1. BEVEL PROTRACTORS / Universal bevel protractor:
Bevelprotractorsarenothingbutangularmeasuringinstruments.
Typesofbevelprotractors :
Thedifferenttypesofbevelprotractorsusedare:
1)Vernier bevel protractor
2)Universal protractor
3 ) O p t i c a l p r o t r a c t o r
O p t i c a l p r o t r a c t o r :
Working principle:
-Avernierbevelprotractorisattachedwithacuteangleattachment.
– Thebodyisdesigneditsbackisflatandnoprojectionsbeyonditsback.Thebaseplateisattachedtothemain
bodyandanadjustablebladeisattachedtothecircularplatecontainingvernierscale.
– Themainscaleisgraduatedindegreesfrom0°to90°inboththedirections.Theadjustablecanbemadeto
rotatefreelyaboutthecenterofthemainscaleanditcanbelockedatanyposition.
– Formeasuringacuteangle,aspecialattachmentisprovided.Thebaseplateismadefiatformeasuringangles
andcanbemovedthroughoutitslength.Theendsofthebladearebeveledatanglesof45°and60°.
– Themainscaleisgraduatedasonemainscaledivisionis1°andvernierisgraduatedinto12divisionsoneach
sideofzero.Thereforetheleastcountiscalculatedas
OneMainscaledivision
Leastcount= --------------------------------------
Numberdivisionsonvernierscale
= 1/12(Degrees)
=(1/12)x60=5Minutes
Thus,thebevelprotractorcanbeusedtomeasuretoanaccuracyof5minutes.
Applications of bevel protractor:
Thebevelprotractorcanbeusedinthefollowingapplications.
1 . F o r c h e c k i n g a ‘ V ’ b l o c k :
2 . F o r m e a s u r i n g a c u t e a n g l e :
3 . F o r c h e c k i n g i n s i d e f a c e o f b e v e l e d f a c e o f g r o u n d s u r f a c e :

2. SINEBAR
- Sinebarsarealwaysusedalongwithslipgaugesasadeviceforthemeasurementofanglesveryprecisely.
– Theyareusedto
– 1. Measureanglesveryaccurately.
– 2.Locatetheworkpiecetoagivenanglewithveryhighprecision.
– Generally,sinebarsaremadefromhighcarbon,highchromium,andcorrosionresistantsteel.Thesematerials
arehighlyhardened,groundandstablished.
– Insinebars,twocylindersofequaldiameterareattachedatlieendswithitsaxesaremutuallyparalleltoeach
other.
– Theyarealsoatequaldistancefromtheuppersurfaceofthesinebarmostlythedistancebetweentheaxesof
twocylindersis100mm,200mmor300mm.
– Theworkingsurfacesoftherollersarefinishedto0.2 micromilimeter Rvalue.
– Thecylindricalholesareprovidedtoreducetheweightofthesinebar.
–