BXA holder in a AXA post?

[bulgie]

Hello, anyone tried this? I'm hoping I can get a BXA-41D boring bar holder to tighten up in an AXA QCTP. At first glance it looks like it could work by grinding some off the back of the holder to bring it closer to the post, then shimming the dovetail. Are the dovetail angles the same, different only in the linear dimension?

The reason is to get a 1-1/4" diameter boring bar holder, which doesn't seem to exist in AXA size (1.0" max), correct me if that's wrong. I'm not really using a 1-1/4" boring bar, I am notching thinwall tubing with a holesaw held in the headstock, tube held in the toolpost. I don't have a mill, so I'd like to use the lathe. Other suggestions welcome for how to do this.

I know clamping the tube directly to the cross slide somehow, no toolpost involved, could be more rigid. But I always have the QCTP mounted, so not needing to remove it for tube notching will be convenient. And I'm optimistic that this method of holding the tube in the AXA will be rigid enough. I have a AXA-41D coming, so soon I'll be able to test it on 1" tube.

I guess the other unanswered question is will my tubes be precisely sized enough to slide into the boring bar holder. I've seen tubes a couple thou oversized, so getting them to load into the holder might be too much of a PITA. I'm using high-quality alloy steel tubing with a good surface finish and reasonably tight tolerances.

Any experience along these lines? Grateful for any tips.

Thanks
Mark B in Seattle

 

[Aukai]

Have you looked up boring bar sleeves/bushings?

 

[Chewy]

Having done weird stuff like this in the past, here is what I would do. Take some kind of material a couple of inches long and secure it to the tool holder. It could be a piece of round Delrin or square aluminum or anything in between. Grind the sides down to a ledge or attach a small strip of metal to the side with screws. Doesn't need to look pretty, doesn't even need to be straight. Insert into a regular tool holder. Chuck a drill or drill and boring bar in the headstock and make the hole where you want it. Use a hacksaw and cut a groove along the side. Grind a flat spot on top and bottom. Position the piece and use a C clamp to squeeze the holder. That will lock the pipe in place and account for slight differences in diameter.

This is as about as backyard as it gets, but you say you don't have a mill which would make all this easy, maybe 30 minutes work. You can rough cut the ledge on the side with the hacksaw to save some grinding. I have done this before (without the ledge) to hold round stock in a bench vise.

 

[bulgie]

Have you looked up boring bar sleeves/bushings?

Sleeves let you use a smaller bar in a bigger holder. I need the opposite, something to hold a bigger bar (or tube in my case) than my toolpost handles "natively". Let me know if I misunderstood your suggestion.

 

[ttabbal]

I think I would get a AXA holder and bore that out if I didn't have a mill.

 

[Aukai]

I see, put a boring bar that fits you holder in a 4 jaw chuck, dial the bar in, then with the holder in the tool post, dial that in so it slides on and off the bar acuratly. Center a milling cutter back in the 4 jaw, and enlarge the hole on the boring bar holder, it might have to be cobalt, or carbide, depending on the hardness of the holder. I'm laying here after foot surgery, so I may be blowing stupid bubbled at you right now. Or maybe a boring head would work, but I worry about the interrupted cut....

 

[bulgie]

Having done weird stuff like this in the past, here is what I would do. Take some kind of material a couple of inches long and secure it to the tool holder. It could be a piece of round Delrin or square aluminum or anything in between. Grind the sides down to a ledge or attach a small strip of metal to the side with screws. Doesn't need to look pretty, doesn't even need to be straight. Insert into a regular tool holder. Chuck a drill or drill and boring bar in the headstock and make the hole where you want it. Use a hacksaw and cut a groove along the side. Grind a flat spot on top and bottom. Position the piece and use a C clamp to squeeze the holder. That will lock the pipe in place and account for slight differences in diameter.

This is as about as backyard as it gets, but you say you don't have a mill which would make all this easy, maybe 30 minutes work. You can rough cut the ledge on the side with the hacksaw to save some grinding. I have done this before (without the ledge) to hold round stock in a bench vise.

Thanks for that Chewy, but I didn't quite follow what you mean.

I think I might try this jury-rig style, pics grabbed without permission from a This Old Tony video, see, like and subscribe here:

Just two rods welded to a steel plate:


Maybe not the greatest for strength, rigidity or precision, but good enough for my use case I bet. I do have a welder but I might braze it with "nickel-silver" (zero silver content) — a strong repair braze filler, like brass/bronze only stronger.

I'd probably attach (weld or braze) the rods to the back of a 3/8" or so thick piece of steel, then make the tube-holding block out of aluminum, and bolt it to the steel backplate. Aluminum mostly because I have a chunk of scrap thick enough so it's essentially free, and also easier to bore the 1-1/4" hole

I'm still interested to know if I could use a BXA-41D holder, since that would be so easy, all the hard parts are done already — dovetail, bore, slit, pinchbolts.

 

[bulgie]

I think I would get a AXA holder and bore that out if I didn't have a mill.

They say they're hardened, anyone know how hard they are to bore?

 

[bulgie]

I see, put a boring bar that fits you holder in a 4 jaw chuck, dial the bar in, then with the holder in the tool post, dial that in so it slides on and off the bar acuratly. Center a milling cutter back in the 4 jaw, and enlarge the hole on the boring bar holder, it might have to be cobalt, or carbide, depending on the hardness of the holder. I'm laying here after foot surgery, so I may be blowing stupid bubbled at you right now. Or maybe a boring head would work, but I worry about the interrupted cut....

Are we sure an AXA-41D with the 1" hole has enough "meat" to enlarge to 1-1/4"? Between that and the unknown (to me) hardness, makes me want to either get something already bored 1-1/4", or else make a new holder in aluminum. I can't afford a solid-carbide endmill in that size, or one for carbide inserts, and I question whether my little lathe would have the power to run one even if I had one.

I know aluminum is strong and rigid enough for tube-holding blocks. I've used 6061 blocks to do a ton of tube notching and the blocks lasted for many years of daily use. That was at my place of employment; now I'm setting up a hobby shop.

 

[ttabbal]

They say they're hardened, anyone know how hard they are to bore?

Name brand might be, but I bet imports aren't. I don't have a one to test though.