First boring head selection advice?

[abarton]

I'm getting close to convincing myself that I need a boring head. But I've never even personally seen one in action. So, I have lots of questions.

My immediate need is to make some through holes in 1/4" thick 6061. Three holes will be 3/8" and three more will be 3/4". Yet another "hole" will be an arc of 1.5" radius where cutting will only be happening for about 30 degrees -- so it's an interrupted cut. I'd really like the 3/8" holes to be as closely positioned and sized as I can make them. (At least within .005, but hopefully better than that.)

Up 'till now I've been locating and pilot drilling my holes in one setup. Then for each hole I recenter the work on the rotary table and use an endmill to finish the hole to size. It's worked out successfully so far, but has taken me a really long time for each hole.

So, I'm considering getting a 2" or even 3" boring head. Something like this. But I'm not really sure what I need to get. I also see that I'll need a shank to fit my R8 spindle. And then some kind of boring bar tool thingie to plug into the bottom.

According to Enco, the 2" head can bore holes up to 2.5" in diameter. And I've read on this board that the 3" head with its 3/4" tool shank is sturdier in addition to having a larger max bore. But it costs a bit more. Has anyone bought one and wished they got the other?

I'm leaning toward getting the Criterion with the "buy it good and buy it once" philosophy. (Lesse, $388.91 amortized over the rest of my life is only 3.5 cents per day! Not expensive at all!) But I hear that the Chinese ones "aren't that bad" "for the money". Does anyone have opinions or experience one way or the other?

There are sets sold with a selection of carbide boring tools. The Enco set including the R8 shank, 2" head, and assortment of import boring tools is less than just the head and shank sold separately. I'm assuming that those boring bits are junk. McMaster-Carr has a similar set, but the boring bars seem to add quite a bit more to the total cost, so maybe those bars aren't junk? Maybe even worth buying?

I don't have much experience with using carbide. After reading other posts here, I'm completely sold on HSS tooling. But I can't seem to find for sale a ready-made boring bar to hold HSS cutters. Is carbide the way to go with boring heads?

Would it be reasonable, in order to save some money, for me to turn my own HSS boring bar holder out of some 1018 that I have handy?

If I did go with the carbide tools, I'd want C2 for aluminum, right?

I've heard that carbide doesn't like interrupted cuts. Would I not want to use carbide to cut a 30 degree by 3" diameter arc in the side of an aluminum part?


Those are all the questions that I can think of this morning. (I'm sure 20 more will occur to me just after I hit Post.) So, on this subject I'd like to solicit free wisdom, advice, opinions, anecdotes, rants, and funny stories.

Thanks for putting up with such a long-winded post,
Alexander Barton

[JimGlass]

I recomend the 3" boring head and R8 shank that ENCO has. I bought one years ago with a set of carbide boring bars for around $90. The head is made in Taiwan. It is very accurate.

I bought several 3/4 shank HSS boring bars over time. I know MSC has them. Warning, they are not cheap.

I inherited a 3" APT boring head that uses 5/8 shank boring bars. It is also a good boring head. I also have a 2" APT that uses 3/8 shank bars.
The 2" APT required some tweeking with the gib plate. The 2" APT is great for smaller holes requiring higher spindle speeds.

I also have a 2" un-named inport boring head that uses 1/2" bars. These usually sell (or did) for around $50. They are not bad heads either but the feed dial is calibrated 1:2. Dial in .010 and remove .020.

I have a mix of HSS and carbide tipped and solid carbide boring bars.

Jim

[John Evans]

Plus 1 for what Jim just said. A import 3" will do you just fine. I have a 2" import ,a 3 "BP and a 3.5 or so Chandler-Duplex boring/facing head. The BP is the most used,but a have a bunch of 1/2 " shanked tooling so the import gets used for the smaller holes too. Sleeves are available or shop made to allow the use of smaller shanks.

[Napper]

I have tried most brands of boring heads at work. I personally own 2 criterions, and 1 narex facing head. If you have the coin, buy the criterion you will never regret it. The criterion will barely notice the interupted cut. The off shore heads vibrate easily, and they lack consistancey when adjusting the feed screw. The fit of the dovetail and the accuracy of the feed screw in the criterion are superb. A word of warning regarding the criterion, the dovetail slide has 3 setscrews that secure or lock the dovetail in place. The center screw is the only one that is ever used. the two outside setscrews are for factory preloading, never adjust these. Use a R-8 adaptor for any boring head it is significantly more rigid than a 3/4 straight shank adaptor. For a choice of boring bars use worn Hss 2 flute endmills grind 1 flute off. Grind back relief of 1/4 of a degree up the length of the remaining flute and save a lot of money. For the home machinist carbide tipped boring bars look fancy but they are prone to chipping. Hss tooling will generally yield better machining results in aluminum. As for cutting the larger radius Use a short end mill as described above , insert into side of boring head and run mill in reverse. bore as usual. Make sure your boring head is really secure on your adaptor or it could unwind while you are making a cut. As per a previous post make sure you pay the up charge and buy a direct reading adjustment screw, ie .01 on dial = .010 on bore.

[GlennW]

I If you have the coin, buy the criterion you will never regret it.

Couldn't agree more!

Just spent a day with my DBL-202 and repeatability is dead on. It's an enjoyable little critter to work with, except for the two Allen wrenches required to run it! (Wolhaupter has it figured out as it uses knurled wheels turned by hand to set and lock the slide )

[schwabw]

No disagreements with what other posters have said, but I have the 2" Enco set with and R8 shank, and have had very good luck with it, including interrupted cuts. I generally use a dial indicator to adjust it.

Bill