Boring bar holder ineffective

Batmanacw said:
The half moons pull together from top and bottom. Lining up the split between them will pull the slits closed and grip the bar.
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no, these are not split half moons. the half moon slides up and down.
I just took mine apart. This is what it looks like.
IMHO it actually looks like 12 oclock would offer the most lock up, not 3. 3 would just pinch the slit, 12 would close half the sleeve..
PXL_20240328_154336080.jpg
edit: changed from 6 to 12 oclock.. they are not 1/2 moons, sorry, 1/4 moon.
 
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No one has suggested this, but if I ground the bushings away so that the barrel nuts with tapered flats bear directly on the bar they would certainly hold well, wouldn't they? The interference is more than adequate. I've not measured the bar diameter, so that would be a good thing to check.
Agreed, the holder is generally wasted metal in my instance. Marking up the shank is a concern because these bars also used in a boring head, where they are, you guessed it, held by set screws! So one bar has a flat ground on it.
DanK
 
Dan Krager said:
No one has suggested this, but if I ground the bushings away so that the barrel nuts with tapered flats bear directly on the bar they would certainly hold well, wouldn't they? The interference is more than adequate. I've not measured the bar diameter, so that would be a good thing to check.
Agreed, the holder is generally wasted metal in my instance. Marking up the shank is a concern because these bars also used in a boring head, where they are, you guessed it, held by set screws! So one bar has a flat ground on it.
DanK
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NO it won't reach Just make a new sleeve.
 
woodchucker said:
That holder is a good holder. The way it clamps does not deform the bar, it also supports the bar 100% in the sleeve so no issues there. Any deflection is at the end of the holder. The statements that they are junk are based on what? Throw up some info to prove it. Because from an engineering point of view the only drawback is that the boring bar is slightly farther away from the tool post. Other than that, it has no inherent weakness. If you think it does, make a case.
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Challenge not accepted, but decaf maybe?


Never in my 35 years as a toolmaker have I ever seen a major manufacturer make a “Fitzall” boring bar holder in this style.

Every “bushing” you add will need clearances you will not be able to fully take up without torquing the **** out of the fixing bolts, and even then…. Meh.

A one piece boring bar holder and matching boring bar is superior in every way, just like the pic you posted.

Didn’t even need to use bold text.
 
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woodchucker said:
no, these are not split half moons. the half moon slides up and down.
I just took mine apart. This is what it looks like.
IMHO it actually looks like 12 oclock would offer the most lock up, not 3. 3 would just pinch the slit, 12 would close half the sleeve..
View attachment 484656
edit: changed from 6 to 12 oclock.. they are not 1/2 moons, sorry, 1/4 moon.
Click to expand...
I was incorrect. I have two that I drilled and tapped to turn them into set screw style holders.
 
I need a new holder for a 1 1/4" boring bar for my new lathe. Instead of buying a nice Aloris clamp on version for $150, I'm going to buy one of these and drill and tap it for set screws.

www.ebay.com

Shars CXA Quick Change Tool Post Holder #41 Heavy Duty Boring Bar 250-341 CNC #} | eBay

Certificate for each batch. HOLDER NUMBER #41. Center bolt thread : M10x1. HOLDER CAPACITY 1 Or 1-1/4. You may ask for freight cost before buying tools. They have different type of numbers and logos, they can't be used by mismatch.
www.ebay.com


ETA: I ordered the holder in the link and a CME 1 1/4" bar off Amazon. The holder will be drilled and tapped for set screws and the boring bar will never be used with any other holder.

I've got a 1" holder that came with my Phase II qctp set that will be drilled and tapped through the sleeve so I can hold my 3/4" solid carbide boring bar in it.
 
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I have a similar boring bar holder. I made a solid bushing for it that I drilled and tapped for set screws. Of course, the set screws have to be below flush in the sleeve. The holder holds it rigidly and it’s not dependent on squeezing a slotted sleeve. If I do my part it hits dimensions a produces a decent surface finish.
 
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