Toolpost sizing

[SteveM]

Tony, try the usual suspects, Little Machine shop, Victor machinery, for Phase II, Shars for import.
If you're budget conscious, start off with just the QCTP and some holders, square tool holder, a cutoff tool holder
and buy extra holders as you need them, that's how I started . Phase II and Shars tool holders are inexpensive.

Try ebay for the toolpost as well. There's a Phase II wedge set there for $199. If you can find a used one, it will be cheaper.

CDCO has the cheapest price on toolholders, but you get what you pay for. The dovetails are slightly different between pieces somethimes, but mostly that means that the handle ends up in a different position. Nothing major.

Steve

[TechTony]

Took some measurements of my current toolpost, here's the pics. Given this information, any more thoughts about size to get? Hopefully something more specific....

[TechTony]

couldn't get this one in the last post

[Torch]

Btw, Torch, what is that lever thing on the right side of your compound?

I like the coiled flat-spring leadscrew cover. Did you buy that, or is that something you made?

The "lever thing" is my table lock modification. The original locks were thumbscrews. I documented that mod here.

I ordered the optional lead screw covers with the lathe. They are mostly stock, except I had to make my own adapter to accomodate both the cover and the thread dial -- as shipped, the two were mutually exclusive.

Got a link? For example. Or price range at least? Did it come with the various tool holders? I'd very much prefer to get a full kit rather than piece making it, if I can.

It was 6 years ago. But what do you know: I still had the e-mail and the same vendor is still selling the same kit on eBay:

http://www.ebay.com/itm/BXA-NEW-10-15-Q ... 2057882504

It comes with one each of the basic holders. I made several more myself. I've never used the knurl -- I have a scissors type.

[TechTony]

I ran through the chart and compared the measurements of their TP to my own, and I'm stumped. I have no idea which model is going to work best for me. The smallest seems to make sense but in some cases, the measurements of the second to the smallest make sense.....

[Harold_V]

Keeping in mind, I do NOT use this type of tool post-----and do not claim to be an authority---
The size of post you select will determine how large the shanks on tools that can be accommodated. As the post gets larger, while they can hold larger shanks, the tool can't be adjusted to center because the holders are larger in size. By selecting a post that's too large, you may find that you can't use anything larger than, say, a ¼" tool bit. The larger post rigidity ends up costing you tool size. For that reason, if no other, make your choice the smallest post that will still accommodate shank sizes you expect to use. That way you should be able to achieve center height, which is ultra critical when turning. It is HIGHLY doubtful you'll even load this machine in such a way that you'd require a more robust post.

Harold

[TechTony]

I thought that the beauty of this style of toolpost was that I could either buy or make a new attachment for it for any size tool shank and that size would have an impact all things far reaching, like height of the post itself (impacting tool centering) and the base stub on which the whole mechanism rides in the groove on the top of the compound (thus affecting it's ability to be mounted).

I think I'm going to consult the vendors to see what their recommendations are regarding sizing - both the machine vendor and the toolpost vendor. I was hoping that it was going to be as simple as someone else pointing out what measurements I actually need to pay attention to and pointing me towards a specific size so I could get moving with the purchase but it seems that there's just too many nuisances for such simplistic hopes. Thanks anyways though.

[warmstrong1955]

Some things have no absolute definitive answer. You need to measure, and take your best shot at what tooling you are going to use.
My first lathe was a 14-30. per the specs, the 'B' series was recommended. That's what I got.
The 'A' fits much better. Got one shortly after.
And, about all the turning tools I use are 1/2" or smaller. The largest boring bar is 1". All available for 'A' in 'A' size tool holders.
I have a couple of tools that are 5/8", so I modified one tool holder by milling it. No big deal.

I agree with Harold.....what he says is what I learned. You will gain little, looking at pic's of your machine, by using a 5/8" or 3/4" tool, and you may not be able to anyway.....measure measure measure. Where is the centerline of the cutter going to be?


Bill

[BadDog]

Regarding sizing, also remember the configuration is not set in stone. You don't have to mount it right where (or as) the old post was mounted. We are machinists, or at least we try/pretend in our best effort. So if you need to make a part, make it.

In my case, the lathe dimensions really suited a CX best, which oddly enough, is the next size larger than CXA (where in the smaller size, the prefix denoted matching size and the "A" suffix denoted wedge as opposed to piston. Anyway, if I bought based on the numbers, I would have a CX on there. On the up side, it's very beefy and will take a 1" tool or insert holder (which is the size where the price really drops, if you care). On the down side, CXA is the largest size readily available at a very good price in the import market (CDCO specifically). I can't afford to stock up on Aloris brand blocks (or other nearly expensive brands), and don't care to make that many. So I bought the CXA Phase II "kit" and another 20 or so blocks from CDCO. That was about 7/16 or so too low for full range adjustment allowing 1/4 to 3/4" tools to be put on center without "packing" (spacers). So I made a suitable sized spacer from some plate scraps I had lying around, and I've been very happy with the results. I would say near perfect in fact, at least for my needs.

And believe me, I've never had occasion to wish for more rigidity, or notice a lack thereof. It will plow metal quite well and I generally like to see it producing substantial chips when roughing, and as a result I've managed to stall that 7.5 hp lathe a few times. What I've learned is that in many cases really pushing it with heavy cuts often produces the best finishes, if you can maintain size. Point being, if it were lacking in rigidity, I should have seen it in those fantastic mirror finishes I so often get while roughing, produced while cutting near the limits of what the lathe can do. I go into all that because I've had more than one person express grave concern for the loss of rigidity putting a CXA on my lathe, but that's not been my experience at all. Will the same be true for your if you could fit a BXA and decided to space up and use an AXA, maybe not. But it did work out well for me.

[TechTony]

Ok, I've watched lots of youtube vids and I've read more than a few reviews and lots of documentation over the last week trying to figure this out and it dawned on me this evening why this seems so difficult to me - the toolpost t-nut groove in my compound is really small. So now I'm wondering - do I need to take my compound and the t-nut plate that would come with a CXA to a local real machine shop and have them widen the groove on my compound and machine the plate to fit? Would widening the t-nut groove on my compound compromise the rigidity of it? Should I just replace the compound with something that's designed for something bigger?

[BadDog]

Hold up there, full stop.

In general, it's always modify the tool post/nut/whatever to fit. The base castings on a machine can certainly be machined as required or needed, but the machine is the long lasting bit, and tooling is more like a consumable, you may have several different options used by you or other owners over time, so tooling is almost always fitted to the lathe by modifying the tooling. And the "nut" that comes with it is basically a threaded plate that is relatively huge and will never fit regardless of what lathe you have (that I ever heard of anyway), so it was meant to be machined to fit the lathe.

That said, I'm pretty sure you will regard choosing CXA as a huge mistake for that lathe. It's kinda what I was getting at earlier, the measurements for selection are just one parameter in the selection process. That size/type/capacity of lathe is really more suited to (IMO) an AXA most likely, and a BXA at most (note again that I would not consider a piston AX or BX unless budget situation was dire indeed). There are relative size/capacity points to be made, but if it doesn't actively interfere with function, those mostly resolve down to subjective observations and choices. However I would offer an objective point. The cost of CXA blocks is substantially higher than smaller blocks, particularly AX(A) blocks from CDCO. They also take less space to store. And if you feel you need and/or can use insert tooling and want to save a few bucks on the cheaper less sought after holders, just mill them down to 1/2" instead of 3/4", no big deal (I did that to several used on my 11" lathe). And I really don't think your lathe is going to gain any benefit from the added rigidity of a BXA, much less a CXA.

So, if it were mine, it would be AXA, and the machine what is commonly referred to as a "plinth". Just a block of steel like my spacer that gets the tool post to your idea of the ideal height to get tooling edges on center. And while you are at it, consider also making one tall enough to eliminate your compound. On small machines, eliminating the compound when not needed can make a HUGE improvement in rigidity and capability, particularly with higher load flex sensitive operations like parting. Getting a solid block of suitable dimensions may be difficult and cost a bit, but it is possible. If you can weld, nothing wrong with a fabricated then machined laminated weldment. In fact, it can make a lot of things like managing the mounting tabs and pockets for nuts much easier. You can even do it without a welder, though that would be a separate discussion better managed on another thread. You can also fabricate suitable t-slots if you like. I've seen them done completely of bolt together fabrication, and saves on expensive cutters if you don't otherwise need them.

[TechTony]

In general, it's always modify the tool post/nut/whatever to fit. The base castings on a machine can certainly be machined as required or needed, but the machine is the long lasting bit, and tooling is more like a consumable, you may have several different options used by you or other owners over time, so tooling is almost always fitted to the lathe by modifying the tooling. And the "nut" that comes with it is basically a threaded plate that is relatively huge and will never fit regardless of what lathe you have (that I ever heard of anyway), so it was meant to be machined to fit the lathe.

I know - but the groove on mine seems so small that I figured if I went CXA then I might should widen it a little for added width on the plate. I considered the plinth idea (didn't know that's what it was called) previously but shrugged it off as newbie nonsense - it actually cracks me up to think that it was a legit idea. Most of the tooling I've used thus far has been 1/2" stuff and probably will be going forward as well. I expect that so long as the BXA will be 1/2" tooling compatible, then I'll probably go with the Phase II BXA wedge. I've got a project that's currently at a standstill until I get it bought - I really need that stationary boring bar holder. Tried bolting one in the stock toolholder that came with this machine but that thing is a joke.

Thanks for weighing in, Russ! It's been helpful!