We use mostly ASTM A484 Table 12, and A108 Table A1.4 to check for straightness of 10' to 12' lengths of barstock. We've evolved from using string and a ruler for measuring the bend, to a 5' calibrated straightedge and feeler gages. However, we're still unsure as to how to take the measurement and interpret the results. Do we just measure the net bend, such as when it appears the last 3' of the bar is bent? How do we keep the 5' straightedge from interferring with the net bend? Do we average out the bend over the length of the bar? Any suggestions you can offer would be greatly appreciated.

Sue

Hi, Sue :bigwave:

How you measure it and interpret the results depends entirely on what amount of bend per however many units of length the process which uses the material can tolerate.

What are you feeding the barstock into? How tight are the guides, etc.?

Follow the directions in the ASTM Table. Anything over 1/8" variance over any 5 foot section (for Hot Rolled) puts the bar out-of-spec. You need not be concerned with the variance over the entire lengths unless your customer has required a tighter tolerance.

We use automatic bar feeders in swiss style machines so straightness is very important to us.
We put the bar on a table with three points to push the bar against. We then measure any bow with a rule. We don't see the need for accuracy greater than 1/16" so we don't bother with feeler gauges.

In the great majority of cases the bow is across the whole bar.
Once in a great while we'll get a bar where the bend occurs toward an end but our table will handle that.
We hold our suppliers to the appropriate ASTM standard for each material we use (brass, SS, and Al mostly) for automatic screw machine use.

I must say - this is a HUGE problem for us (on the order of 40 rejections in the last 4 months - mostly round and hex) and as I understand from a Star Micronics sales guy a lot of American companies are having issues with bent bar stock in domestic brass.