Thread: Table traverse for Chinese mill.

Hi Guys,

Having decided on the big plastic gear in this picture,

Driven_Gear-01.JPG Driven_Gear-02.JPG

and that the 6 mm bore in the hub is far too small to fit the 10 mm shaft on my mill I decided to machine the centre out to fit.
This meant that I had to make a hub bush to both fit the mill drive shaft and secure the plastic gear. In addition I had to accommodate cutting a 4 mm keyway into the hub so that it would provide a positive drive from the gear to the shaft.

This is what I came up with.

Table_Gear-a03.JPG Table_Gear-a04.JPG Table_Gear-a05.JPG Table_Gear-a06.JPG Table_Gear-a07.JPG

I turned these two parts from an off cut of 30 mm hex brass bar. I then matched the bore in the plastic gear so that the web was sandwiched between them. If you look closely at the two end pictures you can see where I had to cut notches to clear the radial spokes in the plastic. The holes were drilled 2,5 mm and those in the hub sleeve threaded M3. the others to clear M3. The screw heads turned out to be very tight to the edge of the hub. I had thought of replacing the philips head screws with hex socket cap screws at some point.

Table_Gear-a01.JPG Table_Gear-a02.JPG Table_Gear-a08.JPG Table_Gear-a09.jpg Table_Gear-a10.JPG

I used the same technique of home made soft jaws for the three jaw chuck on the lathe to hold the plastic gear so that I didn't do any damage to the teeth whilst gripping it so that I could trepan the centre out. I also used the same tool to machine the ribs so that they were clear of the hub. Unfortunately I forgot about the sides of the hex collar which is why I had to either set it back up in the lathe or put little slots in to clear the spokes.

More to come...

I've added a picture of the home made soft jaws used to hold plastic gear without damaging the teeth on it.

Hi Guys,
Done some more work on how I'm going to put things together. Having stripped the end off the mill table and made measurements so that I can see what goes where, I needed a plate to support the motor assembly.

Mill_Table_drive-01.jpg

So I cut a piece of 6 mm mild steel plate and drilled holes in the various places as needed. Since this plate was going to sit on the outside of the mill table end frame I had to drill a hole that was going to fit over the boss on it. Not having a 42 mm drill I used a 38 mm hole saw and then mounted the plate on the rotary table and bored the hole to the required size with a boring head. Unfortunately I got that involved in getting it setup I forgot to take pictures of the work. The holes that go through this plate into the existing threaded holes in the mill table were countersunk and I will use a pair of hex socket counter sink bolts to secure this plate.

There are two additional holes at the top right that are drilled 6 mm clear and countersunk from the other side. These are to secure a piece of 12 mm mild steel plate that supports the wiper motor. In order to get the top of the drive flush with the surface of the mill table and keep the motor above the drip tray so it doesn't collide with it, I had to extend out behind the mill table. This positions the wiper motor body horizontal and conveniently sets the motor and mill table shafts in a horizontal line.

Mill_Table_drive-04.jpg

The drawing shows the layout of the table and tumbler gears as they will be on the finished drive. The tumbler is shown in the neutral position where there is no drive to the big gear.

Driven_Gear-03.jpg Driven_Gear-04.jpg

These photographs are after the large plastic gear and its hub have been assembled and test fitted to the mill table shaft. It surprised me how rigid that hub makes that gear. When I was machining the gear it flexed quite a bit and I did wonder if it would be up to the job of turning the table drive shaft without disintegrating. Having got it on there and turned it by hand I'm happy that it will function satisfactorily.

Later:

Originally Posted by BaronJ

It surprised me how rigid that hub makes that gear. When I was machining the gear it flexed quite a bit and I did wonder if it would be up to the job of turning the table drive shaft without disintegrating. Having got it on there and turned it by hand I'm happy that it will function satisfactorily.

Later:

Hi Baron,
the (serendipitous) strengthening by the hub is all part of the 'master plan' (as we say in the trade)
Still lovin' this thread, great work.

Phil

Originally Posted by Steamwhisperer

Hi Baron,
the (serendipitous) strengthening by the hub is all part of the 'master plan' (as we say in the trade)
Still lovin' this thread, great work.

Phil

Thank you Phil, Your advice and encouragement are appreciated.

Hi Guys,

Done some more bits and pieces and realising that I've not enough holes in the right places. I did a drawing of the bit of 12 mm plate that I needed to support the motor and fasten it to the main support plate.

Mill_Table_drive-02.jpeg

I needed two holes in each edge of the plate. Each hole drilled 5 mm and threaded M6. Since I also needed to make sure that all the holes on both edges lined up accurately with the plates on either side. I clamped the piece of 12 mm thick plate to the main support plate using a 123 block and spot drilled the two holes on one edge. I had already drilled the modified original plate that the motor was mounted on in the car it came from. So it was convenient to drill one hole right through and thread it from either end since the tap wasn't long enough to go right through.

Table_Drive-b6.jpg Table_Drive-b6a.JPG Table_Drive-b8.jpg Table_Drive-b9.jpg
Table_Drive-b12.JPG Table_Drive-b13.JPG Table_Drive-b14.jpg

As you can see from these pictures, the chunk of 12 mm plate needed the end cutting off in order for it to finish at the edge of the motor mounting plate. I really really need to get myself a power hacksaw. The original lump of 12 mm plate was an 8" circular cover plate intended for a high pressure water line inspection cover that had been cut to the wrong size but not drilled. One of the advantages of having a friendly engineering company nearby.

Mill_Table_End-07.JPG Mill_Table_End-06.JPG Mill_Table_End-05.jpg

The above photographs show a trial fitting of the various parts as the would be in the completed table drive assembly.

More later !

Hi Guys,

Did some trial fitting of the various parts just to see what goes where and what I need to get round to doing next.

Trial_Fitting-01.JPG Trial_Fitting-02.JPG Trial_Fitting-03.JPG Trial_Fitting-04.jpg

Trial_Fitting-05.jpg Trial_Fitting-06.JPG Trial_Fitting-07.JPG Trial_Fitting-08.jpg

I made a support pillar from a bit of 12 mm square bar. Drilled it in the end 5 mm and threaded it M6. Then put it in the four jaw on the lathe and turned the other end down to 6 mm diameter and threaded it M6 for an M6 nut and washer. I also cross drilled it 7 mm and threaded the hole M8. I decided that I needed some method of indexing the tumbler support to make sure that it stopped in one of three positions. So I'm going to make a spring loaded index pin that will go into the edge of the tumbler support collar. You can also see the large hole in the middle of the mounting plate that goes over the boss on the mill table end plate.

That's all for today folks. More later.

Hi Guys,

Almost finished and ready to run !

Assembly-07.jpg

The photograph shows the competed unit nearly ready to mount on the mill table. I made a dummy spindle so that I could measure and set the spring loaded index pin. I also decided to put an arm and crank on as well to bring the tumbler control to the front of the unit. The red thing is the jaw of a spring clamp that I used to get the crank arm set in the right place.

Assembly-06.jpg Assembly-05.jpg

This is the view inside. You can see better the arm for the tumbler shift. Also the dummy spindle with the large gear in place.
The motor will be supplied voltage from my variable power supply unit for the time being.

Assembly-04.jpgAssembly-03.jpg Assembly-02.jpg Assembly-01.jpg

The photographs above show better the tumbler control arm and the spring loaded index. The pivot for the control arm is done in the same way as the shafts for the two tumbler gears with the addition of a spacer collar and fibre washer. I used a circlip to secure the arm. The arm is made from a short length of 3 mm thick aluminium strip.

For the spring loaded index pin I used a long 3 mm diameter boiler rivet and a spring from an old ball catch. The threaded part is a short length of M8 threaded bar drilled through 3.2 mm and counter bored to take the spring. The dimples in the tumbler support collar were done with a 7 mm drill just turned by hand.

More Later.

Hi Guys,

I got some more done on the crank and its mountings. Bolted it all together and got it fitted on the mill for testing.
Just a few photographs of some more bits.

Index_Assy-01.JPG Index_Assy-02.JPG Index_Assy-03.JPG

The above are pictures of the index assembly.

Bell_Crank_Hub-01.JPG Bell_Crank_Hub-02.JPG Bell_Crank_Screw-01.JPG Bell_Crank_Screw-02.JPG Bell_Crank_Screw-03.JPG

The parts above are the aluminium disc that I made to act as a crank for the tumbler control arm along with the securing screw pivot for supporting it. The disc is 6 mm thick and the thread on the screw is M6. I also cut a screwdriver slot across the head of the screw so that it could be tightened with a screwdriver rather than a counter screw as I was going to do originally. Hence the 3 mm diameter hole through the middle.

First_testing-01.jpg First_testing-02.JPG

These two pictures show the drive mounted on the mill table end and being run under test. I'm using my variable voltage power supply unit to feed 12 volts to the motor. I get 40 mm a minute from one speed setting and 30 mm from the other. Doubling the voltage to 25 volts gets me 40 mm and 52 mm per minute. 30 volts gets me 45 and 60 mm per minute. All in either direction.

The unit has had the crank and control arm added is is now back on the mill table.

Later:

Hi Baron,
I really like the work you have done here.
However i think you may find the feed is too slow, and you may cook the motor if you run it for too long at voltages higher than 12. Although my mill is much bigger it's feeds range from 1.6" per min to 39"(?) per min.
For running a carbide face mill you will want well more than 60mm/min.

Ew

Originally Posted by Ueee

Hi Baron,
I really like the work you have done here.
However i think you may find the feed is too slow, and you may cook the motor if you run it for too long at voltages higher than 12. Although my mill is much bigger it's feeds range from 1.6" per min to 39"(?) per min.
For running a carbide face mill you will want well more than 60mm/min.

Ew

Hi Ew,

Thank you for that information. One of the reasons for measuring the traverse speed was because it looked too slow when I tried it. Yes after about ten minutes at 30 volts the motor did get a little warm (about 60C as measured with a thermocouple on the case) a bit too hot to hold your hand on for too long.

These motors are permanent magnet type which means that they don't have any field coils to get hot, so all the heat is from the armature. The only way that the armature can get rid of the heat is by conduction through the shaft. You can guarantee that the windings on there will have been way way hotter than the temperature measured on the case.

I suppose that one way to speed up the traverse would be making the driving gear a little larger in diameter and the tumbler gears a little smaller. One of the trade off's when using salvaged gears.

Originally Posted by BaronJ

I suppose that one way to speed up the traverse would be making the driving gear a little larger in diameter and the tumbler gears a little smaller.

I'd be tempted to that anyway - the gears you are using are from a photocopier and so are only designed for light loads. As a traverse drive they may break up after a while so making up some replacements now that you have proved the concept could be a prudent move.

Michael

Originally Posted by Michael G

I'd be tempted to do that anyway - the gears you are using are from a photocopier and so are only designed for light loads. As a traverse drive they may break up after a while so making up some replacements now that you have proved the concept could be a prudent move.

Michael

Hi Michael,

I'm inclined to agree with you about making up some more gears. The salvaged ones are quite robust ! I did load the hand wheel at the other end of the mill table when I was measuring the speed and found it very hard to slow the motor down. What I did find was that the tumbler gear support collar moved and pushed out of mesh under the load. Now that was unexpected ! Some one commented about a safety clutch. Having seen this behaviour in both directions, I think a clutch unnecessary.

Gear-06.jpg

Hi Guys,

A few more photographs of the "Nearly" finished table drive.
Attachment 315969 Attachment 315970 Attachment 315971

These three photographs show the table traversing in each direction and in the neutral position.

Attachment 315972 Attachment 315973 Attachment 315974

Some pictures of the mechanism ! Please excuse the camera shake and slight loss of focus in some of these pictures. Its hard on the knees trying to balance looking from underneath.

Last few shots.

290514-3.JPG 290514-2.jpg 290514-1.jpg

I've found a couple of issues that need sorting out before I package this up and put a nice painted cover on it.
One of those is making a new tumbler gear set to increase the top speed. The other is the operating arm fouls the boss on the mill table end just under the large gear wheel.

I'll add pictures of the final product when I've got it all done.
Until then. Thanks for looking, adding your thoughts, encouragement and expertise. Its much appreciated

Fantastic work BaronJ,
Not only does it work but you have the modifications and improvements thought out as well.
I would almost go so far to say I have enjoyed this more than you have.
Thanks for posting your work.
The best part is being able to look back at a record of how you made it happen.

Phil