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Member postings for Gary Wooding

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

Thread: Ebay screen
02/04/2020 07:18:47

Michael's link looks fine on my Firefox 74.0. I too am running ad-block and various other add-ons.

Thread: Sounds familiar.
30/03/2020 16:36:47

Two elderly men taking about their weekend experiences.

1st man. 'We went to a super restaurant on Saturday. Excellent food and remarkably good value.'

2nd man. 'Oh, that sounds interesting. What was it called?'

1st man. Thinking hard with no success. 'Erh, oh erh, what's that flower that has a nice smell and lots of sharp thorns?'

2nd man.' Oh, you mean a rose?'

1st man. 'Ah yes, that's it.' Then shouts 'Rose, what was the name of that restaurant we went to?'

Thread: Recent conversions of Warco WM18 to CNC?
28/03/2020 12:14:04

I helped a friend convert a WM 16. We had to machine the table a little to accommodate the X-axis ball nut, but that was the only machining required.

Thread: Tom Senior light X Axis power feed
27/03/2020 10:10:52
Posted by John Haine on 27/03/2020 08:23:23:

Stick the magnet on the steel or iron pulley with a dab of epoxy underneath and leave to set. You only need a very small magnet, say 3 x 2 mm. It won't come off nor significantly unbalance the pulley. Remember the larger the radius it's fitted the smaller the unbalance force.

Are you sure? For a given RPM the unbalance force is directly proportional to the radius. Double the radius, double the force.

Thread: The Home Workshop Dictionary - FREE E-BOOK
26/03/2020 09:16:05

Thank you Neil, that's very generous of you.

Thread: Tom Senior light X Axis power feed
26/03/2020 07:56:45

Have you checked that the windscreen motor is happy to run in either direction? Some, as I discovered to my cost, are designed to run in one direction only, and the brushes wear rapidly if run in reverse. A window winder motor is designed to run in either direction.

Thread: Lathe levelling
23/03/2020 13:49:09

Bill,

The term 'lathe levelling' refers to removing the effects of bed twisting. It's actual level is not important.

23/03/2020 13:45:47
Posted by Howard Lewis on 23/03/2020 12:05:32:

Working off the Saddle introduces further possible sources of inaccuracy, and error.

Howard

Why?

23/03/2020 10:11:22

Well, after reading the comments I'm convinced that I'm right. My original post was only about levelling the bed - not about headstock and tailstock alignment. The objective of bed levelling is to ensure that the position of the cutting tool tip relative to the lathe axis remains constant as the saddle moves along the ways.

I really can't see why supporting a level on temporary blocks is more accurate than supporting it on a purpose-made block - ie. the saddle.

The diagram shows a level, 'A', supported on a raised 'V' way and a block, 'B', resting on a flat way. If the height of block 'B' exactly matches the difference in height of the two ways (as in '1' then fine, but rather unlikely. If it doesn't, then the horizontal position of block 'B' can have a noticeable effect on the orientation of 'A', as can be seen in the difference between diagrams '2' and '3'. Can you be certain of precisely positioning block 'B' for each measurement? I think not. But by using a purpose-made block (ie. the saddle), the uncertainty is completely eliminated.Once the best position of the level on the saddle has been found, then you just leave it there and wind the saddle along the ways to take the readings.

It's how the saddle rides the ways that's important.

lathe levelling.jpg

Edited By Gary Wooding on 23/03/2020 10:31:56

21/03/2020 14:39:15

I totally agree that the final arbiter on lathe levelling is measuring taper, but that is not what my posting was about. I want to know why measuring bed twist with a level supported on packing from the bed ways is considered to be more accurate than using the same level actually supported by the saddle. Surely its the saddle that ultimately guides the cutting tool, so its use must be more accurate. Am I wrong?

One of the videos can be seen **HERE**

21/03/2020 13:03:24

By accident I came across a video about lathe levelling by means of an engineer's sensitive level. The person demonstrating it took great pains to clean the ways and then place packing on them to create a shelf with which to support the level. It occurred to me that I'd seen similar videos where the level was supported on packing blocks on the lathe ways. But why?

Why not use the saddle to support the level? It's the saddle that guides the cutting tool, so why not use the level to see how the saddle itself leans because of twisted ways? Using the saddle as the support also allows observation at any point along the bed. Is my reasoning faulty?

Thread: Bending and shear force confusion....
15/03/2020 15:42:22

Here's Case 2.

pininskt.jpg

pininskt stress.jpg

15/03/2020 15:41:22

I decided to try the FEA facility of Fusion360 on this.

I created 2 models. Both with a 30mm diam. boss on the end of a 13mm screw thread. I didn't bother to model the thread so its just shown as a 13mm bar.

Case 1. A 12mm diam. tommy bar, 200mm long, passes through a 12mm hole through the boss.

Case 2. The hole in the boss is a 12mm socket that 'just' reaches the screw thread. The tommy bar is the same 12mm diam. It fills the socket and extends the same length as one half of the through bar.

In both cases I fixed the bottom end of the screw thread and applied a 1000N force to one end the the bar.

The pictures show the stress results. The faint dotted lines on the stress diagrams show the greatly exaggerated displacements.

Here's Case 1. (I can't put 4 pictures in, so Case 2 is the next post.)

thrubar.jpg

thrubar stress.jpg

Thread: rotary to screw force calculation
05/03/2020 17:52:26

Whoops, I used a pitch of 5mm where it should have been 2mm. So multiply my 128Kg by 5/2 to give 320Kg.

05/03/2020 14:13:54

The torque of the motor = 1N, or 1 Newton at 1 meter (1000mm). The effort, E, provided by the motor is then 2*PI*1000 Newtons for each revolution. For each revolution of the screw the load , L, is lifted through 5mm.

Assuming no loss due to friction, then the effort E must equal load L, so...

2*PI*1000 = L*5, therefore L = 2*PI*1000/5 = 400*PI Newtons, or approx 128 Kg.

If the leadscrew is a ball-screw then friction will be very low and the load should be a little over 100Kg, otherwise friction is likely to be nearer 80% and the load will be reduced to around 35Kg at a guess.

Thread: VFD remote (pendant) design
03/03/2020 14:07:45
Posted by Gene Pavlovsky on 03/03/2020 10:38:36:

Gary, I understand your wiring and the way it works is fine, as long as you don't hit the NVR stop button every few minutes . I just think that you could get rid of the KM1 magnetic contactor, and just wire the buttons connected to it directly to the VFD's digital inputs. On the other hand, why mess with something that works for you?

The only reason for hitting the NVR stop button is for an emergency, and it's location on the lathe control panel is very handy for such use. The KM1 output is at mains voltage so is certainly not suitable for connecting to the VFD digital inputs.

03/03/2020 10:17:15

Gene,

My VFD (a Mitsubishi) is powered directly from the output of the NVR relay. When I first switch the lathe on from the wall socket, nothing happens. But when I press the Power Start button the NVR relay is energised and the VFD is powered up. The VFD then remains powered up until I switch the lathe off at the wall socket, or I press the RESET button.

Here's a schematic of the wiring - all the original relays except KM1 (the NVR) and wiring have been omitted for clarity. The speed ctl pot is a 3/4 turn version that I find is exactly right for my use.

wiring.jpg

03/03/2020 07:37:47

I converted my Chester 12x36 Geared Head lathe to VFD some years ago. I wanted to be able to operate the machine exactly as before, but with the addition of a speed control knob. It has a control box which houses the wiring and relays that implement the NVR and motor forward/reverse functions. It was a complicated mass of wires and devices that seemed impossible to modify.

Modification for the VFD turned out to be very simple. The VFD output goes straight to the new 3ph motor, and both are outside the ctl box. There is a power lead that supplies 220v to the ctl box, so that was unchanged. I used a voltmeter to discover the power supply output from the NVR relay and used that to power the VFD directly. Nothing else in the ctl box was powered from the NVR relay. It was an easy job detecting which wires were used to activate the motor direction relays, and these were used to control the VFD. There was a jog button which I never used, so I replaced it with a suitable speed ctl potentiometer for the VFD, and made a suitable label for it. That was it. It was much easier than I originally thought.

Different VFDs need different speed ctl pots, so you will need to check the manual for your VFD.

speed ctl.jpg

 

Edited By Gary Wooding on 03/03/2020 07:49:57

Thread: Turbo CAD Query.
23/02/2020 10:43:59

Pleased to be of assistance.

23/02/2020 07:57:11

Its because you changed the workplane and the plane and view don't match.The easiest way to reset things is to right-click anywhere in the drawing area, then choose the view you want, then click 'Plane by active view'.

This is what I do in Tcad ProProf, Tcad Deluxe should be the same.  I don't use Tcad as much now that I've switched to Fusion.

workplane.jpg

Edited By Gary Wooding on 23/02/2020 08:11:25

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