Holes through tubes - again!

[hotponyshoes]

Hi all,
Much like the post below I am needing to cut some holes through some tube.

I am using 316 stainless tube of 2 1/2" o/d and I would like to put some 2" holes in it. (so i can put the 2" tube inside the 2 1/2")

I have marked a line and the positions of the holes but whats the best way to cut the holes?

I have tried those hole saw type things, In my drill press they work ok but it is hard to hold the tubes steady (they are 5' long) so I have been doing it with the tube clamped to the bench and the hole saw in a hand drill.

I have got through the saws real quick unless I use the carbide coated 'grit' versions but these take ages to go through.

I am now thinking abuto clamping them to my mill table using a set of v blocks but what would be the best cutter to get for a 2" hole?

Thanks!

[matsuura]

You could drill as big as you can and then use a boring head or the hole saw on the mill slow rpm and oil

[DareBee]

Clamp firm to a drill press or mill and cut with a bi-metal hole saw.
SS must be kept cooled and lubed (LOTS OF CUTTING FLUID/COOLANT).
If it work hardens you are toast. Unless you wish to pay for EDM'ing

[ctate2000]

If you have a mill you should invest in an anular cutter. Also known by trade name Rotobroach. My spelling my be wrong.

These things look like beefy hole saws. Their intended use is with mag drills for structural steel in construction. However I have had great success on a similar job. I cut 1.5 diameter holes in 3 inch 304 tube. They will not work very well in a drill press. You have to have the rigidity of a mill spindle to cut on the radius of a tube.

[greg b]

If you dont have any v blocks try cutting some out of 1.5 mdf board they work great at holding tube and dont damage the surface ,clamping the tube in the milling machine is really the only way to go.If you use coolant with a good quality hole saw at a slowish speed and medium to fast feed you should be able to cut these holes fairly easy .Dont put the coolant near the mdf for to long.regards greg b.

[davereagan]

Buy a $30-40,000 CNC mill and interpolate the hole with a 1/4" endmill. :<)

[ImanCarrot]

What about this gadget?

http://www.victaulic.com/content/holecuttingtools.htm

I have no relationship with the company, just found it on google.