Boring Bar Tool Set Up...?

[EmilioG]

I'm getting ready to bore my first holes in 1/2" 7075 aluminum. They will be 2" through holes.
I have an APT boring head and a borite 1/2" bar with a carbide insert. How do orient the tool blade to the opened hole? I may start with a hole saw then use an indicator to find center.

Should I square up the stock first?

I need a very accurate hole. 2.20"

This will all be done on a BP mill with an acurite II dro. I've never use the DRO either.
Please advise.

 

[ferlum]

If the position of the holes in relation to the edges of the workpiece is critical, you should absolutely square up the stock first. I would do it just for easier/more secure clamping in the vise (assuming you're using one) at the very least.

Square up your workpiece, find edges and zero the DRO on a corner. Then locate the first hole. Use your hole saw or whatever to start the hole. Without moving the setup, change to the boring head and bore to size. Or just note the coordinates and return to the location after all hole saw operations are done. I'm sure the DRO has more advanced functions but I've never used one either. I'm also sure it's accurate enough to return you to the center of a hole -- as long as you don't move the workpiece.

 

[EmilioG]

Great, good idea. After the hole saw, replace with boring head, but where or how do I place the bars cutter?
I will need to cut another .200"
After the 2" hole saw cut.

 

[kd4gij]

This video might help out.

 

[mikey]

How do orient the tool blade to the opened hole? I may start with a hole saw then use an indicator to find center.

I think I see what you're asking. As you turn the calibrated screw CW the head will move outward to increase the size of the bore you're cutting. This is accurate only if the boring bar tip aligns with this axis of movement. Simply align the flat of the bar with the center of travel of the boring head. If your head has a square edge, you can use an adjustable square to touch that flat and the end of the blade to align the boring bar tip. I hope this is clear. I tried to upload a pic but for some reason the site software isn't allowing me to do that today.

To cut, use a Sharpie and mark a small section of the bore and turn the head back and forth by hand while adjusting the feed of the boring head outward until you make contact. You will see a mark in the Sharpie mark. Now you're in contact with the work. Set a small depth of cut, make a pass and then measure the clean surface of the bore. Now you know what your starting ID is and can reset your depth of cut until you're at the target ID.

 

[RIMSPOKE]

Great, good idea. After the hole saw, replace with boring head, but where or how do I place the bars cutter?
I will need to cut another .200"
After the 2" hole saw cut.

THREE PROBLEMS WITH THE HOLE SAW .

THEY BUILD UP A LOT OF CHIPS WITH NO WAY TO CLEAR THEM .
THIS MEANS YOU WILL HAVE TO CONSTANTLY PULL IT OUT AND BLOW OFF THE CHIPS
OR THE ALUMINUM WILL PACK IN BETWEEN THE TEETH & LOAD UP THE SAW .
CUTTING FLUID HELPS GREATLY .

THE ONES I HAVE DON'T QUITE GO 2" DEEP . I HAVE DONE WHAT YOU ARE ATTEMPTING
BY GOING HALF WAY THROUGH AND FLIPPING THE PART FOR THE OTHER HALF .
IF YOU START WITH A 1/4" THROUGH HOLE , THE PILOT ON THE SAW CAN FOLLOW IT FROM EITHER SIDE .

HOLESAWS ARE NOT ACCURATE TOOLS . THEY RUN OUT & CAN MAKE AN OVERSIZE HOLE .
BE SURE TO LEAVE ENOUGH MATERIAL FOR A FINISH CUT WITH THE BORING BAR

 

[EmilioG]

Hey Mikey, thank you.
The diameter is 2.20", the aluminum plate is 3/8" and 1/2" thk. I'm making Albrecht Chuck clamps., a set for my C 160.
Both aluminum plates will have through holes. I still need to know, how do I place the cutting edge of the tool against the hole edge? If I don't use a hole saw, I will need to drill a large hole first, 3/4" with an S&D drill? Maybe use an end mill after to get the hole straight sided?

I'll also have to purchase a few more carbide indexable cutters. Which brand is recommended ?

 

[EmilioG]

Thanks to all for the great suggestions.
I'll post some photos when I finish the work. I'll probably have to do a few bores to get what I want.

Thanks.

 

[mikey]

I would use a hole saw to rough the bore. I've done this exact job a number of times and the hole saw works fine. I use stick wax lubricant for this and it goes right through aluminum. For the larger hole, a 2" saw would work. Once the hole is cut, do not move the table. Just replace the saw with the boring head and you'll be on center. Install the boring bar and bore the hole.

I suggest a solid bar for this, either HSS or cobalt or a brazed carbide bar. Even those cheap Chinese bars will work fine for this job.

Orient the bar as suggested above, touch off on one wall of the roughed out hole and set the adjuster screw for a small depth of cut (maybe 0.005"?). Start the boring head and feed it down through the part until you cut through; the bar will hit the side of the hole but since you've removed most of the material inside the hole it should cut fine. When your pass gets through the thickness of the material, raise the head and repeat the process. Keep going in small increments until you get a smooth cut all the way around the hole, then measure it to see where you are. Keep going with light cuts until you get used to boring with a boring head - it isn't hard and you'll get the idea very quickly. The idea is to measure carefully, dial in a cut, make a pass, measure and so on until you hit the ID you need.

You won't need the DRO for this job because once you drill a pilot hole for the hole saw you will not be moving the table.

 

[EmilioG]

Excellent. Thank you. I have a solid bar also, HSS. Why is the insert bit boring bar not as good though?
I'm think it's too small of a cutting edge for a large, smooth hole?

Do I face the cutting edge so it faces me, straight against the edge of the hole? After the hole saw, which will
probably leave a hole larger than 2", I have to go another .020" for the larger of the 2 clamps.
I'll go slowly with the cuts. What about RPM, 1000? 1,200? or adjust speed if I get any chatter?

Thanks Mikey. Great explanation as always. Thanks to all of the members. This is such a cool place.
A Brain-trust!