##### What is recommended inside bending radius in sheet metal fabrication?

For hard materials (CRCA and stainless steel), Minimum inside radius is 0.7 times of sheet thickness. For softer materials (for example Aluminium) minimum inside radius is equal to sheet thickness.

##### What is minimum required Flange Length in Sheetmetal Bending?

Minimum flange length shall be equal to 4 times of sheet thickness plus inside radius.

Minimum Flange length = 4 X T (sheet thickness) + R (Inside Bend Radius)

##### What is minimum recommended Hole/Slot distance from Edge?

Minimum Distance = 3 X Sheet Thickness + R (Inside Bend Radius)

##### What are the general Tolerance followed during sheet-metal Design?

ISO 2768-m can be used as default tolerance.

##### What is bending allowance?

After bending total length (Length + Height) of sheetmetal part is not equal to Flat Length. This increase in overall length is known as bending allowance.

Flat Length = Length + Height – Bend Deduction

You can use this calculator to calculate sheet metal bending allowance

##### What is K-factor in sheet metal fabrication?

K-Factor is a constant, used to calculate the Sheetmetal flat length. Value of k-factor depends on material, Bend radius, sheet thickness and machines used. Mathematically K-Factor is a ratio of position of neutral axis and sheet thickness.Value of K-factor is always less than 0.5

##### What is Y-Factor in Sheet metal?

Y-factor is similar to K factor. It is used to calculate sheet metal parts flat length.

##### What are various surface finish operations done on sheetmetal parts ?

Following are commonly used sheet metal surface finish operations:

• Pre-Treatment : Phosphate Conversion Coating, Chromate Conversion Coating, Derusting, Descaling
• Powder Coating
• Anodising
• Plating: Zn Plating/Galvanising, Tin plating, Silver plating
##### What Factors affect selection of sheet metal materials ?
• Product IP-Rating
• Working Temperature
• Corrosion Resistance
• Required Part Strength
• Part Weight constraints
• Final Finish operation
• Part joining Methods (Riveting/Welding/Screw)
##### What are the reinforcement techniques used to improve sheetmetal parts strength?

Reinforcement techniques improves part strength in localized section.

• Bending: Bending in direction 90 degree to load applied, hem bend
• Forming tools: sheet-metal rib, louver, lance & Tab
##### What is the application of press tool in sheetmetal ?

Press tools are used in hydraulic, pneumatic & mechanical presses to produce stamped sheet-metal parts. Press tools can be classified based on operation: blanking, piercing, bending and forming.

##### What is stamping operation?

Stamping is a process of shaping sheet-metal parts using press tool. Blanking, punching, pressing, piercing, bending and forming operations are done with stamping dies.

##### What are various sheet metal manufacturing operations?
Various types of sheetmetal operation includes cutting, forming, joining and final finish operations:
• Sheet metal Cutting operations: Punching, Piercing,Perforation, Cutting off, Parting off, Dinking, Trimming, Shaving, Shearing, Notching etc
• Material Removal Operations: Deburring, Grinding
• Sheetmetal Forming: Straight bend, Angle bend, Hem bend
• Material Joining Operations: Welding (Tig, MIG, GAS Welding), Riveting, Folding, Screws
• Final Finish Operations: Passivation, Chromate Conversion Coating, Plating, powder Coating
##### What are various sheet metal assembly operations?

Following techniques can be used to join sheetmetal parts.

• Screws: self tapping screws, machine screws
• Welding : arc welding, TIG welding, MIG Welding
• Folding Techniques: Lap Joint, Hem Joint
• Riveting
• Press Fitting: PEM Inserts

Check out in detail about sheet metal assembly operations here

##### What is the application of dowel pins ?

Dowel Pins are used to align two or more sheet metal parts during assembly.

##### What are the effects of grain direction in sheet metal during bending?

Grain structure of sheet metal is aligned in rolling direction during cold rolling process. Bending in rolling direction in softer materials result in cracks. Therefore bending in the direction perpendicular to rolling direction is always preferred.

#### Conclusion :

To sum up, knowledge of sheetmetal design, materials, manufacturing and assembly process is required to  crack the interview. You can continue reading sheet metal interview questions part-2 here.

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