Thread: Pebble Tumbler !

Hi Guys,

I've got some more work done today.

A few more pictures showing how the assembly will look !

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These two pictures show the canister sat in the frame and resting on the two rollers.

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At the moment I am proposing to only use one of the two drive rollers to turn the canister. In the second picture you can see the large disk that will be used to drive only one roller. A flat belt will run around this and the driving pinion. Which will be to the right of it. I haven't yet made any provision for the pinion since I have not got the drive belt yet.

The drive motor will be mounted inside between the end plates under the canister and rollers. I have a 12 volt 1 amp DC transformer type wall wart that I will use for motor power. It has a built in thermal overload, its ex internet router so should be of reasonable quality. I also have a small 12 fan that I can press into service should I need to apply cooling to the motor.

More to come:

Will be interested to see how goes when finished.

Hi Guys,

I only had one, well two jobs to do on the end frames ! One of them was widening the slot for the canister screw to fit into, and the big one, rounding off the end frame tops.

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Since rounding the top of the end frames was a milling job and I'm too lazy to get the rotary table out for what isn't a precision job, I drilled a 6 mm diameter hole in a piece of oak and pressed a 6 mm pin into it. This serves as a poor mans RT. By placing the end frames on this pin I am able to rotate the workpiece by hand. I just clamped the piece of oak in the mill vise. Since I had originally drilled a 6 mm hole at the centre of the radius it was a simple matter of setting the pin under the centre of the cutter and then moving the table away the right distance.


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For anybody contemplating using this method, you do need to make sure that you always move the work piece into the cutter ! Failure to observe this precaution will result in the cutter grabbing the workpiece, with a risk of injury and possibly a broken cutter.

As can be seen I removed material in 1 mm steps. Whilst a little tedious the job completed quite quickly. About ten minutes. The downside is that it produces an awful lot of swarf, which, being plastic, becomes statically charged and sticks to everything.

Thanks Guys, more to follow.

Hi Guys,

My drive belt came this morning !

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You can see from the pictures that its a toothed belt, actually intended for a radio controlled model racing car. I need to machine a flat bottomed groove in the wheel for the belt to run in. I also need to make a slot for the drive pin in the wheel centre, in order to create a positive drive.

Hi Guys,

As promised here is the drawing and the template for a 14 tooth 3M size pulley.

Small Gear.png

The left hand drawing is the outline template for the pulley. All the small holes are 3 mm diameter, with the blue outer circle indicating the extent of the drill holes and the inner green circle the centre line of the 3 mm holes. The 14 radial lines delineating the hole positions. The two lines 20 and 60 are there so that a printer printout can be calibrated if necessary.

The right hand drawing is the finished pulley and is based on a 6 mm diameter centre bore. Actually the hole circle function on the mill DRO should make producing this pulley a doddle.

Hi Guys,

A few pictures and notes about the first prototype pulley as per the drawing in the previous post !

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I drilled and threaded an M6 hole in a piece of Oak in order to make a mandrel to support an alloy disc 16 mm diameter. I glued a paper template with the lines representing the angle for each hole. You can see a red dot that I used as a marker. The nut was there just to nip the alloy disc and stop it moving whilst drilling. A 3 mm drill only just clears the flats on the nut.

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By stepping the blank disc around I was able to drill 14 holes on a 13.37 pcd. I did try to set up the DRO to drill a hole circle without any success ! I will have to study the chinglish manual more, its quite confusing.

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Sorry that these two pictures are quite poor, they don't look out of focus in the camera's viewfinder. Anyway this pulley is a scrapper ! The aluminium tears and smears when being turned plus the holes are too deep, there is supposed to be a lip on the far edge, although I'm not sure that it matters. I'm going to try again using a piece of brass this time.

One thing that I did find out, the measurements given for the belt size don't match the physical belt, the humps and gaps are nearer 2.5 mm than the 3 mm shown in the pictures for an M3 belt.

I'm away for the next five days, so I will have another go next weekend.

Hi John,
Would a dividing head be better to use to make the pulley

Originally Posted by BaronJ

Hi Guys,

I drilled and threaded an M6 hole in a piece of Oak in order to make a mandrel to support an alloy disc 16 mm diameter. I glued a paper template with the lines representing the angle for each hole. You can see a red dot that I used as a marker. The nut was there just to nip the alloy disc and stop it moving whilst drilling. A 3 mm drill only just clears the flats on the nut.

By stepping the blank disc around I was able to drill 14 holes on a 13.37 pcd. I did try to set up the DRO to drill a hole circle without any success ! I will have to study the chinglish manual more, its quite confusing.

.

The way you have made the pulley can work I have done that sort of thing my self a few times - however if you have a DRO then it is very worthwhile persevering with the hole circle function - I have used it many times and it works well - I did have to take some time to get my head around the user manual's Chinese to English translation, I did some dummy runs initially with only 4 or 6 holes and a felt pen in the chuck to make a mark on some paper before I went on to the real thing. From memory you select a radius, a starting point in degrees, an end point in degrees and the number of holes - in done correctly you are rewarded with a set of X,Y coordinates for each hole.

Originally Posted by Turbine Builder

Hi John,
Would a dividing head be better to use to make the pulley

Hi Mark, yes it would, but I don't have one !

I can actually buy a pulley off the bay, but its much more fun to make one.

Originally Posted by familyguy

The way you have made the pulley can work I have done that sort of thing my self a few times - however if you have a DRO then it is very worthwhile persevering with the hole circle function - I have used it many times and it works well - I did have to take some time to get my head around the user manual's Chinese to English translation, I did some dummy runs initially with only 4 or 6 holes and a felt pen in the chuck to make a mark on some paper before I went on to the real thing. From memory you select a radius, a starting point in degrees, an end point in degrees and the number of holes - in done correctly you are rewarded with a set of X,Y coordinates for each hole.

Thankyou for your post, its encouraging to know that someone else has done the same thing as me.

I'm going to have to play around some more with the DRO ! I can't seem to get it to use the centre that I've chosen and the coordinates are somewhat confusing. I'm not at all sure that I'm understanding how it works, yet !

Plus I need to figure out why the dimensions given for the belt don't correspond to the belt or the holes that I've drilled after turning to the stated size.

I'm going to play some more !

Thanks:

Hi Guys,

In between playing about with the DRO setting to create a hole circle, I have ground a lathe tool to machine a 3.2 mm wide groove in the driving pulley to suit the width and depth of the 3M belt that I have.

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These two pictures show the roller driving pulley mounted on a mandrel and the tool used to machine the groove.

The next operation on this pulley is to cut a vertical slot in the centre to locate the 2 mm diameter driving pin.

Hi Guys,

I finally figured out how to use the DRO to drill a hole circle ! The Chinglish manual gives you the needed steps to take to drill X number of holes in a circle but doesn't tell you how to save or change a setting once set. It also doesn't like a fractional number, like 7.5, it likes 7 or 8, but not one with a decimal point in it. Otherwise it seems to work Ok.

I made a new pulley blank from a bit of brass scrap bar and mounted it on the M6 mandrel screwed into a block of hardwood held in the mill vice. Here is the first gotcha the DRO has to be accurately centered over the workpiece and then all axis zeroed. At this point pressing the hole circle button records this position, from this point you select the radius for the hole circle.

This is where I discovered that I cannot enter a number with a decimal point in it ! Also The save/enter key changes, pressing the wrong one causes the numbers to change to a previous setting. The next step is setting the start and finish angles, zero for both means a ring of holes, the next step asks for the number of holes, in my case 14, followed by pressing the enter key 14 times. The display now shows the number 1 and changes the X and Y figures to a new set of numbers. Zero these by moving the handles to get to the first hole, pressing the down arrow moves to hole number two and the X - Y display changes to a set of new numbers, you move the handles again until the display reads zero and then drill your second hole.

Pressing the down arrow key steps you through all 14 hole positions. Pressing the hole circle key at this point zeros the whole display returning you to the point before you started.

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These two pictures show the first attempt at making the toothed pulley based on measuring the belt directly. Notice that the hole circle is slightly off centre ! I'm not sure why. But at least it proves that the DRO works.

I will have another go and see if it still end up off centre.

Thanks for looking:

It's good that you've come to grips with the circle hole function it is very useful, not only for your pulley but also for drilling 3 or 4 equally spaced holes for things like a flange or a cover or boss, the other one to get a grip on is the linear hole function, first time I used this was to make a turret/tag board for an amplifier project, 2 rows of 34 holes at 8mm spacing, can be done manually but the linear hole function made it easy.

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 .

Hi Guys,

Just a quick catch up on the DRO issue with entering a hole circle value with a decimal fraction. I have to press the enter key after entering the value before the decimal point and then press the enter key twice before entering the decimal point, and then fractional part. After that the DRO remembers all the values until you change them.

A gotcha here is that you must remember to set the work centre and zero both axis before selecting the hole circle function otherwise your hole circle will not be where you expect it to be !