[KSky]

I need to cut some round parts that are basically "M" shaped on my cnc lathe. About 1.25 around and made from aluminum. I am thinking a round bar holder with a 55º Diamond insert, but the ones I can find have the insert at a right angle to cut the sides. I need one with the insert facing straight on. I can find a square holder, but that's not good for boring.

Any ideas here?

[Jim Dawson]

Hi neighbor. I'm in Sandy, Oregon.

I would just make a tool holder that would do the job. I built special tool holder the other day out of a 3/4 inch grade 8 bolt. You could also modify a square tool holder to work, would take a little surgery.

[KSky]

Howdy Fellow Oregonian.

I have to make several thousand of these, so I need something pretty rugged. I was thinking custom tool, but I'm not make 10K of them. Just enough to make it a big issue.

[Jim Dawson]

Not trying to be contrary here but a grade 8 bolt is pretty rugged and pre-heat treated. Or a socket head cap screw is roughly a grade 9, a bit tougher than a grade 8, different alloy. Or grab a chunk of 4150 or S7 and make a tool holder out of that. Heat treat and draw back to about a RC35. I have been known to build a special tool for a single part if I need it. If I had a few thousand parts to do, I would build 2 or 3 holders just in case.

BTW, I'm in the market for a small CNC lathe, maybe 5 to 7 HP spindle. Don't care if the controls are dead, I can fix that. If you happen to know of one.......

[KSky]

I might just give it a try, I guess I was reluctant as I have never made such a thing before.

What's the best way to go about it? Cut the front to get the basic profile and then cut the relief?

[Jim Dawson]

Ahhhh, as a old tool & die maker, I just see a project like that as just another tool. I'm assuming you have a CNC mill here. Just make the basic bar much like a boring bar, then profile the tool bit pocket. You'll need to drill a relief hole at the base of the tool bit for clearance. Use the smallest endmill you have to do the final tool pocket profile. I would use one around 0.078 or so. The after you have the tool bit fitted, then cut what ever relief you need on the holder to clear the radius of the part. The goal is to get maximum support on the tool bit, and still have clearance on the part.. I would first draw up the holder in your favorite CAD program,. and machine all the steps in your head before making any chips. At least that's the way I normally do it.

I hope all that makes sense.

[ToolHIT]

I'm not sure the exact specs of your internal cone shape you need to bore out and making your own bar like Jim suggested may be the best way to go but if you would like to go with a standard off the shelf item then we would have it. Below are links to Boring Bars designed for Internal Spherical Machining (or cutting a cone into your part) that holds a VBMT221 Insert in either a 1/2" or 5/8" Shank (we only carry them for 35 degree inserts, not 55 degree inserts).
1/2" Shank: https://www.toolhit.com/products/thc89319
5/8" Shank: https://www.toolhit.com/products/thc89317
Inserts for each bar for aluminum: https://www.toolhit.com/products/tkb07585

If these don't meet your specs then let me know and I can try to search for one that can.

Mike

[KSky]

That looks like it will work very well. And thanks for putting the link in there for the aluminum inserts.

I don't know about other people, but I really like it when vendors post replies with products that would fit my needs. I don't always have time to dig through tool catalogs and it's great when someone who knows their products steps in with a solution.

I'll be ordering these soon.

Kevin