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91
Project Logs / Re: Small carbide tool grinder
« Last post by John Rudd on April 18, 2018, 02:44:52 PM »
Hey Doc nice job so far... :bow:  but..... Have you a link to the motors you used? Ebay perhaps?

Cheers
John
92
CNC / Re: Electricuting the lead screw
« Last post by awemawson on April 18, 2018, 02:20:27 PM »
If this lathe is to have an electrocuted lead screw, will you have to wear thick rubber gloves using it  :lol:


https://en.wikipedia.org/wiki/Electrocution


(sorry I couldn't resist, your English is infinitely better than my Finnish )
93
CNC / Re: Electricuting the lead screw
« Last post by eskoilola on April 18, 2018, 02:06:04 PM »
If you're dreaming of rigid tapping in the future, a spindle encoder with a few thousand counts per revolution would be in order.
If the spindle is running at 1500 RPM there will be around 100.000 interrupts for the uC to be served each second. I know from experience that a PIC18F runniing at 64MhZ will be capable of serving around 30.000 intererupts per second if those interrupts are fast executing, simple things like advancing a counter. I know for sure that 100.000 is way too much.
94
CNC / Re: Electricuting the lead screw
« Last post by eskoilola on April 18, 2018, 01:38:05 PM »
As PK in his project page describes, a lathe electronic control can be (and should be) brought that tiny step further making it a partially capable CNC lathe. This in turn involves precise control/sensing  over spindle and both axes.

I am really tempted to make this just that. A lil' bit more capable as it actually does not seem to be awfully more stuff to do.

What I am going to have fun or struggle with (which ever way one wants to put it) are the mechanical things. Electronics and uC programming are easy for me. And as it seems most of this modification is actually just that.

I have also thought about using a servo motor on this one. It is my assumption that a servo motor controller needs some sort of PID controller to work as intended. In addition it needs either a rotary encoder or better yet a linear encoder  to tell the position of the saddle. I'll check what the stepper can actually do speedwise. The stepper is actually a nominally 120 volt device dc voltage for nominal current being around 30 volts. No problem as then the currents are smaller.

Of course this would be quite a bit more than just a electronic lead screw (ELS) but on the other hand - making the lathe to understand G-code (or whatever it is named) would make it compatible with GPL software which in turn has a temptation on me. Being a programmer makes me want to do everything in a computer.

I have an old Gerber photo plotter in my posession. This unit has one meter long ball lead screw with two nuts and another 70 cm long equally with two nuts. The steppers are too weak and slow for this application but because the unit has to work very precisely (being a foto plotter) the lead screws are quite massive (about 2 cm in diameter). As my lathe has a lead screw of about 90 cm length this could quite easily be replaced with that ball thing.

Using a ball lead screw has it's implications. There is no more a half nut to disconnect. This means that the apron handwheel has to be electricuted as well. Maybe a torsion sensor for manual control making it feel exactly as sloppy as it is now. Another torsion sensor to the end of the leadscrew handwheel and that thing could be operated exactly as it is operated now in a manual mode. The current half-nut lever and the auto-feed clutch would then be simple switches to disable/enable the manual handwheels. All this would of course mostly spoil the feel and touch of the manual operations.

On the other hand the ball lead screw is very precise and the lead screw backslash is mostly eliminated by using two nuts. Backslash originating from the leadscrew ends is a bit more difficult to eliminate - not much though.

I have to sleep on this one - this may run out of hands.....
95
Project Logs / Small carbide tool grinder
« Last post by Doc on April 18, 2018, 01:00:44 PM »
One last quick little project I've been meaning to do. I have a carbide tool grinder but wanted to make a smaller unit. I found some CBN wheels really good price for 4inch dia unfortunately they came busted in the mail. The seller gave me a refund but I really did want a set of wheels and asked if he'd just try it again. Apparently didn't want to deal with me again and just gave me a  refund oh well. I found some other wheels a little more on the price so we will see how they come.
  In the mean time I had a piece of aluminum channel 5" wide so I started. I'm making 2 as a friend of mine is just starting setting up a home shop  so I'm making one for him. The motors I'm using are   12volt motors  high torque really nice motors and I'm using old computer power packs for the power. Should work really good. I used one of these motors for the power feed conversion on my lathe. I ordered a couple more. Anyway this little project shouldn't take too long provided I get CBN wheels this time that aren't smashed and broken.
96
How to's / Re: Homemade layout fluid
« Last post by mcostello on April 18, 2018, 12:36:00 PM »
I use copper sulphate on a job with lots of grinding as it holds up to heat better.
97
CNC / Re: Electricuting the lead screw
« Last post by JHovel on April 18, 2018, 11:16:30 AM »
Have a read of this page and all relevant linked pages: http://www.autoartisans.com/ELS/
I've built this ELS and it works very well. My encoder is, in fact, a small tab screwed to the main spindle inside the headstock and passes through the gap in an HP IR optical sensor. That's enough.
There is now a complete kit available and John is amazingly helpful with all questions relating to driving leadscrew and cross-feed screw on lathes and other machines.
98
How to's / Re: Homemade layout fluid
« Last post by Fergus OMore on April 18, 2018, 09:53:57 AM »
Bordeaux Mixture for fruit trees?

Copper Sulphate, lime and water?

Used it on my Apple PC and there isn't a virus left :lol:

Norm
99
New from Old / Re: Rebuilding A Grotty Chicken Shed
« Last post by awemawson on April 18, 2018, 04:32:42 AM »
As Triggers Broom in Only Fools & Horses  :lol:

Oh yes - that gallon of paraffin and a match would have been SO much less hassle, but it was decreed otherwise  :bang:

The roof, 2/3rds of the floor, and the entire back will be original  :med:
100
Project Logs / Re: let ther be light
« Last post by DaveS on April 18, 2018, 04:07:20 AM »
Bob,

Have you a rough idea as to the dimension of the spring, if so I'll have a rummage in shed.

Dave
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