hand reaming and broaching

7/27/2019 Hand Reaming and Broaching

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Reaming andBroaching

Session 9


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Shop Tools and Techniques 2

Hand Cutting Tools

Reamers Used to bring hole to size and produce good

finish

Broaches Used with arbor press to produce special

shapes in workpiece

Multi-tooth tool forced through hole

Lapping Where very fine abrasive powder,

embedded in tool is used to remove minuteamounts of material from surface


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Solid Hand Reamer

Made of carbon steel or high-speed steel

Available in inch sizes from .125 - 1.500 inch

Metric from 1 26 mm in diameter

Non-adjustable and may have straight orhelical flutes

Should not be used on work with keyway or

any other interruption


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Expansion Hand Reamer

Designed to permit adjustment ofapproximately .006 in. above nominaldiameter

Hollow and has slots along length of cuttingsection

Tapered threaded plug fitted into end ofreamer provides for limited expansion

Cutting end of reamer ground to slight taper


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Adjustable Hand Reamer

Has tapered slots along entire length of body

Inner edges of cutting blades have taper so

blades remain parallel for any settings

Adjusted by upper and lower adjusting nuts

Blades have adjustment range of 1/32 in. on

smaller reamers to 5/16 in. on larger ones

Manufactured in sizes to 3 in. in diameter


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Taper Reamer

Used to finish tapered holes accuratelyand smoothly

Made with either spiral or straight teeth

Roughing reamer Nicks ground at intervals along teeth

Used for more rapid removal of surplus

metal


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Reaming Precautions

1. Never turn reamer backward(counterclockwise), it will dull teeth

2. Use cutting lubricant where required

3. Always use helical-fluted reamer inhole that has keyway or oil groove cutin it

4. Never attempt to remove too muchmaterial (maximum = .010 in.)

5. Frequently clear taper reamer and holeof chips


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Reaming a Hole

1. Check size of drilled hole (.004-.005 in.smaller than finished hole size)

2. Place end of reamer in hole and place

tap wrench on square end of reamer3. Rotate reamer clockwise to align with

hole

4. Check reamer for squareness with work


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Reaming a Hole

5. Brush cutting fluid over end of reamer

6. Rotate reamer slowly clockwise andapply downward pressure

7. When finished, clean hole and checkwith gage for correct size.


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Broaching

Process in which special taperedmultitoothed cutter forced through anopening or along outside piece of work

to enlarge or change shape of hole First used for internal shapes (keyways,

splines)

Now used for external shapes


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Broaching

Cutting action performed by

series of successive teeth Each tooth protrudes .003 in. farther

than preceding tooth

Last three teeth same depth

and provide finish cut


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Advantages of Broaching

1. Machining almost any irregular shape

is possible

2. Process usually in one pass

3. Roughing and finishing cuts

combined

4. Variety of forms, internal or external,may be cut and entire width of

surface may be machined


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Broaching Keyways

Keyways may be cut by hand quickly

and accurately by means of broach

set and arbor press

Broach set covers wide range of

keyways

Equipment necessary to cut keyway

Bushing to suit hole size

Broach size of keyway to be cut

Shims to increase depth of cut of broach


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Cutting a KeywayWith a Broach1. Determine keyway size required

2. Select proper broach set

3. Place workpiece on arbor press Use an opening on base smaller than

opening in work so bushing properly

supported

4. Insert bushing and broach into

opening

Apply cutting fluid if workpiece is steel


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8. Insert second shim and third shim ifrequired, and press broach through

again This cuts keyway to proper depth

9. Remove bushing, broach, and shims

10.When finished, check broachedkeyway for size with appropriatekeystock

Cutting a KeywayWith a Broach


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Lapping

Abrading process used to removeminute amounts of metal from surface

Reasons for lapping

Increase wear life of part Improve accuracy and surface finish

Improve surface flatness

Provide better seals and eliminate need forgaskets

Intended to remove only about .0005 in.


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Lapping Abrasives

Natural and artificial abrasives used

Flour of emery and fine powders madeof silicon carbide or aluminum oxide

used extensively For rough lapping, abrasive should be

no coarser than 150 grit

Fine powders run up to 600 grit

Fine work uses diamond dust in pasteform


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Flat Laps

Close-grained cast iron laps used for flat

surfaces

Roughing operation Lapping plate scored with narrow grooves

.500 in. apart both lengthwise and

crosswise to form square or diamond

Finish lapping done on smooth cast-iron

plate


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Internal Laps

Holes accurately finished to size and

smoothness by lapping

Made of brass, copper, or lead

Three types

Lead

Internal

Adjustable


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Lead Lap

Made by pouring lead around taperedmandrel that has groove along length

Turned to running fit into hole

Sometimes slit on outside to trap looseabrasive

Adjust by lightly tapping large end of

mandrel with soft block


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Internal Lap

May be made of copper, brass or cast

iron

Threaded-taper plug fits into end of

lap

Slit for almost its entire length

Lap diameter may be adjusted by

threaded-taper plug


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Adjustable Lap

May be made from copper or brass

Split for almost full length, but both

ends remain solid

Slight adjustment provided by means

of two setscrew in center section


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External Laps

Used to finish outside of cylindrical

work pieces

Made of cast iron or may have split

brass bushing mounted inside by

setscrew

Must be some provision for adjusting

lap

hand reaming and broaching

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