Thank you for the feed back. I did say very accurate in my first post and at that time had though the accuracy was down to my skill reading a frequency meter and selecting and soldering resistors which is qualitative.
But after that this whole subject of the variations in the 555 chip and the resistors mainly down to heat and volts came up, this was something I had not taken into account.
I was a bit concerned as I thought it may be a large variation may be 10 or 15%, but once I had looked at the specification as advised, and for a astable circuit there was a maximum of 3% from heat and for other 555 circuits only 1% which was ok for me and did mention.
I am how ever interested to find out what the generally variation for the whole thing whilst working - the capacitors, resistors, 555 chips and LED's together, as some may be drifting in one direction and others in the other direction.
so I am now going to commence building it and will take frequency reading when cold, working for 5 mins, 10 mins, 15 mins, 20 mins, hot room, cold room.
and will post the results on this thread as they may interest some people as in the spec I think it is a maximum rating and it is hard to know how all these different variations will affect each other at least it is for me.
I would like it to be accurate to about 3% between hot and cold. I don't need it to be accurate for my self and if I pass them on to friends I can let them know the variation from my tests.
I am also very interested if there is much variation when it is running warm and not due to the heat.

 

...so I am now going to commence building it and will take frequency reading...

This is often the best approach.

I don't know if you plan to use a breadboard or plan to go directly to pcb. If you are going directly to pcb, use an IC socket instead of soldering the 555 timer directly to the board. That way, you can test several chips to see if they all perform as needed since, as Audioguru used to say, "you can't buy an IC with 'typical' performance, you just get what they sell you".

 

I am going to use a breadboard but I think I will do as you say and use an IC socket. My soldering skills are not so good at this stage and I would guess its harder to burn an IC socket than a 555 chip, also at later dates it would be easier to fix. Thank you for that I did not know IC sockets existed.

 

Thank you, I just thought those 555s were more accurate than that.

Always helps to read from the Pros!

If you mean me, you got the wrong guy. I'm just a retired die maker try ing to learn a new skill.