Question on Boring Bar Holder

[TomKro]

Hello Tool Junkies:

I picked up an Armstrong boring bar holder in nice condition. When I looked over the bar slots, I noticed one of the positions is labeled 1J6C8 on one half, but 2J6C8 on the other. At first I thought it must be some sort of mismatch, but when I looked on e-bay, I saw similarly labeled bar holders.


The slot radius is clearly different between the top and bottom. Just wondering what goes in there. Can anyone school me on these things?
Really just curious. It's a No. 1-B, and I think it's way too big for my lathe.

 

[randyc]

I think that it may just be an illusion. I enlarged the photo and measured the depth of the two radii and they appear to be the same.

If it's too big for your lathe, just cut the bottom part down and shorten the stud. It's probably medium hard but nothing a carbide lathe tool or a carbide end mill can't easily handle.

Nice score - I have a full set of Armstrong tooling EXCEPT for the boring bar holder. Not that I need it but for nostalgic reasons I'd like one, LOL. It's surprising how handy that Armstrong system can be for weird turning problems !

 

[TomKro]

Good eye on those radii.

I checked it with a 1/2 inch bar, and it's tight all around.

I just noticed that the numbers are directly across from the 1/2 inch opening. Now I'm wondering if the numbers are just some sort of model number to call out the different size holes.

 

[kd4gij]

Probley just part numbers for the 2 parts.

 

[4GSR]

My NOS one has the numbers "109" stamped on each half. This is fairly common to stamp "match" or "sterilised" numbers on parts to keep them in matched sets. They may also serve as a serial number for the tool post, but I doubt it. Armstrong probably made up into the 100's of thousands of these over the history of the company!