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Member postings for AdrianR

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

Thread: capacitance in long cables
11/09/2020 08:26:27

I don't quite understand why you think it would go to half 12v. The peak voltage on the signal cable would be dependant on the capacitance of the cable and how fast the voltages rise on the 5V and 12V. The examples I have seen on Google give capacitances of 100pF/m.

I assume the signalling you are talking about is manual on/off, not fast data signalling. I would connect a capacitor e.g 470nF on the signal wire. This would not only suppress any transients caused by the switch on, but also suppress any mains hum on the signal wire.

Adrian

 

*** I see Joseph beat me to it with a much better explanation

 

Edited By AdrianR on 11/09/2020 08:28:42

Thread: capacitor droppers and power factor
17/08/2020 08:02:15

Capacitors as voltage droppers work great at 50Hz, but are a terrible idea if there are harmonics or spikes.

I had a fancy Philips coffee machine on my canal boat, well that was till I switched from shore power to inverter. A bang and cloud of acrid smoke reminded me that I had left it plugged in.

The inverter was a quasi sine wave, the higher harmonics of the square steps in voltage went through the voltage dropping capacitor and fried the electronics.

It was still under guarantee so I took it back, a few weeks later I got a call from Philips asking how it happened. I was so impressed they were following it up I told them how it happened.

Adrian

Thread: Two factor Authentication and Ruralism
06/08/2020 09:03:23

Paypal allows you to connect a 2FA app in place of the PSD2 OTP text. You can either have the app on your phone, or you can get apps for your PC.

I used to use a Chrome extension for 2FA before I had a smartphone

**LINK**

Adrian.

Thread: Coping with deafness
01/08/2020 16:00:21

You can get vibrating wrist bands that can alert for fire alarms and doorbells, but of course, that means she would have to wear it and recharge it. Which if she is anything like my mother was would not happen.

Adrian

Thread: Opions sought on using the USB Photo Stick for photo storage
30/07/2020 09:01:08

I am not a Mac user but at work, they used Time Machine which Mac's come with.

Thread: Using Counterbores
22/07/2020 09:05:45

How embarrassing, having my counterbore quoted. Don't make one the same as mine, it has a numpty mistake, it runs backwards. What is worse I sharpened it three times trying to make it cut, before I realised my mistake.

Once the reverse button is pressed it cuts a perfect counterbore, lot cheaper than buying a set too.

Adrian

Thread: What Did You Do Today 2020
19/07/2020 16:46:37

Today I made an M3 counterbore, came out great, cuts wonderfully. Except for one small rooky mistake.

counterbore.jpg

Thread: Heating HT steel
18/07/2020 12:57:34

I would say it would be very unlikely to not affect its strength. The 8.8 specification is for medium carbon steel, quenched and tempered.

You also don't say if the red heat is under load or is how you are operating it.

Personally I would bin it. If it is for something critical you cant trust it, and if it is in your bits box you may end up using it for something critical. An accident waiting to happen.

Adrian.

Thread: Is this a plug tap
17/07/2020 16:35:46

Well, just to add to the confusion, our transatlantic cousins apparently call second taps plug and plug taps bottoming. I wonder how many plug taps we buy are really second taps.

Of to the grinder I go.

Adrian

17/07/2020 14:00:44

Hi,

I need to tap an M3 thread for 4.5mm in a 5.5mm deep hole. For this I thought I would need a plug tap, So I bought one, and I was surprised that it has a point at the end.

plug-tap.jpg

I was expecting a plug tap to have a square end. When buying it I had a choice of taper, second and plug, to me this looks like second. Am I wrong in expecting a square end?

Thanks

Adrian

Thread: Nivellator
15/07/2020 19:01:12

I dont think it means parachute but chute as in coal etc.

I dont speak german, but if you google "gefälle steigung" and then translate the page you get this **LINK**

Which is a site that calculates the same things as the Nivellator

Thread: Trembling laptop
15/07/2020 12:35:14

I have found that some people can feel these currents others can't. You are one of the (un)lucky ones who can. The picture looks like it is an original PSU so design-wise should be fine, but four years of unknown abuse could cause a little extra leakage. The number of times I have pulled a blistering hot PSU out from the sofa cushions, darn kids!

If you have the funds, for peace of mind pick up a good quality replacement PSU, Looks like you can pick one up for about £20. Avoid the generic bargain bucket PSUs, they are built down to a price and often are just the safe side of lethal. But any 20V 3.25A (probably 3A too) will work as long as the plug polarity and type is correct. The little diagram after the 3.25A shows the + is the pin and the - is the ring.

Oh incidentally as I found out after finding a server I was working on gave me the trembling feeling. The equipment can be perfectly earthed, it can be the building that floating.  

 

Adrian

Edited By AdrianR on 15/07/2020 12:42:02

Thread: We need Pi
05/07/2020 18:05:44

My two favourite methods to calculate Pi are using random numbers https://www.youtube.com/watch?v=RZBhSi_PwHU  and using a balance beam **LINK**

Hopefully promotion of his book and patron page dont fall foul of the new rules.

 

Adrian

Edited By AdrianR on 05/07/2020 18:06:36

Thread: Voltage feeding DRO "usb" digital scales?
02/07/2020 08:33:57

Robin,

The chipset used in the senors is designed to run from battery e.g. in digital callipers. For low power consumption, you need to use lower voltages and smaller components in the ICs.

Examples of low voltages for power saving are the voltage on phone CPUs is below 1V, the latest ones about 0.7V and PCs are about 1.3V.

Adrian

Thread: Poor mans mill feed speed control
01/07/2020 15:09:02

While twiddling my knob thinking of other pastimes two things occurred to me;

  1. I have not got a clue how fast to twiddle to get the optimal feed.
  2. Twiddling RPM is slow and in the range of musical Beats Per Minute.

A quick trip to the Android Play Store and I downloaded the free app "Simple Metronome" Which incidentally has a handy flash the display on the beat feature.

So now If I want 140mm/min with my 2mm pitch lead screw I set the BPM to 70 and twiddle away in time with the beat.

For really slow feeds it is worth having two beats to the twiddle.

Next on the world domination list is make a MIDI-controlled mill.

Adrian

Thread: Mill unexpectedly cutting crooked
01/07/2020 14:43:59

All my tests were with the spindle, Z and X all clamped down. Have not tried it with a loose spindle.

I have discounted a bent cutter as I have tried 4 different cutters, 3 of them were different makes, one was brand new out of the sealed box.

Also doing two spring passes removes the undercut, so the tool must be parallel and running true.

I think the most likely cause is head vibration, the cutter gets forced away from the work while in contact and then springs back between cuts. Which is why at high RPM it cuts true, it does not have time to move between cuts and the head deflection is averaged out.

I had a look with a magnifying glass and the undercut is not straight but convex which could also be explained by the above movement.

30/06/2020 18:39:16

I have done some more tests.

I checked for the work moving, it is rock solid. I also put a digital level on the head and on the work while cutting. They did not move.

I tried a 16mm cutter and see similar undercutting.

I changed from the right to the left side of the vice. It still undercuts towards the vice. ie the direction is reversed.

I tried 0.25mm, 0.5mm and 1mm cuts all gave the same undercut.

I tried using the top of the cutter instead of the bottom (tip) and the undercut disappeared. For both the 16 and 12mm cutters.

I repeated the top and bottom of the cutter using an ER collet instead of R8 collet. It cut square at the top of the cutter, so the distance from the spindle is not the issue, but the length of the cutter is.

Over the 6mm height, the undercut is 0.15mm, if I do a 0.15mm cut on an undercut edge it cuts square.

All a big puzzle, I will carry on with what I am making and report back if I find any cause.

29/06/2020 19:00:39

Hi,

I think I have the answer to why but just wanted to check my reasoning is right.

I was squaring the edges on a piece of EN32B 100mm square and 6mm thick. All went well and the finish was fine, then I noticed the edges were not square to the face. i.e. the 6mm edge to the 100mm face. I worked out the mill had undercut the sides at about 2 degrees.

The setup was. The piece was held in the vice on parallels with the working side to the right. This meant swarf was thrown backwards and conventional cuts were from front to back. The 12mm 4 flute cutter was in an R8 collet and was running at 800RPM. I was taking 0.4mm to 0.5mm conventional cuts.

I know my SX3 can cut square as I had just finished making some parallels and used the same setup to trim the ends. But that was using a 14mm cutter and running at 1600RPM.

I had used the speed indicated in Tubal Cain's Model Engineer's Handbook. Group D in table A on page 5.14 to find the 1600RPM. But I was not sure about running so fast and had calculated 800RPM from the 80ft/min figure given on page 5.15. I have since re-read and think I have too high RPM.

Feed was about 140mm/min.

I checked the head trimming, about 0.015mm over 200mm. I checked the surface of the parallels in the vice and they were similar. So the workpiece was flat and the head square.

Then to find the problem I tried squaring the end of a 40x6mm bar.

Same result;

  • Using conventional or climb cuts.
  • Using a brand new different make cutter.
  • For 0.1mm cuts, and less undercut under this.
  • Repeating the same cut without moving the X removed 1/2 of the slope. I.E only cut the top 3mm of the bar.
  • To rule out the R8 collet I tried an ER collet, but the same result.

I then tried changing the speed, running it at 1600RPM I get square cuts even with a 0.5mm cut.

I can understand that a tool is pushed away on a deep cut and hence the need for a spring cut, what stumps me is the undercut.

My hypothesis is that the cutting edge first contacts at the bottom of the piece. Then as it rotates the cutting edge engages higher up, but at the same time, the tool/head flexes away. When the flute is passing the piece the tool springs back. This vibration of the head causes the sloping face.

Does this sound right?

Adrian

Thread: Harold Hall basic grinding rest
27/06/2020 17:10:06

I have just started on making the simple rest too, good to hear it is rigid. I was a little worried if I had made the right choice. But I thought, my grinder has two wheels, I can always use it on the rough end and make an advanced rest for the fine end.

Adrian

Thread: Change to the Code of Conduct
23/06/2020 17:40:28

Ah, this explains why a couple of my links disappeared recently. Sounds completely reasonable. I know of the product links on youtube, but must admit I take no notice of them myself. I will check before posting links in the future.

Adrian

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