Boring head for a mill - getting started

[WobblyHand]

Have a 2" boring head for my PM25. Took it out of the gloppy oil for the first time. It's sort of cleaned up now. I have 1/2" boring bars in HSS. It's pretty obvious they aren't ready yet for use. They are not sharp edged. My only frame of reference is lathe HSS tooling. Do I run them on a diamond hone on the surfaces to make the edges sharp? Where the edge should be one can see a bright line indicating it is flat and reflecting, not an edge.

This boring came with no instructions. I understand the basics, but is there anything I should watch out for as a first time user? My first application is an interrupted cut in low carbon steel. I have cut an arc (less than a half moon) out of some plates with a hole saw. I want to slightly enlarge the hole and clean it up with the boring head. I understand tiny cuts, but anything else to be aware of?

Thanks for any tips and advice! That hole saw was really eccentric! Haven't seen anything that off balanced in a while. About 0.1" wobble. Fortunately it was all at low RPM. The cardboard in the vise prevented any lift or movement. The line you see is when I readjusted the hole saw, trying to make it less eccentric. Didn't help. If nothing else, I'd like to use the boring head to "erase" the line and make it even. Really don't have to remove much at this point, but I'd like to do it by machine so it is identical.

 

[rabler]

I'll be interested in the answers you get, I've used a boring bar a few times, just enough to know I'm clueless. Getting the angle/rotation of those boring bars correct is important. I hand honed mine with a diamond stone. Those sets seem to be pretty brittle so proceed slowly. Use the shortest fatest one that'll work. You can use other tooling, even a lathe insert boring bar, in those heads, although I've had best luck with the HSS ones in terms of finish, if the angle is right.

 

[WobblyHand]

@rabler That makes two of us that are clueless!

 

[benmychree]

Also you might be able to use a lathe HSS tool bit in the cross hole of the boring head if the diameters allow it.

 

[WobblyHand]

Watched a video by Mr.Pete and Don of Suburban Tools. Both were informative, but Don actually both showed and described how to align the boring bar. Learned about doing a spring pass for a boring bar. In the notes on YT also read about increasing RPM to shave off maybe 0.0005". I'll have to try that sometime.

Did the cut. Finish isn't great, but I suppose it is pretty good for an interrupted cut and first try ever at this. The bit really wasn't sharp, but it was much improved over how I received it. The edges weren't banged up, but none of them were sharp. The arcs are more than good enough for what I need, so I'm happy. Was sort of intimidated by the imbalance so ran it at a low 400 RPM. Everything was controlled and only stalled the motor once. Once I tuned into the sounds of the cutting it was easier to maintain a slow but reasonable (manual) feed rate.

Have to say, there's a lot more to this than meets the eye. Some subtle stuff makes a big difference!

 

[benmychree]

What was the radius?

 

[WobblyHand]

I used a 2" head. The radius is about 1.05" or so.

 

[Mitch Alsup]

A couple of points on using a boring head.

a) the relief on the back side of the tool face determines how small a hole that can be bored.

b) when trying to take a big cut, the tool deflects in such a way as to take a larger cut than estimated--so sneak up on the final diameter.
{This is opposite from the way a tool deflects on the lathe while turning.}

 

[benmychree]

The speed of 400 RPM would be about twice too fast for HSS tools on that diameter.

 

[WobblyHand]

The speed of 400 RPM would be about twice too fast for HSS tools on that diameter.

Gosh, didn't even think of that. That would be 220 sfm or so, and I should keep it under 100? Have to put up a sticky in the shop for that. Lot's to remember. Have to check the bit then and see what kind of a mess I made.