EDM noob question

[PDSI Mike]

The company I work for just bought a used sinker EDM.

Mitek 45 ZNC (circa 2000)

It was given to me to figure out how to use it. I have ZERO experience with EDM other than a little portable crackerbox for burning out taps.

I have a manual that is a bad photocopy of a bad photocopy..... and it is written in Engrish

IE: For action begin to push button for white screen ON OFF of setting or lower setting.

Some sentences are even worse than that.

My question.....

How long should it take to burn a 1/4 inch keyway inside a 2 inch bore, 1/2 an inch deep?
One shot to size.
10 minutes?
an hour?
5 hours?

I know a good burn needs both rough and finish to properly hold tolerances.

I have it working, it is burning and "pretty close" to size but I don't know how fast it should be actually cutting.

Thanks!

[ltkettch17]

I can't find any information on that machine, but from what I'm used to - that burn should take about 45 minutes to an hour.

[PDSI Mike]

Thank you very much!

I need to push a little harder then..... fastest I have got is about 2 hours.

Just not sure how much is too much yet

I appreciate the help.

[ltkettch17]

2 hours is not unreasonable.

What over-burn are you using? Use the largest overburn (smallest undersized) electrode you can so you can maximize the power on your rough setting. I guess I should make sure that you are orbiting your electrode and not making several different sized electrodes. I'm just not familiar with that machine or its capabilities.

[PDSI Mike]

This machine does not orbit. Straight down Z feed is all it has.

I haven't had a chance as yet to try both rough and finish electrodes.

I'm using a .244 graphite to burn a .250 key..... just playing.... NOT real parts yet.

I've read that about .003 per side overburn is to be expected and that does somewhat fit what I have seen so far.

I've been cranking handles since 1977 so I do know my way around the shop but this EDM is a completely different animal.

Thanks for the input!