Member postings for Y C Lui

The head could move, but just downward, not upward above after a certain point. The threads parted from the nut coiled around the lead screw preventing the nut to move upward over that point.

The compression of the slot is not entirely controlled by the locking nut but the weight of the head. I have never over tightened that nut and as a matter of fact, it often got lose by itself and I could not figure out why.

I haven't taken any pictures but the nut has two slots cut half way across the body at the upper end. These two slots are meant to be for backlash control. By compressing these slots, the threads in that portion will shift relative to each other so the backlash can be eliminated or reduced but that's IN THEORY. The same design is used in the cross-slide nut of my Emco Compact 8 lathe. This design does not work for me. The compression of the mentioned slot resulted in the threads in that portion totally stripped but the rest are OK.

It appears that I will need to make spare nuts out of 7075 aluminium. That will not be too difficult but I would like to know if there are other ideas.

Edited By Y C Lui on 28/06/2022 18:57:17

The head of the mill suddenly could not be moved upward during use today. It didn't take me long to find that the problem was due to the thread of the Z axis nut partially stripped. I removed the stripped threads with a boring bar and the mill is now working again but it probably will not last long. Would like to hear from FB2 owners your solutions .

Um.... I am afraid I cannot understand.

Just wondering how to prevent the scale from tilting after tightening the mounting bolt ..... would like to hear some thoughts.

I bought this Japanese version some 20 years ago. Very well made but I never used it because I found it to be inaccurate when I first tried it out on my Emco FB2 bench mill. Then as I learned more about my machine, I found that the error was solely due to the misalignment of the mill. Neither the column nor the spindle was perpendicular to the table so the X Y shifted when the head is moved up or down. Now the aligment issue is sorted out but I still do not use the tool because I had to move the head up by quite a lot before there is sufficient vertical space to accomodate the tool. Kind of tiring. Will let it go if anyone is interested. The condition is close to new.

Mechanical edge finder is my prime tool for edge detection and I have no intention to replace it with anything other means. The only limitation is that the tool is good for X Y only. For the Z axis, I need something else. I have got a Z axis tool setter but the set up is kind of slow and you need to know the height of the reference surface of the workpiece above the table. This means additional measurement and calculation hence time.

I haven't tried the cigarette paper + oil method but I have tried tapes. The method works but if the tool is not an end mill or the part of the workpiece being touched is not a flat surface, it is not usable. Just some examples that I have come across : 

- The pointed tip of a chamfering tool touching the workpiece surface

- The end of an end mill touching the corner of a workpiece clamped at an angle

- The tip of a boring tool touching the inner surface of a hole

Edited By Y C Lui on 15/06/2022 08:27:56

This is actually not my idea. I learned about using changes in resistance to detect contact from this article . The arthur has also got a Youtube video . I am in the process of building the detector which is very simple and should work very well.

I tried today using my 30+ year old and cheap multimeter as a touch sensor for my Emco FB2 bench mill and much to my surprise, the precision is VERY good !

With one probe touching the table and the other touching the arbor, the resistance measured is 1.1 ohm when the tool is not in contact with the workpiece. This value varies a lot depending on the angular position of the spindle. It can go up to something close to 10 ohms but it never went below 1 ohm. As soon as the tool comes into contact with the workpiece, the reading would drop sharply to zero.

To test the precision, I made a shallow cut on the top of an aluminium block with the end of the mill ( 8 mm carbide ) to get a clean datum surface. Then I raised the head, connected the multimeter and very slowly lower the mill head until a sharp drop in reading occurred. Then I locked the head, painted the workpiece surface with a marker pen and did another pass. The paint was not scratched a bit. After that I lowered the head by just 0.005 mm ( or 2 tenths of a thou ) and cut again, the paint was completely removed. This proves that cutter was brought back to the original Z position with practically zero error.

I will definitely use this method a lot more in the future.

I have never been able to get good finish when turning mild steel ( the kind used for making bolts ) no matter what RPM or feeding speed I used. Using sharper inserts produced slight better results but still the surface was not shiny. Before long I accepted that the metal is to be blamed because there is no such issues on aluminium or stainless steel. Today, I did it again without doing any finishing pass and much to my surprise, the finish is very good. It turns out that the DOC selected in the past was just too small ( < 0.1 mm ) and today I set it to 0.5 mm. Just want to share this experience with other beginners like me.

I have got two facing mills that use inserts. 60 and 40 mm in diameter. Great for cutting aluminium but not so for steel until I use inserts for aluminium ( much sharper and rake angle larger ) for cutting steel. Light cutting only though ( DOC 0.2 mm ). I know the tool life is going to be short but as these inserts are very cheap ( 0.6 pound each ) so I will just live with it. My mill is a light one ( Emco FB2 ) so I believe I don't have much choice.

There are two choices of tip radius for the insert : 0.4 and 0.8 mm and I wonder which one produce lighter load on the machine hence more steady speed of rotation under the same rate of material removal.

Edited By Y C Lui on 31/05/2022 03:11:12

In the internet era, not too many people go to books. Youtube is more popular

Edited By Y C Lui on 28/05/2022 16:38:32

Yes, I can get ductile cast iron , EN-GJS-600-3 or 500-7. Do they product abrasive chips like grey cast iron ?

Thanks, Dave. The explanation is exactly what I am looking for. Now I feel more comforable with machining cast iron.

I have done some machining on grey cast iron recently and was amazed to find how easy it is but further reading on the subject makes me worry a bit.

Some on-line sources mentioned that the swarfs are highly abrasive and will do harms to bearing surfaces of machines. Others said that only the swarfs coming from the material on the surface is abrasive but not those from the core. Some even said that the graphite in the material is abrasive but my understanding has been that graphite is a lubricant .....

So it's all very confusing for me.

Can anyone shed some light on this ? Are there any difference between grey and ductile cast iron in this regard ?

Edited By Y C Lui on 27/05/2022 05:48:24

Use Rollies Dad's method ( my preference ) or glue 2 aluminium rings to the ends of the steel rod and cut the aluminium.

Edited By Y C Lui on 27/05/2022 05:28:32

The fact is I don't even have an angle grinder because all the stuffs I made are rather small. The workpiece in the question is just 45 mm long / wide. I have tried dremel-like tool + cut-off wheels but the wheels break quite easily. Will seriously consider getting an angle grinder. Looks like a must-have.

That is the cutting process I have been dreaming about but 5000rpm and 300mm/min feed is way outside the envelope of my 300 lb bench mill ( Emco FB2 )

It appears that even with appropriate cutter and machine it is still not possible to do a full-depth cut of 2 mm in one go as three passes were done in the video ( DOC was 0.7 mm in each pass ). Is that because of chip evacuation problems ?

I have got the idea of using roughing end mills because my 6 mm roughing end mill cuts slots ( DOC 3 mm ) in mild steel with significantly less effort compared with my regular mill of the same diameter. Furthermore, the chips produced are smaller which should help to avoid clogging.

Edited By Y C Lui on 26/05/2022 08:20:00

The sheet is 2 mm thick. SAE-AISI 1018 cold roll. I need to cut out a plate taking the shape of several arcs combined so end mills is the only tool option for me. I have tried 2-flute 5 mm end mill which is OK but the amount of materials removed seems to be more than necessary. If I go for smaller diameter end mills, chip evacuation will be a problem. Will roughing end mills be better ? 4 flutes or 2 ( haven't seen such type ) ? what diameter and RPM will be optimum ?

Thanks for the details which certainly help.

It seems that SiC particles do not really get embedded in the workpiece but just loosely stuck to the surface so they can be wiped off quite easily. This is more in line with my experience with SiC sandpaper but I have seen some Youtube videos mentioning the opposite. Will try it out.

I noticed that your laps are all made of copper. Is that because you wanted to get the SiC particles embedded into the copper , become stationary and cut out a smoother surface on the workpiece ? I am planning to make a set of grey cast iron laps, just thinking whether I should make another set made of copper before trying out SiC.

Edited By Y C Lui on 05/05/2022 12:37:28