That's great, thanks for the reply Carl.? Sounds like it's full of reading for the winter evenings...

Cute toolbox !

Thanks Phil for that and the tip. I’ll keep my eyes out for a copy.

Hi Peter, we have the book (Engineers Bible) over here in the UK it's about 80mm thick so it has every bit of information you could need in it keep a look out for a copy.
On another note over the use of stainless bolts I use nothing else in many different metals and have done so for many years, but I always brush a film of copper grease on them and have never had any problems at all.

Phill?

Thanks Bill. Is that an American book? ?We are (for our sins) now?generally metric over here in the UK, I wonder if there is an equivalent?

Some queries about bolts.

- common sense would say that a bolt should be softer than (or equal in hardness to) the thread that is is going in to, the bolt being replaceable where the threaded item is maybe not. If threading into aluminium there seems little option than to use an aluminium bolt but in the back of my mind I am highly suspicious of aluminium (like it might meld back together like the Terminator!). It’s strange stuff. I’ve heard that you shouldn’t use stainless steel in aluminium (galvanic reaction apparently), are there any other combinations of metals that are unadvisable? ?I have anti-seize compounds, one copper based and another, from bicycle maintenance days, do folks use these in general engineering?

- is there a standard formula for the size (width and thickness) of bolt hex heads? ?(I’m making some M14x1 bolts).

- given light loadings (we’re not dangling stuff from cranes, or pulling supertankers) is there any difference in the strength of fixing between (say) a 10mm, a 20mm and a 30mm bolt? Is there any point to the length of a bolt apart from reaching down to a thread?

(I think this nearly qualifies for the ‘Dumb questions’ thread !)

开云体育

SL is 25 mm dia

Don’t know about the DB200 but the U3 is around 28mm in diameter.

Is the vertical column diameter the same on both the DB200 and the Unimat 3?
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Hello Bill:

Hello Bill:

Hello:

I am not sure about the Belleville washers to be honest, I would have thought they would be way too strong for the belts to overcome, especially when the forces from the belts are in the opposite (vertical) direction. That said, the washers are inexpensive so it my be worth a try.

If you are having issues with play, you might want to also check your bearings, even though they are new! Unfortunately there is a massive problem with fake bearings. I've had fake ones that felt like they were worn out straight from the box!

Hello:

> ... formula for correct belt tightness.
> ... change between different manufacturers ...
> ... "snap fit" and you won't go far ...
Yes, I have read abot 5%, 10%.

But the thing is that I have seen small lathes run with loose belts and wonder if that isn't the right way or if it dependent on lathe size/load factors

And then there's the issue of the Belleville washer fatigue on the U3.
eg: mine was 43 years old last month and like I mentioned, the bearings were shot, (really shot) when I got it.
If the bearings were shot beyond use, in what state are the Belleville washers?

They are there to interact with the spindle/bearings arrangement and if they suffer (or not) fatige is something to be considered.
A belt that is too tight will force the spindle's axis and the washers counteract that force.

Thanks for your input.

Best,
JHM

There is a formula for correct belt tightness. I can't remember off hand, but it is something like, belt circumference minus 10%

This will change between different manufacturers and different grades of belting.?

If you want to be less technical, aim for a moderate "snap fit" and you won't go far wrong.

Hello:

I make the belts for my U3 from ? 5mm green textured PU, material I found on Aliexpress.
Works fine and slips much less since I turned a new spindle pulley in Al to replace the lousy plastic OEM pulley.

First thing I did when I purchased it (a year ago or so), after a thorough cleaning and taking stock of what was what, was to replace spindle bearings which were shot and install a new 24V/200W PWM regulated motor, later upgraded to a 400W one.

From then on, the U3 slowly has morphed into a project in itself as I am still adjusting issues that kept cropping up every time I started to do something.
eg: carriage, tailstock and headstock alignment, saddle/carriage gibs, new carriage leadscrew, new carriage handwheel arrangement and so on.

Not unexpected from a 43 year old unit with an evident lack of maintenance and an unknown number of previous owners.
Had I known ...

But I digress.
While taking spindle runout readings I noticed that the belt (on or off) had a marked influence on the spindle, albeit noticeable only with the dial in place.

I assume (?) that the Bellville washers fitted along with the bearings are directly related to this axial movement, their being some sort of protection for the bearings/tool if and when the tool would decide to dig into the material being turned.

Not that something of the sort would ever happen to me ...? 8^°

Refecting on this, a couple of questions popped up:

1.
I have seen photos/videos of other round belt driven lathes where they actually seem to be loose.
Just how tight does the spindle belt have to be on the U3?
How can this tightness be measured?
There is no provision to regulate it, has anyone ever found a way to do it in a simple and efficient manner?

2.
Do the Bellville suffer material fatigue? ie: would they need replacing after many years' use?

Thanks in advance.
Best,

JHM