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Fixed Diameter Boring Tool for Mill

J

Jay Fleming

Hot Rolled
Joined
Aug 7, 2014
Location
Noble, OK
I'm trying to find out if there are commercially available boring tools with replaceable inserts that are a fixed diameter. I tried Google but I may not be looking for the right terms. Or is this more of a "make it as you need it" type of thing?

I have bearing pockets that I'm rough boring on a CNC Knee Mill and would either like to go straight to a fixed diameter tool (80mm and 1-5/8 OD) or move them to the manual mill for a second op, again using a fixed boring tool. buying multiple adjustable boring heads is a worse case scenario.

Jay
 
Jay,

Yes, Kaiser makes a whole line of them, duel insert, one 'roughs', one finishes. We used them to make motor housings back in the day. Best of luck,
Chris
 
Shelf mount cartridges are easier to make a pocket for than a Valenite EZ-Set or Sandvik equivalent.

The shelf mounts you either set by trial, with bench centers, or a presetter. There are two adjusting screws to them, axial and radial. No graduations unless you go with a Rigibore UFP, and the pockets for those are tougher to make than a standard shelf mount, plus they're alot more spendy.

The Ez-Set cartridges are graduated with a nice sized dial, but like I said, the pockets are trickier to make. Dependent on your insert and lead angle,you're going to set up your boring tool at and angle proper for the graduations to actually work. Most of them I've made are presented at 40°+- off of horizontal.

The pocket geometry is simple, a bore and counterbore with three screws 120° off countersunk so you have pull down on the cartridge, but your angle needs to right and the bores need to be a slip-fit, nothing more.

In your case, I believe I'd go with a shelf mount. Make your pocket so that you have minimal radial jack-out for the most rigidity. Put an insert in your cartridge and measure over the cutting edge and figure from centerline where your pocket floor needs to be for that cartridge to make that bore.

I'd shoot for a pre-load of .003" radially.
 
or, you could just take a piece of barstock, mill a slot in the end, drill and tap a few set screw holes, stick in a carbide tool bit and call it a day.
 
Are the Circle tools a true, interchangeable copy of the DeVlieg cartridges?

For the OP, yes there are off the shelf options. But when you say knee mill I get worried. Worried about things like spindle taper, rigidity, and range of acceptable length. You may be better off making a tool with an integral taper shank using replaceable boring cartridges. I would make it a twin bore unit (both set same diameter and depth). If your mill won't handle both inserts, you can remove one. Or you could set it up so one cartridge bores a smaller diameter, but the insert is about 3x the feed per rev further ahead than the larger boring insert.

If you are not familiar with dual cutting edge boring bars, you will be impressed how aggressive you can get with your feeds when the spindle load is balanced.

Here is a similar unit to what I am referring. This one is from Kennametal.

Screw-On Cartridges
 
Currently using (2) of Allied machine Cri twin heads..

Two heads required to go from 2.375" to 3.3125"

They work rather well for a SWAG. I actually thought the would be more trouble then their worth on a manual 18hp German milling machine.

Needless to say I'm a happy camper. They work rather well for my application.

AlliedMachine.com
 
Thanks for all the info, especially regarding the cartridges. Those seem like the way to go. The other offerings are too far out of the budget to be dedicated to one bore diameter for the rest of its life. Could someone post a pic of what they've done with the cartridges? I think I understand how they're to be assembled on an "arbor" but I would like to see how someone else did it.
 
Jay-

I can't post pics of the cartridge boring bars I make because I make them on the clock for someone else. Wish I could, some of the shit is crazy.

What's the machine and the spindle taper you're planning on running this job on? What mat'l, how much are you needing to bore diametrically, blind or through, undercut or radius at the bottom?
 
BridgeportinD2 said:
Jay-

I can't post pics of the cartridge boring bars I make because I make them on the clock for someone else. Wish I could, some of the shit is crazy.

What's the machine and the spindle taper you're planning on running this job on? What mat'l, how much are you needing to bore diametrically, blind or through, undercut or radius at the bottom?
Click to expand...

The machine is a Supermax CNC Knee Mill with CAT 40, or Supermax manual knee mill with R8. 6061-T6. If you're asking what diameter, 80mm and 1.625", or are you asking like .020" finish pass. Blind. Square-ish corner on the bottom, but up to .031 radius should be okay.
 
Jay-

I forgot to ask what depth the bore is, but if it's for a bearing race it'll be fairly shallow vs. the diameter unless there are details projecting. That means a short tool overhang, so even a bar held in a 3/4" or 7/8" collet on a Bridgeport type mill cutting aluminum with a small DOC will give good results.

How many bores are you planning on making with this setup?
 
You'll have no problem doing what you want with cartridge bars made for the jobs.

Do you heat treat, OD grind, have a dividing head or indexer?

You can get away with just making the boring bar out of 4140 prehard and turning the shank with no grinding, but make it straight and on-size.

In my world, the bars made of E4340 at 43-45 Rc. If you're planning on doing alot of bores and don't have HT at your disposal then consider making a sizing plate to go under the cartridge made of hardened tool steel, ground. This will keep the radial jack screw from digging into the pocket and shrinking the diameter with adjustments and tool pressure.

The mounting screw on shelf mounts are at 70°, or 20° off vertical. A simple and uncouth way is by placing the bar in a v-block and indexing with a protractor head and picking up the mount slot with a pin then spot with an endmill, drill and tap.
 
plenty of old devlieg microbore stuff on ebay, most have no idea what to make of it, so it goes cheap. Easy to set up for specific jobs, and IIRC they make indexable insert holders for them if you're doing longer runs.
 
BridgeportinD2,
Thanks for all the information but I think I've decided for now to get a couple cheap R8 boring heads and a couple indexable insert boring bars and get it done. May not be the cheapest route, although it could be, but by far the quickest and simplest after looking at all the options. Doing that will net me a tool for each bore for about $150 for each size and can be easily modified in the future.
 
Jay Fleming said:
BridgeportinD2,
Thanks for all the information but I think I've decided for now to get a couple cheap R8 boring heads and a couple indexable insert boring bars and get it done. May not be the cheapest route, although it could be, but by far the quickest and simplest after looking at all the options. Doing that will net me a tool for each bore for about $150 for each size and can be easily modified in the future.
Click to expand...

Jay-

Sorry about my last post, I must have deleted part of it concerning making the pocket before I posted it.:willy_nilly:

Sounds like you've got it figured out. At least with the boring heads you can get more use out of them if things change vs. having two cartridge bars with a very small range of adjustment, made for a specific bore.

I do have a few cartridges that I saved from the scrap hopper when they were 5S-ing the shop if you ever change your mind. I'd give them to you and help with making the bars if the time comes.

I own a Bridgeport and a dividing head, so if you didn't have the time or tooling to make them I could give you a hand there.

Let us know how things go.
 
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