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Member postings for mike T

Here is a list of all the postings mike T has made in our forums. Click on a thread name to jump to the thread.

Thread: Thread Milling
10/01/2016 17:08:29

Ian,

Forgot to add, that line of G code simple says rotate the RT 10 times while moving the Z axis down by 10mm and that produces a 1.0mm pitch thread. Change the sign from minus to plus give you right or left hand threads

Mike T

10/01/2016 16:46:03

Ian

Correct, the thread mill diameter needs to be smaller than the hole, but not by much. Unlike a lathe, the single point thread mill is rotating and cuts a 60 degree Vee in a helical path down the hole. The speed of rotation of the cutter is fast and the feed along the helix ( rotation plus Z motion) is slow. very little material is removed for each revolution of the cutter. i.e. the chip load is small.

It should be possible to go to full depth in one pass but I have not tried it yet. The single point of the modified tap survives because the chip loading is so small.

The thread of a modified tap will never be quite as perfect as a £70 thread mill cutter but it works adequately. When I use this method in anger, I will mill the thread slightly undersize and finish the thread with a full size bottoming tap.

Mike T

10/01/2016 15:46:59

I asked how well a single point thread mill made by grinding off all but one flute of a conventional HSS tap would work. The answer is remarkably well. Some of the cleanest threads I have cut.

I mounted the work piece in a rotary table and the home made single point thread mill in the spindle. The RT rotation is synchronized to the downward Z axis movement of the head by the single line command G01 A-3600 Z-10 F1. This cuts ten turns of thread at 1.0mm pitch into a blind hole, did not even need to run a tap down the thread to clean it up.

Jobs a good un.

Mike T

Edited By mike T on 10/01/2016 15:47:43

09/01/2016 17:17:02

John Stephenson wrote

"You can also use a tap with all but one flute ground off.

One pitch cuts all if it fits into the hole."

John, how well does this work? Have you tried it? Is it really a viable method or wishful thinking?

Mike T

Thread: Emco Compact 5 Motor Problem
05/01/2016 22:26:21

There is a three way switch on the Emco 5 CNC, it is not a forward/ reverse switch. It is the motor's manual mode / CNC mode /off switch.

The motor control board has three wires going to the motor. Motor +ve, motor-ve and ground. There is a large 33mH choke in the motor +ve line which controls the inrush current. The old Emco wiring, the choke and particularly the motor connector (both halves) on the back panel are all candidates for a short to earth. You should be able to check these out with a normal test meter.

I have circuit diagrams for the Emco 5 CNC lathe and also for the Emco F1 CNC mill. As well as the Motor control board. If anyone wants a copy, then send me a PM with your e-mail address.

Mike T

Thread: Emco compact 5 cnc lathe with Welturn
02/01/2016 18:20:42

Will, Trevor

You can clearly see the problems with these old motor controllers. The Emco controller and now perhaps the Denford controller are stand alone boards which do not connect to the rest of the control gear, therefore their zero volt may be allowed to float (bad electronic practice). The problem happens when you attempt to connect them to an external system such as the Mach controller or make voltage measurements. THEN you must connect up all the various zero volt (earth) connections so they all refer to the same zero volts.

Ask yourself if you really MUST control the speed by software. Consider the risk, if you are not that experienced in electronics and settle for manual control and turn the speed pot by hand. In practice you don't change the spindle speed very often. I still use manual control of the spindle speed of My Emco F1 mill and my Emco Compact 5 lathe; never found the need for the software to control the speed.

For Will, I could have a go at replacing the LM324 chips for you. No guarantees just best effort.

Mike

02/01/2016 16:47:40

Bad luck Will.

However it more or less confirms that motor card was not properly grounded. The board ground and the chassis ground should be the same potential and would have had no permanent effect. But as you say, that's now history.

There may still be a way of sorting it out. The motor control occupies the lower half of the board, the display is the upper half of the board. There are only two chips of the lower motor control half. Both are UA324 or LM324, quad low power operational amplifiers, ( an equvilent chip is theNTE987 ). If you can get these two chips replaced, you may get lucky.

For your information X21 pin 6 is the end pin on the right nearest the centre of the board. There are several unused positions in the connector which don't count.

Mike

02/01/2016 15:17:10

Muzzer, What you say is correct for a correctly wired installation. But it does not explain Wills unusual voltage measurements.It could be that the machines earthing has been disturbed during all the modifications leaving some boards floating.

Connector X21 pin 6 on the speed control card is the wire that ties the motor and the speed controller to ground, therefore a good place to check

Mike

02/01/2016 13:46:57

Hello Will

According to my Emco circuit diagram for the motor spindle speed board. The speed control pot (50K) is connected between +12 volt and ground via a 27K dropper resistor. Therefore the voltage across the pot should be about 8 volts and the voltage on the pot wiper should vary between + 8 volt and 0 volt.

I cannot understand where the 50 volt to ground comes from. Make sure you are measuring using the chassis earth ( connector X21 pin 6) and not mains neutral.

Hope this helps

Mike

02/01/2016 11:16:08

Hello Will

You are making good progress with your machine update program. Well done.

I am not clear about what you discovered about the voltages on the Emco motor speed board pot. Can you give a bit more detail?

I made some triangular pieces to fit under the lathe base to tilt it forward until box at the back was vertical. This gives a semi slant bed, which improves visibility and helps clear the swarf . You also gain a flat surface on top of the box to put stuff.

Keep up the good work

Mike

01/12/2015 17:41:51

Emgee

Correct, the L297D interface board (three chips) sits between the 25 Pin parallel port and the 2 (3) input connectors on the Emco stepper drive card. The connectors are disconnected from the on-board computer, which I no longer use. The interface board is simple enough to be hard wired, does not need a PCB.

As I said in an earlier post, I use DeskNC control software or LinuxCNC. The 25 pin parallel port will also be compatible with Mach.

Do you have contact details for Henk Versuren? I cannot find him with Google

Mike T

01/12/2015 15:23:45

Emgee

I designed an interface board using L297D chips to convert the incoming step /direction pulses into the four phase drive signals required by the Emco stepper drive boards.

Later I replaced the Emco steppers and driver boards with M542 drivers and new steppers, just as John Stevenson did.

What did you do to control the Emco spindle motor?

Mike T

01/12/2015 14:30:16

Sam, Your reply came in while I was answering the other posts. Thanks for you input, I will need study it carefully.

An hour ago, I only had manual control of the spindle, now thanks to you guys, I have several options available.

Good stuff on this forum

Mike T

01/12/2015 14:23:58

Emgee The lathe is a Compact 5 CNC with integral computer. However I have by passed the onbord computer on both machines and have a 25 pin (Mach 3 compatible) parallel port connection to my external PC. I currently use the DeskNC control program and now starting with LinuxCNC, which looks good.

John, This sounds like the way to go!!!!! Can you recall which of the KB motor speed boards you used. Can I assume you continued to use the existing Emco spindle motor?

Will, Thanks for the insight into the theory. On/ off motor control via the parallel port sounds straightforward but how do you do the variable voltage to vary the speed?

Thanks to you all

Mike T

01/12/2015 12:22:05

Quote. "Emgee was kind enough to advise how to control the original motor board from Mach3"

I have an Emco 5 CNC and also an Emco F1 CNC mill. Both are controlled by an external PC. I would like to learn how to control the original Emco motor control board from an external PC.

Does it control the motor speed like the manual knob, or does it just switch the motor on and off? Either function would be very useful.

Thanks

MIke

Thread: Internal Combustion Engine Supercharger
29/11/2015 17:10:38

Hello Martyn

I am currently building a 1/3 scale working model of a two stage supercharged Mercedes Benz W165 Grand Prix engine, from 1939. I have almost completed the two stage Roots type supercharges. I am sure a single stage Roots blower is all you will require for your Austin.

For my 1/3 scale model, I machined the casings and rotor from a solid billet. A large casting would be a better starting point for a full size blower. You should be aware that the synchronising gears must be made to a very high precision with minimum backlash, as their function is to prevent the two rotors from crashing together.

You can see some of what is involved at http://www.modelenginemaker.com/index.php/topic,5142.0.html

Hope this helps

Mike

Thread: Belt splicing tape
10/11/2015 11:43:00

Sounds like another product from "Unobtainium Inc"

Thread: Andromeda Galaxy
15/10/2015 13:51:03

Hello Neil,

Keep a look out for the bit of round metal that launched itself into outer space when it came loose in the chuck. I think it went in that general direction

Mike

Thread: Learning to Love the Metrinch
25/03/2015 20:20:50

This sounds like the EU directive that everyone should drive on the right hand side of the road. Those countries who prefer the left side will be required to drive on the right whether they want to or not. As a concession the EU has decided to phase in the transition from left to right over a short period of a few days. The Heavy goods vehicles will change on day one, any surviving car drivers on day two etc. This is also due to take place 01/04/2015

25/03/2015 14:10:01

Neil, you are a bit early for 1st April.

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