Sage-Tips

Can you add a hem to a bend profile?

Adding a hem in the ‘middle’ of a bend profile can open the doors to a variety of profiles not possible without fasteners or welding. Even without sophisticated seaming machines a combination of two hems can create strong, tight joints with little or minimal fastening.

What is the minimum size or length of a hem?

The minimum size or length of a hem is going to b determined by your v opening of your die. It is going to be wise to check your hem length after bending because the final step of flattening the metal can be a bit un-predictable in terms of how it stretches and flattens.

What is a hem and why do I need one?

Hems can even be used to strategically double the thickness of metal in areas of a part which may require extra support. Hems used in the food service industry should almost always be closed for sanitary purposes (very difficult to clean inside the opening).

How do you calculate the allowance for a hem?

Attempting to calculate the allowance for a hem like this will just lead to frustration. Instead a rule of thumb of 43\% material thickness is used when calculating the allowance. For example if our material is .0598” and we want to achieve a 1/2” hem we will take 43\% of .0598, .0257 and add that to the 1/2” giving us 0.5257”.

What is the MRR of a hem tool?

HEM involves using 7-30\% of the tool diameter radially and up to twice the cutter diameter axially, paired with increased feed rates (Figure 4). Accounting for chip thinning, this combination of running parameters can result in noticeably higher metal removal rates (MRR).

What is Hemming and how is it done?

The term hemming has its origins in fabric making where the edge of cloth is folded back on itself and then stitched shut. In sheet metal hemming means to fold the metal back on itself. When working with a Brake Press hems are always created in a two step process:

How much Hem do you leave on a flat pattern?

For example if our material is .0598” and we want to achieve a 1/2” hem we will take 43\% of .0598, .0257 and add that to the 1/2” giving us 0.5257”. Thus we must leave 0.5257” on the end of the flat pattern to achieve a 1/2” hem.