Offshore Boring Bar Mod For Boring Head

[PeterT]

Another experimental project. My boring head has 1/2" holes. Thus far I've been using Borite HSS cutters. For a whopping 18$C including shipping, I bought this CCMT insert boring bar off AliExpress which is quite similar to what I use on the lathe. Its a 16mm nominal diameter shank which is next bigger metric size as they don't do inches. I lopped it off (sacrilege!) & turned down the end. My 3J chuck didn't quite grip it properly due to the opposing 2 flats orientation, 4J chuck is better. Seemed like reasonably tough mystery material but nothing onerous.

I thought about making the turn down stub length so the bar would be flush against the boring head underside. Aside from aesthetics, I couldn't see a good reason as they bottom out in the hole. The Borites just extend the 0.5" shank & neck down from there. These have even more meat than a stock but I'll give it a bit of chamfer just for looks. Besides, if the bar ever rotated it would scratch my shiny boring head

I considered leaving the stub round in order to rotate to different position & effectively tweak the rake angle. But now I think I'll replicate the flat to preserve the tool angle. I figure if it works in the lathe it should work in the boring head. Also with a flat, any set screw marks will occur there vs. marring the round & maybe make tool removal problematic since its not hardened.

Anyway, the general idea was maybe I could make some custom sizes for reasonable cost using inserts I already use. The same principle should work for large cutting radii with bar held horizontally, although I'd have to get left hand if I ran in same direction.

 

[Bofobo]

I just picked up my boaring head! Could you be so kind as to provide a link to this lovely boaring bar? My old shop had many sized boaring bars, one at least specifically fit the boaring head but I'm thinking something exactly like what you've done here rather than spend on the el cheapo box of mild steel brazzed tip bars. Thanks

 

[PeterT]

Sure, here is the one I got. They are offered by a few different vendors with slight or no variation, but they seem generically the same best I could tell by pictures. This particular vendor was one of the least expensive. https://www.aliexpress.com/item/S16...32603661551.html?spm=2114.13010608.0.0.dMlRAf

Boring bars are also available in different inserts, so if you happen to prefer something else, or already have a different insert, you can probably find something similar. I'm not up to speed on tip geometry but as mentioned I have CCMT &they seem to cut nice for my application. For example Mesa sells a TPGB style which gives you 3 cutting corners vs. my 2. Not sure how insert prices compare. http://www.mesatool.com/products/boring-bars/
According to the blurb, they make theirs from tool steel & harden. Suspect a bit better than what I bought, but more $.

ps - be careful with some of those Chinese carbide brazed tip cutters for boring heads. I'm sure there are some ok ones but many have completely screwed up geometry with the cutting tip sitting at a (non) centering position that can't possibly cut properly. This has been documented in a few places. You can grind away at the carbide with a green wheel to correct but kind of defeats the purpose of buying them expecting ready to use. Also the shanks can be poor tolerance.

 

[Bofobo]

Yeah I found myself modifying the few that were close enough to decent, but my set is not 1/2 inch, they are smaller to fit my tiny lathe tool post (a cx704) so is non compatible. One solid example of spend a little to get a whole lot more. Thanks

 

[PeterT]

FYI - I retract what I said about using 4-jaw. I've got a smidge of runout & now I know why, The boss material under the insert area sticks out proud a bit from the overall nominal diameter. Just that bitty part. I suspect one of my jaws was touching this so has the possibility of not turning concentric to shaft. A better way is turn a donut with ID = shank OD, slit it & then use that as a collet to grip shank in 3-jaw.

 

[Dabbler]

Thanks for the link to Mesa tools!

 

[Bofobo]

Very interesting tooling for boaring bars there. Oops

 

[Bofobo]

My new Mesa boring bars arrived, I failed to recognize the orientation required for using the "side hole" of my milling head, need an opposing set. Whoops

 

[PeterT]

I guess the tool orientation for side mode or cross mode or whatever its called would be a left hand boring bar if head turning in conventional clockwise direction looking down from top. I've often wondered if you could just run the spindle direction in reverse with a RH bar...but I probably shouldn't suggest things I'm not familiar with. Will they exchange it for you?

 

[Bofobo]

I'll just order the lefty and call it a day, my mill does not run in reverse and I like the quality of the bars I ordered

 

[kylemp]

If you can use them I'd probably buy them off of you. What size are they?

 

[Louis Dusablon]

I use my boring head with 1/2 boring bar and I run in reverse works fine

 

[PeterT]

Finally got around to testing with (uncoated) insert on aluminum. Works totally fine, very nice finish. The AliExpress metal seems rigid & pocket seems to hold insert securely. I think the mass of the bar is helping rigidity wise, no measurable amount of material comes off with a spring pass. Well.. these are light cuts on aluminum, steel may well be different. Now I feel confident enough to order some more and make myself a progressive length series & maybe some LH bars for large bore/radius horizontal mode. I don't really have a large diameter project in mind, but may as well make them in a batch. For those I think I will turn down a longer cylindrical length for even more contact area inside the boring head, cant hurt. One thing I noticed is these AliExpress bars have a different size Torx screw than my other boring bars, so something to be aware of.