dividing head /indexing

+1 to this thinking, so much so that the Brian Thompson article in MEW" gear hobbing without change gears" is for me the next step. Problem, the IC's are now marked as obsolete. Any electronic wiz out there have any comment?

I'm sure John, you remembered Steve Ward.

Thanks Paul.

Since electronics will last about 5 years before going phut that will give you time to make a proper mechanical replacement.......

hello, If 5 years is the working time forecast, that will be long after I go phut and if not could still be long after me.

regards Paul

I haven`t responded to the stepper motor stuff, as i have no interest in cnc or electronically controlled machining . No disrespect to any one who does prefer that method but i prefer to learn manual or semi manual machining on a strictly hobby basis.

Hopper interesting ideas.

heres a piston indexing head!

**LINK**

Paul, thanks, Steve Ward of course. Apologies if he is reading this, but his circuit is really excellent and I'm sure will last a lot longfer than 5 years,

Which ICs are obsolete? When was that published? I've looked at a couple of articles on electronic hobbing, including on here from Sir John. As far as I remember they assume you need a high count encoder on the spindle to get enough division range, but I don't think I've seen one with the obvious addition of a phase locked loop to multiply up the spindle frequency to give an extra dimension for wide ratios.

SMEE digital workshop people have done an Arduino based version. It's on my 'to do' list, and getting nearer the top!

Anyone know which iussues of ME contained GHThomas dividing head?

John, thanks for your reply. I must again agree that Steve Ward contributed greatly with his design, and help he gave to others trying to build it.

The article by Brian Thompson was in MEW no.108 Aug 2005. The ic's -HEF4059, VN10LM, are the problem units.

Your comment on encoder and alternative is very interesting and timely as I'm at the procurement stage for this section of the unit. I am not familiar with, phase locked loop, but if it simplifies the project i'd like to be.

Mark Smith, my interest in the electronic approach is because I built the mechanical set up and quickly tired of the

set up times when the unit was applied for 1 off hobby use.

Regards Paul.

Paul, before you go the Brian Thompson route, tale a look at this post for about a week ago.

Gear hobber

Clickable link added.

Edited By John Stevenson on 17/11/2016 11:35:55

John S. Thanks for your posting and direction. The thread is interesting in part because it answers a question

raised when I read recently that your black box failed and you went Linux way. Now I know the story.

Again many thanks.

Paul.

Don't get me started. I have a six inch diameter Cummins piston sitting under my bench that I have been wondering what to do with.

Really though, when you look at the work involved still, I reckon you are better off to get some 75mm x 16mm BMS flat bar or whatever it takes, cut it up and and screw and dowel it together to make a Harold Hall head from scratch.

I wish I had the patience to sit down and learn about computer coding, stepper motors and PCB boards etc but I'm afraid it just is not my idea of a fun time for some reason. Whereas wrestling greasy bits of metal is. Go figure.

Edited By Hopper on 17/11/2016 12:40:33

Paul, the 4059 is a generic CMOS 4000 series part, widely available, probably Maplins have them. The VN10 is just a mosfet, probably it's driving the stepper motor? If so then anyway I'd just buy a complete stepper driver these days, cheap as chips.

The PLL would use something like a 4046 which is a complete PLL on a chip. It would be set up to take pulses from an encoder on the spindle and synchronise its internal oscillator to N times their frequency, using an external divide by N (such as the 4059). So if you had one pulse per rev from the spindle and N was 1000, the internal oscillator would run at 1000 pulses per rev. Then you can divide that down with another 4059 to drive the stepper that turns the gear blank.

Well i bought this from GM tools ,i think ill be able to make something usable out of it, if not it may come in for its intended purpose. I think the centre height is just under 6" .

My bigger mill has a 101/2" wide table but not that long. Thing i like about it is it has a hole built in as well for an arm so i can still do something along the lines of the GHT .

I think its 5c collets but not sure ,as there was little info and not even sure if its complete . But for 25 quid plus vat /delivery i thought it was worth a punt.

Any thoughts? Theres one left at G&M if anyones interested.

Probably same as this only alot cheaper

http://www.ebay.com/itm/Phase-II-End-Mill-Cutter-Sharpener-Stock-235-001-with-Wood-Case-NICE-/192027340157

Edited By mark smith 20 on 17/11/2016 16:47:39

Edited By mark smith 20 on 17/11/2016 16:54:14

Good god, those FETs are from The Ark. I recall using VN66AF and VN10KM (originally from Siliconix) back in 1979 or possibly 1980. The VN66AFs were one of the first power MOSFETs I came across. You could drive them directly with CMOS (eg 40106 Schmitt trigger buffer). Expensive but so easy to use compared to valves and bipolars.

I made a simple, portable 2MHz AM RF transmitter receiver using one of these and a linear (audio) power amp. That was before I got my RSBG license G8XCN, so yes, it was illegal but ironically I stopped doing RF stuff once I got licensed. I guess the thrill had gone...

Without seeing the circuit, I imagine a modern logic level power MOSFET would work fine (better) and cost peanuts, something like this.

John, many many thanks for a most helpful and informative posting.

Your comment on the VN10 is spot on, the purpose of its inclusion was lack of output to the stepper driver when

Brian Thompson first built. the unit.

The explanation of PLL you gave is most enlightening and produces an alternative for the one part of the project that raised concern in my mind. The concept is clear to me but I lack the know how to set up the circuitry.

One of Steve Wards objectives in his divider design was for a self contained small unit and that is what I wanted with the hobbing device.

thanks for your help. Paul.

Muzzer, thanks for your posting. The 80's , oh yes I remember them well (cue for a song).

I expected things to have moved on in the world of electronics since 2005 and the circuit function requirement is simple. My ability in this area is monkey see monkey do.

Your suggested replacement is noted thanks. How about 2N7000?

regards Paul.

It's possible that the 2N7000 may be a close replacement for the VN10KM but the gate threshold voltage looks rather low to be a "logic level" device and could be a problem here. I assumed blindly that it was driving a motor, hence the device I suggested may be way OTT.

Is there a schematic to look at? It's not sensible to suggest alternatives without some idea what the application looks like, as I've just illustrated!

Muzzer, thanks for response. The use of the device is to provide input to stepper driver, what John Haine described as, cheap as chips.

The only schematic I have is from the MEW article. I'm not sure of the protocol of posting it here, I could E-Mail

a copy if you leave me a message with your address.

Paul.

I've managed to find the article, I actually have that issue! The VN10 LM is just used as an inverter to give a bit more current to drive the stepper moter driver itself. A normal NPN transistor like a 2N3904 with a 1K resistor driving the base from the inverter would be a perfect substtitute or wire the 2 unused gates of the CD4070 with their outputs in parallel, one input on each to ground, the other inputs connected together and to pin 23 of the 4059 would probably work as well.

The unit depends on a quadrature encoder with its outputs XORed to double the frequency, you therefore need lots of pulses per rev. Using a PLL one would replace everything from the encoder input to pin 1 of the 4059, I'll have a think about what is needed.

To help, what is a typical spindle speed for a hob cutter? That determines some of the characteristics of the PLL design.

John, you have been busy. The cutter speed is 150 RPM. I today ordered a 6oo P/R encoder described as AB two

phase. The stepper will be driven by one of your "cheap as chips" TB6600 2/4 phase hybrid motor driver.

Your outline is very encouraging.

regards Paul.