BB CX701 lathe spindle nominal measures?

[PaulL]

My lathe is a Busy Bee/Craftex CX701. I'm trying to figure out my nominal spindle dimensions: nose, bolt pattern.
The spindle flange is 125mm. The nose is 70mm (2 3/4")across, with a 43.5mm (1.7") passthrough.
I've measured across the studs on a chuck, subtracted the diameter of one stud to get 84.4mm, and divided by sqrt(3) to get a nominal radius of 49mm (+- 0.5 on a lack of measurement repeatability), giving a bolt hole radius of 98mm, or 3.86", effectively.
I've been looking at tables of spindles, including, for instance, that at https://www.northlandtool.com/spindle-nose-standards/ .
Since there are no bolt holes in the nose itself, I expect it to be a B2 class spindle nose, but there is *nothing* I can see with anywhere near that bolt-hole radius.
Any idea where else to look up my nominal specifications? The manual is, of course, no help.
I'd love to know my nominal nose taper, for example, before machining a back plate to fit it. The landing is so short (7.14mm) that it's difficult to get a confident angle off it even with a DTI in the compound.

 

[DavidR8]

I know the GM at the factory where it was made. Would you like me to ask him?
Edit: email sent.

 

[PaulL]

I know the GM at the factory where it was made. Would you like me to ask him?
Edit: email sent.

You, sir, are a veritable fount of knowledge and contacts. Thank you.

 

[DavidR8]

@PaulL This is the drawing I received.
I've asked for a closer shot of the cut off side of the page.

 

[PaulL]

@PaulL This is the drawing I received.
I've asked for a closer shot of the cut off side of the page.

That is gloriously helpful! Just missing the nose angle in the cut off side.
No ISO-702 spindle has a 98mm bolt circle
Paul

 

[PaulL]

The real question, of course, is how we can get our hands on these drawings in a more "regular" way. Critical components should be drawn like this in the manual!

 

[DavidR8]

The real question, of course, is how we can get our hands on these drawings in a more "regular" way. Critical components should be drawn like this in the manual!

I'm working on helping them with their documentation.

 

[jcdammeyer]

Wow! You got the 98mm bolt circle correct. I'm guessing the #5 means it's an MT 5 taper. If I were to eyeball the bevel at the nose I'd guess a 45 degree chamfer.

 

[PaulL]

Wow! You got the 98mm bolt circle correct. I'm guessing the #5 means it's an MT 5 taper. If I were to eyeball the bevel at the nose I'd guess a 45 degree chamfer.

The chamfer is easy, but I expect some angle on the nose, given that my chucks slip on wobbly and get tighter as I press them home. But it won't be much.

Though I don't see anything on the drawing. So... back into the shop for a minute.

 

[jcdammeyer]

It's also possible your chucks have a slight taper. From the drawing it doesn't look like the end of the spindle does. Perhaps turn a piece of scrap with that ID from the drawing and see if it slips on. Tedious I know but might give you a clue.

 

[PaulL]

Though I don't see anything on the drawing. So... back into the shop for a minute.

Oh, there is no taper. At all. Just the chamfer. I wonder how much that limits repeatability of chuck mounting? Only a problem for the 3-jaw, I guess.

 

[DavidR8]

Oh, there is no taper. At all. Just the chamfer. I wonder how much that limits repeatability of chuck mounting? Only a problem for the 3-jaw, I guess.

I wondered if there was a taper.

 

[jcdammeyer]

My guess is they've added a taper, very slight, to the inside bore of the chucks and face plate. So it becomes almost a press fit and that's how it's centered.

 

[PaulL]

My guess is they've added a taper, very slight, to the inside bore of the chucks and face plate. So it becomes almost a press fit and that's how it's centered.

Yes, I can make out a tiny difference in light reflection in the chucks and backplates. It also explains the slight worn spots on the spindle nose, which appears to be gaining a matching taper ;-)

 

[DavidR8]

Yes, I can make out a tiny difference in light reflection in the chucks and backplates. It also explains the slight worn spots on the spindle nose, which appears to be gaining a matching taper ;-)

Get some lapping compound and call it a day

 

[PaulL]

I really feel like it's time to make a camlock adapter for this thing.
Not that I trust my precision particularly at this point...

 

[whydontu]

There is a spot in Hell reserved for manufacturers who make up chuck mounting dimensions that don’t meet any know standards.

 

[DavidR8]

There is a spot in Hell reserved for manufacturers who make up chuck mounting dimensions that don’t meet any know standards.

Oh you mean like the 60mm-8tpi threaded spindle on my 12x37?

 

[YotaBota]

Must be the same guy that that decided 98mm diameter bolt circle. Why not not make it an even 100mm and go easy on us?

 

[Susquatch]

Critical components should be drawn like this in the manual!

If only that could be true.

But I've never seen that available from any of them.

Any that do are prolly outside my price range.