Mechanical Engineering

Lathe Operations - Project - Straight Turning Between CentersPart Specification

Tolerance Unless Specified
Scale: NTS

Fractions 1/X:    +/- 1/64 Drawn Date

(2) Place X.XX   +/- 0.010 Description: Thread Diameter Turning

(3) Place X.XXX   +/- 0.005   Material:

Angles   +/- 30 Minutes Part No: PSN1-3

Turning Machines - Lathe Maintenance

Posted by Unknown at 2:44 PM

Turning Machines - Lathe Maintenance

The engine lathe is a precision machine tool and must be treated with great care. Regular cleaning and maintenance will help to assure that the lathe will maintain its service life and accuracy for many years. This unit will cover basic lathe maintenance. The procedures you find within this document should be able to be performed by apprentice or beginning machine tool students. Lathe maintenance that requires more extensive disassembly should only be done by, or under the supervision of, qualified personnel.Drive Belts

The drive belts supply power from the motor to the spindle. Access to the drive belts is gained by removing the end guard on the headstock (Figure 1). Make sure that all power is locked out before removing any guards.

Figure 1 Head stock end guard.

Figure 2 Each belt should have approximately the same amount of tension.

Drive belts come in matched sets and should only be replaced with a matched set of belts. Visually inspect the drive belts for excessive wear and cracking. If you notice that one or more of the drive belts appear to be excessively worn or cracked, bring this to the attention of the instructor. Check the belt tension by applying finger pressure to each belt at a point midway between the two pulleys (Figure 2). For correct tension a deflection of about 3/8 of an inch should be evident in each belt. If the amount of deflection is more than 3/8 of an inch in any one or more of the belts, bring this to the attention of the instructor.

Gib Adjustment

All lathes employ precision slide ways. The saddle, cross slide, and the compound slide all ride along a box slide way or dovetail slide way. After time the parts that ride along the slide ways begin to wear. To compensate for this wear, machine tools are equipped with adjustable parts called gibs that allow you to eliminate the space that has been created by the wear between the slide ways. (Figure 3).

Figure 3 A tapered gib located on the cross slide of a lathe

Figure 4 A compound slide utilizing a straight gib

There are two types of gibs, straight gibs and tapered gibs. Straight gibs are adjusted by screws spaced out along the length of the gib. The screws push the gib in to create more contact with the sliding mechanisms (Figure 4).

Tapered gibs use two screws. The screws are located in each end of the tapered gib. One screw acts as an adjustment while the other screw acts as a locking mechanism. Because tapered gibs are wider on one end than the other, they slide in or out creating more or less contact between the sliding mechanisms (Figure 5).

Figure 5 Tapered gib with screws

Cross Slide Gib Adjustment

Wear in the cross slide ways must be adjusted by using the screw on the front face of the cross slide. (Figure 6).

Figure 6 Front gib screw

The procedure is to first loosen the similar gib screw on the rear face of the cross slide (Figure 6a), then re-tighten the front screw to lock or adjust the gib in its new position.After the adjustment, traverse the cross slide over its entire travel to be sure of smooth, even operation.

Figure 6a Rear gib screw

Compound Slide Gib Adjustment

Wear in the compound slide ways must be adjusted by using the screw on the front face of the compound slide. (Figure 7).The procedure is to first loosen the similar gib screw in the rear face of the tool slide, then re-tighten the front screw to lock or adjust the gib in its new position. After making the adjustment, traverse the compound slide over its entire travel to be sure of smooth, even operation.

Figure 7 Tool slide gib screw

Wipers Pads

Most lathes are equipped with wiper pads (Figure 8). Wiper pads are typically made of felt that will hold oil.Wipers are designed to keep out small chips and dirt between the slides and the ways. Wipers are saturated with oil to catch the fine particles of dirt or debris before they get between the two sliding surfaces. The wipers should be removed, cleaned, and re-saturated with oil regularly. You should never use compressed air for cleaning a lathe. Compressed air will push the fine particles trapped in the wiper between the mating surfaces of the slides, causing premature wear on these precision surfaces.

Figure 8 Wiper pads

Adjusting the Tailstock Clamp

The lock position of the bed clamp lever on the tailstock is adjustable and should be located before top dead center (Figure 9).

Figure 9 The lock position of the bed clamp lever on the tailstock

Figure 10 Tailstock locking lever adjustment bolt

The lever is adjusted by a self-locking bolt located on the underside of the tailstock front clamp plate and between the bedways (Figure 10). Turn the bolt clockwise to increase the clamping action. Lathes may also be equipped with an auxiliary bolt on the tailstock. This bolt is used to give additional clamping action when required. It does not require any adjustment.

End Gearing and Backlash

The end gearing on the lathe connects the spindle rotation with the feed and threading rods (Figure 11).

Figure 11 Lathe end gearing

Figure 12 End gear chart

The gears supplied with a lathe allow the operator to obtain an extensive range of feeds, metric threads, threads per inch, module and diametral pitch threads. To cut threads over a broad range, the lathe operator will need to make changes to the end gear train. Basic lathe setup and operation includes being able to properly change the gears in the train. Most lathes are equipped with charts that explain the gear positioning for certain types and ranges of threads (Figure 12).

When the proper gears have been selected and set in the gear train, the mounting or clamping bolts should be lightly snugged in place with a strip of paper or feeler stock placed between the gears (Figure 13).

Figure 13 Setting the backlash in the end gear train

The gears should then be pushed together against the paper shim. The clamping bolts should then be tightened. Remove the shim. The space left between the gears, where the shim was placed, is known as backlash. On most lathes the backlash amount should be between 0.007 and 0.011 inches. If the gears are noisy, more backlash space should be made between the gears. Finish the backlash adjustment by placing a small amount of lubricant on the gear train.

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Turning Machines - Lathe Lubrication

Posted by Unknown at 2:43 PM

Turning Machines - Lathe Lubrication

Lathe Maintenance-LubricationProper lubrication of machine tools is the responsibility of the operator. In order to ensure that the machine runs properly and maintains its accuracy, regular lubrication is required.
Before operating the lathe, make sure that all lubricants are at their proper levels. Being that all lathes are different, it is impossible to cover the lubrication schedule for all of the types of lathes found in the machine shop. Use the chart below as a guide for the proper lubrication points found on most types of lathes. If you find that the machine that you are using is drastically different from the machine found in the illustration, ask an instructor for the lubrication schedule for your particular machine.

HeadStockSpindle bearings, headstock gearing, and shafts are lubricated continuously from a distributor tank located beneath the headstock top cover. The oil is supplied either by a pump or an oil slinger found in the headstock. Evidence of supply is shown in an oil sight glass located on the headstock front face (Figure 1).

Figure 1 If the machine is equipped with a pump, oil should be visible when the motor is running. If the machine is equipped with a slinger, oil should be visible in the headstock reservoir sight glass.

Ensure that the oil level in the system is kept topped off. On lathes with an oil pump, oil is usually added through a filler tube in the oil tank located behind the headstock end guard cover. (Figure 2).

Figure 2 The oil filler tube is typically found behind the headstock end guard cover.

Figure 3 Oil filler plug located on the top of the headstock of a lathe equipped with an oil slinger lubrication system

On lathes with an oil slinger, oil is usually added through a filler plug on the headstock cover. (Figure 3).

Some types of lathes are equipped with both a reservoir sight glass and an oil flow sight glass (Figure 4). The reservoir sight glass is located on the lower half of the headstock while the flow sight glass is located near the top of the headstock.

Figure 4 Lathe headstock equipped with both flow and reservoir sight glasses

Gearbox

Gears in the gearbox are splash lubricated from an oil tank that is part of the gearbox. An oil sight window is typically situated on the front or side face of the gearbox (Figure 5).

Figure 5 When the lathe is off, oil should be visible at all times in the gearbox oil sight window.

Figure 6 Typical filler elbow found behind the end cover of the headstock

To top off or fill the gearbox, find the filler elbow behind the headstock end cover (figure 6).

Apron

The apron gears are splash lubricated from an oil tank that is part of the apron. On new style lathes, the apron oil tank is also the reservoir for the manually operated pump (Figure 7) that lubricates the bedways, cross slide ways, and nut.

Figure 7 Before operating the lathe, give the one shot lubricator a pump to ensure proper lubrication to the bedways, cross slide, and nut.

When the oil level falls below the level on the site glass on the apron (Figure 8), the system can be filled through the filler plug found on the saddle (Figure 9).

Figure 8 Apron oil sight glass

Figure 9 Apron oil filler plug

For trouble-free operation, keep the lathe clean and regularly maintained. Use the generic lubrication chart in Figure 10 to locate and maintain a regular lubrication schedule for the lathes in your machine shop.

Figure 10 General lubrication chart

Grease each week - rack and end train gears (change wheels) Shell Alvania RA.
- Chuck (manual) Molycote"D".

Oil each week - Tailstock, Leadscrew, Endgear, Bushes and Topslide, Shell Tellus T37 (ISO VG37)

Apron. Check level and top up each week - Shell Tonna TX68 (ISO VGT 68) Total capacity 1.2 litres.

Headstock. Check level and top up each week - Shell Tellus T37 (ISO VG37) Total capacity 16 litres.

Gearbox. Check level and top up each week - Shell Tellus T 37 (ISO VG 37) Total capacity 2.6 litres.

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Drill Press Part

Posted by Unknown at 2:39 PM

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Title: Drill Press Parts

Author(s): Kelly Curran

Drilling Machines - Feed Rates Calculations

The feed rate for drilling depends upon the hardness of the material, the type of material the drill is made of, and the size of the drill bit. In this information sheet we will concentrate on feed rate factors and calculations for high-speed steel drills.
Although some carbon steel drills are still available, most drills used by industry are either high-speed steel or carbide. Carbide drilling will be covered in the carbide unit.
The spindle feed rate on drilling machines is given in terms of inches per revolution (IPR). Inches per revolution is the rate at which the tool will advance into the work every revolution of the tool. The feed rate that can be used is determined mainly by the size of the chip that the drill can withstand. As the size of the drill increases, the feed rate of the drill also increases.
Drill feed Table 1 gives you the recommended feed rates for general-purpose work using a two-flute drill. Like in any other type of machining, it is better to start with a slower feed rate, then increase the feed rate to the capacity of the machine tool, the setup, and the desired surface finish.

Table 1 Recommended Feed Rate for High-Speed Steel Twist Drills

Drill Diameter, Inches

Feed, Inches per Revolution

Drill Diameter, Inches

Feed, Inches per Revolution

Drill Diameter, Inches

Feed, Inches per Revolution

1/16 to 1/8
1/8 to 1/4

.001 to .003
.002 to .006

1/4 to 1/2
1/2 to 1

.004 to .010
.007 to .015

Over 1

.015 to .025

If the recommended feed rate for a 1/2-inch drill is 0.005, the operator sets the machine feed on the drill press to 0.005 feed in inches per revolution. Most drilling machines are set up to feed in inches per revolution. If, however, the feed rate for the machine is set up in feed rate in inches per minute (IPM), the operator needs to multiply the operating R.P.M. of the drill by the feed rate in inches per revolution.
Let’s try some feed rate calculations for IPM. Follow along using the recommended feed rate charts in Figure 1.
A 0.500-inch high-speed steel (HSS) drill is to be used on a piece of 1018 steel with a brinnel hardness of 200. The closest RPM setting to perform this cut is 800 rpm. Look up the feed rate in inches per revolution (I.P.R.) in the charts and calculate the feed rate in inches per minute.

RPM = 800

Feed in inches per revolution (I.P.R.) = 0.004 low side

Feed (in. / min.) = RPM x I.P.R.

Feed (in. / min.) = 800 x 0.004

Feed = 3.2 in. / min.
If we need to calculate the feed rate for a drill that has more than two flutes, adjustments need to be made to the feed rate calculations. Consult the tool manufacturer for information on feed rates.

Drill Press Work-Holding Device

Posted by Unknown at 2:36 PM

Drill Press Work-Holding Devices

Work Holding

Because of the forces being created when drilling, all workpieces must be held securely. There are a number of forces being created when drilling: the downward pressure that the tool is creating while trying to bite into the workpiece, but also the forces of the workpiece trying to climb up the flutes of the drill(Figure 1). A very serious injury can occur when a drill gets caught in a workpiece and is spun around. It is of great importance that we adhere to all safety practices and make sure that all work is held securely in the proper type of work-holding device.

Figure 1

Drill Press Vise

Figure 2 Drill press vise

The drill press vise is by far the most common type of work-holding device used on the drill press. Modern drill press vises are capable of holding round stock, flat stock, or any other small parallel-sided parts. Most drill press vises come equipped with V shaped slots for holding round stock and stepped jaws for holding parts up off of the base of the vice (see Figure 2). This will avoid contact between the drill and the vise.

Angle Vise

Angle vises are used when an angular hole needs to be drilled into a part(Figure 3). Angle vises have an angular adjustment that allows the operator to tilt the vise.Another method of drilling angular holes, on certain types of drill presses, is by tilting the drill press table.

Figure 3 Angle Vise

Angle Plates
Angle plates (Figure 4) are used when drilling odd-shaped parts that need to be drilled at 90 degrees to the axis of the table. An angle plate is an L-shaped piece of cast iron or steel that has tapped holes or slots to facilitate the clamping of the workpiece.

Figure 4 Angle Plates

V-Blocks
V-Blocks hold and support round work for drilling (Figure 5). V-Blocks come in many different sizes.

Figure 5 V-Blocks

V-blocks typically come in sets of two and have clamps for holding small, round parts. Large, round parts supported by V-Blocks are typically clamped directly to the table.

Figure 6

Small V-blocks with clamps are usually held in a vise(Figure 6).

Direct Workpiece Mounting

Work that is too large or has an odd configuration is customarily bolted directly to the table (Figure 7). This method of work holding takes the most ingenuity and expertise.There are a number of accessories that can be used to help you set up parts.

Figure 7 Direct Clamping

A variety of commercially available clamp sets can be used for directly mounting workpieces (Figure 8).

Figure 8 Clamp Kit

Parallels

Parallels are pieces of steel bar stock accurately machined so that the opposing sides are parallel to each other(Figure 9). Parallels are provided in sets of two with identical dimensions. Parallels are used to provide clearance under the work so that the drill does not damage the machine table or the vise base(see Figure 7).

Figure 9

Figure 10 shows some acceptable and unacceptable clamping practices while using clamps and parallels. Study them carefully.

Figure 10 Clamping Practices

Drilling Jigs

Drill jigs are tools built exclusively to hold the workpiece. Accurately guide a tool to the proper location on the part (Figure 11). Jigs are typically found in a production atmosphere where a large quantity of the same parts need to be drilled.

Figure 11 Drill jig


Tolerance Unless Specified	Scale: NTS
Fractions 1/X: +/- 1/64	Drawn	Date
(2) Place X.XX +/- 0.010	Description: Thread Diameter Turning
(3) Place X.XXX +/- 0.005	Material:
Angles +/- 30 Minutes	Part No: PSN1-3

Figure 10 General lubrication chart
	Grease each week - rack and end train gears (change wheels) Shell Alvania RA. - Chuck (manual) Molycote"D".
	Oil each week - Tailstock, Leadscrew, Endgear, Bushes and Topslide, Shell Tellus T37 (ISO VG37)
	Apron. Check level and top up each week - Shell Tonna TX68 (ISO VGT 68) Total capacity 1.2 litres.
	Headstock. Check level and top up each week - Shell Tellus T37 (ISO VG37) Total capacity 16 litres.
	Gearbox. Check level and top up each week - Shell Tellus T 37 (ISO VG 37) Total capacity 2.6 litres.