Dimensioning A Slot Pattern
This information applies to the American Steel Industry.
Directly dimensioning each of the positions within the pattern to each other may be acceptable in some scenarios, but likely isn’t a very clear choice for larger feature patterns. The problem with this scheme is that it can be very difficult to determine the true accumulation of the tolerance stack-up. Within the Pattern command we are able to increment a feature through the spacing or size, we can control this using a dimension and even override individual instances. In this example we have a slot located on the origin and created a linear pattern going vertically above with 8 instances. The correct calculated values are 2.962 and.976 instead of the 2.972 and.986Quickly shows how to use GD&T to locate and size 'slots' or 'slotted holes' in. How do you go about dimensioning slots in drawings? In SW I would create the dimensions, edit the radius one to add SLOT at the begining and then select the length dimension to add it to the string. Then the dimensions were linked to the part and not just dumb text. I am not finding a simular functi. Same double-slit assembly (0.7 mm between slits); in top image, one slit is closed. In the single-slit image, a diffraction pattern (the faint spots on either side of the main band) forms due to the nonzero width of the slit. This diffraction pattern is also seen in the double-slit image, but with many smaller interference fringes.
Holes and Slots
Standard Holes
Standard hole sizes for bolts are made 1/16-in. larger in diameter than the nominal size of the fastener body. This provides a certain amount of play in the holes, which compensates for small misalignment’s in hole location or assembly, and aids in the shop and field entry of fasteners. In the absence of approval by the engineer for use of other hole types, standard holes shall be used in high strength bolted connections.
Although most holes for high-strength bolts are made 1/16-in. larger in diameter than the bolt body, certain conditions encountered in field erection require greater adjustment than this clearance can provide and approval from the engineer is required.
The maximum sizes of holes for bolts are given in the table below, except that larger holes, required for tolerance on location of anchor bolts in concrete foundations, are permitted in column base details.
Standard holes shall be provided in member-to-member connections, unless oversized, short-slotted or long-slotted holes in bolted connections are approved by the designer. Finger shims up to 1/4-in. may be introduced into slip-critical connections designed on the basis of standard holes without reducing the allowable shear stress of the fastener.
Oversize and Slotted Holes
When approved by the engineer, oversize, short slotted holes or long slotted holes may be used subject to the following joint detail requirements:
(1) Oversize holes may be used in any or all plies of connections in which the allowable slip resistance of the connection is greater than the applied load. Oversized holes shall not be used in bearing-type connections. Hardened washers shall be installed over oversized holes in an outer ply.
(2) Short slotted holes may be used in any or all plies of connections designed on the basis of allowable stress on the fasteners provided the load is applied approximately normal (between 80 and 100 degrees) to the axis of the slot. Short slotted holes may be used without regard for the direction of applied load in any or all plies of connections in which the allowable slip resistance is greater than the applied force. Washers shall be installed over short-slotted holes in an outer ply; when high strength bolts are used, such washers shall be hardened.
(3) Long slotted holes may be used in one of the connected parts at any individual faying surface in connections designed on the basis of allowable stress on the fasteners provided the load is applied approximately normal (between 80 and 100 degrees) to the axis of the slot. Long slotted holes may be used in one of the connected parts at any individual faying surface without regard for the direction of applied load on connections in which the allowable slip resistance is greater than the applied force. Where long-slotted holes are used in an outer ply, plate washers or a continuous bar with standard holes, having a size sufficient to completely cover the slot after installation, shall be provided. In high-strength bolted connections, such plate washers or continuous bars shall not be less than 5/16-in. thick and shall be of structural grade material, but not be hardened. If hardened washers are required for use of high-strength bolts, the hardened washers shall be placed over the outer surface of the plate washer or bar.
(4) Fully inserted finger shims between the faying surfaces of load transmitting elements of connections are not to be considered a long slot element of a connection.
Nominal Hole Dimensions
Anchor Bolt Holes
Hole sizes for steel-to-steel structural connections are not the same as hole sizes for steel-to-concrete anchorage applications. In the case of steel-to-steel connections, the parts are made in a shop under good quality control, so standard holes (bolt diameter plus 1/16″), oversized holes (bolt diameter plus 3/16″), and short and long-slotted holes can be used quite successfully. However, the field placement of anchorage devices has long been subject to more permissive tolerances (and often, inaccuracies that exceed those tolerances anyway and may require consideration by the structural Engineer of Record).
AISC published Steel Design Guide Series 1, Column Base Plates back in the early 1990s. At that time, it was recognized that the quality of foundation work was getting worse and worse. To allow the erector (and designer) greater latitude when possible, the permissible hole sizes in base plates were increased. These same larger hole sizes were included in the 2nd ed. LRFD Manual. The values there are maximums, not a required size. Smaller holes can be used if desired. Plate washers are generally required with these holes because ASTM F436 washers can collapse into the larger-sized holes, even under erection loads.
The larger hole sizes are primarily intended for the majority of base plates that transfer only axial compression from the column into the foundation. The anchor rods don’t usually do much after erection in that case.
To allow for misplaced bolts, holes in base plates are oversized. The AISC Manual of Steel Construction recommends the following oversized hole diameters for each bolt diameter:
Anchor Bolt Hole Dimensions
AISC, Steel Design Guide Series 1, Column Base Plates, suggests that using oversize holes meeting these criteria may still not accommodate field variations in anchor bolt placement and suggests adding 1/4 in. to the hole diameter listed. The guide recommends using a heavy plate washer over the holes. The AISC Structural Steel Educational Council cites the following example: “If bolts are misplaced up to 1/2 inch, the oversized base plate holes normally allow the base plate and column to be placed near or on the column line. If the bolts are misplaced by more than 1/2 inch, then corrective work is required.”
Based on AISC oversize holes, the AISC Structural Steel Educational Council recommendations, and concrete contractor anchor-bolt placement techniques, ASCC (American Society of Concrete Contractors) concrete contractors recommend the following tolerance for each bolt location:
- 3/4-in. and 7/8-in. diameter bolts: ±1/4 in.
- 1-in., 1-1/4-in., and 1-1/2-in. diameter bolts: ±3/8 in.
- 1-3/4-in., 2-in., and 2-1/2-in. diameter bolts: ±1/2 in.
End of article.
Dimensioning A Slot Pattern Blocks
PartDesign PolarPattern |
| Menu location |
|---|
| Part Design → PolarPattern |
| Workbenches |
| PartDesign |
| Default shortcut |
| None |
| Introduced in version |
| - |
| See also |
| None |
|
Description
The polar pattern tool takes a selected feature and creates a set of copies rotated around a chosen axis. Starting with v0.17, it can pattern multiple features.
Above: a slot-shaped pocket (B) made on top of a base solid (A, also referred to as support) is used for a polar pattern. The result (C) is shown on the right.
Usage
To create a pattern:
- Select the feature (introduced in version 0.19 or several features) to be patterned.
- Press the PolarPattern button.
- Define the Axis. See Options.
- Define the Angle between the last copied occurrence and the original feature.
- Set the number of Occurrences.
- If you have several features in the pattern, their order can be important, see the image below. introduced in version 0.19 You can change the order by dragging the feature in the list and you will see the result immediately as preview.
- Press OK.
Effect of the feature order
To add or remove features from an existing pattern:
- Press Add feature to add a feature to be patterned. The feature must be visible in the 3D view:
- Switch to the Model tree;
- Select in the tree the feature to be added and press Spacebar to make it visible in the 3D view;
- Switch back to the Tasks panel;
- Select the feature in the 3D view; it will be added to the list.
- Repeat to add other features.
- Press Remove feature to remove a feature from the list, or right-click on the feature in the list and select Remove.
Options
Axis
When creating a polar pattern feature, the PolarPattern parameters dialogue offers different ways of specifying the pattern rotation axis.
Normal sketch axis
An axis being normal to the sketch and starting in the origin of the sketch of the feature being used is taken as axis for the polar pattern.
The pattern direction can be reversed by ticking 'Reverse direction'.
Horizontal sketch axis
Uses the horizontal axis of the sketch for axis.
Vertical sketch axis
Uses the vertical axis of the sketch for axis.
Custom Sketch Axis
If the sketch which defines the feature to be patterned also contains a construction line (or lines), then the drop down list will contain one custom sketch axis for each construction line. The first construction line will be labelled Sketch axis 0.
Base (X/Y/Z) axis
v0.17 and above Select one of the Body Origin's standard axis (X, Y or Z) as axis.
Select reference...
Allows you to select either a DatumLine or an edge of an object or a line of a sketch to use for axis.
Angle and Occurrences
Specifies the angle to be covered by the pattern, and the total number of pattern shapes (including the original feature). For example, four occurrences in an angle of 180 degrees would give a spacing of 60 degrees between patterns. There is one exception: If the angle is 360 degrees, since first and last occurrence are identical, four occurrences will be spaced 90 degrees apart.
Limitations
- See linear pattern feature limitations.
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Dimensioning Slot Pattern
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