# Offset boring head.



## Brian Rupnow (Oct 25, 2008)

I bought an offset boring head for my milling machine last week. Not because I had any particular work in mind for it, just "Because". I ended up with a little "found money" ---Federal government had overcharged me on one of my taxes last year, and found it in their heart to send me a refund cheque!!!! I knew in theory how to use this tool---(I am a great reader and internet researcher), and I knew that sooner or later I would have need of it. It so happened that it came "sooner", as today when I was machining the bearing stands for my current "double horizontal" engine, I needed to bore them for an 11/16" o.d. ball bearing. What a nice tool to use!!! I have a collection of 1/2" shank carbide boring bars that I bought when I got my lathe last March, and they fit into the boring head. It doesn't like high speed, as it rapidly becomes "unbalanced" as you increase the offset, but it seems to work very well at about 650 RPM. It has a small dial on the face that you adjust with an Allen wrench to increase the offset of the tool. I didn't know what the different graduations signified, but a little trial and error showed that for each graduation on the dial it increases the bore diameter by 0.002". Its one more tool in my rapidly expanding "arsenal" of machining attachments, and I really like it. This is the only picture I have on file showing the tool in operation. The set-up leaves a bit to be desired in terms of "rigidity" (or so I've been told), so look at the tool, DON'T copy the set-up.


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## rake60 (Oct 25, 2008)

Nice boring head Brian!

By their very design they will show an off balance situation 
at some speed. That speed is dependant on the rigidity of the machine
they are used in. 

It beats the heck out of the old way of boring with a mill.
You would take a cut then mic the bore. If there was .019" left, an
indicator was placed on the tip of the tool, loosen up the screws holding the
tool, bump it out .0095" and take the finish cut.

It was much better balanced, and did work to a point.
Most bores were actually _finished_ with a burr gun. 

Cool Toys!

Rick


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## Brian Rupnow (Oct 25, 2008)

What the heck is a "burr gun"???


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## rake60 (Oct 25, 2008)

Brian Rupnow  said:
			
		

> What the heck is a "burr gun"???



Brian you made my night with that! ;D

A straight burr gun with an abrasive cartridge roll of flapper wheel has been used
to finish many critical bores. Often accompanied by under the breath comments
of the user as well as comments from guy working near by like: 
_"Oh, is that a finish cut?"_

It's the only practical answer when you missed the size by a gnats eyelash.

Rick


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## bentprop (Oct 25, 2008)

I,ve seen many articles for building your own boring tool,but have always held back.My understanding is that the tool needs to be manually moved up and down the bore,unless you have a powered Z axis.
So how smooth does the bore come out with hand winding the z?
I could certainly use one at times. 8)
Hans.


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## Brian Rupnow (Oct 25, 2008)

Hans--I tried to take a picture, but my camera batteries are dead. I guess my answer would be "smooth enough", as none of the axis on my mill are power feed, and I never use the power feed on my lathe. Poor answer, I know.


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## Tin Falcon (Oct 25, 2008)

Point of info here. Most of the boring heads I see for sale are a bit on the large size for the popular Seig 2 Mini mill, as well as Taig,Sherline,
and the Unimat etc. I came across a Criterion S 1 a while back that seems to be a nice size for the smaller mills. The S-1 is similar to the current S-1-1/2 except the s-1 is only 1 1/4 inch high. anyway there are several nice little boring heads available but use a bit more z axiz space. 
The criterion web site also has some good info on using a boring head as well as some general machining info
http://www.criterionmachineworks.com/
Tin


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## jack404 (Oct 25, 2008)

well done Brian

and thanks for the link Tin

cheers eh

jack


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## BobWarfield (Oct 25, 2008)

For some reason, I always particularly enjoy running the boring head in my mill. 

I guess I'm just easily amused!  :big:

I got an old old "beater" Criterion off eBay. It works great and produces a very accurate finish. Recently I got some of those crazy boring bars that are designed to go in both holes of the boring head for greater rigidity, but I haven't had a chance to try them out yet.

Cheers,

BW


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## Maryak (Oct 26, 2008)

Brian,

I'm very happy you asked about a burr gun ;D ;D

I didn't have a clue either :

And thanks for the low down Rick :bow:

Regards
Bob


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## jack404 (Oct 26, 2008)

hmmm 

i may be wrong but i always thought a "burr gun" was a deburring handset or just a highspeed air hand set with deburring tools 

but for bores used bore honing stones generally a triple stone setup that self adjusts to hone the bore, thats what i used in the past

i'll dig out my old hones ( dont have the air gun , no compressor large enough to run them) and take a pic for you

cheers

jack


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