Is it legal to work employees 35 to 45 hrs call them part time to avoid giving benefits

In companies that provide optional benefits, that is those not required to be provided by law (e.g. dental insurance, vacation time, etc.), the line between full and part-time employment can be determined in whatever way an employer chooses. In other words, for these purposes an employer can define part-time employment in whatever way that makes sense for the business. The fact is that most work relationships are "at will" which means that an employer can set the conditions of employment much as they see fit absent some form of legally actionable discrimination or an employment/union contract to the contrary. That having been said, for legally mandated benefits the distinction between full and part-time employment is more important. For example, for rights under the ADA (Americans with Disabilities Act) or FLSA (Fair Labor Standards Act) for overtime pay, etc.

In companies that provide optional benefits, that is those not required to be provided by law (e.g. dental insurance, vacation time, etc.), the line between full and part-time employment can be determined in whatever way an employer chooses. In other words, for these purposes an employer can define part-time employment in whatever way that makes sense for the business. The fact is that most work relationships are "at will" which means that an employer can set the conditions of employment much as they see fit absent some form of legally actionable discrimination or an employment/union contract to the contrary. That having been said, for legally mandated benefits the distinction between full and part-time employment is more important. For example, for rights under the ADA (Americans with Disabilities Act) or FLSA (Fair Labor Standards Act) for overtime pay, etc.