My Prvomajska ALG-100, English manual coming

[AlfaGTA]

Felt, or not?

I have been scratching my head for a while on the the lubrication of this, now I have figured that out I'm putting it back together.

Have another small doubt, there is should be a felt ring, 5mm thick 15mm high, just above the top of the taper bearing.
View attachment 407245

Red / crosshatch in the drawing
View attachment 407247



Incidentally, the assembly on my unit is different from the drawing and description as there is no adjusting spacer 67. Instead, washer 64 has a shoulder of corresponding height. I think this makes sense, because even with a the precise spacer, pre-loading of the lower thrust bearing id done with the external threaded nut 65, so why bother with an extra part.

I should like to see a sketch of what you mean by the lower spacer ring (64) having a "shoulder"
In the drawing the spacer #67 sets the axial position of the entire spindle, so its thickness controls the position and hence the clearance of the main spindle/ bushing.
Also,be careful here, plate ball thrust bearings are NEVER preloaded, unlike a radial ball bearing or tapered roller bearing there is nowhere for
compression forces (preload) to go!
They should always be setup with some end clearance. suspect on that setup one would need to have .0002-.0003" of end float.
Remember that the thrust bearings are directional....there will be a race that has the inner ID smaller to be a fit on the spindle while the opposite race will have clearance to allow the spindle to rotate.
Have seen more than one assembly done incorrectly which prevents the thrust bearings from functioning correctly.

Looks to me that the felt is there to keep oil from running through the spindle so that some will remain at the ball bearings and some available to
feed the upper end of the bushing, ( its sits vertical and the upper part of the bushing will not see much oil from the middle felt.

Cheers Ross

 

[jdm1]

I should like to see a sketch of what you mean by the lower spacer ring (64) having a "shoulder"

64 the is the washer on top of the lower thrust bearing. It is flat in the drawing, but it has a shoulder on my unit. In the last picture above.

In the drawing the spacer #67 sets the axial position of the entire spindle, so its thickness controls the position and hence the clearance of the main spindle/ bushing.

But it's not present in my unit, so I can't do like the last paragraph of the manual says below.
The lower thrust bearing sits directly on the spindle. However, with washer 64 in place, shoulder down and nut tightened, all appears to be positioned correctly or very close to it. I just did a quick dry run without the upper thrust bearing, will take exact measurements once I do the final assembly.

Adjusting the milling spindle (Fig. 17)
All radial forces are absorbed by the tapered section of the milling spindle, which is mounted in a bronze sleeve. The axial forces are absorbed by thrust bearings, which are fastened in the quill by the washer 64 and the screw 65. If the bearing play has increased due to prolonged use, the nuts 66 should be tightened and then clamped together. Here, the bearing must be adjusted until there is radial play, which must not exceed 0.01 mm, and the axial clearance should not exceed 0.01 mm. If the bearing cannot be adjusted in this way, the adjusting ring 67 must be readjusted, whereby reduction in thickness of 0.1 mm reduces the radial bearing clearance by 0.01 mm.

Also,be careful here, plate ball thrust bearings are NEVER preloaded, unlike a radial ball bearing or tapered roller bearing there is nowhere for compression forces (preload) to go!

Correct. Used the wrong term, and brainfarted also in saying that nut 65 has any role in adjustment.

Have seen more than one assembly done incorrectly which prevents the thrust bearings from functioning correctly.

Fortunately they were right on mine. I didn't check the balls cage orientation.

Looks to me that the felt is there to keep oil from running through the spindle so that some will remain at the ball bearings and some available to feed the upper end of the bushing, ( its sits vertical and the upper part of the bushing will not see much oil from the middle felt.

That makes good sense, keeping an oil reserve of some amount there, I didn't thought of that, thank you.
And thinking better the felt should stay with the housing, not the spindle.
When there is too much oil it will come down around the quill.
The bushing hosts three felt pads, spaced over height, 120° from each other, they are in very good nick.

 

[AlfaGTA]

Correct me if I have the setup wrong.
That ring between the two thrust bearings has the step toward the top as it sits in the machine,yes?
Further that ring is held tight against a step in the quill by a ring nut.

If both these things are true , then you don’t have any adjustment to the axial position of the spindle or its radial clearance.
The position of the spindle is a result of the location of the ring locating step in the quill and the lower thrust bearing thickness.
Only thing you can do with that setup is to grind the lower thrust bearing thinner.
Just does not seem right.
Cheers Ross

 

[jdm1]

That ring between the two thrust bearings has the step toward the top as it sits in the machine,yes?

No, toward the bottom as I wrote above. The height of the step (2 mm) appears to be the same as the spacer ring that is not on my machine, so the total distance between the step on the quill, and the one on the spindle is the same in the two cases.

Further that ring is held tight against a step in the quill by a ring nut.

Correct.

1If both these things are true , then you don’t have any adjustment to the axial position of the spindle or its radial clearance.
The position of the spindle is a result of the location of the ring locating step in the quill and the lower thrust bearing thickness..

Correct.

Only thing you can do with that setup is to grind the lower thrust bearing thinner.

Or reduce the step on the washer, which is not hardened.

Just does not seem right.

I understand what you mean. I can't exclude that in the past the spacer ring went missing, or there was a clearance issue, and to remedy the stepped washer was made.
I will know where I stand once I have the missing felt ready. Since the bearing shaft races are a slight interference fit I don't feel like doing unnecessary push and pulls on them.

 

[AlfaGTA]

No, toward the bottom as I wrote above. The height of the step (2 mm) appears to be the same as the spacer ring that is not on my machine, so the total distance between the step on the quill, and the one on the spindle is the same in the two cases.



Correct.


Correct.


Or reduce the step on the washer, which is not hardened.


I understand what you mean. I can't exclude that in the past the spacer ring went missing, or there was a clearance issue, and to remedy the stepped washer was made.
I will know where I stand once I have the missing felt ready. Since the bearing shaft races are a slight interference fit I don't feel like doing unnecessary push and pulls on them.

 

[AlfaGTA]

Ok so that was the part that I missed and makes all the difference.
Only part that I dislike with having a step control the spacing is that it’s much harder to keep all three register surfaces dead parallel.
Cheers Ross

 

[jdm1]

Only part that I dislike with having a step control the spacing is that it’s much harder to keep all three register surfaces dead parallel.

And below the importance of that exactly, explained by Robin Renzetti.

https://youtube.com/watch&v=grUdsTTRGl4&t=1535s

Honestly I can't get my current work to a level that is possibly even "sufficient" by these standards. But at least I can learn and try to make my machines more usable and precise.

 

[jdm1]

Down the rabbit hole

Just because I have paint left from the cabinet repair.
Star was an Italian manufacturer of power tools, good solid stuff. I think they folded already in the 80's.

 

[jdm1]

This is not a restoration thread this is not

Bakelite sheet in the electrical cabinet had broken, made a new one from a slightly thicker material.


Trivia, the electrical diagram shows fuses on both output wires of the transformer, which makes no sense.
Since mine is the fabled 1962 edition, extra fuse was removed, that's where the empty space is.

Also made a new lower deadbolt and key which were missing.