Disassembling of Minimill / X2-clone / XJ-12 Ballbearings

[Roberto dassoParticipant @robertodasso55459]

Yes..for downloading that file, it is required to join the group..

[John ShepherdParticipant @johnshepherd38883]

Ok Lets try this way. (For some reason it would appear that Yahoo URLs change frequently.)

There have been many posts and articles about the need to align the carriage and spindle housing on the X2 or its variants. The following does not repeat the methods that may be used to measure and correct the alignment but shows a simple modification that will take some of the hit and miss out of the adjustment.>>

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Basically the modification is a bar bolted to the motor mounting plate with two adjusting screws with lock nuts that “rock” the casting into alignment. I hope the picture shows the principle and I will not give dimensions as they are not critical. I did originally consider just drilling and tapping two holes in the mounting plate for the adjusting screws but having looked at the under side, its shape does not lend itself to this so the bar was added as an extension. The only modification to the machine is two 6mm tapped holes in the end of the motor mounting plate to attach the bar.>>

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The photograph shows the prototype – At some stage I will probably replace the adjusting screws with socket screws. I may also consider putting two locating dowels in the bar/motor mounting plate. >>

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In use the head is lifted nearly off the column so that the four bolts holding the carriage and spindle housing together are slackened slightly. I then used Rolies Dads Method (RDM) that is well described elseware to achieve alignment. The two adjusting screws are initially set to just touch the carriage casting and one of them adjusted to correct the error. I found that very fine adjustment can be achieved without having the four bolts too loose. This and the bar itself means that there is less chance of movement when everything is tightened up. Leaving the bar in place will also help to prevent future movement and provide a reference if you have to dismantle.>>

 

Edited By John Shepherd 1 on 07/06/2010 08:20:37

[Roberto dassoParticipant @robertodasso55459]

Ok.. i got the mini-mill today..

It is not bad, it seems a good  little machine

I measured the spindle runout (outside): less than 0.01 mm.. the report included  says 0.01 at the end of the spindle and 0.02 100 mm to the end of the splinde

 

Anyone has checked the spindle runout of this kind of milling machine?

 

About the dials.. on the cross table are graduated 0.02 mm.. 75 x revolution total 1.5 mm/rev (0.02*75)  

75 of course is the number of the minor graduations, not 0.75 mm /rev

the vertical fine feed.. 0.025  x 60 ..again 1.5 mm/rev

 

 

 

 

[Peter G. ShawParticipant @peterg-shaw75338]

Hi Roberto,

 

Agree with the dials, but still difficult to use. I have a conversion table on my mill giving the number of divisions for varying amounts of travel, eg say 1mm and 0.25 mm. So if I want 1.25mm, I add the two numbers together. Job done.

 

Haven’t checked spindle run out.

 

Regards,

 

Peter G. Shaw

[John RuddParticipant @johnrudd16576]

Marcus,

 

I changed the bearing out on my X2 clone (Chester Conquest) when I moved over to a belt drive conversion…Taper rollers from a local bearing supplier (SKF brand).

I didnt bother with the smaller bearings as I didnt replace the countershaft.

 

My mill is much quieter post conversion.

[Roberto dassoParticipant @robertodasso55459]

Posted by Peter G. Shaw on 09/06/2010 12:48:52:

Hi Roberto,

 

Agree with the dials, but still difficult to use. I have a conversion table on my mill giving the number of divisions for varying amounts of travel, eg say 1mm and 0.25 mm. So if I want 1.25mm, I add the two numbers together. Job done.

 

Haven’t checked spindle run out.

 

Regards,

 

Peter G. Shaw

 

Hello Peter

it is a very good idea.. i will do the same,  your table is very  helpful !

Thanks

Regards

Roby

[Peter G. ShawParticipant @peterg-shaw75338]

Hi Roberto,

 

Does this help?

 

I mounted mine on the front of the motor casing.

 

Regards,

 

Peter G. Shaw

[Roberto dassoParticipant @robertodasso55459]

Posted by Peter G. Shaw on 09/06/2010 20:37:26:

 

Does this help?

 

 

Hi Peter

 

Yes.. it helps a lot!!!!

ehehe

Thank you very much

 

Regards

Roberto

Edited By Roberto dasso on 09/06/2010 21:04:19

[pfavParticipant @pfav]

Hi all,
I just subscribe the forum, and I am a novice.

I start metalworking in support to my interest on Kite.
2 years ago, I bought a mini lathe (C3 like) and after one years a minimill.
 I bought a 2nd hand minimill that is the same model as warco.
 
Using slitting saw I broken spindle gear.
 
I start replace the gears and I’m thinking to use metal gears on spindle and plastic on coutershaft.
 After remove the spindle i found a problem: bottom bearing is damaged (may by some metal or plastic garbage)
I try to find a replacement  and for an SKF 7206 AC I have to pay Euro 150.00!!!
Now some considerations:
the bearing position require a sealed version, but the 72xx model doesn’t have sealed version.
The tapered version, more cheap, has the same problem.
There is not space to use sealing ring.
 
Considering the overall machine precision, the SKF expert suggested me to use 2 6206 2ZR. The axial load is around 200Kg and a skf ball bearing is more precise of a Chinese 7206!
 
What do you thinks ?
 
regards
Paolo

[Clive FarrarParticipant @clivefarrar90441]

Well chaps I have just started to convert mine to belt drive.

I have the drawings and info from John Rudd I will need some carefull thought to mod these to suit my WARCO due to the spped controller box location.

 

I have stripped it all down today and after extracting the small gear that had broken into about 20 bits and removed 4 teath from the other gear.

The first job was to replace the bearings with taper rollers.

My bottom ball bearing also fell apart when removing the shaft from the head. The inner race was a VERY tight fit on the shaft. If I did not have a No3 broach press I would not have got it apart.

They have been replaced with Nachi H-E30206J bearings from ARC Eurotrade. These are exactly the same as those used in the mini lathe, as mentioned above.

I also needed the press to get them back on. Fitting these has reduced the length of shaft above the bearing by approx 4 mm.

As I have no intention of using gears ever again I have removed the layshaft from the head.

I have left the small bearing in the head and blanked the centres with grommets.

 

I know the tapers are open at the bottom but so are the ball bearings and the metal fling washer and plastic collar over the bearing obviously do their job as there was NO contamination in the old ball race.

 

If only the rest of the mod would go as easily.

 

Regards Clive

[pfavParticipant @pfav]

Thanks Clive,

agree to use tapered bearing if you remove Gears from head.

I’d like to use gears for a while, so I’m worried about contamination.

(let me prepare my own belt conversion Kit )

 

Have someone used a couple of 6206ZZ for upper and bottom sides ?

Is the precision worst?

 

regards

Paolo

 

my mill

 

[Sub MandrelParticipant @submandrel]

It was only recently it ocurred to me that replacing those stupid 75 division index wheels with 60 division ones would give me 0.025mm/division which is close enough to a thou for my agricultural approach. Also 10 divisions = 0.25mm, 40=1mm and I can ignore that discontinuity at 75 divisions. Best of all, its the same as my lathe then, so only one set of thought processes needed!

 

I plan to modify teh existing or make new dials soon.

 

Neil

[Roberto dassoParticipant @robertodasso55459]

Yesterday I have  checked the run out  of the stock spindle and bearings

 

This is the video

It seems very good (the dial indicator is metric 0.01 mm).

The accuracy report of the machine says 0.01 mm at the end of the spindle, and 0.02 mm 100 mm to the end of the spindle.

 

[Clive FarrarParticipant @clivefarrar90441]

Mine is a WARCO mini mill and the switch box gets in the way of both mode I have seen and leaves no space to dog leg round the back of it.

 

After a bit of measuring and ponderingI worked out that I could move it down so the top was level with the head thus giving me space fot the T shaped mounting plate.

 

The draw back is that it is now below the bottom of the head.  The just acceptable news is that that bottom edge is level with the morse taper mouse.

that should not be a problem for me as I nearly allways use an ER32 collet chuck which drops the cutter some 50 mm + below that point.

 

Now to start on the metal.

 

Regards Clive

[Sub MandrelParticipant @submandrel]

> morse taper mouse

It’s good to know that we can obtain pets that are compatible with our tools. A friend spent ages trying to get hold of a Browne and Sharpe gerbil.

 

Neil

[MarcuSwedenParticipant @marcusweden]

“

On both my mill, and my friends mill, the fine feed did not work. The manual did not even mention it, and it wasn’t until I downloaded a document from the Little Machine Shop in America that I found out how to make it work. What my friend and I discovered is that there is a gross misalignment between the the support block and the bracket adjacent to the fine feed knob such that the support block requires shimming out along its front edge (as you look at it from the front). Furthermore, the support block housing is too short for the actual worm itself, causing binding of the worm inside the block. This is cured by, in my case, adding washers between the end cover plate and the support block thus giving clearance for the worm to rotate. In addition, my friend discovered that his was seized up due to gunge.”

 

Peter :

 

Can You please explain a little bit more about the “support block and the bracket adjacent” and also “the support block housing” , my problem here is that i acctually dont understand thoose english words, but i have the schematic with all parts numbered so i can easily see what part that is discussed. 

 

 

 

 

click to enlarge.

 

 

Edited By MarcuSweden on 04/07/2010 23:06:34

[Peter G. ShawParticipant @peterg-shaw75338]

Hi Marcus,

Firstly, sorry about the words I used. I was probably trying to be very precise in what I was saying assuming  good  English.

 

Second, your drawing is the same as mine, and therefore wrong as my machine is not quite the same. I will now go and take some photos etc.

 

I’ll report back later.

 

Regards,

 

Peter

 

ps. I sent you an email via “My messages”. Did you get it?

 

[Peter G. ShawParticipant @peterg-shaw75338]

Three photos which I hope will make it easier to understand what I did.

 

Here goes…..

 

Does this help? If not ask again.

 

In the top photo, I used a piece of shim steel about 15mm wide and the full depth of the black block. It has one hole through which the top screw fits. The shim then just hangs there until clamped by both screws. Th idea is to twist the block round vertically so that the horizontal shaft moves away from the milling head itself.

 

In the second photo, the two washers are placed between the cover plate and the block and over the screws. It can be fiddly as they are small, and drop off easily.  The idea is to lift the cover plate away from the block thus allowing the worm inside freedom to rotate.

 

In the bottom photo, the idea is to move the block around  until the shaft can rotate without binding, and the knob can rotate without binding against the block. It could even be that turning the black block round through 180 degrees sideways could help. It all depends on the location of the various holes. Mine are very poorly drilled, and I have plans to replace it sometime.

 

Regards,

 

Peter G. Shaw

 

Edited By Peter G. Shaw on 05/07/2010 14:04:31

[MarcuSwedenParticipant @marcusweden]

Thankyou wery much ! This did help ! Now i understand what to do and also why.

 I´m now ready with my conversion from  gearwheel to belt, I will post some photos as soon as im done with some cleaning around the machines.

Today i tried the minimill for the first time, and it was actually better than i thought, milled some steel with a 12mm endmill and also some aluminium with a 16mm endmill, it was really fun !

 

 

I have also bought one low price tachometer that i used today for checking the spindlespeed, i bought it from :

 

 http://www.dealextreme.com/details.dx/sku.18239

 

The price of the tachometer is very low and the quality is more than good enough for measuring millingmachines and lathe, free shipping also. The parcel came after 2 weeks and it works wery well.

 

Right now i found the mail in “My Messages” , I will start looking at the messages more frequently! I will answer with message !

 

[Clive FarrarParticipant @clivefarrar90441]

Well chaps my belt drive conversion is now finished.

 

To suit my machine I had to make several small dimensional modifications to the drawings I was working from.  Mainly because my motor is totally different to that drawn.

 

Once I had sorted out the excessive bearing pre load that meant top speed was about 60 rpm it is running great.

 

It is much quieter than the gear drive.

 

Hi low top speeds have gone from 1100 to 1700 , 2500 to 3200 a good range and a good increase. Although for me I susspect it will rarely be out of low gear.

 

Very very pleased with the result and I would recommend the job to anyone who smashes their gears.

 

regards Clive

[Ian S CParticipant @iansc]

Hi Clive, what is the minimum speed the mill will run at? I find that the important speed, perhaps I try to do jobs that are too big, my mill is a bigger one, with a minimum speed of 90 rpm, I would like it to be 60rpm or less.Ian S C

[Clive FarrarParticipant @clivefarrar90441]

Ian I can not say for sure as the only rev counter i have is for model aircraft and works in steps of 100.

 

It flickers on 1 but the tippex marks are going round too quick to count so I think it is fairly close to 100. It does not take much of an increase on the speed pot for it to steady at 1.

 

I have not tried cutting anything at that speed but I suspect it will only do very fine cuts when going that slow.

 

Mind you the pullys were easy enough to turn up so a slightly bigger one, 90 mm ?, would probably get you down to the speed you need.

 

Regards Clive

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