boring bars for a small lathe

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thomas harris
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boring bars for a small lathe

Post by thomas harris » Sat Aug 04, 2007 3:26 pm

What works best for my 618 atlas in terms of boring bars. I have attempted to grind some from 1/4 blanks with limited success. I also need parting tools for the same mahcine. Tried grinding them from a blank with limited success. I am interested in small lboring bars to clean out and touch up inside diameters on bearings. Most of my regular tools leave a lot to be desired. Sometimes my grind works great, other times it's scraper blade. This is improving little by little. Right now I have no boring bars or parting tools. I use a lantern style toolpost. I see the tooling on E-bay and have bought plenty there, but am somewhat confused on the setups availible for boring bars, parting tools, and thread cutting tooling.

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Post by spro » Sat Aug 04, 2007 5:25 pm

I wish that I knew your answer to one question before I tried to go any further.That is if you are cleaning up internal bearing surfaces and do not want scraping action then by what means are you increasing the dia of the shaft? Perhaps there is a std oversize shaft or crank which can be fitted. Also it follows you must have a very precise holder or plate affixed to the spindle to where the OD of the sleeve bearing/or unit is held in alignment while the ID is bored.

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Post by RET » Sat Aug 04, 2007 6:58 pm

You might want to take a look at Harold's tool grinding tutorials. If you study what he says carefully, you will probably find a lot of the information you are looking for.

Like many others, I've downloaded the compilation onto my computer and I expect to refer to it over the years.

Just a suggestion. Best of luck.

Richard Trounce.

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Post by JimGlass » Thu Aug 09, 2007 6:22 pm

Here are some pics of boring bars showing examples of improper set ups.
The Pics were taken from "Machine Tool Practices" written by
Richard R Kibbe and John E Neely. This book was used for most of the ten years I taught machine shop at a local junior college.

I have always wanted to post these pics so today is the day. Even though these pics were taken from the lathe chapters the same principals apply to boring in a mill as well.

I'm rather fond of boring holes in particular. When boring holes, the material should peal off effortlessly. There should not be any squealing or hawking noises. When the chips from boring are as soft as the hair on a dogs ear, you are do-in it right.

Most common set up mistakes are having the boring bar above or below center. The largest possible boring bars is best but allowance for chips is also a consideration. Boring bars extended to far from the boring head or toolpost (lack of rigidity) is a common cause of chatter.

Always bore holes to finish size :shock: Never plan to bore a hole then ream to size, that is how sissies do it. With a little practice and a good setup with sharp tools one should be able to bore hole to size within

When a complete set of carbide tipped boring bars can be bought for $20 why try to make boring bors. Your time can be put to far more effective use.

Boring bar without enough clearance angle.
Pics show tools above center, below center
Tool & Die Maker/Electrician, Retired 2007

So much to learn and so little time.

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Post by seal killer » Thu Aug 09, 2007 6:37 pm


I can't see the pictures. Is it you or me?

ps Well, it was me. I see them now. Logging in to this forum is indeed a strange and mysterious procedure.

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Post by Al_Messer » Sat Aug 11, 2007 5:53 pm

Have a look at the boring bars and bits offered by MicroMark. They also have miniature cut off tools and blades.
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Post by deltaenterprizes » Sat Aug 11, 2007 6:35 pm

How do you download Harold'S tutorial?

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Post by Mcgyver » Sun Aug 12, 2007 10:16 am

ditto on reading Harold's work

Thomas, I don't know that lathe but here a bunch of ideas. First, you need some basic reference books, old sr high school texts are my favorites - skim reading a few good texts will shoot you up the learning curve. In the interim before you procure them, google US army marchining and find the lathe pdf, free online machining text. this was written a while ago so there'll be lots of lantern style set ups.

To do good work, to get a tool bit to cut properly requires a bit of knowledge of the geometry. read up as per the above, there's not much to learn before you have the basics down, rake and clearance, but once you do you will be away to the races in engineering a tool to do what you want it to rather than grinding and hoping.

Next, make a boring bar holder. The lantern tool posts suck and you'll want to think about making or buying at quick change tool holder at some point, but the lantern setups for boring bars are terrible. boring is already a less than rigid operation and the lantern boring bar set up cantilevers it out further and is awkward to adjust. Here's the boring bar holder i made, the design is simple and sturdy... might have come from Home Shop Machinist, can't remember. (shame on me for having unnecessary overhang!) Anyway it should be apparent from the pic how it works/is made.


so far as what's out there or what to get, get some catalog's, kbc, macmaster carr, etc. There is a huge selection of boring bars from ones that hold hss bits like in the pic, insert holders or great little micro hss boring bars. The variety is large and varies by what dia you're trying to cut. i agree grinding your own from hss blanks is tedious, i do it sometimes when a specialized tool is required, but there just too much to grind away for it to be any fun.

like spro, I'm wondering what type of bearing you are trying to bore. perfectly normal if you're making a bearing but seems strange to do to an existing bearing.

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Post by BadDog » Sun Aug 12, 2007 12:46 pm

My guess is that he's talking about brass/bronze/babbit (aka "plain", not roller) bearings.
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thomas harris
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Post by thomas harris » Mon Aug 13, 2007 3:58 pm

The first part I bored was not really a bearing, but constructed exactly like one. It was the surface a perforating blade butts against on a perfing/scoring/folding machine. The tolerances were very tight. I made it out of nyloil. Came out quite well, considering it really was my first ever attempt at actually machining something to a specifications. I attempted my first threads last night and must say that's a cool process-cutting threads on a lathe. They came out as a nice snug, but smooth fit.

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