Recommend a boring bar for mass material removal

Zahnrad Kopf · Sep 22, 2017

We have a turning job that will require installing a 4.5" bore in solid material, among other ID and OD features. Due to timing, there is no time to entertain having the blanks water-jetted to a nominal bore size for cleanup in the turning center. Plus, the price won't allow it.

So, with that said we're looking for recommendations on a boring bar and insert combo that might help us remove material faster than we might normally. Machine is 15HP spindle with gear drive transmission, so I think the power is there. And, it's as stout as any other machine in its size range that I have ever run. So, I'm not worried about that. However, since the vast majority of what we do is typically MUCH smaller and not usually removing this much material, I'm not really sure what I can expect to achieve. Right now, I am thinking to hold it in Pie jaws since I am only going to get .500" to hold onto. ( which obviously will also have effect on how large a cut we can take ) Part gets flipped for 2nd op install of feature on other face.

Material is 4140 Pre Hard. 6" diameter, solid. 2.125" thick. Any recommendations on a tool/insert combo?

Thanks.

Milland · Sep 22, 2017

For a slug that large in diameter and that short, I'd look into trepanning. Might be able to find something off the shelf that'll work, or even design a tubular holder for parting tool inserts.

Mtndew · Sep 22, 2017

Are you going to be using a large indexable drill to make a hole first?
The Allied drills from Carbide Depot are truly a steal for how well they perform.
ALLIED REVOLUTION

Then I would use a 2" bar from Sandvik with a CNMG 432 insert.
2" boring bars are NOT cheap lol.

DMF_TomB · Sep 22, 2017

spade drill make a 2.5 or 3" dia hole is a good start.

Zahnrad Kopf · Sep 22, 2017

Milland said:
For a slug that large in diameter and that short, I'd look into trepanning. Might be able to find something off the shelf that'll work, or even design a tubular holder for parting tool inserts.

Thank you. That's a great idea that I had forgotten about. Any specific recommendations?

Mtndew said:
Are you going to be using a large indexable drill to make a hole first?
The Allied drills from Carbide Depot are truly a steal for how well they perform.
ALLIED REVOLUTION

Then I would use a 2" bar from Sandvik with a CNMG 432 insert.
2" boring bars are NOT cheap lol.

I'm not sure I can get a 2" bar in there. ( long story ) Actually had to make a tool block to use bars from 5/8" to 1", and am making more shortly. My preliminary plan is to drill with 1" - 1.5" insert drill ( because it's what we have ) and then bore from there.

However, I'm definitely open to suggestions and willing to entertain them. I'm going to go look at those Allied drills shortly. Thank you.

Bobw · Sep 22, 2017

That's only a little better than 30 cubic inches, that's not a whole
heck of a lot. If you can use all your HP, be like 3 minutes.

Punch the center with the biggest insert drill you have.. Then maybe a 1.5"
bar hanging out 3" or so.. At that size, you have your pick of insert..
CNMG's are CHEAP.. Then get busy...

As for holding it.. Might be best to get a good solid bite on the OD to "make tubing"...
Then save the dainty work holding for the finish work. Though, its short, so holding on a
1/2" shouldn't be to bad, and all your forces will be toward the back of the chuck.

dodgin · Sep 22, 2017

If you need a drill we use some 3"+ "quad" drills from Ingersoll to plug big holes in first, and they work great. We also have some Metcut and Performax by Seco that we use routinely and love, but not sure if they come bigger than 3".

For boring I'd say check out a Mitsubishi S-MCLN, 2" diameter boring bar, with the CNHX insert. We run these on our big Doosan at around 700 SFM, .020 IPR and a .250" DOC. Looks like you'll be able to keep it short and rigid and we've found that Mitsubishi makes affordable tools that do well for hogging material on the lathe.

Finegrain · Sep 22, 2017

1. Drill as big a hole as you dare, preferably something that will allow a 1-1/4" boring bar to get to work.
2. 1-1/4" boring bar choked up in the holder
3. Inserts are personal preference but I am happy with my Korloy HMP NC3120's (I use CCMT) from Curtis Payne, aka ExKenna
4. Adjust feeds and speeds to suit

Regards.

Mike

DMF_TomB · Sep 22, 2017

just remember big spade drill needs hp. often have to make a smaller pilot hole and then make a 2.5 or 3.5" dia hole
.
you can have part move in vise, chuck fixture if you push too hard on it with too much hp. i have had happen before. that and trip the machine overloads trying to do too much at once

Milland · Sep 22, 2017

You could talk with these guys about trepanning tooling:

Trepan Tools

But I'd be real tempted to make a tubular sleeve, ramp the ends for chip clearance, cut insert slots at the top of the ramps for parting tool inserts (3 or 4), then use a plunge and retract method of cutting, perhaps 1/8" per pass. A tubular holder does a better job of controlling the slug then a "finger style" trepan tool.

How many of these parts do you have to make? If it's less than 100 I would just bore them.

litlerob1 · Sep 22, 2017

Depending on a couple factors. There are some massive hole making tools from KM that don't require a 2" holder, but will make you a 4" hole (not cheap). Also don't know if you have TSC.

As far as bars go, I would goto CNMG 432. But you could use a larger IC to go deeper in the cut #5 is a big insert. I've use 644 on a CNC lathe for a very specific job, I think .6 DOC and a pretty aggressive speed. BUT that was on an old Okuma with 55hp spindle. I think getting the biggest hole in there possible is the best consideration.

R

DMF_TomB · Sep 22, 2017

once had machinist wanted to buy carbide insert drill in big 2.5" size
.
hp going faster came out to like over 30 hp to drill hole with carbide at max. cnc only had 15 hp and spending over $1000. for drill is expensive way to learn about hp needs.
.
salesman rarely mention you going to need a bigger machine to run that drill at max. they just want to sell you the $1000. + tool

Dan from Oakland · Sep 22, 2017

Keep it simple- 1 1/2" insert drill to start- bout 1200-1400 rpm .003" feed, then a 1.25 MCLN boring bar with CNMG 432 insert- keep it short and rigid. Same as some of the suggestions above. If ya want to get fancy buy some hi zoot fancy inserts or just some garden variety Kenna KC850s will get the job done. With that setup you can go pretty much till you peg the load meter. Screw the spade drill- it won't be much faster but will drain your pocket book. Just my opinion.

Clive603 · Sep 22, 2017

Milland said:
But I'd be real tempted to make a tubular sleeve, ramp the ends for chip clearance, cut insert slots at the top of the ramps for parting tool inserts (3 or 4), then use a plunge and retract method of cutting, perhaps 1/8" per pass. A tubular holder does a better job of controlling the slug then a "finger style" trepan tool.

Following up on this idea Rotabroach carbide tipped hole saws have proper provision for chip evacuation and go out to 100 mm diameter so might be worth a look for your starter hole. Unfortunately only officially rated to 25 mm deep in a mag drill which isn't enough but I suspect there is a bit more clearance you could exploit in a proper machine tool. Maybe another brand goes a little deeper. Hafta flip the part and go easy on the feed but still probably a decently quick process overall compared to big drill and several boring passes.

Ordinary Rotabroach only goes to 65 mm Ø.

Clive

uncledenny · Sep 22, 2017

I`ve got spade drills up to 3 1/2,coolant thru and boring bars for sale. Appx. 1/2 price of new in excellent condition. The only kicker is they are M5 taper. If you are interested lemme know.

djm77 · Sep 22, 2017

I'd use a 2" u-drill which you can then use to rip out the bulk of the bore and finish with whatever normal boring bar you have. A nice 2xD u-drill will be nice and sturdy no you can give it some without deflection.

Sent from my iPhone using Tapatalk

kalim · Sep 22, 2017

you may buy or craft a holder for wnmg insert; SECO ( and maybe others ) sell such toys

for lower vibrations, clamp the tool as close as possible to turret face : this will reduce the momentun created by machining forces; the closer you are, the higher the specs

FK · Sep 22, 2017

I'm doing something similar; 6" bore 4.5" deep in 15-5. Using a 1.75" Seco insert drill. SD503-1750-525-1500R7-C Not sure what type its called. NOT A SPADE. One insert for the outside part of hole and the other insert for the inside part of hole. Anyway, I drill thru like normal then off set it in X for another .2 per side like a boring bar. Then go in with a 1.5" diameter CNMG boring bar. I first used a 1.125 drill because I was worried I wouldn't have enough Z axis poop. No problem went to the 1.75. Could have went bigger.

Anyway, your welcome to try one of mine if you like.

Milland · Sep 22, 2017

Another reason to like trepanning or Rotabroach (as mentioned) is easier chip control. Turning large amounts of metal into chips leads to time removing them from the machine. Doing a couple large Al jobs at the moment that are piling up barrels, but without solids removal as part of my strategy it would have been a lot worse...

dkmc · Sep 22, 2017

DMF_TomB said:
just remember big spade drill needs hp. often have to make a smaller pilot hole and then make a 2.5 or 3.5" dia hole

You use Spade Drills with a pilot hole?
Allied recommends no pilot hole with their spade drills.
The couple times I tried it, the spade drill chattered like mad due to no center support.

Anyway, a spade drill will be the most economical tool to use for this job.
Even if you slug them up in an old turret lathe to drill them.

Recommend a boring bar for mass material removal

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