tumbler reverse

[savarin]

Its been a long time since I got any shed time but managed a bit in the last week.



Made the angle plate from 8mm plate and welded it together. Managed to control the welding distortion and kept it square.
I was rather pleased with the 8x1mm thread, it came out pretty good, not perfect but more than good enough.
The end of the feed screw was hand filed square (sort of) likewise the hole in the handle. It only has two ends because I couldnt turn a four handled one.
The aluminium casting is an old one from my gingery lathe (never finished)



As I will be cutting a 40 tooth gear I needed a means of indexing it.
This site will print an index wheel for any divisions you want.
http://www.cgtk.co.uk/metalwork/divider
I used spray adhesive to stick the divider to a thin sheet of steel and sealed it with lacquer.



The angles are bolted to the slide with 5mm c/sunk screws, 4 in each angle.
The shaft is 8x1mm, and is the best thread I've cut so far.
The gap between the top of the handle and the index wheel is actually larger than it looks in the photo.
Still have to make the pointer then its onto the lathe and have a go at cutting the gear.
No idea when that will be but I hope its soon. I was suffering from shed withdrawal symptoms.

 

[Bill Gruby]

Re: tumbler reverse/ spark eroder

Its alive, its alive. AT last I have the spark eroder working in a lash up.
Its amazing, it burnt through 5mm of broken tap in approx 15 mins.
I'm using an enameled length of 3mm copper wire as the probe so it only contacted at the tip and not the hole walls.
Buzzing like a champion.
Then, oh! calamity, I think I shorted the power lead to the bench, the bridge rectifier cooked and so did the lead to the discharge cap.
I will see if the cap is usable tomorow.
These were very quick pics before it self destructed so bare with me, better ones to come (eventually)

View attachment 47144

if you look very closely you can just see the arc at the bottom of the probe, its actually down about 3 mm into the hole here and the kero is turning an opaque black, the surface ripples are from the unit vibrating as the probe slams up and down very fast.
View attachment 47145

How about doing a build on this one for us? I could use one of these at times.

"Billy G"

 

[savarin]

Re: tumbler reverse/ spark eroder

How about doing a build on this one for us? I could use one of these at times.

"Billy G"

Hi Bill, my lash up is not a good project to get others to make as its a tad on the unsafe side.
This is a way better version than mine
http://mikesworkshop.weebly.com/a-spark-erosion-apparatus.html
and this one is supposed to be the best
http://tech.groups.yahoo.com/group/EDMHomeBuilders/

 

[BRIAN]

Re: tumbler reverse/ spark eroder

How about doing a build on this one for us? I could use one of these at times.

"Billy G"

Me two please, seems like a good tool to have.
Brian.

 

[savarin]

Re: tumbler reverse/ spark eroder

I've used it three times now and think its an excellent tool.
The one on the yahoo group is definitely superior and works faster but is more complex.
I followed this plan and circuit but used wood and what I had laying around.
http://www.homemodelenginemachinist.com/downloads/files/Easy_Spark_Eroder.pdf
I wound the coil on the plastic spool the wire came on, it was just the right inside dia.
The chuck came from an old clapped out battery drill.
Its really simple to follow and will give reasonable performance.
Instead of buying a large mains transformer I used an simple arc welder as the power plant as thats basically just a transformer.

 

[savarin]

Whoo Hoo, it worked.
Heres the set up, note the bicycle saddle cam lock bolt used as a lathe saddle lock bolt.:thumbsup:



Starting



The final result.



The aluminium one in the middle is the new gear.
Looks ok but this was just a test of concept.
In actual fact it rolls in one direction smoothly with no problems but reverse the direction and the teeth just catch a teeny teeny bit.
I think I didnt have the centre of the cutter exactly on a direct line to the central axis of the blank and so cut the gear teeth slightly off.
Considering that I only hand ground the cutter by eye and set the cutter on the blank the same way, never measured to find the depth of cut I'm still rather impressed with what I ended up with.
I set the blank position so the cutter just missed it, started the lathe and wound the vertical slide upwards. Slacken the nuts, move round one index mark, tighten and cut again.
When I got to the last tooth I re-set up to re-cut the first one again just to see if there was any difference.
It just made a slight hiss as it kissed the blank without cutting anything so it all lined up.
I think a little more care grinding the cutter and setting up square will produce excellent results.
It took approx 2 hours to cut all 40 teeth so its not fast but as I have no experience to relate to I dont know if this is good, bad or average.

 

[savarin]

At long last its finished and working.
I added a spring detente to make finding neutral easier and drilled the two new shafts so they can be oiled although I dont know why I did the reverse shaft as it cannot be reached :shrugs:



That chunky handle will be knurled once I get the tool.
Why so large? It was a left over from some casting.



I added a couple of cams at each end of the slot for exact placement of the gear shifter. Not my idea but I saw it somewhere and thought that was a goodie.
A huge problem I have is that virtually every gear (except the one I made:biggrin is oval and a real pain to align so they dont bind.
I made a new keyed centre for the 120/127 set that helped a little as even that was bored off centre and I can now get it running in forwards and reverse without them making the unholy noise they did but round gears would be so much nicer. I will have to make new extensions for the gear cutter to enable a 127 gear to fit it.



Plenty of clearance, I never had to cut the back plate but did replace one of the cap screws with a standard hex head bolt to get sufficient clearance for the reverse gear.



All in all I'm well pleased with the mod. Particularly with all the lessons learnt.
I've left the aluminium gear plain as I will cut another one and ensure I am spot on with the indexing and add a brass bush.
I could bore this one for a bush if it wears too much so I thought I would see how long it would take to wear out.
Next job, QCTP coming soon so do I alter the compound? Make a plinth for it?

 

[Bill Gruby]

Bout time you got that done, very nice. Now it's time for the autofeed cross slide. I'm almost done with mine.

"Billy G"

 

[hman]

Next job, QCTP coming soon so do I alter the compound? Make a plinth for it?

I used the Little Machine Shop #3712 adapter post to mount an AXA (from CDCO) atop the compound on my G4000. http://littlemachineshop.com/products/product_view.php?ProductID=3712&category=

The adapter is just $10+shipping. Works well - I can lower 3/8" tools to about 1/16" below centerline. The adapter I got had a slight problem (10mm bore not deep enough) that I fixed with a 25/64" bit. I emailed them about this a month ago, and they replied they would check. They're a great outfit to deal with, and they probably have the issue fixed by now.

 

[savarin]

Bout time you got that done, very nice. Now it's time for the autofeed cross slide. I'm almost done with mine.

"Billy G"

yer not wrong Bill, too many other projects preventing me from shop time.
The auto cross slide will be a long time coming.
I really must get on with the giant binos and the tilting trike now I can make more parts.