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  #1  
Old 01-26-2024, 02:23 AM
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arizonian arizonian is offline
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Default Boring Bar Holders

I have a few small boring bars that are too large for the Aloris QC tool post, so an article in the Home Shop Machinist magazine spurred this project on. A quick look at prices in the latest Shars catalog convinced me I am on the right track.

I purchased a length of 1-1/2 x 1-1/2 stock from a local supplier, cut it into ~3" long chunks and set the mill up for cutting dovetails.

Once the dovetails were complete, I offset the parts in the 4-jaw chuck and drilled to size. I don't have a reamer for the correct diameters so I drilled to the closest undersize and finished to size with the drill bit.

After drilling, the holders were slit on the band saw.

Drilled and tapped the three and now waiting on delivery of the studs for the height adjustment. I still need to make the knurled stop and the nuts to lock the height down.

I don't have a 1" drill bit so I will have to finish the last holder with a boring bar in the lathe

I'll provide a sketch at a later date.
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Last edited by arizonian; 01-26-2024 at 02:31 AM.
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  #2  
Old 01-26-2024, 06:29 AM
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Nice job. More tool holders are on my “to do” list too. Especially when I manage to get my shaper and big mill setup. Just because I can projects.


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  #3  
Old 02-02-2024, 01:27 PM
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So I promised sketch last post and will deliver it here.

First use of the 3/4" boring bar and holder

A spring pass and the 1" bar fits

Almost broke thru on the inside of the dovetail, you can see a small protrusion

All lined up, almost ready to go

Working sketch


There is barely enough material using 1-1/2" square stock for the 1" bar. The center of the bore was held .025" further away from the tool post than the vertical dimension to prevent breaking thru into the dovetail. The clamp screws are also held .025" higher to avoid breaking thru into the bore.

All holders received the treatment at Detail B. My dovetail cutter measures 5/16" tall and will leave an uncut lip at the top, so the edge was pushed back enough to remove the lip plus a bit.

The original drawing I saw calls for 1.000" between the gage pins, but that did not fit over my tool post, and now I know why. The deeper the dovetail cut is, the wider it must be to hold the same dimension at the top. Somewhere my depth was off, so adjustments were made.

On that last note, one of the holders was just a bit tight to smoothly fit the tool post so a flat file across the top face of the dovetail decreased the depth just enough to smoothly slide over it. The wedging surfaces of the tool post are the top face and the angled sides and the depth needs to be just enough to clear.
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Bill in sunny Tucson

I believe in gun control.

Gun Control: The ability to consistently hit what you are aiming at.

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  #4  
Old 02-02-2024, 01:32 PM
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Quote:
Originally Posted by toprecycler View Post
Nice job. More tool holders are on my “to do” list too. Especially when I manage to get my shaper and big mill setup. Just because I can projects.


Sent from my iPhone using Tapatalk
Bingo! And it costs a lot less until you factor in your time.

I think it's in Dubby's sig line, I've always had more time than money
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Gun Control: The ability to consistently hit what you are aiming at.

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  #5  
Old 02-02-2024, 10:58 PM
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That's a mighty fine job now I am going to try for some BXA holders
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  #6  
Old 02-12-2024, 05:20 PM
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I know I am probably being a bit anal but...

Somewhere I read that a bit of talcum powder on a Morse taper will keep the taper from spinning as long as you don't use too much. Is this a common practice? More importantly, does this practice work?

I haven't had a boring bar slip yet but I'm thinking of having some talc around for when I do change or adjust bars/tools. I have had the collet slip in the mill before.
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  #7  
Old 02-12-2024, 08:06 PM
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Quote:
Originally Posted by arizonian View Post
I know I am probably being a bit anal but...

Somewhere I read that a bit of talcum powder on a Morse taper will keep the taper from spinning as long as you don't use too much. Is this a common practice? More importantly, does this practice work?

I haven't had a boring bar slip yet but I'm thinking of having some talc around for when I do change or adjust bars/tools. I have had the collet slip in the mill before.
I have used chalk line chalk for this as well. yes very little. I think the real issue turned out to be a burr in the bore caused by a damaged tool, we polished the burr out and did not need chalk after that.

If the taper is clean and burr free you should be able to clean it out with brake clean or a quick drying solvent and it should hold stronger.

Blue up a taper and send it home and remove it and you should be able to tell how much contact you have. You might be surprised how little contact it takes for the taper to hold.

Scott
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  #8  
Old 02-13-2024, 11:59 AM
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Quote:
Originally Posted by arizonian View Post
I know I am probably being a bit anal but...

Somewhere I read that a bit of talcum powder on a Morse taper will keep the taper from spinning as long as you don't use too much. Is this a common practice? More importantly, does this practice work?

I haven't had a boring bar slip yet but I'm thinking of having some talc around for when I do change or adjust bars/tools. I have had the collet slip in the mill before.
It is considered generally good practice to use a bushing when holding a
boring bar. It aids in controlling vibration/harmonics and also aids in
overcoming imperfection in fit.

Using chalk or talc is just a bandaid when you damaged component. Nothing
you have should be damages yet.
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  #9  
Old 02-13-2024, 12:18 PM
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If you have a fairly good slip fit, and you are able to tighten the holder down with bolts like drawn, you probably will have no problem.

Now, if the bolt was just tightened against the boring bar, like typical boring heads, then you might have a bit of slippage problem.


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  #10  
Old 02-14-2024, 09:22 PM
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Default New Holder

Well, I have taken the plunge toward insert tooling. A friend bought a toolbox with contents and had no use for this tool and the inserts. A benjamin got me this and 20 CNMG432 inserts. Ten of the inserts are import, not sure of the other ten inserts. Twenty inserts should give me 80 cutting edges, which might last a while. Or not.

A trip to my local steel supplier for another chunk of bar stock, into the saw and then start whittling away.

First a few measurements. This a much bigger bar and clearances up and down are important.

Whittling is complete.

View of the writing on the tool. All holes have been drilled and tapped and tool installed.

Nine import inserts in the package, one in the tool. The other two are some of the unknown origin.

Sketch of the QC holder. There is more pressure down on the front of the holder than upward on the rear so I made adjustments to maximize the material underneath.

When I set the QC holder on the lathe, the adjuster screw was too short to allow it to set on the centerline so I swapped screws with another holder to get it to the correct cutting height.

I have no clue what material the inserts are for and whether they are for roughing or finishing. Any help will be greatly appreciated.
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