Thread: Pebble Tumbler !

I've had a look at the bolt hole circle function on my chicom DRO and also found it very confusing; haven't yet had a need to spend the time translating it. Apparently th start and finish locations can be entered as '0' and '0' for a full circle, or '0' and '360', but I suspect this might require entering a value in the number of holes that is one more than required, i.e. entering 7 for a 6-hole circle, so that hole 7 is in the same place as hole 1. Is this correct?

Originally Posted by Pete O

I've had a look at the bolt hole circle function on my chicom DRO and also found it very confusing; haven't yet had a need to spend the time translating it. Apparently th start and finish locations can be entered as '0' and '0' for a full circle, or '0' and '360', but I suspect this might require entering a value in the number of holes that is one more than required, i.e. entering 7 for a 6-hole circle, so that hole 7 is in the same place as hole 1. Is this correct?

Hi Pete,

Not quite, on my DRO you have to enter zero for start and zero for end if you want a full circle, the manual never mentions 0 - 360 for a full circle ! Though I suspect that if you entered say, 375 you would get an extra hole after its done the full circle. In my case I wanted 14 holes equally around the circle, which I got without having to add an extra hole. Hole 14 ends up right next to hole number one.

I also noticed that there is no indication of sign when doing a hole circle, all values have to be moved to zero on both X & Y axis, this confused me at first until I realised that a quick look at the work indicated the direction to move in.

HTH.

Thanks for clearing that up, as mentioned I have not had the need yet to spend the time trying to figure out what the non-English speaking translator was trying to communicate when they wrote the manual. A good youtube tutorial on the functions of the generic chicom DROs would be useful.

Originally Posted by BaronJ

Hi FamilyGuy,

It would have been more help if the manual told you which key was which rather than just having a Chinese character printed on the key ! Of all the keys the "Enter, Save and Reset" keys just show a Chinese character, all the other keys are self explanatory !

Anyway I've now got it cracked, I will do a write up that I can put with the manual. Just in case I forget in the future .

John i have a google translate app on my phone and it has a function for the camera, basically you push the camera button when in the app and hold the phone with the text in view on the screen and the chinese is translated to english, i find it best to hold it there for a little while as it sometimes changes its mind a bit about the translation. It might not be perfect but this has helped me out a few times now and it will translate all/most other languages also....

Hi John, Guys,

All you posh people with smart phones , mine is just a plain old style large button one with a simple camera ! Being a tight Yorkshire man, I just use PayG, no contracts, just put the odd fiver on when I need too.

Not like my children that are each paying out £20+ per month, in addition to line rental so they can have the internet for their smart TV's and tablet computers.

Anyway I've stuck a label on the appropriate DRO keys so that I don't forget which is what.

Hi Guys,

These are the pictures for belt pulley number 3 !

14-09-2022-001.JPG

This first picture is with an earlier pulley in the lathe, trying to center up on the ring of holes. I did consider just boring out the centre to true it up ! But decided to bin it, and try again.

14-09-2022-003.JPG 14-09-2022-004.JPG 14-09-2022-002.JPG

So I had another try. As you can see it is a much better match to the belt and at least its on centre. After drilling I turned the pulley down to the calculated diameter of 13.37. Used the specified 3 mm drill size for the holes rather than the 2.5 mm I measured on the belt. The belt fits the drilling’s but the edges between the holes is very sharp leading me to think that the hole circle radius is slightly too large.

I'm open to comments on this, do I have another try or call this one done !

I still haven’t cut the slot in the large plastic pulley yet !

Thanks Guys:

"All you posh people with smart phones , mine is just a plain old style large button one with a simple camera" So I am not the only one!

Originally Posted by BaronJ

Hi Guys,
14-09-2022-002.JPG
I'm open to comments on this, do I have another try or call this one done !

John you really need a u shape and then round off the outer corners of the teeth to fit the belt, i think i would drill to the width of the belt tooth then turn the diameter to the root of the dia of the belt teeth, endmill the grooves then round the corners for the root of the belt teeth. If you dont have a way to hold and index it with a bit of care you might be able to mount the pulley on a short shaft to hold it and machine the first tooth and then use an indexing tab to rotate to the next position.
It will require a bit of homework tho.....and a few hrs

Personally i like the ebay idea....

Originally Posted by BaronJ

Hi John, Guys,

All you posh people with smart phones ,

haha....posh wouldn't be the word i'd use...lol

Hi Guys,

I've done some more work on the drive mechanism for the pebble tumbler !

15-09-2022-003.JPG 15-09-2022-002.JPG

I’ve drilled the drive shaft and fitted a 2 mm diameter roll pin, its a good push fit. I've cut the slot in the centre of the large pulley wheel for the drive pin to fit into. A very quick job with a two mm slot drill.

15-09-2022-004.JPG

Here is the toothed pulley with a 6 mm shaft placed through it. It's not fastened to the shaft yet so it's free to rotate. as you can see, it, like the two earlier ones is off centre. In this case by a whole mm. I'm not quite sure what is happening here. I can't believe that the DRO is out by that much in the "Y" axis since the teeth in the "X" axis are just about spot on.

Anyway I continued and did a test assembly.

15-09-2022-001.JPG 15-09-2022-005.jpg

These two pictures are of the test assembly with the large pulley fitted to the driven shaft and the belt looped around it and the toothed pulley. You can see that I've cut the excess length off the driven shaft, and I am using it to support the toothed pulley in place.

You may also notice that there are now pressed in ball races fitted to support the roller shafts. Six in all, four for the rollers and two for the toothed pulley. I've a dozen or more of these bearings, so it's a shame not to use them.

I've ordered a 3 mm ball ended slot drill so another go at making a toothed pulley is on the cards.

In the meantime I'm going to clock the DRO against table movement and try to see if its out at all and in what direction !

Thanks Guys: Your input is appreciated.

Originally Posted by BaronJ

In the meantime I'm going to clock the DRO against table movement and try to see if it out at all and in what direction !

John the adjustment is the Linear Compensation.

Hi John,

Do you think that a 1,2,3 block clamped in the mill vice and a dial gauge in the spindle will be Ok to check the axis ?

Originally Posted by China

"All you posh people with smart phones , mine is just a plain old style large button one with a simple camera" So I am not the only one!

can we get to three?

Originally Posted by BaronJ

Hi John,

Do you think that a 1,2,3 block clamped in the mill vice and a dial gauge in the spindle will be Ok to check the axis ?

Hi John, yes, i think i used 3 or 4 1,2,3 blocks for the X axis and 2 for the Y axis but clamped them flat on the table, make sure that they are square to the travel and bolt or clamp a parallel to the start end of the block/s to measure from, measure your block/s accurately so that measurement is known to compare to your dro measurement, i say measure because your 1,2,3 block/s might not be accurate so best to check and note the measurement, i have 4 of those blocks and i think 2 of them were a bit out of size, if i just assumed the size was right i would have mucked up the adjustment.
Best to secure your indicator to something solid as the spindle will move.

Hi John,

Thanks for your reply and notes:

One of the things that I did when I got the pair of 1,2,3 blocks was checked them for size and the flatness ! They are well within whatever tolerance that I can measure. As far as the mill spindle moving, yes that could be a problem. I can lock the spindle but only with the tool ejector slot, and that imposes a limit on how far up or down the spindle is.

After reading your post I took this picture of the setup. Now to do some actual measurements.

16-09-2022-1.jpg

Unfortunately the Mitutoyo gauge only goes to two decimals plus or minus a half (third digit is either a zero or a five).