Educate Me on the ASA A1-5" Lathe Spindle Nose

I am considering purchasing a lathe with an ASA A1-5" spindle nose. I have found a few drawings and pictures on the interwebs, but there is very little information regarding the pros, cons, and 'how to use them'. It seems that this was the precursor or alternate to the D1-5" spindle nose that takes the cam-lock chucks.

When I looked at the lathe, the owner removed the chuck by simply holding the chuck against the spindle and removing three bolts from the back side of what appeared to be a back plate. He then lifted the chuck off. Does this mean that with the A1-5 system the backplate is always left on the spindle nose?

If so, that seems like a pretty inconvenient setup which would require one to re-true the chuck onto this backplate every single time it is replaced. Each of the chucks had a counterbored step that mated to the backplate (one was 0.132" deep and the other was 0.201" deep). That isn't the 'short taper' is it? The owner said that there is very slight play between them to adjust for any runout. That's fine as long as it holds using those three bolts, but I can't see a way to remove the backplate and chuck assembly together from the spindle nose without removing the chuck first.

Unless I am missing something obvious (which is most likely the case) this spindle nose might be a deal breaker. Any additional information, tips, tricks, etc. (especially videos) of this A1-5 system would be greatly appreciated.

Thanks in advance!
JJ

A is bolt on D is camlok. Lathe Spindle Nose Mounting Systems

The backplate does not stay on the spindle, there is a tapered register which assures allignment and repeatability, its less convenient that the camlock style but accuracy and repeatability should be exactly the same.

rblalexander said:

The backplate does not stay on the spindle, there is a tapered register which assures allignment and repeatability, its less convenient that the camlock style but accuracy and repeatability should be exactly the same.

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So does that mean that the owner removed the chuck in an incorrect manner, causing my confusion?

Is there a picture or video of a A1-5 backplate/chuck assembly being installed and/or removed anywhere? I don't have the lathe in front of me, so it is hard to imagine by just my poor memory.

Its simple - the A type uses bolts thru chuck body that screw into spindle nose. That is what the one or two bolt circles of tapped holes are for on the face of the spindle nose

You describe an alternate way in which the bolts to the spindle nose are only holding on a back plate, and the chuck was then bolted to the back plate.
Not what the standards committee had in mind

See ASA / ASME B5.9 Spindle Noses

The owner removed three bolts from the back. I think he did it wrong. If what you are saying is correct, then there should be 6 bolts (similar to a D1-5 with 6 studs). Are these six bolts accessible from the front of the chuck or from the back of the spindle nose?

I think a picture would really help me out.

ETA: I think the best drawing/picture I have found is here: Lathe Spindle Nose Mounting Systems

That clearly shows the six bolts to attach 'stuff' to the nose. I'm guessing that the back plate that is currently on it must be something home-made, because the chuck came off with only 3 bolts and they are inserted from the headstock side into the chuck pointing toward the tailstock...its probably safe to assume that the chucks are not really A1-5, but have been adapted to fit using this backplate? I wish they were true A1-5 chucks.

So a true A1-5 chuck must have some number of holes in the front of it that match the bolt pattern to remove it from the spindle nose, correct? If so, that is a nice set up...too bad this lathe doesn't have the correct chucks for the spindle nose.

I think I see how a true A1-5 chuck should mount from this picture with the three bolts accessible from the chuck face:

I think I see that on this picture:

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You have it now

3 or 6 or more on three jaws, differing of course on four jaws - the reason for the MANY tapped holes in the spindle nose

Well no wonder I was confused! The lathe has an 8" 3 jaw, 10" 4 jaw, faceplate, and 5C hand collet closer...and not ONE of them is a true A1-5 attachment. That's really too bad. All of the ease and convenience of a A1-5 spindle nose and no attachments to take advantage of it.

I am also finding that there are virtually no used A1-5 attachments available...anywhere. Holy crap are new chucks expensive! I really wish it was a D1-5.

Yeah the A series these days commonly are used on CNC's were your not changing the chuck virtually ever, Very few direct fitting manual chucks for that, nearly all use a back plate. You want frequent engine lathe duty, you want the D series spindle noses. For real speed the only thing that beats that is the old L series interface which is just the one Nut to undo - redo.

When buying a lathe, the spindle type is very important if not the most important feature of the machine. It is critical when it comes to availability of chucks and other accessories. For this reason, I stick to D1-4 and D1-6 machines. Other D variants are also rather scarce and expensive when you find them.

adama said:

Yeah . For real speed the only thing that beats that is the old L series interface which is just the one Nut to undo - redo.

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I disagree, L series are awkward, you must hold the chuck on while you are trying to engage the nut plus you are allways pulling on a taper.It is never fully seated.The d series has a taper and a face contact.
With the d series you can hang the chuck and take both hands off of it while you pick up your wrench..Edwin Dirnbeck

I don't have to hold onto mine??? either chuck sits on the taper under its own coefficant of friction just fine here in the uk, maybe our gravity is weaker (probably takeing 20% of it as GAT ((gravity added taxation)) because they tax everything fucking else right now!

Biggest issue with the L series mounts is the folk who hammer the spanner the wrong way when trying to take a chuck off. Plenty of short half or less length ones about to prove it.

Was taught to set the spindle with the key uppermost when fitting chuck. Always found things sat in place better that way, especially with big chucks.

Clive

I only have a L00 spindle which i thinks the baby of the range, i do like it though, changeing chucks is well under the 1 minute mark and whilst i have never tested axial length holding, run out repeats identically every time, one customer damn near pissed em self when i marched in with the 10" 4 jaw with a really wacky part in it to try a id thread at site, took it back and one final skim and all i did was loosen and tighten that collar! No re-clocking, no re-picking up the lead or anything, just lugging 20 od KG of chuck and part about!