OWNER: POSITION AUTHOR: POSITION Dan Boettcher Director of Engineering Richard Richardson Vice-Dir of Engineering

Transcription

1 KRESS CORPORATION ENGINEERING Design of Thru and Threaded Holes Standard DOC ID REVISION A TYPE PORTAL OWNER: POSITION AUTHOR: POSITION Dan Boettcher Director of Engineering Richard Richardson Vice-Dir of Engineering SUBJECT: This specification provides drawing callout information and dimensions and tolerances for torch cut & drilled thru holes and drilled & tapped threaded holes. The machining of taper lock stud holes is specified in standard and is not covered in this standard. DRAWING CALLOUT: Non-threaded Torch Cut Thru holes: The callout that will be used on Kress engineering drawings will be as follows: The nominal holes diameter will be shown to the two places decimal. Default tolerance of ±.06 will apply. Examples: Ø.75 Ø X Ø 3.81 Non-threaded Drilled holes: The callout that will be used on Kress engineering drawings will be as follows: The nominal holes diameter will be shown to the three places decimal. Default tolerance of ±.010 will not apply to the holes diameter. Non-threaded drilled holes, especially after hardening, may deviate from the default tolerance (See table 1 below for acceptable holes tolerance allowances). If the hole is blind, the depth of drill will be shown after the holes diameter to the two places decimal. Default tolerance of ±.06 will apply to the depth of drill. Examples: (Thru) Ø.250 Ø THRU 6X Ø Examples: (Blind) Ø Ø X Ø TABLE 1 (Clearance Hole Tolerances) Hole Diameter Hole Tolerance Over Thru (Bolt Clearance) Hole Tolerance* (After Hardening) * These tolerances apply after hardening to holes produced to Bolt Clearance holes tolerance in the un-heat-treated condition. Page 1 of 6

2 Threaded Drilled holes: (Unified Screw Threads) The callout that will be used on Kress engineering drawings will be as follows: The nominal tap drill holes diameter will be shown to the three places decimal (See table 2 for tap drill sizes). Tap drill tolerances will be shown after the holes diameter (See table 2 for tap drill tolerances). If the hole is blind, the depth of drill will be shown after the holes diameter tolerances to the two places decimal. Default tolerance of ±.06 will apply to the depth of drill. A second line under the tap drill diameter will show the thread tap size & tolerance class. If the tap depth is blind, the depth of minimum full thread will be shown after the thread tap size & tolerance class to the two places decimal. Default tolerance of ±.06 will apply to the minimum full thread depth. For blind holes, the tap drill depth should be a minimum of six threads beyond the required minimum full thread depth. If a bottoming tap is to be used; the tap drill depth should be a minimum of two threads beyond the required minimum full thread depth or consult with Manufacturing for special cases. Examples: (Thru) Ø THRU 6X Ø UNC-2B THRU UNF-2B Examples: (Blind) Ø X Ø UNC-2B UNF-2B 1.88 Examples: (LH Thread) Ø X Ø UNC-2B-LH UNF-2B-LH Kress standard thread engagement is 1.0 times the nominal thread size for 100,000 PSI Yield Steel, 1.5 times the nominal thread size for mild steel, and 2.0 times the nominal thread size for aluminum. For tap depth up to 2.0 times the nominal thread size, manufacturing will use the standard tap drill shown in table 2. For tap depth greater than 2.0 times the nominal thread size, manufacturing will use an oversized tap drill based on recommended holes size limits per the table in the tapping section of the Machinery s Handbook. This is done to prevent tap breakage. If a part is to have a heat-treat operation after it is drilled and tapped, then a.005 oversize tap is to be called out on the drawing for those holes because the holes will shrink during heat-treat. Examples: Ø X Ø UNS-2B.005 OVERSIZED UNS-2B.005 OVERSIZED 1.50 Table 2 (Tap Drill Sizes & Tolerances Unified Screw Threads) Tap Size & Threads per Inch Drawing Designation Tap Drill Size (inch) Hole Tolerance (Inch) # UNF-2B.047 # UNC-2B #53 (.060) # UNF-2B #53 (.060) # UNC-2B #50 (.070) Page 2 of # UNF-2B #50 (.070)

3 # UNC-2B #47 (.079) # UNF-2B #45 (.082) # UNC-2B #43 (.089) # UNF-2B #42 (.093) # UNC-2B #38 (.101) # UNF-2B #37 (.104) # UNC-2B #36 (.107) # UNF-2B #33 (.113) # UNC-2B #29 (.136) # UNF-2B #29 (.136) # UNC-2B #25 (.150) # UNF-2B #21 (.159) # UNC-2B #16 (.177) # UNF-2B #14 (.182) UNC-2B #7 (.201) UNF-2B #3 (.213) UNC-2B F (.257) UNF-2B I (.272) UNC-2B UNF-2B Q (.332) UNC-2B U (.368) UNF-2B UNC-2B UNF-2B UNC-2B UNF-2B UNC-2B UNF-2B UNC-2B UNF-2B UNC-2B.766 Page 3 of 6

4 UNF-2B UNC-2B UNS-2B UNC-2B UNF-2B UNC-2B UNF-2B UNC-2B UNF-2B UNC-2B UNF-2B Combination Drilled holes: (Counter Bore) If a hole is a combination drill with a counter bore, a second line under the holes diameter will show the counter bore diameter. The depth of the counter bore hole will be shown after the counter bore holes diameter. Examples: Ø X Ø X Ø.531 v Ø v Ø ±.03 v Ø.88 ± UNS-2B UNC-2B.38 Combination Drilled holes: (Counter Sink) If a hole is a combination drill with a counter sink, a second line under the holes diameter will show the counter bore angle. The diameter of the counter sink will be shown after the counter sink angle. Examples: Ø X Ø X Ø.578 w Ø1.15 X 60 w Ø.38 ±.03 X 90 w Ø.694 X UNS-2B UNC-2B.38 Threaded Drilled holes: (American National Standard Pipe Threads) The callout that will be used on Kress engineering drawings will be as follows: The nominal tap drill holes diameter will be shown to the three places decimal (See table 3 for tap drill sizes). Tap drill tolerances will be shown after the holes diameter (See table 3 for tap drill tolerances). If the hole is blind, the depth of drill will be shown after the holes diameter tolerances to the two places decimal. Default tolerance of ±.06 will apply to the depth of drill. For blind holes, follow the recommended minimum blind holes depth (see table 3 for tap drill blind holes depth). A second Page 4 of 6

5 line under the tap drill diameter will show the thread tap size & thread series and form. If a controlled minimum tap depth or tight joint min. length is to be shown, the depth of minimum full thread will be shown after the thread series and form to the two places decimal. (See table 3 for tight joint min. length). Examples: (Thru) Ø THRU 2X Ø NPTF NPTF Examples: (Blind) Ø X Ø NPTF Ø NPTF.69 MIN Examples: (Grease Fitting) Ø X Ø NPSF.31 MIN Ø NPSF.31 MIN Table 3 (Tap Drill Sizes & Tolerances American National Standard Pipe Threads) Drawing Blind Hole Tap Drill Size Hole Tolerance Designation Depth Nominal Pipe Size ** ** *** ** ** ** ** ** ** ** ** ** ** ** NPT, NPTF, NPS, or NPSF *** For grease fittings, use 1/8 NPSF tap drill Ø.344 For hydraulic fittings, use 1/8 NPTF tap drill Ø.339 Tight Joint Min. Length For grease fittings with NPTF thread, tap NPSF to.31 for minimum full depth threads. For grease fittings with SAELT (Tapered Thread), tap unf-2b to.25 minimum full depth threads. Page 5 of 6

6 Threaded Drilled holes: (Metric Threads) The callout that will be used on Kress engineering drawings will be as follows: The nominal tap drill holes diameter will be shown to the three places decimal (See table 4 for tap drill sizes). Tap drill tolerances will be shown after the holes diameter (See table 4 for tap drill tolerances). If the hole is blind, the depth of drill will be shown after the holes diameter tolerances to the two places decimal. Default tolerance of ±.06 will apply to the depth of drill. A second line under the tap drill diameter will show the thread tap size & tolerance class. If the tap depth is blind, the depth of minimum full thread will be shown after the thread tap size & tolerance class to the two places decimal. Default tolerance of ±.06 will apply to the minimum full thread depth. For blind holes, the tap drill depth should be a minimum of six threads beyond the required minimum full thread depth. Examples: (Thru) Ø THRU 6X Ø.578 M6X1.0-6H THRU M16X1.5-6H Examples: (Blind) Ø X Ø M6X1.0-6H.25 M16X1.5-6H.94 Table 4 (Tap Drill Sizes & Tolerances Metric Threads) Tap Size & Threads per Inch Drawing Designation Tap Drill Size (inch) 06 X 1.0 M6X1.0-6H #9 (.196) 08 X 1.0 M8X1.0-6H J (.277) 08 X 1.25 M8X1.25-6H X 1.25 M10X1.25-6H X 1.5 M10X1.5-6H R (.339) 12 X 1.75 M12X1.75-6H Y (.404) 14 X 2.0 M14X2.0-6H X 1.5 M16X1.5-6H X 2.0 M16X2.0-6H X 1.5 M20X1.5-6H X 2.5 M20X2.5-6H X 3.0 M24X3.0-6H X 3.5 M30X3.5-6H X 1.5 M36X1.5-6H Hole Tolerance (Inch) REV DETAILED DESCRIPTION DATE A INITIAL RELEASE 01/09/2013 Page 6 of 6