I have some small boring bars ( 1/4 and 3/8 ) with the usual shank configuration, four flats and four round areas around the circumference. The flat areas take up a lot more of the circumference than the round areas do. I was wondering if I could get away with putting these in ER collets in the turret and bore with them? I know the collets will take a lot of side load from the mill but I'm concerned about the reduced contact area with the ID of the collet.

I guess an alternative method could be to make up some sleeves with .125 wall thickness and slit them long wise to act as an interface between the boring bar and the collet.

Vern

Use a solid holder not collets for boring bars.

Solid holders are more rigid, deflect a lot less, allow deeper Depth of Cut, plus they are cheaper to replace if damaged.

BTW: If your Boring Bar has Flats never use a collet.:D

Oh dear I am going to disagree with tobyaxis.:D

I use ER collets, 5C collets and R8 collets for holding boring bars with and without flats and it works perfectly well. Very little torque is applied to a boring bar and small boring bars only take small cuts so the side loading is not much.

One thing I have found with ER collets is that it is sometimes tricky to make sure the tip of the boring bar is on center because occasionally the collet rotates a little bit as you tighten the nut. You have to guess how to put the tip off-center so it is correct when the nut is tight. 5C and R8 collets being pulled in from the back don't have this problem.

And just in case you wonder where I get 5C and R8 collets holders for the lathe, I make them.

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And just in case you wonder where I get 5C and R8 collets holders for the lathe, I make them.

I have copies of a thread from a year or so ago with several pieces of your home made tooling in it, as I recall, your C-5 tool holders were pictured there as well. I'll give it a try tomorrow. I will not be taking any big cuts.

Vern

Oh dear I am going to disagree with tobyaxis.:D


LOL, I knew you would:D

I guess it is more of my preference to use solid holders. I hate centering my tips and enjoy High Feeds, Speeds, and DOC's.:D

[QUOTE=tobyaxis;674875...I hate centering my tips and enjoy High Feeds, Speeds, and DOC's.:D[/QUOTE]

Centering the tip, as I mentioned, is a bother.

High Feeds, Speeds and DOC? Come on, we are in the Haas lathe forum.:D

I like using collets to hold micro tooling it is a fast way to do it. I do have a knack for alignment though which ticks off my buddy in the shop who runs another lathe. I also have taken a old burned up 1" square holder and made one which holds 5/16 and 1/4 inch diameter bars. I use two small set screws to hold on the flats of the micro tools. I also drilled out two holes at an angle about 1/8 diameter to allow coolant. I use the plastic flexable coolant line to line up the nozzle to the hole and it usually works great. Also we take old cutoffs from boring bars and size the Id and then put in a couple of small set screws to hold the tool and since the cutoffs have flats they align nicely and takes the guesswork out of alignment. This helps an old man like me to cheat sometimes on alignment.

we just made sleeves to hold all our boring bars, with a slot in them to run the set screw down to line up the boring bar on the flat