Steel hardness?

[DRAHandyman]

I am a newbie to machining and have what many might think is a stupid question! I am boring a hole in a large piece of steel and am finding that some parts of the steel cut fine (good chips) and then it doesn't cut well and then it cuts fine again (all on the same pass of the tool bit)! It is as if there are parts of the steel that have different cutting/physical characteristics than others. Is this at all possible? It is like when you turn wood and come across a knot in the wood! The cutting characteristics change.

Am I doing something wrong?

 

[Latinrascalrg1]

Did you buy the steel from a reputable seller dealing Known material Type or is this mystery metal? What you are describing are characteristics of a low quality material thats used in things like exercise weights as a "Filler" so yes what you are describing is very much possible.

With that said, its also possible that you could be doing something that is causing a work hardening situation. Taking to light of a cut, Overheating the work, running to fast, using a dull tool, etc... are part of a long list of factors that can add to the problem.

 

[DRAHandyman]

I bought a large length of 3 1/2inch diameter scrap cylinder from a local scrap and new metal merchant here in the SF Bay Area. Had to get them to cut it up into smaller sections so I could fabricate what I am working on! They had a lot of this material that has accumulated over the years. I am wondering if it is caused by work hardening as you state. The area is under the steady rest that I am having to use and it does heat up. I really appreciate your comments. It helps me understand and hopefully fix the issue.