Lathe Boring bars ???

[Sevens0n]

I have my atlas 12x36 lathe set up and running ,have made some test parts and even a couple of useful things. Have been sorting through the the abundance of tooling that came with it. I have found several nice looking boring bars, both carbide and HSS. The only tool post that I have is the original lantern style.

Question for you experts... What is the "old School" way to mount a round boring bar to the compound? I obviously need some type of toolpost holder. Is this something that I need to just make to suit as needed? Please don't tell me I need a $500 Aloris quick change. Just not sure how the previous owner held these bars for boring...Any hints or tips would be appreciated...

Thanks
B.Hall

 

[pineyfolks]

Heres a few different styles

 

[mikey]

Mr. Hall, I'll bump this for you and give you some input for what it's worth.

You mention that you don't want to be told to buy an Aloris but at some point you might want to reconsider that notion. It isn't the quick-change feature as much as it is the ease of height adjustment that these tool posts provide. Just a thought.

You can easily make a boring bar holder from steel or even aluminum if the bars are 1/2" or less. It simply has to be solidly bolted to the carriage. However, ideally you want to make it adjustable for height to allow you to accommodate tangential forces.

Regardless, the hole the boring bar fits in should be accurately bored or reamed and should be at least 4 times the diameter of the boring bar. For example, a holder for a 3/8" bar should be about 1.5" long at minimum. A better way to think about it is that the holder should hold the remaining portion of the bar when the stickout is at maximum extension. For a typical 3/8" OD, 6" long carbide bar the maximum stickout would be 3-3.75" so the holder would need to be, at minimum, 2.5" long.

You might consider making the holder for the largest bar you have and make sleeves to accommodate smaller bars.

If you can, make the boring bar hole about 0.005-0.010" above the lathe centerline to accommodate tangential cutting forces. Be absolutely sure you know what the lathe centerline actually is. Every lathe is different and you need to zero a bar in a 4-jaw chuck, make a test bar and measure it to find the centerline accurately.

It is best not to use screws to hold the bar in place. Rather, use a clamping arrangement like this:



Such an arrangement will hold the bar very solidly. Keep in mind that a finely reamed finish in the holder will reduce chatter in use.

Good Luck!

 

[Sevens0n]

Sorry for not getting back here sooner, I've done some more homework, and sorting through things. Taking advice, I ordered the phase two AXA toolpost set from Enco at a good price. Weighing all things it seems like the best way to go in the long run. Thanks for the direction, I'm now much more comfortable with the tooling I have to work with.


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Thanks...