FINALLY Arrived

[chris mabbott]

Next I tackled the Z screw assembly, they have a kinda odd setup to hold the grub screws in place. They aren’t the usual allen head grub screws but slotted screw. There is a ridge machined into the gear flange which the screw slots are supposed to line up with. Then they wrap a wire around the whole deal, feeding it across the screw slot, then twist tie it.
A little crude, so I wonder if there were problems on the previous models, and this is their answer to that prob? I might just change them for the allen head type, sharpen the ends and locktite them in place? They’ve drilled two holes into the shaft to prevent slipping and for the screws to bite in to.

At first I thought that they’d painted the gear black, but I was happy to see that it is a black oxide finish and tough to come off as I wire brushed it after degreasing. A nice touch to prevent rust in a seldom accessed area. I’m sure I wont touch this again, hopefully for a few years

[chris mabbott]

As usual every part was rough to the touch, everything feels like it is covered in grit or sand.
Once the gear and bearing block had been removed, I could see the start of rust on the shaft, seems to be a common thing so far.. as does the lack of any lubricant 😮

If you look at the two tension nuts, you can see the rough, gritty texture that I’m talking about.

[chris mabbott]

So by the time I cleaned up these parts and re-threaded the block back in place, it had been yet another 5 hours.
With the cleaning, wire wheel treatment, touching up some of the damaged threads, followed by a grease job, the threaded block flew back on and with a good spin, it got almost four complete turns on its own 😆 Way better than when it came off, I had to fight a little with it.

So to end the day I cleaned the paint from the micrometer mounting flange. Funny thing, they had put tape over the hole to protect it from paint, then painted over the tape. Instead of removing the tape, they just mounted the micrometer flange over the top of the paint and tape 😆 So that added about 20 thou thickness, HUH.
Here’s a before and after…

Hopefully I’ll have some more time tomorrow to continue. I’m also thinking about changing the cheap sealed roller bearing atop the shaft, it almost feels rough to turn, and looks quite cheap.

[arutha]

That machine is going to be worth twice what you paid for it by the time you’ve finished with it
Paul.

[chris mabbott]

Paul, yes, with my labor and the new bearings, all, unfortunately, non-refundable

I spent a few more hours yesterday on the head rotating mounting plate. I shouldn’t be surprised, but I still am, that this also was starting to rust and felt like 800 grit sandpaper, everything, even parts inside housing, kinda weird how that would be?

You can see where the main mounting pin is quite rough inside it’s round housing. There is a spring loaded nylon pressure plate that sits inside this area.
You can also see the rotational locking device, quite an ingenious invention, I didn’t even realize that it was a splined shaft that mated with the teeth in the pin..

[chris mabbott]

The splined lock pin shaft was also blackened but so roughly finished that I had a hard time sliding it out of its housing. So starting at 80 grit and finishing with 1500, I managed to get it somewhat smoother.. you can see how rough cut it is, I wonder if they meant it to be for lubrincation purposes, although with these high ridges, it would just cause uneven wear.

[chris mabbott]

Just a quick update…

I found a new bearing for the Z axis screw shaft and also new and better thrust bearings for the support blocks. The old bearings were OK, but cheap, they even felt cheap and lite when I removed them. The new shaft thrust bearings have a proper metal race and not an alloy type, they are also twice the weight, which is good.

[chris mabbott]

FINALLY, the welders showed up today and mounted the trolley on the table, they also kindly helped me to lift it aboard, three pairs of hands, no problem..
Now comes the re-assembly

I found some really good hard timber for underneath, to act as a dampener and to raise it to a comfortable height so I’m not bending over.

I’ve put 3mm brass plate between the wood/base, mainly for easy cleanup, it gives a classic look, and the bare wood would become stained and embedded with filings. I’ll also attach brass plate around the edges of the wood to finish it off…

[tmac1956]

Chris:

From where do you order your replacement bearings?

Thanks!
Tom

[david pierce]

Tom,
Most major industrial supply houses such as MSC and McMaster Carr sell bearings. They can also be purchased by looking up bearings on the internet. Standard ABEC 3 angular contact ball bearings will work ok in standard tolerance machines such as drill presses and mills. The price difference between the ABEC 3 and ABEC 7 or ABEC 9 is alarming and there is no real adavantage to use ultra precision bearings on a machine that is not an ultra precision machine.
david

[chris mabbott]

Hey Tom, yep, what David said is spot on.
If you’re ordering online just make sure you get good id od measurements or the numbers from the old bearings. Mine had no numbers.

Just simply replacing the original bearings with these makes things a lot smoother, and they aren’t expensive, just better quality than whatever make the originals were…

I finally found a place here that sells a good selection of bearings, what a joy

[tmac1956]

@Chris Mabbott wrote:

Just a quick update…

I found a new bearing for the Z axis screw shaft and also new and better thrust bearings for the support blocks. The old bearings were OK, but cheap, they even felt cheap and lite when I removed them. The new shaft thrust bearings have a proper metal race and not an alloy type, they are also twice the weight, which is good.

Chris:

Is that some sort of bearing puller shown in the last picture?

Thanks!
Tom

[chris mabbott]

Tom, yes it is, a simple 2 leg puller for bearings, gears/sprockets etc
You can also get them with 3 or 4 legs..

You can use a punch on the inner race, but you have to hit at 4 clock points, 12, 6 etc it’s a pain.
This bearing was pretty tight so ….

[chris mabbott]

Ach zo, a mini progress report ja 😆

What with other obligations, visitors, too hot weather and being knackered combined with slightly jaded I finally managed to build up some steam yesterday..

So, With the help of the welders, we got it boarded. I reinstalled the Z-axis and after about 4 install, take apart, adjust, install attempts, I finally was happy with the amount of backlash I achieved although I didn’t put a dial on it to get the exact reading, and I don’t really trust the mic on the machine, but this is the amount registered before the gears mesh, call it what we will 😆 . When it arrived it had about 12mil +_. I blued the gear teeth to check the mating, so this is about as good as it gets, fine for my purposes.

[chris mabbott]

With the new bearings, the removal of all the debris and sand, a good cleaning and thread chasing, proper lube etc, it’s a smooth a my head 😆

I actually installed the head/spindle/handwheel but didn’t take a shot yet, so I tried it under some weight, still smooth. Before the touch up, it was stiff and rough.

One thing I am thinking about is… You can see the small open “chamber” below the gear, the hand wheel gear sits just below the halfway mark.
I’m toying with the idea to fill this cavity, half way, with some heavy gear oil which will come half way up on the wheel gear. As this is such a hard place to access, you have to disassemble the electrical cabinet, remove the cabinet, then remove another cover in order to add lube in the future…
Because of the close mesh of the gears, eventually , even now, the grease will get squeezed out and just sit outside doing nothing. With an oil bath, the gear will be submerged, half way, in gear oil, always picking up lube then it will drip back into the reservoir. That should be good for many years as it is slow moving, it shouldn’t cause a mess etc… Still on the thinking stage..

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