ASME B18.2.1:2012 pdf free download Square,Hex,HeavyHex, and Askew HeadBolts and Hex,HeavyHex,Hex Flange, Lobed Head, and LagScrews (Inch Series)
1INTRODUCTION
1.1 Scope
1.1.1 This Standard covers the dimensionalrequirements for nine product types of inch series boltsand screws recognized as American National Standard.Also included are appendices covering gaging proce-dures, grade markings for bolts and screws, formulason which dimensional data are based, and a specificationto assist in identifying a product as being a screw or abolt. Where questions arise concerning acceptance ofproduct, the dimensions in the tables shall govern overrecalculation by formula. Heavy hex structural bolts,formerly covered in ASME B18.2.1, are now covered inASME B18.2.6.
1.1.2 The inclusion of dimensional data in thisStandard is not intended to imply that all of the productsdescribed herein are stock production sizes.Consumersshould consult with suppliers concerning lists of stockproduction sizes.
1.2 Comparison with lSo Standards
Since these are inch fastener standards, there are nocomparable ISO standards.
1.3 Dimensions
All dimensions in this Standard are in inches andapply to unplated or uncoated product. When platingor coating is specified, the finished product dimensionsshall be as agreed upon between supplier and purchaser.Where nominal sizes are expressed in decimals,zerospreceding the decimal and zeros in the fourth decimalplace shall be omitted.
Symbols specifying geometric characteristics are inaccord with ASME Y14.5.
1.4 Options
Where specified, options shall be at the discretion ofthe manufacturer unless otherwise agreed upon by themanufacturer and purchaser.
1.5 Terminology
As used in this Standard,”short bolt” or “short screw”means a bolt or screw of a diameter-length combination
that is required to be threaded for full length, whereas
“long bolt”or “long screw” means a bolt or screw of adiameter-length combination that is not threaded for full length.
body length,Lg: the distance measured parallel to theaxis of the bolt or screw from the underhead bearingsurface to the last scratch of thread or, for rolled threads,
to the top of the extrusion angle. Where specified, theminimum body length,LB, min., is a criterion for inspection.
grip gaging length,Lc: the distance measured parallel tothe axis of the bolt or screw from the underhead bearingsurface to the face of the appropriate noncounterbored,noncountersunk specialGO thread ring gage, assembledby hand as far as the thread will permit.The maximumgrip gaging length, Lc, max., is a criterion for inspection.point length: the length from the pointed end to the firstfully formed thread at major diameter as determinedby the distance that the point enters into a cylindricalNoT GO major diameter ring gage (refer to Gage 3.1in ASME B1.2).
thread length: the length from the extreme point of thebolt or screw to the last complete (full form) thread. Forbolts and screws in this Standard , other than lag screws,the nominal thread length,Lz, is a reference dimensionintended for calculation purposes only.
transition thread length, Y: the length that includes thelength of incomplete threads,the extrusion angle onrolled threads,and tolerances on grip length. Wherespecified, transition thread length is a reference dimen-sion intended for calculation purposes only.
For definitions of terminology not specified in thisStandard, refer to ASME B18.12.
1.6 Referenced Standards
The following is a list of publications referenced inthis Standard.
ASME B1.1,Unified Inch Screw Threads (UN and UNRThread Form)
ASME B1.2,Gages and Gaging for Unified Inch ScrewThreads
2 GENERAL DATA FOR BOTH BOLTS AND SCREWS
2.1 Heads
2.1.1 Top of Head. Top of head shall be full form andchamfered,withthe diameterofchamfercircleequal to the maximum width across flats, on square or hex head products and the “B” dimension shown in Table 9 for lobed head screws with a tolerance of −15%.
2.1.2 Width Across Flats. The width across flats of head shall be the overall distance measured perpendicu- lar to the axis of product between two opposite sides of the head in accordance with the notes in respective dimensional tables.
2.1.3 Head Height. The head height shall be the overall distance measured parallel to the axis of product from the top of the head to the bearing surface and shall include the thickness ofthe washer face where provided.
2.1.4 True Position of Head. The true position of the head shall be no greater than 6% of the maximum width across flats or lobes. For referee purposes, the evaluation shall be made by holding the body in a collet or chuck one bolt diameter from under the head and rotating the part. With the indicator in line with the axis of the bolt or screw, find and record the lowest point on each flat or the highest point on each lobe. The true position is one-half of the largest absolute difference between the high and low values for any opposing set of flats or lobes. 2.2 Bolt or Screw Length The bolt or screw length shall be the distance mea- sured parallel to the axis of product from the bearing surface of the head to the extreme end of the bolt or screw, including the point if the product is pointed.
2.3 Body Diameter The body diameter minimum/maximum limits are defined in each of the respective applicable tables. Unless otherwise specified by the purchaser, the body style supplied shall be full-size body.