[Adamj12b]

I am trying to mill out a section of the saddle on my knee mill to allow room for a newly installed ball-screw system. I have the saddle bolted down to the table on my X2, and tried making a few passes last night. I am trying to create a recess to allow the larger nut to fit in.

I dont have any experience milling anything harder then aluminum, and not sure where to start. I know that it is better to use a 4 flute cutter on steel. The only 4 flute cutter that I have is a .5 inch HSS. Not sure how fast to feed, RPM, and DOC I should use.

Maybe somebody could hive me some ideas to get me moving in the right direction. Adam

[bilinghm]

Adam,

A few questions before I offer any suggestions: What kind of machine is the saddle from? Approximate weight? What is the size of the opening you are going to create/enlarge?

Bill

[Adamj12b]

The saddle is off an old jet jvm-830 knee mill. It is about 18 inch's in overall length, and is about 9 inch's wide. It weighs between 35 and 45 lbs. I need to create a rectangle pocket about 1.5 inch's wide and 1.75 inch's long, and about .225 inch's deep. There is already a .75 inch hole in the saddle right in the middle of where I need to cut my pocket. It was used for mounting the old brass nut. This pocket will not provide support for the new nut, just need to make room because it is alot bigger then the old brass nut.

EDIT: If this helps here are a few pictures of the machine. Fresh paint and new enclosure mounted to the side for the CNC conversion in the works. If you look closely on the second one you can see the hole on the right side of the saddle near 2 bolts.

-Adam

[bilinghm]

Cast Iron is actually pretty easy and pleasant to machine. Your 1/2" HHS end mill is probably a decent choice, although it may be dull by the end of the job. Carbide would be excellent, but not essential. I have machined tons of cast Iron with HSS. Cast iron is abrasive and come off in a granular powder rather than chips. Careful clean-up is important, cast iron powder is tough on lead screws and ways. Just recognize that you are operating near the physical limits of your X2, and proceed with care and caution. Check the chart for appropriate RPM and go towards the low end of the recommended range (500 to 600 RPM would probably work fine). Make your cuts conservative in both depth and feed rate, and plan on spending a fair amount of time slowly cranking.

Bill

[Adamj12b]

OK. My machine is cnc'd, so i was just going to let it run and take it down. I was thinking .005 DOC per pass and 5 IPM. Dose that sound ok?-Adam

[bilinghm]

Check out this calculator for RPM and in/min (thanks to Hoss for the link)