Turning & Machining a Boring Bar out of O1 Tool Steel! Part 2

I always felt like making your own tooling was a great sense of accomplishment. I had a problem with poor surface finish from an Asian/import carbide-brazed boring bar on a prior project which is why I wanted to make a boring bar from scratch! Should be a fun project involving a lot of shop skills: CAD, making a drawing, turning, machining, heat treating and grinding!
More info at nyccnc.com and nyccnc 5 Reasons to Use a Fixture Plate on Your CNC Machine: bit.ly/3sNA4uH

[@lumpygasinavacuum8449]

John the heat it self will distort shape of parts. A .010 over size per 6" of length is a good rule. If you have a machinery handbook I think that is covered? I'm not looking at the book right now, this feature size is what I've seen on prints in my career. Thanks for your help in teaching people. I'm not online that often. You can also braize carbide blanks onto tool steel for boring bars. When building boring bars keeping centerline is very critical. Your angles are very important as well. Using a surface grinder and preset angles will help. So build yourself a sine bar and a tool makers vise. Make them well square flat parallel in .0002 or better. Take your time in grinding. Use coolant. Stone very small radius on cutting edges.

[@lumpygasinavacuum8449]

I really like how you are humble and do not come across as a know it all. In this trade it is hard to know it all.

[@Flachzange1337]

Hi, i would harden the boring bar first and then grind it for two reasons. The surface will be oxidized and therefore be rough. Also the edge could become too hot. Here it is not a big problem but if you have a really sharp edge like on a knife, then there is a chance that the edge will be burned during the hardening process and will not get the final hardness that you want.

[@lumpygasinavacuum8449]

John take your cut and stop spindle after .200 length to reference diameter. Take at least .008 per side. Your loosing tool life and compromising surface quality by rubbing your tool on your light cuts. Thank you for posting videos. If I could I would. You are a good man we need more like you.

[@meocats]

Oh by the way, heat treating won't do anything to dampen the bar, so you'll get the same poor surface finish on your parts, (elateive to something better). Full carbide boring bars have the same problem. See the mitsubishi 'dimple bar' for suggestions how you could have improved damping, on google images.

[@glennedward2201]

We’ve thought here that heat treating may actually cause further harmonic issues.

[@alexandermcgilton9204]

Your statement is true that all steels regardless of their hardness or tensile strength, will deflect at the same linear rate with applied load. Where they differ is when you exceed the yield strength of the lesser steel, the harder one will continue a steep resistance to deflection while the other will plateau. You could easily exceed the yield point and not even know it,only to have it then become lower next time its deflected. There is every thing to gain and nothing to loose if hardened.

[@Tajs0013]

If you want to avoid the chatter when you exit the cut on the mill, use a exit radius so you don't have full engagement of the cutter, use a smaller cutter and program in the radius so you can use the Cut exit

[@alexandermcgilton9204]

If you payed attention to the vary Mitsubishi video you referenced, you would notice that a lighter boring bar is better. Its not so much the density I worry about, but the lose of high strength materiel from within. The tensile strength of lead is so low, the bars strength well more closely resemble a hollow one.

[@Liberty4Ever]

I love how you use a Haimer to measure on the Tormach and use RCBS calipers to measure on the lathe. :-) BTW - I was thinking about making a small boring bar and a small internal threading bar, with both using carbide inserts. There doesn't seem to be much selection of decent quality small boring/threading tools at a decent price. I bought a cheap 8mm internal threading tools on eBay this morning and it's on a slow boat from China, but I'm not expecting much. For the larger tools (1/2" shank and larger), Mesa Tools makes good stuff at good prices. I wish you'd do a video on small shop tools for 3 HP and under CNC machines. KZbin is great for how-to machining videos, and I can pick up incidental tool tips, but I've found tool selection to be a very important practical matter that is not easy to get from KZbin videos. Show us your tool rack! Show us your (fully commented) tool table! Mill and lathe! What are your favorite tools? I like the SuperFly a lot, but I am now irrevocably committed to making a scaled up version using the 5" fly cutting bar from Suburban Tool (SubTool.com) with a TTS compatible arbor that I turn on the lathe and machine on the mill. It should be a simple project. I'll document it in a KZbin video, probably in a month or two. It's added to the list for my Summer Of Awesomeness (all CNC and miscellaneous shop projects).

[@glennedward2201]

How is O-1 for turning rigidity? Have a project with 7mm diameter and wondering how it turns without a steady rest? Anyone can answer.

[@meocats]

your appreciation is appreciated

[@giantstickerman]

He is the Yoda Master of machining :-), anyway, I enjoy his and your clips very much please keep them coming.

[@meocats]

It's not too late to improve your bar, here's what you do: Drill it, tap the holde, pour molten lead (like fishing weights), put a setscrew on the end, freeze it, tighten the setscrew, then its good to go.

[@rhost714]

Always Heat treat then grind. Although it might not be an issue for this project, heat treating will release stresses in the steel and and may throw off your geometry.

[@lumpygasinavacuum8449]

If it is tool steel to be heat treated it will bend and .010 per side needs to be left behind per 6" length on tube type steel. Just good practice unless you have a press to manually staighten with.

[@alexandermcgilton9204]

You have to ask your self what you intend to make. If you are making a boring bar for R&D purposes, then go ahead and cast it full of lead. If you are making general purpose cutting tool for use in the home shop then go with the foolproof solid steel. We both agree that a lead filled boring will out perform a hollow one, however it would be a great disappointment if the perimeters weren't tuned right and became inferior to a solid one.

[@meocats]

The damping effect occurs on the interface of the lead and iron (internal shear friction). There's a phd thesis on this too, the hollow tube theory, floating on CNCzone. The oil won't do anything, its 'bro-science'. Compression of the core is a parameter for the damping effect. This is a separate theory.

[@DavidKirtley]

I would rough grind (leaving plenty) then heat treat and final light grind and hone.

[@alexandermcgilton9204]

The most compete and intuitive video of most hardening is watch?v=3_BH6HqpPtk. As for grinding, there is no consequence or need to grind while the steel is soft. Keep in mind you will need to have an allowance of a few thousandths before hardening, your mill or an equivalent manual mill can operate reliably to the thousands or better, all you will gain is better finish prior to heat prior to hardening.

[@alexandermcgilton9204]

Indeed they do, but they are not simply filed with molten lead. Either they are filed loosely with Lead shot then oil to the top, or there is a floating mass often tungsten suspended by rubber dampeners. watch?v=VNut54ovOrc Lead is not self dampening like cast iron which dampens by its carbon inclusions. The lead shot method might have been what you were thinking of, and it would explain why you need a set screw.

[@alexandermcgilton9204]

I don't see why you need to insult those who suggest to heat treat first, when you say your self it makes no difference. I believe the contrary and agree with Flachzange for the same reasons, I would even go as far as filling a radius on the cutting edges. Because the corners attract heat faster then the rest of the material placing then in the gamma region of steel, and when quenching will shrink faster then the rest causing them to collapse. Gamma iron should never be quenched as it cracks.

[@alexandermcgilton9204]

Making a dampening system for a boring bar would be vary difficult to tune and balance. A company like Sandvik has the best engineers and and a lot of money to throw around. So they can invest in experimenting with harmonics and frequency. Doing this yourself may result in more loss of rigidity for being hollow then will be gained from the dampener.

[@glennedward2201]

Unless you attempt how would you know the results? I got to believe there wouldn’t be any disadvantage filling the core with lead. Might even try it here though we make a-2 boring bars and holders and they work excellent as is, better than most commercial holders. The non-hardened ones seem to dampen frequency better though we don’t have any real back to back comparatives to prove the theory.

[@BulletCastDuo]

Why don't you grind most of it in pre-harden-state and just leave a tiny littly bit "meat" on it so that you can easily grind it of after it has been hardened? That way milling is easy and it realy does not matter if it gets bigger or smaler after HT :D

[@johnnym1320]

I would harden first then grind.

[@lumpygasinavacuum8449]

You heat treat first. You never grind first.

[@giantstickerman]

I wont be able to help but please ask Keith Fenner, I think he could help you out.

[@stucapco9111]

Four jaw? I don't see it.

[@stucapco9111]

Sorry batch deleted my youtube emails. I mean are you indicating these bar stocks in a four jaw? Wouldn't it be easier to throw up a three jaw on the spindle? Center assumed for easy repeatability?

[@MacoveiVlad]

Ben Krasnow has a interesting video about heat treating, if you know what characteristics you wand form the metal maybe that video can help you find the answer. /watch?v=ulfCxDsVTWo I have no experience in machining, so that video could lead nowhere near the answer. But it is definitely worth watching, if you haven't already.

[@meocats]

No shit?. But if you payed attention yourself, you'd know lead core dampened boring bars exist too, and they work because lead has damping properties. Look it up if you don't believe me, its been done for decades. Are you even paying attention to the damping properties, or too busy giving a psychoanalysis about how I should be paying attention?

[@meocats]

There's only one proper way to cast the lead in this scenario, not like you suggested. You are fundamentally incorrect (the entire previous comment, and then some). In that case, humans might not have invented the wheel, sent probes to jupiter, or invented penicilin. If you own a lathe, you're not running a manufacturing operation, but that didn't stop you from making videos about it on youtube, or commenting. It's not "R&D purposes just because you've never done it [properly] before.