Boring Bar Setup?

[mikey]

Thanks for the replies. That clears things up, my main concern was mostly about HSS or Carbide. and whether or not I was missing something on round base boring bars versus something else. I guess the holder was mostly a no brainer. Thanks again for the replies. Jess

Jess, I would do some homework on bar and insert geometry so you can choose a bar that fits your needs, and then if you can afford it I suggest you buy it in carbide. A steel bar is fine but a carbide bar will go twice as deep for any given size of bar and you will save money in the long run by going with that. Except for tiny bores, I no longer use solid bars on the lathe. I prefer the accuracy and consistency of an inserted tip bar.

I would avoid buying bars in sets, especially the import sets, unless the bar geometry and insert geometry is exactly what you need. Be careful what you buy - good bars are expensive and a mistake is going to cost you.

 

[Dan_S]

Where have you found them in HSS? I have a couple but have not seen them for sale any ware.

Enco sells sets of their house brand "interstate" and they also have this set by apt.
http://www.use-enco.com/CGI/INSRIT?PMAKA=325-2549

a bunch of places sell apt hss individually, msc wholsale tool etc.

you can get them from amazon with free shipping for example.
http://www.amazon.com/s/ref=nb_sb_n...rch-alias=specialty-aps&field-keywords=cobalt

 

[joshua43214]

Unless you are a professional where time is money, there is no situation I can think of where an insert tool will ever save you money on the long run, and they are not convenient unless you can afford to have a really substantial amount of money tied up in different inserts, and know which insert will do the best in a given situation.

I can regrind the profile of a HSS bit in the same amount of time it takes to replace and insert. A single HSS tool cost less than a single quality insert, and will last me years if not decades.

Unless I am trying to turn hardened steel or titanium, I will always have the exact right tool for my machine and the job with HSS.
Also, the quality difference between a cheap import HSS tool (assuming it really is HSS) and quality HSS is small compared to the difference in quality of insert tooling.

This is not to say the insert tooling is bad, it is very good. It is just not an investment that will ever pay itself back in long term savings or convenience. In fact, I would argue that dependence on inserts is a huge limiting factor in what you can do unless you can afford to pay for custom ground carbide tooling.

 

[mikey]

Unless you are a professional where time is money, there is no situation I can think of where an insert tool will ever save you money on the long run, and they are not convenient unless you can afford to have a really substantial amount of money tied up in different inserts, and know which insert will do the best in a given situation.

I can regrind the profile of a HSS bit in the same amount of time it takes to replace and insert. A single HSS tool cost less than a single quality insert, and will last me years if not decades.

Unless I am trying to turn hardened steel or titanium, I will always have the exact right tool for my machine and the job with HSS.
Also, the quality difference between a cheap import HSS tool (assuming it really is HSS) and quality HSS is small compared to the difference in quality of insert tooling.

This is not to say the insert tooling is bad, it is very good. It is just not an investment that will ever pay itself back in long term savings or convenience. In fact, I would argue that dependence on inserts is a huge limiting factor in what you can do unless you can afford to pay for custom ground carbide tooling.

I'm certainly no pro but I do need to bore precisely on occasion despite that. Sometimes that precision bore will be in a relatively deep hole and the bore needs to be accurate all the way down the bore. Within the generally accepted limits of bar elasticity, many bores will be too deep to bore predictably with a steel bar. In that case, carbide bars are the most common option. As it turns out, buying a steel bar and then finding out that you need to go deeper than that bar can accurately cut often results in buying a carbide bar of the same diameter so you can get on with it. This has happened to me on more than one occasion and I know it happens to others, too. Buying a carbide bar from the beginning is not a bad idea if you know what you need and can purchase it for a decent price.

Boring is about predictability. That may not be true if all you're boring is a model canon but if you need to bore a fitting for a line-to-line fit for a bearing with tolerances in the very low tenths then predictability is important in planning an approach to final size. A good inserted tip bar with the right geometry, coupled with an insert with an appropriate geometry and the correct nose radius, will give me that predictability when I use it correctly. A solid bar, HSS or otherwise, quite often will not and this is especially true if the bore is deep for the given bar diameter.

With just three carbide bars, two of which take the same inserts, I can bore a hole from just under 1/4" ID out to as large as my lathe can hold, and from very shallow to 5" deep or more. Each will cut accurately, predictably, without chatter and provide superb finishes. All are top quality bars with top quality inserts. that cost under $300.00 on ebay for all of them. Given that they have served me consistently and well for just under a decade now, and given that I haven't run through more than a few inserts in that time, I figure it works out pretty cheaply. Moreover, each of these bars will bore pretty much any material I commonly use in my shop so no, they are not limiting in my view.

I have nothing against HSS. I own sets in cobalt, HSS and even one of those cheap Chinese brazed carbide sets. However, they are all used in a boring head on the mill nowadays. I do use micro-100 bars for tiny bores, though. I am not altogether unfamiliar with HSS tool grinding and I've ground my share of boring bars and lathe tools but I have found them to be far less predictable and capable for deeper bores than inserted bars. Hence, my choices as stated.

I have used all sorts of bars over the years, have owned over 20 different inserted tip bars over that time, understand bar and insert geometry well enough to bore rather accurately in my little shop and the advice I gave is what I feel to be the best advice I can give based on my experience.

Use what you like, Josh. We don't need to argue about every single thing.

 

[Charles Spencer]

Unless you are a professional where time is money, there is no situation I can think of where an insert tool will ever save you money on the long run, and they are not convenient unless you can afford to have a really substantial amount of money tied up in different inserts, and know which insert will do the best in a given situation.

I can and I think you'll agree. I had a chance to pick up some name brand inserts (I forget the brand) for $4.00 each recently. I had some pretty good 5/8" round stock sitting around. So I made a boring bar to hold the carbide inserts that I already had.

Hey, it does a pretty fair job of boring and it cost me $4.00 and a piece of scrap. Is it ideal for every situation? Hardly. But it's not too shabby either.

 

[joshua43214]

@mikey
Sorry, I was not trying to argue. You are a far more experienced machinist than I am, and judging from the quality of your comments, a much better one as well.

It may seem like I am arguing for the sake of an argument, but I am not. In fact, I can't think of a single time I have disagreed with you on a fundamental concept or method for machining, and I have learned plenty from your comments in the past I regard debate as healthy for the community, and especially for the OP. I agree with you 100% that boring a deep and very precise hole requires extra care in tool selection.

I can step up onto an anti-HSS soap box just as easily. HSS has numerous issues of its own.

Please accept my apologies if you have taken offense to anything I have said.

 

[T Bredehoft]

Just a comment, there are carbide boring bars and then there are boring bars that use carbide inserts.

The first are SOLID CARBIDE and hold a carbide insert. The rigidity of the solid carbide accounts for their use, almost totally eliminating chatter from the work. They cost a mint.

The normal steel bars which hold inserts are OK for normal use, but again a steel bar with a HSS cutter will usually do the same job, just not as fast.

We hobbyists are not concerned with pieces per minute, or for that matter pieces per hour, usually we're just making one piece, not production runs. This is why HSS is so satisfactory for our work. It's cheap compared to carbide, and will do the same job, at lower cost.

 

[Dan_S]

Their are bunch of different types of boring bars, avaialable.

The simplest & cheapest are hand ground bars. I did this when i first started, and i have to say its no fun at all,as it takes forever to grind a new bar. If you start from square stock, you're depth is limited to how much clearance you grind. If you use round stock, your limited by how far you have to kick out the holder to generate clearance.






The next step up the price wise are the boring bars most commonly associated with boring heads. They have a steel shank, and then have a hss, cobalt, or carbide braised on cutting edge. They are fairly cheap, but are not overly stiff, and have the same clearance problem as above.


Similar to above, but at at a higher cost, are solid carbide bars.


The cheapest type of insert bars are ones that take hand ground tool bits. They are double ended and let you hold the cutter either perpendicular to, or at a 45 degree angle to the bar. These are really useful for stuff like custom profiles and deep hole threading.


You can even buy Everede bars like this and swap back and forth between hss and carbide, and grind any profile you like.



Modern carbide insert bars come in multiple flavors, steel shank, heavy metal shank, carbide shank, with and without coolant holes etc etc. Good steel shank bars can be had for around $30 new, while carbide shank bars start at around $100.



If you do much machining, you will most likely end up a few of each in your shop. The benefit of insert tooling (hss or carbide), is that clearance is built into the tool, and stick-out can be adjusted to maintain maximum rigidity.

 

[chevydyl]

Nice post dan, I have a variety of all of them except solid carbide indexable. Try making a super thin delrin bushing with an indexable bar.... not gonna happen, you need a razor sharp high rake hss bit. There is no one size fits all, you basically need all varieties. The exception is you don't absolutely need a solid carbide indexable bar, that's a luxury. BTW the thin delrin bushings were for a number matching Rochester qjet on a 71 formula, for the throttle shaft in the base. Was cheaper for me to make the bushings than to buy a bushing kit that comes with bronze bushings and you have to drill out the base plate, my method required no drilling and was smoother in operation than the bronze bushed version (we bought one for another carb)

 

[Dan_S]

I've had good luck in delrin and other plastics with the high positive rake polished inserts designed for aluminium. You have to be careful putting them in or you'll slice you fingers open in a heart beat, don't ask how I know!