Try this. There are charts all over the place with different speeds and feeds. The people on this forum are all over the place on feeds and speeds due to the individual machines and how rigid/powerful.
1018 steel is about 100 SFM x 4 divided by cutter diameter. So 1/2 HSS end mill is about 800 RPM and 5/8" is about 600 RPM. With 1/2" endmill set at 800 RPM touch off and go .015 DOC on steel. Slowly start increasing the X feed rate while watching and listening. 1. if the machine starts vibrating reduce speed until right at edge and then 2-3 percent below that. 2. If the chips start turning dark color, slow down feed rate. The chips should be bright and curly cued. Light blue is to be watched, dark blue to black is costing you money.
If you make it all the way across and it looks good, increase DOC to .020 and try again. Maybe increase RPM by 50 and try again. Maybe decrease by 50 RPM. The only way to figure out feed and speed rate FOR YOU is to sit there and cut metal for a couple of hours. Soon you will learn what is best for your machine. When I use carbide end mills I jack up the speed a couple of hundred RPM. Also if you buy used endmills from Ebay, they will not be sharp and that will throw you off on the calculations. By a brand new 3/8" or 1/2" 4 flute end mill and try it against one that you have and see the difference. Also, unless you have a 2000 lb. Bridgeport or clone, you will not be able to cut like the You Tube guys. Almost all of cutter speed, DOC, IPM and material information is set for professional machines, not HF specials.
If you took all of a popular machine like the PM 25 that the readers here have and lined them all up, everyone would cut at a different speed and feed rate. Rule of thumb; If the machine is happy, I'm happy!!!
Charles