Boring Head Q's

C

cg 2005

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I need to purchase a boring head for a new project. Having never used one, I have a few questions:

1. When the description says it is a 2" or 3" boring head, does that refer to the maximum diameter that can be bored or is it that diameter plus 2 times the offset .

2. I cannot image how to use the horizontal bore rod hole found in some boring heads except as some type of fly cutter. What use is the horizontal bore rod hole?

3. Is it better to get a boring head that accepts 1/2" or 3/4" boring bars or a boring head that has an adapter to permit the use of both diameters?

4. Are boring heads typically run at the same rpms as a similar diameter fly cutter?

5. Would the maximum diameter of the boring head be be restricted the same as the mill's specification for the maximum size face cutter? Example: my G0704 manual suggest a maximum face cutter of 2 1/2 inches.

6. I reserve this space because I know I forgot something.

Thanks
 
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1. From what I can tell the size refers to the diameter of the head.
2.Typicley the side hole is used for boring larger holes. At least that is what I have used them for.
3. for the G0704 1/2" boaring bars will be fine.
4. not shure of the crect speeds but I have a 2 1/2" boreing head. I usly run about 400-500 rpm for ruffing then 800-900 for a finishing pass and take 3 spring passes.
5. 2 1/2" is a good fit for the G0704 I have boared 6" holes with mine.
6. If you can find a name brand at a fair price go that rought. I am using an import for now and it does what I need it to do.



Marty
 
1) I think that refers to the actual size of the boring head itself, which may also coincide with the largest hole you can bore with the vertical holes. The larger heads typically have 2 or 3 vertical holes for doing larger or smaller work, but I think that the largest diameter you can turn with the farthest vertical hole roughly coincides with the overall diameter of the head itself.

2) You can flycut with this hole, although only in limited circumstances since your tool will typically not extend lower than the head itself. It's useful for surfacing a cylinder, since there is a celarance in the middle for the head itself. It's also useful for boring a large hole, i.e. a hole much larger than the head itself.

3) The larger the boring bar, the less flex it has, and the more accurate your hole is. I'd recommend getting a head that takes 1/2" tooling, unless you're going to be doing lots of very small work. I find that for small holes I usually just use a drill/reamer and only break out the boring head for stuff over 1", at which point 1/2" tooling fits fine. You didn't say what size your mill is, however, and a head that takes 1/2" tooling might be too big for your mill.

4) I don't know what everyone else does, but I usually run mine pretty fast. Similar to a fly-cutter I suppose. You can calculate a proper sfm rate for the cutter as though it were in a lathe and use that to figure out your rpm.

5) No, you can run a larger boring head than your max recommended face mill. A face mill takes much effort to turn than a boring head or a fly cutter. I wouldn't go a lot larger, however. I'm guessing your Grizzly mill is the one you want a boring head for? I'd think you can turn a 3" head without trouble. You can take as light a cut as necessary for a large diameter, and you'll know when you're approaching "too big".

I bought the 3" Shars boring head last year for a job, the one listed here for $110.95 (202-8021):

http://www.shars.com/files/products/catalog2011/page100.pdf

It comes with a servicable set of cemented carbide boring bars and such. It's a little rough around the edges, standard pac-rim quality control, but it works ok. You won't be boring cylinders for an engine to .0001 with it, but you'll be able to hit any size hole from 1"-3" to within a few thou.
 
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Thanks for the replies. My number 3 question had a typo. I was actually asking about 1/2" vs 3/4" boring tool shafts.
 
If you're getting a head that takes 3/4" tooling, buy 3/4" tooling. I can't think of a reason to run smaller tooling and an adapter. Like I said, for holes too small to get a boring bar into I just drill/ream. The Shars head I bought takes 3/4" tooling, and I have never wished for smaller.
 
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