You should specify the type of machine you are referring to.
If you use a guillotine (shear) to cut steel plate you need to adjust the blade gap according to the type of steel and the thickness.
With mild steel you need to adjust the cutting gap to approximately 20% of the thickness. With stainless steel to about 10 to 15%.
The next adjustment is to get the sheet square in the machine, you may need to do a squaring cut first and then cut to the required length.
If you use a bending brake (press brake) to bend steel sheet you need to get the correct "V" opening of the bottom tool.
The "V" depends on the pressure of the machine and the thickness of the sheet.
The "V" opening also influences the inside radius of the bend.
Any good machine should have a guide table on the machine whereby you choose the best "V" for the job.
You must determine the bending allowance for the material. A quick rough estimate is that the inside dimensions of the finished item is the blank size of the job.
For repetitive bending you must set the bottom stop for the machine and lock it.
For a once off bend you may do an "air bend".
The most important factor to keep in mind is to set the force of the blade to the required force according to the machine table. Never exceed this (for the length of the bend) as it will damage the tools of the machine.
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