# DIY 1" boring bar



## Ischgl99 (Apr 22, 2021)

After watching BladesIIB make his video about a shop made boring bar, I finally got motivated to make one myself.  I have a 12x36 lathe, so I didn't need one as big as his, but since the largest round bar my AXA toolpost can handle is 3/4" diameter, I decided to make one 1" diameter with a 1/2" shank to fit my toolholders.

I had some 1215 bar stock on hand in 1" diameter and used that.  It might too soft for long-term use, but for now it will be fine.  I didn't think to take pictures as I was making it, so these pictures are afterwards.  I faced both ends on the lathe to a length of 9" and then milled a flat 6" long and about 3/8" wide that became my reference surface for further operations.  By milling 3/8" wide, I left a bit of the radius on each side so that I didn't need to chamfer it.  I placed a dial indicator against the end of the bar stock and zeroed it out so that when I rotated the bar for the next operations, I could put it back into the same spot.  I didn't have anything I could bolt to the table for a reference length, so that will probably be a future project.

The flat was placed against the vice rear jaw with parallels underneath to raise it up enough to mill a recess 1/2" wide and 1/4" deep.  After the first one was done, I flipped it and had the reference surface against the front jaw to mill the second recess.  I know that is not ideal, but it worked fine.


Once those were completed, I needed to mill the cutting end to make a flat for the set screws.  By placing the reference surface against the bottom of the vice, it put the bar in the proper oriental to mill this flat with and end mill.  I didn't have a face or shell mill that could radius or chamfer this in one operation.


Now on to the slot for the tool bit.  I have a thin slitting saw, but it was on the dull side, so I decided to try a carbide trim saw blade I bought on a trip to China many years ago that that had the wrong size arbor hole for my trim saw.  I needed to make an adapter bushing for the mill arbor since the hole is 20mm and my arbor has inch steps in it.  Once completed, the saw blade ran true enough to cut the slot.  The saw blade is 2mm thick, I wanted a slot slightly bigger than 1/4" with the top of the bit on the centerline and decided on 0.26" height and 0.25" deep.  I don't have a DRO on the quill or knee of my mill, and I tend to forget how many turns of the handles I have done when I need to make a bunch of passes, so I used a calculator with the height I wanted to mill the slot and the subtracted how much I raised the knee for each pass (don't forget to include the thickness of the blade for the first pass).  That worked well and I might start using that more often.


Once that was done, I put in three setscrews to hold the tool bit and now I am waiting on a project where I need this large of a boring bar.  Ignore the length of the tool bit in this last photo, I know it's too long, I just picked one out of my drawer to show it complete.



This was a nice and easy project to do, if the 1215 doesn't last long, I now know how to make one in a more durable material.


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## Janderso (Apr 22, 2021)

I watched that video.
Nice job! That came out very well.
High quality pics too 
Have you used it? Let us know how it does.
I have a hunch you aren't the only one thinking about it.


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## Ischgl99 (Apr 22, 2021)

Janderso said:


> I watched that video.
> Nice job! That came out very well.
> High quality pics too
> Have you used it? Let us know how it does.
> I have a hunch you aren't the only one thinking about it.



Thank you!  I saw one much bigger than this on a CEE video on YouTube and thought that would be a good addition to the shop, and then once Blades did it, put it high on the project list.

I’m a semi-retired engineer with a photography business, so I took out the good equipment to document what I am working on.  I am working on a twin cylinder steam engine and will post pictures of that after I make more progress.

I haven’t used it yet, once I catch up with some things, I will be trying it out.  I want to grind a thread relief groove tool and see how well that works as well as for general boring.  I generally suck at grinding HSS, so I might need to use brazed carbide with this.  I made an ER40 collet holder to use in a 4 jaw chuck and want to put threads in the rear side to screw in a stop, and this should work well for that.


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## Illinoyance (Apr 23, 2021)

The only wear on the bar itself would be from swarf rubbing on it. It is going to take a very long time for any real wear to occur.  There is no pont going to a stronger material.  It will not increase the stiffness of the bar.  Modulus of elasticity does not change with the alloy or the hardness of the bar.


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## BladesIIB (Apr 24, 2021)

Your bar looks great. Thanks for sharing the pics. I think the end mill radius on the top for the set screw flat looks perfect. That is the beauty of so many projects is to use what you have on hand and make them your own.


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## tjb (Apr 24, 2021)

BladesIIB said:


> I think the end mill radius on the top for the set screw flat looks perfect.


I agree.

You ended up with a very nice boring bar.

Regards,
Terry


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## Larry$ (Apr 24, 2021)

"with a photography business, so I took out the good equipment"
That clearly shows in the quality of the photos. 
Nice boring bar.


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## Just for fun (Apr 24, 2021)

Very nice job!   Looks great!


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## Ischgl99 (Apr 24, 2021)

Thank you all for the compliments, I am very happy how this came out.  I was pleasantly surprised at how easily the end mill worked for doing the flat and radius.  I was afraid it might chatter with that much sticking out, but it machined very well.


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