BXA holder in a AXA post?

[bulgie]

Just to throw this out there…. I know you want to mount a holder in your QCTP and this is not that. Or maybe it could be mounted on the QCTP simply mounting a half inch bar on back of the chuck and put in a regular QCTP holder. Depends on length of tube needed. The chuck below has long jaws and may work.

A 6 jaw chuck can hold thin wall tube nicely because the pressure is spread among the 6 jaws. In this application a 6 jaw could be mounted to stand on the cross slide aligned to the right height to accept the tube. need to be sure the through hole is large enough but if the part is short it would not matter

Interesting idea but not for me. The cost of a 6-jaw, plus the cost of the precision angle plate needed to hold it on the cross slide, makes this too expensive. Even if I had those, my cross slide doesn't have any way to mount anything on it other than a toolpost on a compound. No T-slots, not even any holes. I know, dumb lathe design but it's what I've got.

My tubes are usually 22 to 24" long. (I make lightweight bicycle frames.) Oh also I need a way to "clock" the notches at both ends to each other precisely, which a chuck wouldn't do. Precise clocking results in less twisting during welding, for a better-aligned finished frame. (My customers are extremely picky about alignment, beyond all practical reason for caring — it's a show-off move for the builder to make them perfectly flat.) Normally the clocking is done by attaching holders to both ends of the tube before the first cut. The holders are tightened with it all sitting on a flat surface, so the two holders are in the same plane.

 

[Cadillac STS]

One way to clock or index your tubes is using a Rose Index tool. It bolts on the tube and allows indexing by having sides that are square, hex, etc.. it is not a work holding tool just an indexing tool. With it bolted on you can turn it and get precise sides on both ends.

Rose Index is the brand name product but you could make one There are directions online. If just 4 sides definitely make one. Square with a hole in it and a set screw.

you need to have a way to measure one side level. I use an electronic level but analog level would work.

Hobbyist Rose-Index® 20%off

The Rose-Index is Patented and Trademarked 1 to 2 Inch: This is the same size and shape of the original Rose-Index with a range of 1” to 2” diameters. It is made from aluminum and hard anodized to keep pricing more affordable for the nonprofessionals. Just like it’s steel twin, this tool does...

rosenthalproducts.com

edit: just re read your post and looks like you already have a clocking method.. still nice to know about the Rose Index

 

[bulgie]

One way to clock or index your tubes is using a Rose Index tool. It bolts on the tube and allows indexing by having sides that are square, hex, etc.. it is not a work holding tool just an indexing tool. With it bolted on you can turn it and get precise sides on both ends.

Rose Index is the brand name product but you could make one There are directions online. If just 4 sides definitely make one. Square with a hole in it and a set screw.

you need to have a way to measure one side level. I use an electronic level but analog level would work.

Hobbyist Rose-Index® 20%off

The Rose-Index is Patented and Trademarked 1 to 2 Inch: This is the same size and shape of the original Rose-Index with a range of 1” to 2” diameters. It is made from aluminum and hard anodized to keep pricing more affordable for the nonprofessionals. Just like it’s steel twin, this tool does...

rosenthalproducts.com

edit: just re read your post and looks like you already have a clocking method.. still nice to know about the Rose Index

I wouldn't trust a setscrew bearing down on the side of my thinnest tubes, but I do functionally the same thing with blocks that are sawed in two, with screws that clamp the two halves together. That type of block can hold reliably without slipping, with no localized stress (setscrew) on the tube — it clamps with even pressure all around. Like these from Alex Meade, which are also a lot cheaper than a Rose Index. Disadvantage is you need separate blocks for each size of tube, and you can't do in-between sizes unless you make your own custom blocks. A Rose Index clamps to any size over a wide range.

Mark B

 

[bulgie]

Following up, I got the BXA holder, and it fits great on my AXA post, with a simple .030" shim on one side of the dovetail. No other mods needed, and it centers (height-wise) on my 10" swing lathe with room to spare.

Tested mitering a thinwall tube, it worked perfectly. I have a system, pretty jazzed about it. Just as good as doing it on a Bridgeport like at my previous place of employment, in fact better in some ways.

Thanks all for your ideas.

 

[bulgie]

OK I said .030" shim but that's not right, I ended up with .032, not that it matters that much, it would tighten up either way, but I am happy with this method so I thought I'd share. I bought a couple of these cheap feeler gauges on ebay, $7 each and free shipping.


Unbolted the stack, took the .032" feeler out, and glued it to the holder with Loctite 303 (high strength, green). Clamped it real tight in the post and let it cure overnight, then did the other one (I need two for this method). Now it feels like a part of the holder, but time will tell how reliable the Loctite is.




Proof of concept:



Cuts very smooth, plenty rigid, no tendency to grab or chatter, which I got a bit of on the Bridgeport at my old shop. Some of that is down to the fine-tooth holesaw, but I think this setup might be better in some ways than a vertical mill for this job. Feed (z-axis) was by hand — haven't tried the power feed yet, but I think I will, just to make it a little easier on the operator.

I'll post back if any trouble crops up but for now I assume it's Case Closed.

-Mark

 

[mattthemuppet2]

that's a cool set up, would never have thought of doing it that way

 

[keeena]

I know you just solved it with your approach (nice work!), but another option if it wasn't mentioned already: a drill attachment for your TP/TH. Your work would go in the lathe chuck and you could index the part if made an indexable wheel for your headstock.

The one thing you'd have to consider is your total length available for drills; you're limited by the cross feed travel which can be mitigated a bit by swinging the compound backwards to get the TH as far back from the lathe center axis as possible (obviously not an option if you need to drill at a non-right angle), or make an extension if its something that would see regular use. You could also use a different bit holder (an internal hex like an impact wrench) which could be flush in the TH to give you more clearance. Anyway - just another option; it was handy to have until I got a mill.

 

[bulgie]

I know you just solved it with your approach (nice work!), but another option if it wasn't mentioned already: a drill attachment for your TP/TH. Your work would go in the lathe chuck and you could index the part if made an indexable wheel for your headstock.

Clever! Using the lathe, switched off, as a work holder, who'd a-thunk it.

I can't hold thinwall tube in my spindle though. 5C collets only go up to 1" with full through-clearance for long parts (1-1/8" for short pieces) and I need to miter 1-1/4" tube sometimes. 3- and 4-jaw chucks distort the tube and even when distorted it's not tight/rigid enough unless you put a solid mandrel inside the tube, possible but a PITA, each wall thickness needs a different mandrel.

One of these days I have get set up to make soft jaws for my 3-jaw. Those can be custom-sized to hold thinwall stuff perfectly, like a collet without the size limit on 5C, but they're difficult to make without a mill.

I don't have a project on the horizon yet for an indexer for the spindle, but I can see how that'd be super valuable for lots of things. I'll add that to my "someday" list.

Thanks
Mark