Purchasing right boring bar holder for existing lathe tool post

[benmychree]

I am a big proponent of HSS boring tools for lathe and mill, I particularly like Bokum tools, they have back rake, and so cut much more freely, they are made in 90 degree styles, lead angle styles and threading styles in various diameters, and are sharpened only on the top, as they are form relieved, and they will last for many years with careful sharpening.

 

[Omni-impotent]

Thanks, everyone. I wish I knew about this forum earlier. It would have saved me a whole bunch of frustration over the years!

Just keep in mind that the theoretical depth they can bore to is 4 times the diameter of the smallest part of the shank up near the head.

Didn't know about that. Is this the same for all boring tools? Because I see some are very long.

I actually have a Phase II 250-104 that came with the tool post. I'll try to get an adapter ring with a split made. I was worried if the ring was too thick it wouldn't compress and grip properly.

 

[mikey]

Didn't know about that. Is this the same for all boring tools? Because I see some are very long.

The 4:1 ratio holds true for all steel boring bars, while carbide shanked bars can usually go 8-10:1 depth to diameter ratios.

That type of holder uses two cotters (angled ramps) to put pressure on the boring bar in two places. It is NOT the same as having the entire holder clamp down on the bar like the 4D does. It might work so give it a try but if you get chatter in the bore, suspect the tool holder first.

 

[benmychree]

A thick boring bar adapter can be made to compress easily by cutting a slit through one side and partially through the other side.

 

[i_r_machinist]

Inserted boring bars are stupid cheap on ebay. I was hesitant to buy these but I have not had any problem with them.
i_r_

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[Tozguy]

Thank you! What an invaluable piece of information. While I'm at it, I actually have one more question.

The boring bars I have are in the attached pic. I want to use them on a lathe. Someone told me that these are for boring heads for a mill but "they'll work".

What's the difference between the two?

Those boring bars shown in the picture will work fine in your 250-102 holder. Choose the shortest and fattest that will work. If you are just starting your adventure into boring then it would be important first to make sure the bars are sharpened for the job at hand.
It is also important to minimize overhang in the compound/tool post setup. Lock any axis that is not used for the boring.
The tool has to be on center, horizontal, rigid and not rub in the bore no matter what type it is and how it is held.

The 104 holder is designed for larger boring bars than the 102 holder. The advantage to making a 1/2 sleeve for the 104 is marginal when the 102 holder can do the job.

Get amazed at what you can accomplish with your current boring bars and holders. After you get some boring experience of your own with what you have then it will be more clear in what direction to go for additional tooling.