Open the new ring only far enough to slip it into the groove on the motor shaft.
If you can't find the correct size retaining ring locally, go to: www dot dewaltservicenet dot com - part number 904160.
Delta responded to an e-mail regarding this design defect, as follows:
"We added a pin to the motor pulley to keep the bushing from coming out of the center of the pulley. This was fixed long ago, shortly after the tool came out. If you wish to speak with a technical representative regarding this, please call 1-800-223-7278."