miniature machining

8/7/2019 Miniature Machining

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$100M I N I A T U R E CONTENTS1. Unimat versatility.. ......................... Page 2

M A C H I N I N G2. Introduction & Index.. ..................... Page 53. How to operate the

basic equipment.. ........................... Page 64. Use of accessories.. ........................TECHN I =UES Page 175. Tips for the expert craftsman..........Page 336. Advanced Techniques.. ..... .............. Page 347. Measuring

Tools.. ........................... Page 368. Parts I$ . ............. ..: ....................... Page 37

a general handbook and operators manual

I

9. Table of cutting anddrilling s p e e d s

FROM BEGINNER TO EXPERT CRAFTSMAN

in METAL l PLASTICS l WOOD

nietal turning l drilling l milling l grinding l polishingl sharpening l sawing l surface grinding l threading l

boring l wood turning l special techniques l jigs and

attachments


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READ THESE INSTRUCTIONS TO GET BEST RESULTS

AND TO A VOID DA MA GING YOUR MA CHINE!

Working metal parts of the Unimat

are protected in shipment with a coat-

ing of rust-resistant grease. Wipe off with a cloth dipped in kerosene or ben-

zene. Then l ightly oil the lathe bed,cross slide and all exposed metal sur-faces to prevent rust. Number 10 motor

oil or any light grade machine oil willdo the job.

Though you can use the Unimat as is,

youll find it helpful t o screw the beddown to a perfectly flat board. A pieceof 11 x 18 inch plywood, a/4 or 1 inchthick makes a good working base. The

board shown in the photo was made ofa piece of scrap Formica counter top, amaterial available at most lumber yards.

The white color makes small parts easy

to see and the grease resistant surface

is easy to clean. A complete UnimatWorkcenter (DB 1400 ) is available aslisted on the back cover.

Before you plug in the motor, check

the idler pulley. It should spin freely.

Make sure th e protective greas e hasn thardened around the ball bearings, andthat the clamping screw is not too tight.

This screw should be just snug enough

to keep the assembly from slipping out.Pu t t o o m u ch t en s io n on t h i s sc r ewand it will distort the ball bearing r awand preven t the pu l ley f rom tu rn ing

properly.Th e headstock pulley must clear the

motor bracket. If the cap screw on the

bracket loosens, the spindle spring willpush the motor bracket up against the

pulley causing the spindle to stall. Use

a folded piece of cardpaper (about ,015thick) between the pulley and motorbracket to se t the spac ing and thentighten the cap scrws.

3 J A W C H U C K

DB 1001 UNIVERSAL LATHE CHUCK CENTERS ROUND

SHANK TOOLS AND WORKPIECES FROM ,118 TO 2-l/ 64

There are two lathe chucks available

for your UNIMAT: #lOOl, 3-j, Uni-versal, and #lOOla, 4.Jaw Independen tchuck. Both accessory chucks must be

tr ued to the lat he spindle t o ma ke th emrun dead accurate. Before us ing, machine

chuck backplate as described on page 18under Truing Instructions.

C a r e f u l l y u n w r a p a n d c l e a n t h echuck. It is protected in shipment with

a preservative which must be removed

with solvent - kerosene, gasolene, orlighter fluid will do. Loosen the jaws byrotating the outside knurled ring coun-

terclockwise looking at the face of thechuck.

As each j aw d i sen g ag es f r o m th escroll, it can be removed. The first ja wto release will be #3 , next #2 . and then#I.

Clean jaws and threads. Then oil with

a light film of #lO motor oil or equiva-lent. To reassemble the chuck jaws in

normal posi t ion , ro ta te the r ing un t i l

th e scroll ring appea rs a t a point just

before slot # 1. Engage jaw # 1 by press-ing inward gently. Continue turning thering until it is next to slot #2 . I n s t a l l

jaw #2 , and then repeat for jaw #3

6E Tightening chuck jaws.

Several types of motors are illustratedin this manual. The motor supplied withy o u r Un im a t i s a h ig h to r q u e q u ie t

opera t ing l/lOth HP 110 volt 60 cyclemotor. Motor designs are subject t oix -provement, an d th e m o to r d e l iv e r edwith your unit may have a slightly dif-

ferent appearance. If your motor heatsafter r u n n in g cotius ly for 5 to 10minutes, this does not mean it is defer-t ive. Your motor i s fu l ly enc losed toprotect it from chips and dust and, be-

cause a lot of power is packed in asmall case, there is heat build-up, whichhas been provided for in the design.

Unimat spindle ball bearings are fac-

tory pre-lubricated and will need noadditional at tention for the f irst 30 0hours of use. After this time, follow in-structions on page 33 for disass&nbly ofthe spindle and lubrication.

:

6ELwsm ing c h u c k jaws.When chucks are new they require a

l i g h t i n w a r d p r e s s u r e t o insure tha tthey properly engage the scroll.

In normal posit ion, the chuck jawswill take round work up to15/16 onthe inside. Or using the backs of the

jaws on tubing, etc., you can handle up

to a Z-5/32 diameter. By reversing the jaws, larger work can be machined up

to 2-15/64 diameter. To reverse jaws,remove as explained before, but reverseeach jaw and replace in the chuck in

this order: jaw #3 in slot # l; ja w #2in slot #2; and jaw # l in slot #3 .


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Finish the other side of the cut with

the right-hand finishing bit (DB 1102).While both finishing tools will cut in-

ward from the end of the tool as well as

precision reaming, mandrel turning taperturning and lathe threading.. .

laterally, this is not recommended. Theproper tool for digging into a bar isthe roughing tool, and the finishing toolsshould be saved for final facing cuts.

If you have ever worked before witha really precise lathe, running the Uni-mat can be a amazing experience. Smallwork of the type shown in Photo 9F

takes shape in seconds. If yo keep toolsproperly centered, sharp, and ground atth e proper a ngles, youll often find th atthe lathe tools produce work that looksas though it had been polished.

TURNING TO SIZEAll of the threads on Unimat parts

are metric. The long leadscrew whichcontrols movement of t h e carriage fromone end of the lath e bed to the other, an d

the cross slide screw are both 8 x 1 milli-meter threads. This means that if YOU

turn the hand wheels one complete revo-lu t ion , you get a feed of exactly 1 milli-

meter. The handwheel is further divided

into 20 marks corresponding to a feedof .05 mm per mark.

Though m os t cam era , op t i ca l andinstrument parts are setup with metricsystem threads, you may prefer to workin inches. One millimeter equals .03937inch . For a l l bu t the m os t exac t ing

work, you can round off this decimal to.04, the amount of feed in one turn ofthe handwheel . In inches , each smallmark is a feed of .00.2. It is important toremember that when you are cut t ingacross the lathe bed, that you reducehoth sides of the workpiece at once.

Thus, turning one calibration actuallyremoves double the feed, ,004; a com-plete turn of the handwheel, .OS.

FEED ADJUSTMENTS0 most lathes, there is some backlash

in the feed screws. In other words, thescrew will turn slightly before the toolstarts moving. To adjust this play, loosethe nut that holds the handwheel, adjustthe wheel, and retinhten the nut .

Too much tension on the feed wheelswill give you a stiff slow working feed;too little tension can case tool chatter.

A loose feed is better for fast workingin soft metals, wood and plastic, butyou need a tight feed whenever you cutcast iron, brass or steel. Practice willshow you that the best setup for anygiv,, material is a combination adjust-ment of the handwheel and carriage orcross slide tension screws. The smaller

the work diameter, the tighter thelathe should be.

It is very important to keep the feedscrews clean and well lubricated with

light machine oil. An chips accumulate,remove immediately with a small paintbrush or se a ear syringe to blowthem off. If you are working in brass orcast iron, metals that produce powderysmall chips, yo can protect the lathebed and feed screws by covering with

pieces of household aluminum wrappingfoil, Whenever chips gather on the feedSCRWS do not turn the handwheels sincethis can damage the threads. The easiestway to clean the threads is to place theUnimat in a shallow tray (a cookie bak-

ing tin will do nicely) and flush thechips loose with kerosene fed from a

oil ear i .


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headstock alignment, precision drillingand boring on the lathe.. .

HEADSTOCK SPINDLEALIGNMENT

So far, the photos have show Unimatcutting operations where only roughalignment, of the spindle was needed. Atthe factory, Unimat headstocks and tail-stocks are mounted on the bed, and thenbored in one operation. A alignment pinfeeds through the lip on the front of theheadstock casting down into the lathebed. It gives you a quick way to centerthe headstock when setting up roughcuts, installing attachments, etc. How-ever it is accurate to only about one de-gree of arc.

Precise small work requires that the

lathe run dead trueTo make this setup,loosen the tapered bed clamping screw

(see Photo 7B) and remove alignmentpin. Never force any parts of the ma-chine. Sometimes, if your Unimat isstored in a cold or dry place, and not usedfor months, tight fitting parts may stickin place. Use a pen&ant such as LiquidWrench, a solvent available in smallcans at hardware stores, and follow "Pwith light oil.

Now insert the feed pinion handleverin the headstock and move the headstockspindle as far as it will go to the right.Lock in place with the headstock cap

screws. Move the cross slide. either allthe way left until it almost touches the

headstock, or far to the right out of theway. Then clean the tailstoek bore with

kerosene and cloth, and insert for eenter-ing.

Next move the tailstock over, lock it tothe bed and gently feed it into the head-stock spindle as in Photo IOA. As you dothis! be 8~ that there are no chips orcuttings between head and tailstockcastings and bed, or on any parts in-volved. As the dead center mates withthe headstock spindle, it will line up theheadstock to dead accuracy. Tighten thebed tapered clamping screw, but do notse the aligning pin.

One quick way to check alignment isto se a razor blade as in Photo 10B. Ifthe blade will hang vertically to the bedaxis between the two dead centers, yourheadstock is perfectly aligned. If youfind that there is error, you may need toloose the tapered bed screw slightly andtap on one corner of the headstock cast-ing-(use a wood block or soft rubbermallet) to bring the center into align-ment.

PRECISION DRILLINGON THE LATHE

For ordinary rough work, you can drillholes in workpitxes held in the 3-jawlathe chuck eve though the headstockspindle is not perfectly aligned. Therewill be no trouble with drills down tol/32. However, if you want to drill per-fectly true deep holes, youll find if thesoindle has not been alirned. that the

drill may produce a slightly conical hole.,or the workpiece may eve break drill.With the headstock properly aligned,

and chucks and bed cleaned and oiled,you should have no difficulty in drilling(Photo IOC) as small as a 80 size drill(.0135). This type of work is impossible

on most lathes without special tools.Whenever drilling below l/32-inch, re-member that it is easy to overfeed thedrill. Small drills will tend to bend out ofline slightly while they are making thehole, causing inaccurate bore. It is agood idea to watch the work with a large

magnifying glass mounted over thelathe.

PRECISION LATHE BORINGPurpose of the boring bar (DB1105)

is to turn internal holes. The end of theboring tool is ground at a angle similarto that on the side of the facing tools.Drill the workpiece out to l/4 or 6/l&inch. Then set the boring bar in the tool

holder, centering the edge a8 with theother lathe tools. Be sure to mount thetool in the holder parallel to the latheways. Do not try to cut all the way in onepass. Because chips tend to gather in theworkpiece, it is necessary to r boringcuts slower and at lighter feeds than forexternal work.

As the bore approaches the desireddiameter measre with vernier calipers,or by checking against a fitting part.

As a example, lets say that the boredring in Photo 10D is a bearing that hasto fit smoothly on a rotating shaft. As wemake successive cuts, we can measurewith various types of machinistsgauges. But these gauges are costly andyou may not have one in the exact sizedesired.

The easiest method is to machine theshaft first. Make it about one-half inchlonger than finished size, and turn off theextra material for se as a diametergauge.

Use B fine jewelers file or garnet paperand finishing cloth to polish down cmeend of your plug so it measures aboutl/1000 less than the desired shaft dia-meter. Then as you bore the finish holein the bearing, se this plug to check the

inside diameter. Mark the plug gaugeand save for future use. A set of suchdiameter gauges can be made up as yougo along and will have many uses in theUnimat shop.

When boring large holes with the 3- jaw chuck, it is important to improvisea stop on the bed to prevent the tool fromcutting into the chuck itself. You canclamp a wood block on the bed, or makebed stops by sawing a ring like the oneshown in Photo 10D in half. It is also agood idea to chamfer the end of theworkpiece facing the chuck, to avoid hav-

ing to bore all the way through..


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precision reaming, mandrel turning,taperturning and lathe threading.. .

PRECISION REAMINGThough the Unimat runs more accu-

rately than most common lathes, twist

drills will generally not cut dead accur-ate. Boring tools below l/4-inch are notsatisfactory on deep holes because the

tool may tend to bend against the work-piece. Reaming is a standard techniqueto use whenever you want small holesaccurate to l/1000-inch.

Just like drills, reamers are availablein fractional, number, letter and metric

sizes. The reamer is a stiff fluted tool andshould never be used to remove more

than a few thousandths stock. To makethe precise-fitting camera post (Photo11A) the workpiece was f i rs t turneddown to diameter and then drilled onesize under that of the reamer.

The reamer should not be driven by

the drill chuck in the tailstock, since th is

can cause inaccuracy. Instead hold thereamer in a tap wrench. The back end ofmost reamers has a center hole. Ennasethis on the tailstoek center, and either

with th e work r otating at very low speed,or turning the headstock spindle pulleyby hand, slowly feed the reamer into the

hole. Never force a reamer. Use plentyof lubricant and on deep holes, remove

the reamer f requent ly and clean the

chips. Never turn a reamer backward inthe work since this can dull the cutting

edges.

MANDREL TURNING

Many kinds of work are difficult tomount in the r egular chucks. An exampleis a three step pulley, Photo 11B. Th eworkpiece is mounted between centerson a special hardened dead straight barcalled a mandrel. Mandrels are availablethr ough machinists supply houses an da r e made by drill manufacturers. Oneend of the mandrel is slightly smallerthan the rated diameter, while the other

end is larger.

Thus to turn the pulley, your first step

is to rough turn the stock to approxi-

mate diameter and length in the 3-jawchuck. Then center drill one size beneath

the required shaft diameter. Next theworkpiece is reamed, in this egample

with a l/4-inch reamer. The smaller endof the l/4-inch mandrel is inser ted inthehole and the work tightened by tap-ping the other end of the mandrel with asoft mallet until the work locks on the

shaft.

Both ends of the mandrel have hard-ened centers. It mounts between lathe

centers with the faceplate dr iv ing the

lathe dog. As the work revolves you mayfind that you want to use scrap electricalwire to tie the lathe dog soldily to onefaceplate slot, to prevent vibration in the

cut. Be sure to oil the tailstock centerevery few moments as the machine runs.The tailstoek should not be set so tightly

that the center overheats . I f much of this kind of work is done, you will needa DB 1220(a) ball bearing center.

TAPER TURNINGA taper is a cone- s haped cu t on a

workpiece. Taper-cut pins, shafts , and

fittings are widely used in instrumentsand on machine tools because a tapered

rod does not wear into a hole to cause in -sccuracy. Taper pins, for example, tendto seat in their sockets with a wedgingaction that self corrects for wear.

On most lathes, you cut a taper byoffsetting the tailstock. On the Unimat,it is done by operating the headstock a tan angle away f rom dead center . To

machine a tapered bar or pin, punch theends of your workand mount betweencenters. J f the headstock is angled to-ward the rear of t h e la the, the taperwill cut smaller at tht tailstock end. If

t h e hezadstock i s an g led t oward t h rlathe front, the taper will cut small atthe left.

To establish the taper angle, you will

need a test bar. This bar will have manyother use8 later on. Select a perfect pieceof free-machining steel about 3/X-inchdiameter. Cut it exactly 5 inches long,t rue the ends and m ark the cen te r s .

Punch carefully. Align the lathe centersperfectly and use the roughing tool to

cut the bar down to about ,260. Thenuse the left hand finishing tool to turnthe bar down to an exact l/4-inch diam-eter. If your lathe was properly setup,the diameter should check exactly at .25from one end to the other.

Now to set up a typical ta per cut . Letssay that we want to machine some barsthat have a taper ofl/4 per foot. This isequal to a taper of .I042 per the 5.inchlength ofour test bar. Place the test barbetween centers and adjust the head-

stock angle until you can read a differ-ence of ,104 between the bar and the tipof a tool mounted exactly on center inthe tool holder. Use shim stock (or a dial

gauge mounted in the tool holder) andcheck at each end of the bar.

Some inaccuray may be introducedwhen the centers drive the work at anangle . Therefore make a t r i aL cut onano ther 5-inch bar. Exact diameter isnot required since the taper per foot

ratio will remain the same. Use a micro-meter at each end to measure the dia-meters. Difference is the taper. A slight

adjus tment of the heads toek may be

required.

T a p e r s can also be bored in shortworkpieces held in the 3.jaw chuck. Ifyou plan to do considerable taper turn-ing, it would be best to make a protrae-tor bar which can be chucked in thetailstock for checking headstock offsetagainst the faceplate.

LATHE THREADINGT h e r e a r e t h r e e w a y s o f c u t t i n g

threads on the basic Unimat : with taps,dies, or the Thread Chasing Attach-

m e n t (DB 1 2 7 0 ) . T o c u t i n t e r n a lthreads, you first must prepare the rightsize hole for the thread desired.

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