How to Specify Cold Drawn Square Steel Bar with Corner Radius, Twist and Straightness
Short Answer
A production RFQ for cold drawn square steel bar should state the nominal side dimension, corner condition or radius, dimensional tolerance, squareness, twist, straightness, length, material grade, quantity and secondary operations. The side size may be described as the dimension across opposing flat faces, but a section drawing remains the controlling document. A description such as “19.5 x 19.5 square bar” is not enough when the part also requires four R2 corners, machining allowance or connector-specific holes.
Technical Facts: RFQ Fields That Control the Section
| RFQ field | What to state | Why it matters |
|---|---|---|
| Side dimension | Nominal width across opposing flat faces | Controls the basic square section and downstream machining stock |
| Corner condition | Sharp, natural, controlled radius, or drawing-defined 4 x R value | Affects die design, assembly clearance and finished-part geometry |
| Size tolerance | State tolerance for each critical side or reference the drawing/standard | “Cold drawn” alone does not define the required tolerance |
| Squareness | State any angular or diagonal control required | Important for connector blocks, sliding parts and machined datum faces |
| Twist | Maximum permitted twist over a stated gauge length | Affects automated feeding, fixturing and assembly |
| Straightness | Maximum deviation over the specified length | Affects cutting, machining and repeated assembly |
| Length/end condition | Random or fixed length; saw-cut, chamfered or drawing-defined ends | Changes processing, packing and downstream cycle time |
| Grade and documents | Exact grade, standard, MTC and inspection requirements | Prevents unapproved cross-standard substitution |
What Does 19.5 x 19.5 mm with 4 x R2 Mean?
On many mechanical drawings, 4 x R2 indicates four corners with a nominal 2 mm radius. The buyer’s drawing must still define the allowed radius tolerance, measurement method, datum faces and any machining allowance. Junxiong will not treat a shorthand note as approval to change the finished section.
For the cabinet frame three-way connector application, the correct buying terms are closer to cabinet frame connector blank, cabinet tee connector steel blank or enclosure frame connector block material. This is more precise than searching for a general electrical cabinet supplier.
Buyer Checklist for a Square Bar Quotation
- 2D cross-section drawing with side dimensions and all corner radii.
- Material grade and governing standard.
- Critical tolerances, squareness, twist and straightness.
- Fixed or random length and end condition.
- Machining allowance and finished-part drawing.
- Cutting, drilling, punching, threading, galvanizing or other requested operations.
- Batch quantity, annual demand, inspection and MTC requirements.
- Destination country and export packing requirement.
Common RFQ Mistakes
- Sending only a nominal square size without corner information.
- Using “tight tolerance” without a numeric or standard-defined limit.
- Omitting twist and straightness when the bar feeds into automatic equipment.
- Calling a custom connector blank a generic cabinet product.
- Assuming Q235B, S235 or another market grade can be substituted without drawing and certificate review.
- Requesting a finished connector while providing only a raw-bar sketch.
Junxiong Supply Boundary
Junxiong can review cold drawn square bar and custom-profile requirements by drawing, including agreed cutting, drilling, punching, machining or surface treatment. Every secondary operation and finished-part responsibility must be confirmed in the quotation. A representative product photo does not replace the approved drawing or MTC.
See cold drawn square steel bars, the 19.5 x 19.5 mm cabinet tee connector blank application, and custom cold drawn profiles.
Frequently Asked Questions
Is across flats the correct way to specify square bar?
The dimension is measured across opposing flat faces, but square bar is normally ordered by nominal side size. The drawing should also control corners, tolerance, squareness and twist.
Can a cold drawn square bar have controlled corner radii?
Yes, a square section may be reviewed with sharp, natural or drawing-defined corner radii. Feasibility depends on size, grade, tolerance, quantity and die design.
Does 4 x R2 always mean exactly 2 mm on every corner?
It commonly indicates four nominal R2 corners, but the drawing must define tolerance and inspection. Do not approve production from shorthand alone.
What should I send for a 19.5 x 19.5 mm connector blank quotation?
Send the section and finished-part drawings, Q235B or required grade, 4 x R2 requirement, tolerance, cut length, hole/thread details, quantity and destination.