Is there a guideline for how many hours a soldier can be on extra duty per day (e.g. # of hours on a duty day, non-duty day, etc.)?

No as long as it doesn't carry on to the next day. They can do extra duty from the time they get off until 2359 of the current day, or from prescribed time of showing up until 2359

That's a very good question. I know during basic we would pull extra duty once or twice during basic. The old standard was you only need four hours of rest in twenty four hour period. I don't know if that's still effect. I have never pulled extra duty besides basic. I know most of the people I had that did extra duty were on article 15 duty. You could always tell who was on that by the people in uniforms on the weekend or late in the afternoon after duty hours.

Well I think you have enough answers. But you should have a command policy letter at some level (Company-CORP) within your chain of command that covers this. If you don't have it, then your rank suggest that "you know" everything in the Army doesn't have an exact black and white answer. They leave room for you to climb out of a hole or hang yourself by the same rope. Be smart and make an informed decision. When you can't make a proper decision is when you go seek advice or guidance from your chain of concern. I've pulled more then my fare share of extra dutie from all levels of UCMJ and as corrective training over my first four years in. I'll tell you to be fare and let it be a learning tool for your soldiers as it is designed for. They'll respect you for it and less chances of being caught up in false claims (Soldiers be having IG on speed dial). But in the end you have your backbone (chain of concern), policy letters, Jag and "Regulations" that govern how you conduct extra dutie. Put it to use and see what happens.

Maybe you can plug enough keywords in Google that you may find it. SSG (Join to see)

I have looked through ar 27-10 I could not find anything about hours only how many days are authorized which I am already tracking

I think that would be covered under UCMJ manual. Under punishment, other than that I don't know where you get the answer. You could also contact the local JAG office, I vaguely remember something about 6-8 hours rest per 24 hour period but that may have just been talk.

During the time in which I served in the Army, the "HMFIC's", lol, were only required to give Service Members under their command 4 hours of rest in a 24 hour period. He could basically have the Service Members do absolutely anything during the other 20 hours to ensure that the daily operations of the Unit were met. One thing all Service Members need to understand is that they are on duty 24 hours a day, 7 days a week, 365 days a year as soon as you raise your hand and take the oath and sign your name on the line.

The answer depends on how you are approaching the issue.

If you are asking if there is a mandated sleep schedule (downtime), like mandatory crew rest or maximum flight time per week, there are regulations that apply to that. If you are asking if there are maximum work hours per week, it gets much more vague because operational requirements are fluid.

If we are speaking about Punishment or Corrective action, the UCMJ comes into play and then the type of Duty as well and the number of hours are strictly defined in the proceedings.

In essence, how the issue is approached can affect the outcome. Additionally, things can change if we are talking about individuals vs. groups. If the unit stays until midnight vs. keep PFC Benotz until midnight.... there's a huge difference (perceptually).

As far as I can remember there is not a set number or guideline. It was usually left up to whoever was placed in charge over the unfortunate soldier. Usually that would have been the Plt. Sgt. And Squad leader during the day and the CQ at the end of the day. The soldier usually had to pray that those in charge where not hardcore.