Recommendation for hss boring tool.

[mickri]

There are lots of threads on here about making a boring bar for HSS tool bits. There are also lots of You Tube videos on how to make one. Very simple to make. Turn a steel bar to whatever diameter you want. Or use square steel like the keyway stock you mentioned. A round bar is better than square because it will fit in a smaller hole. Then drill a hole at one end perpendicular to the bar and a hole at the other end at 45 degrees to the bar. Add a set screw to hold the tool bit. If you are using round HSS tool bits you are done. If using square tool bits you will need to file the hole to a square. Here is a picture of mine in it's holder on my lathe. What I am doing in this picture is placing the bar at the depth I want to bore to so I can set a carriage stop to that distance.

 

[mikey]

I'm going to try to take you in a different direction than a shop-made boring bar. Having made many in the past, I will say that a shop-made bar will work; it just may not work as well as a good commercial bar when it is made by a beginner. If your goal is to actually bore an accurate hole or learn to bore an accurate hole then buy a decent bar or set of bars and learn to do it first.

If you have to bore a hole for some project or reason then you have four options - inserted carbide bars, solid carbide bars, HSS bars or brazed carbide bars. There are really good bars in all four types; there are also cheap crappy bars of all four types. Many hobby guys opt for the latter but the smart ones opt for the former so their tools last.

If I were you, I would go buy the 3/8" HSS M42 (8% cobalt) set of boring bars from KBC Tools. This is a high quality set of bars for not that much money that will not only work well but should last a lifetime if cared for properly. They can be used on the lathe or mill and will bore accurately from the get go. They will allow you to learn to bore on your lathe in just about any material you are likely to encounter.

If you need to go deep then look at Micro 100 carbide bars or inserted carbide bars.

Don't get me wrong. You can definitely make your own boring bars but to make a really good one you need to know what you're doing, and it doesn't sound like you're there yet.

 

[benmychree]

I like and use Bokum boring and threading tools, they are form relieved and ground, and are sharpened (only) on top.

 

[ericc]

Those look like nice bars that Mikey is recommending above. I haven't tried them, but I can confirm what he says. Some of these are ready to use right out of the box, and some of them have some issues with their grind. KBC is a reputable dealer. I notice that there is an option to just purchase one instead of the whole set, and that is what I opted to do (but another vendor). It turned out that the tool was great and cut perfectly the first time I tried it.

That said, I made a quick threading tool for coarse internal threads. My current tool only was for about 20 tpi. The tool was made from 3/8" stock to fit my South Bend 9 toolholder. The retaining clamp was forged with hammer and anvil, but alternatively you could make it with a hacksaw and file pretty quickly. The cutter is a drill bit that I accidentally snapped when being careless. I did spark test it for being HSS. Note that when repurposing old drill bits that have failed, about half of them seem to be simple carbon steel. I think that 99% of all drill bits are either M2 or M42 like cobalt HSS. But failed bits, especially when sourced from junk boxes at garage sales, are more likely made from obsolete steels. These can be repurposed into stamps and detail chisels or scribes. If you use them as cutting tools, you have to get rid of the cooked end (there often is a cooked tip) and run them at half speed. Also, care must be taken when sharpening them. Just one dig or cut at excessive speed will draw their hardness and it's downhill from there. HSS is such a luxury; much more forgiving.

 

[intrepid]

Another option is indexable HSS. AR Warner sells these and I have used them in the past. https://www.arwarnerco.com/category-s/151.htm

 

[francist]

I have a few of the KBC bars mentioned above, they are indeed a nice tool and I found they required very little touch up to get going right out of the gate. I use them mostly in my boring head on the milling machine. For use on the lathe I have a generic 5/8” x 6” double-ended bar (45 and 90 degrees) that uses 3/16” bits I think. Works fine and very easy to grind different bit shapes. I use my home built versions the most though — not because they’re any better but probably just because they’re tailored to be the perfect size — so setup is quick. I used regular square HSS tool bits but they do take a bit of grinding to get there. And, in the smaller sizes they can be tricky unless you have narrow wheels to grind with. I can make them in left or right though, so I like that. Internal threading tools I often grind from an otherwise spent HSS tap of an appropriate size.

-frank

 

[D.sebens]

So many choices! It’s like I asked what everyone’s favorite flavor of ice cream is.
To be honest this is great, it lets me see the different tools that can be used to accomplish the same task.
So my Chinese carbide boring tools are brazed. Could I remove the carbide and braze on a hss bit?

 

[mmcmdl]

Not worth the effort in my opinion .

 

[ericc]

So many choices! It’s like I asked what everyone’s favorite flavor of ice cream is.
To be honest this is great, it lets me see the different tools that can be used to accomplish the same task.
So my Chinese carbide boring tools are brazed. Could I remove the carbide and braze on a hss bit?

Simpler to just sharpen the carbide. Depending on the source of the tool and its quality, a touch up can help.

 

[Road_Clam]

Hey, I have a 7x12 and have some cheap 1/2 shank carbide boring bars. They work okay but I’ve noticed in general the hss tools cut better. The last hole I was boring was 1.5 dia 2.75 deep. Any recommendations on a hss tool or some thoughts on making one? Do I really want a boring bar or do I want an internal threading tool?

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