Is it just me?

[muddstopper]

Papa Jack
I don't think I would try hole saws bits for 1-1/2" thick metal. I recond it deponds on the hardness of the metal. .

I have drilled 4in holes in 1 1/2 flat bar using hole saws. Going slow and keeping the bit cool and stopping to clean out the chips is a must, but it can be done. Patience, Patience, Patience, get in a hurry and you will just burn up your saw. Water works pretty well as a coolant/lubricant in this type of situation. Oils (even cutting oils) seem to make the chips stick to the holesaw and doesnt let them run out of the groove being cut. A little compressed air while drilling also helps. On the lathe, I have predrilled with a twist drill and then finished opening the hole with a hole saw about 3inches deep, but that was only because I didnt have the correct tool to machine the hole size I wanted.

 

[JRP]

Hera is a rule of thum for drilling speed:

For softer steels, RPM use 400 divided by diameter. 1/2 hole = 800 RPM

Rpm = 400 / diameter

For harder steel use RPM = 200 divided by diameter.

There was not enough discussion on lubricants. Oil or cutting fluid of tap magic. lubricating fluid will reduce friction and also carries away heat.

Most made in USA bits are good. Unfortunately, most brands we associate with USA, such as Black and decker, Dewalt, Milwaukee are just importing Chinese. Look for made in USA, not just a once USA brand.

 

[CNC Dan]

There was not enough discussion on lubricants. Oil or cutting fluid of tap magic. lubricating fluid will reduce friction and also carries away heat.

lubricating oil and cutting oil are two different things.
Lubricating oil is made to prevent metal to metal wear, cutting oils ( high sulpher?) are made to prevent galling and lubricate at high pressures.

 

[chickenman]

One of the ways a cutting tool cools it self is by cutting into cooler metal, so not using enough feed creates more heat as the chips can't carry away enough heat.

Don't confuse this by thinking it should finish the cut in one revolution.

Learn to figure speeds and feeds or get the tables.