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1
SPRING ALIGNMENT DOWELS/BUSHINGS
2
Spirol’s roll formed hardened bushings are designed to meet oneor more of the following objectives:
� Align mating components,� Eliminate drilling of a separate bolt hole,� Protect bolts from shear loading, and/or� Maintain joint integrity
Although these hollow, lightweight bushings are not precision groundand do not require precision holes, thus saving in component and holepreparation costs, they are capable of precision alignment if the designguidelines are followed. Further savings can be achieved by using theinside of the dowel bushing for the bolt and thus eliminating the cost ofa separate bolt hole. This design concept also protects the bolt fromshear loads perpendicular to the bolt and isolates the forces on the boltto tension loading. Shear forces acting on a bolted joint cause the jointmembers to slip back and forth, which causes the bolts and nuts torotate, reducing the pre-load tension. This is particularly the case withshort bolts with a reduced clamping distance.
SPRING ALIGNMENTDOWELS/BUSHINGS
CHALLENGE US!
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SPRING ACTION
The diameter of the bushing is slightlylarger than the hole. The spring actionof the bushing allows it to be installedinto a drilled or cored hole and assumethe diameter of the hole. It is self-retained once installed.
PRODUCT FEATURESAND BENEFITS
CONTROLLED INSIDEDIAMETER
The inside diameter of the dowelbushings is designed to provideclearance for a bolt through the bushingfor the purpose of fastening the alignedcomponents together. This isolatesthe bolt from the shear loading andincreases the joint integrity. It alsoeliminates the cost of a separate hole.
STAGGERED SEAM
The staggered seam preventsinterlocking, making these bushingssuitable for automatic feeding andeliminating the need to separate themduring manual assembly.
LEAD-IN CHAMFERS
The beveled chamfer around the entireperiphery of the bushing is designedto facilitate ease of insertion and toavoid skiving of the bushing duringinstallation.
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SPRING ALIGNMENTDOWELS/BUSHINGS
Spring alignment dowels are used to accurately locate components with respect toeach other. They are formed around arbors to assure roundness. It is recommendedthat one half the hole tolerance be used for the fixed location of the dowel and one halffor the hole in the mating part.
Dowel bushings are used to locate components in conjunction with bolts which passthrough the inside of the bushing after it has been installed. Separate holes for locatingpins are eliminated. The hardened bushings also absorb shear loads, isolating the boltsfrom these forces.
Part Number: Product Type, Size x Length, Material, Finish, SeriesExamples: BUSH .250 x .500 BK DB100 BUSH 10 x 20 BT DB100 BUSH .500 x 1.250 BK SD200 BUSH 10 x 20 BR SD200
L
O.D.
Standard Lengths Note: .750” size does not require a staggered seam pattern to prevent interlocking.Larger and special diameters are available upon request.
The chamfer on dowel bushings and spring dowels is designed to facilitate insertion into minimum specified holes.
Series DB100 - Dowel Bushings
Max..255.318.396.474.630.786.937
Length
Min..250.313.391.469.625.781.932
Min..260.323.401.479.635.791.942
Max..270.333.411.489.645.801.952
.022
.028
.035
.042
.057
.070
.083
1,660 lbs.2,670 lbs.4,200 lbs.6,070 lbs.
11,050 lbs.16,500 lbs.23,300 lbs.
Min.SingleShear
NominalBolt
Diameter
O.D.Tolerance Range
for Holes WallThickness
#10.250 1/4.312 5/16.375 3/8.500 1/2.625 5/8.750 3/4
.3753/8
.5001/2
.7503/4
1.0001
1.5001-1/2
1.2501-1/4
INC
H
1.7501-3/4
LENGTH TOLERANCE+.000" -.030"
7.4 kN11.4 kN18.7 kN28.5 kN46.5 kN56.1 kN73.5 kN
MinimumSingleShear
5mm6mm8mm10mm12mm14mm16mm
LengthNominalBolt
Diameter
O.D.Tolerance Range
for Holes WallThickness
Max.6.868.18
10.4413.0115.6017.9020.35
Min.6.607.92
10.1812.7515.3417.6520.10
0.560.710.891.071.451.551.78
10mm 12mm 25mm 30mm 35mm 40mmMax.6.487.80
10.0612.6315.2217.5519.95
Min.6.357.679.93
12.5015.0917.4019.85
ME
TR
IC 20mm
LENGTH TOLERANCE+ 0.0mm - 1.0mm
Series SD200 - Spring Dowels
Max..255.318.380.505.630
Length
Min..250.313.375.500.625
Min..260.323.385.510.635
Max..270.333.395.520.645
.022
.028
.035
.042
.057
1,660 lbs.2,670 lbs.4,000 lbs.6,530 lbs.
11,050 lbs.
MinimumSingleShear
NominalDowel
Diameter
O.D.Tolerance Range
for Holes WallThickness
.250 1/4
.312 5/16
.375 3/8
.500 1/2
.625 5/8
.3753/8
.5001/2
.7503/4
1.0001
1.5001-1/2
1.2501-1/4
INC
H
LENGTH TOLERANCE+.000" -.030"
6.9 kN11.9 kN18.9 kN27.2 kN49.6 kN
MinimumSingleShear
LengthNominalDowel
Diameter
O.D.Tolerance Range
for Holes WallThickness
Max.6.58.5
10.512.516.5
Min.6.258.25
10.2512.2516.25
0.560.710.891.071.45
10mm 12mm 20mm 25mm 30mm 35mmMax.6.138.13
10.1312.1316.13
Min.68
101216
6mm8mm
10mm12mm16mm
ME
TR
IC
LENGTH TOLERANCE+ 0.0mm - 1.0mm
MATERIALB Carbon Steel AISI 1070-1080
DIN 177222 CK67-75BS 1449 CS70-80
FINISHK Plain, OiledT Zinc PlatedR Phosphated, Oiled
INSPECTION METHODSO.D. - MicrometerLength - Caliper
HARDNESSHV 420-545
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Doweling for Permanent Positioning
If components are located or positioned by methods otherthan the doweling itself, and the issue is to allow fordisassembly and then re-assembly with the componentsin exactly the same location – then it is recommended thatthe components be drilled together and the dowel installedin the assembled condition. During disassembly, the dowelmay be removed and reinstalled during re-assembly. Thismethod eliminates the need for hole tolerancing and holecenterline concerns. It provides for very accuratepermanent locating.
DESIGN GUIDELINES
Doweling to Fix Relative Location Of Components
The more common application is to use the dowels to fix the relative location of two or more components. In this situation,the dowels are partially installed in one component, the initial installation, and then holes in the mating component arepushed over the exposed end of the partially installed dowel. The following factors need to be considered for precisionlocation:
� Hole dimension tolerance
� Relative depth of initial installation
� Total length of the bushing
� True position of hole centerlines
These factors are interrelated and need to be considered together. The following general guidelines are helpful indetermining the best design in a specific situation.
� Precise holes with reduced hole tolerances increase the cost but also increaselocation accuracy and simplify the design considerations.
� Wider hole tolerances require longer dowels to assure a tight, non clearance fit inboth components.
� Hole tolerance should be minus in the initial installation hole and plus in the matingcomponent hole.
� The maximum hole tolerance should not exceed one half (1/2) of the recommendedtolerance range to allow for hole tolerancing of both holes within the tolerance range.
� Fixing the dowel location in a through hole can be achieved through length ofengagement and hole tolerancing, or both. Generally, an engagement of 60% ofthe total length in the smaller hole is recommended for the fixed location.
� If more than one dowel is used, holes in the upper recommended tolerance rangeallow for a wider tolerance in centerline location.
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DESIGN GUIDELINES
Precise Holes
If the holes are precise and the same in bothcomponents, such as honed or reamed holes with atolerance of .0008” or .002 mm, then the length of thebushing need only receive minor consideration forpurposes of precise relative location. We recommendusing the minimum specified hole in these situations.The bushing will assume the diameter of the initialinstallation hole and the unsized diameter of thenormally exposed end would compensate for thetolerance difference between the holes if any. If nointerference whatsoever is acceptable whenassembling the mating component over the exposedbushing, then it is recommended to keep the exposeddowel length to a minimum, or if practical, to push thedowel through the initial component to size theexposed end. In any event it is recommended toinstall at least two thirds of the total dowel length intothe initial hole so as to permanently fix the dowelposition.
Maximum Tolerance Holes
The maximum allowable tolerance is one-half thetotal recommended tolerance. This is still within thenormal production hole tolerance for drilled or coredholes. The smaller hole, that is the hole with theminus tolerance, should be the hole into which thedowel is initially installed. The larger hole, that is thehole in the mating component, should have a plustolerance. To illustrate: The total recommendedhole tolerance for an 8 mm dowel is 8.00 to 8.13.Take the approximate midpoint and split thetolerance. The smaller hole would be 8.00 to 8.06,the larger 8.06 to 8.13. The smaller hole used for theinitial installation will size the dowel but the protrudingunsized length of the dowel remains larger, with thediameter increasing as the distance from the holeincreases. It normally requires a protruding lengthequal to 1-1/2 times the dowel diameter for a dowelinstalled in a minimum hole to have a protrudingdiameter greater than the maximum hole. For an 8mm dowel in a 8 mm hole, that would require aprotrusion of 12 mm to have a dowel diameter at theprotruding end greater than 8.13 mm. The smallerhole in the initial installation helps in fixing thelocation of the dowel but it is still recommended thatthe greater length of engagement be in the smallerinitial hole. Therefore, in the example used here toillustrate the maximum hole tolerance situation, thedowel would be BUSH 8 x 30 BK SD 200.
EQUAL TO HOLE DIAMETER
≤ 1 OUTSIDE DIAMETER
≥ 60% OFDOWEL LENGTH
TOTAL HOLE TOLERANCE = ∅8.00 to 8.13 mmHOLE FOR FIXED DOWEL LOCATION = ∅8.00 to 8.06 mmMATING COMPONENT HOLE = ∅8.06 to 8.13 mm
∅8.13 MINIMUM (MAXIMUM HOLE DIAMETEROF MATING COMPONENT)
12 mm
18 mm
∅8.00 (SMALLEST DIAMETERWITHIN TOLERANCE)
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Centerline Tolerancing
If more than one dowel is used, centerline tolerancing forhole positioning becomes an issue. In situations with
precision holes requiring precision locating, thecenterline tolerancing needs to be accurate andsimilar to tolerancing used for solid dowels. A
tolerance of .0006” or .0015 mm is recommended.When a dowel is installed in a minimum hole, which
is recommended in these cases, the dowel gap isbutted and further spring action is very limited, if any.
Hole tolerance can be increased to provide for relaxedpositioning tolerances with some sacrifice of rigidity. The
centerline tolerance can be increased to the tolerance ofthe holes, or the smallest tolerance if the tolerances of the
holes are different. In the 8 mm dowel example used,the centerline tolerance can be .06 mm. The net holeat maximum misalignment cannot be less than thesmallest recommended hole; in the example, 8 mm.The misalignment will normally distribute itself
between the dowels.
If it is a dowel bushing application with a bolt passingthrough the dowel into a threaded component, the clearancebetween the minimum inside diameter of the dowel bushingand maximum bolt diameter needs to be enough tocompensate for misalignment. If these guidelines areused, the standard clearance will always be adequate atmaximum misalignment.
SPIROL APPLICATION SPECIALISTS ARE AVAILABLE TO MAKE RECOMMENDATIONSBASED ON YOUR REQUIREMENT OR TO REVIEW YOUR APPLICATION.
Blind Holes and Stepped Holes
Blind and stepped holes can be used for dowel location and stepped holes are generally used for dowel bushings usedin conjunction with bolts. Since blind and stepped holes only fix the dowel location in one direction, it is still recommendedthat the dowel be fixed into location by using the smaller hole and greater length of engagement.
Joint Integrity
Loss of joint integrity due to rotational loosening is triggered by vibration. Loads perpendicular to the axis of the bolt,particularly cyclic loading cause slip at the bolt head or the nut which translates into rotational loosening. Dowels,particularly dowel bushings, reduce or even eliminate rotational loosening. In this instance, the use of the smallest holepossible within the tolerance range is recommended to reduce dowel flexibility after insertion. The shear strength alsoneeds review. In static loading or a long cycle time between loads, maximum load should not exceed of 75% of theminimum shear strength. When the loads are in the form of severe vibration, 50% is recommended.
+ 0.06– 0.00
+ 0.06– 0.00
+ 0.06– 0.00
∅ D
∅ D
C
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APPLICATIONS
ENGINE HOUSING
ENGINE CAM SHAFT CAPS
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INTAKE MANIFOLD HOUSING
OIL PUMP ASSEMBLY
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OIL PUMP HOUSING
TRANSMISSION SOLENOID HOUSING
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SWITCH HOUSING ASSEMBLY
VALVE
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I N T E R N A T I O N A L
© 2003 Spirol International Corporation 15M 06/03 Printed in U.S.A.
e-mail: [email protected]
Canada
Mexico
Europe
U.S.A. Spirol International Corporation30 Rock AvenueDanielson, Connecticut 06239Tel.] 860.774.8571 Fax.] 860.774.2048www.spirol.com
Spirol West645 East Harrison Street, Suite 100Corona, California 92879-1347Tel.] 909.473.5900 or 800.776.9528Fax.] 909.273.5907www.spirolwest.com
Spirol International Corporation Shim Division321 Remington RoadStow, Ohio 44224Tel.] 330.920.3655 Fax.] 330.920.3659www.spirol.com
Ascutney Metal Products2637 US Route 5 NorthWindsor, Vermont 05089Tel.] 802.674.6721 Fax.] 802.674.6121www.ascutneymp.com
Spirol Distribution (Distributor Customers)30 Rock AvenueDanielson, Connecticut 06239Tel.] 800.321.4679 Fax.] 860.774.0487www.spirol.com
Spirol Industries, Ltd.3103 St. Etienne BoulevardWindsor, OntarioCanada N8W 5B1Tel.] 519.974.3334 Fax.] 519.974.6550www.spirolcanada.com
Spirol México, S.A. de C.V.Carretera a Laredo KM 16.5 Interior ECol. Moises SaenzApodaca, N.L. Mexico C.P. 66605Tel.] (81) 8385 4390 Fax.] (81) 8385 4391www.spirol.com.mx
Spirol Industries, Ltd.Princewood RoadCorby, Northants NN17 4ETEnglandTel.] 44 (0) 1536 444800Fax.] 44 (0) 1536 203415Tel.] 44 (0) 8003 890034 (Distributor Customers)www.spirol.co.uk
Spirol SAS21 rue de Baconnes51430 BezannesFranceTel.] 33 (0)3 26 36 31 42Fax.] 33 (0)3 26 09 19 76www.spirol.co.uk
FREE APPLICATION ANDINSTALLATION INFORMATION
COMPRESSION LIMITERS
SPACERS and TUBULAR PRODUCTS
ISO9001:2000 Certificate No. 11168
QS-9000 Certificate No. 5981 QS-9000:1998FM 64050
ISO 9002 Certificate No. Q 09419BS 5750
CaliforniaU.S.A
ConnecticutU.S.A.
England
Canada
In addition to our full line of Spring Alignment Dowelsand Bushings, we also offer a wide selection of standardCompression Limiters and Spacers/Tubular Products tomeet your assembly requirements. Contact Spirol fordetails.
Challenge Us!