Member postings for John McNamara

One way to face two sides perfectly that has worked for me in the past is to:

First face the work piece both sides in the three or 4 jaw it does not mater. then drill and centre one side of the workpiece.

When you take the workpiece out of the lathe chances are that it will be a little out of parallel even if you set it up with a dial indicator, it will probably be a few tenth's out.

The next step is to place a piece of scrap in the lathe and then face the outer edge say 10mm then turn a recess in the centre say 10 thou deep. leave this piece in the lathe. It will be perfectly true.
ithin the limits of the spindle bearings If you want to be technically correct.

Then hold the non centred side of the workpiece and centre it up with the tailstock centre pressed firmly against it and locked. This process works better with a ball bearing centre. Another possibility would be to bolt it through the spindle to keep it pressed against the fresh turned surface.

The last step is using a fine light feed face the centred side, you will leave a small unfinished section in the centre, this can be removed with a file if need be. You should not need a dog if the workpiece is a reasonable diameter. friction will hold it

The method also gives limited access to the back and all the side of the disk. Probably enough to do a riser in one sitting. if you plan it well.

Regards
John

Yes I know this is a segway... assuming the part is a survey mark

It's Been a while since I posted on this forum. The past couple of years have been very hectic.
Next Wednesday we pick up the keys to a new house. After 38 years in one house we are moving to the hills about a 45 minute drive from Melbourne.

I wish to build a new shed and in order to do so the council requires survey, I was on site when this was done in order to discuss the location. And yes the EPOXY CNC mill post on this forum will continue when the shed to house it is built.

A Land survey starts not at your property but at the known reference points in the area. One of those points was in a council field nearby, about a foot below the grass! Using the very accurate GPS station that surveyors use he had no problem locating it. The surveyor told me that there are many of these hidden reference marks around the city. The importance of the mark determines how it is founded, the more important ones may sit on hidden but massive concrete foundations.

Hi David George.

If the mill was running I would have shown it here.
My posts re the mill are up to date.
Alas it has had to just sit there reminding me. Hopefully I can get back on it soon.

Regards
John

Hi All
Yes I know I have not been around here much.
2019 was a pretty tough year, a high workload and a fair smattering of other issues.

Anyway back to the topic. There was a time when elaborate mechanisms were time consuming to build and therefore costly. Creating complex shaped parts has now become a very much automated process. From CNC laser and plasma cutting, CNC punch pressing, CNC metal machining machining to microns if necessary, all created with CAD CAM Design.

There is a shortage of contemporary published books on Mechanisms. And those that are published tend to feature reprints of older authors.

Those old books may be more relevant to today's engineering needs than you think.

Regards
John

Edited By John McNamara on 14/01/2020 05:41:00

Hi All
Link to a well prepared video of the Expedition Prepared By Arron Powter.

**LINK**

Regards
John

Hi All

I ran further tests with a new webcam, outstanding results!

This project keeps getting better.

See the end of this post here.

**LINK**

Regards
John

Not all of the images in the presentation represent catastrophe, precipitating Lithium salts by solar evaporation in ponds in a very arid area of Chile to me is greenhouse gas positive when it goes into electric storage batteries that replace carbon based fuels is a good thing. Not all industrial processes are bad.

The large scale production of food is essential to the survival of most but not all of worlds population without the terrible famines of the past. Regrettably Famine still exists, driven not by lack of food production, but by despotic politicians, not all of whom reside in the third world.

I think the images are a good thing the good, the bad and the ugly all equally represented.

Regards
John

Drill a hole in it!

**LINK**

Hi Michael
I sent you a Gmail and a PM

Hi All

I Just uploaded some further results from my experiments here: **LINK**

I am rather pleased with the results and there are further improvements possible.

Regards
John.

Hi

I think the first consideration is the math on life expectancy, According to the UK census at a current age of 70 the average life expectancy is another 14.77 years as of the last assessment made a couple of years ago. This number is the average only, many people beat the average a few by decades.

ttps://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/lifeexpectancies/datasets/nationallifetablesunitedkingdomreferencetables

I think any plans for the future need to take these statistics very carefully into account.

Being caught short a a vulnerable state of age when planning could have avoided it is a very unsatisfactory state of affairs.

Regards
John

Thanks Michael I responded with an email.

Hi All

I Bumped this post because there are some worth wile changes.
**LINK**

There is an executable version available, A Jar file so you will need the current version of Java installed.
If you have a webcam preferably one with a lead attached not the one in your laptop although it will work. it is all you need to experiment.
**LINK**

Regards
John

PS:
The program code for the latest version has also been updated on Github for those that can program.

Edited By John McNamara on 27/08/2019 01:32:56

Hi Andrew

I meant to say this as posted at the other place

"Now for the exciting part; Hidden at the bottom of the Gaussian graph there is a tiny numeric value, It followed my indicator movement when I moved the slide. very roughly a value of 1 to 4 on the graph value to 1 to 4 ticks on the 0.01mm indicator. I assume this correlation may not have been planned however with the particular camera I used it was very convenient.

I ran the test several times and it was repeatable.
0.01mm is equal to .00039" (about 4 tenths)
A very good result from a crude setup."

There is an error in the scaled value that needs to be explained. The dial indicator readings and the values on the screen correlated and were repeatable.

Hi Clive

Yes there is more work to do on this project, For a start I want to use the sensor to work with backlit .008" stretched wire without a laser and no lens, just the shadowed area of the wire on the sensor. I am working on something I intend to show at the MSMEE Exhibition in Melbourne in 5 weeks.

You are right using a modern PC enables number crunching speed unobtainable not that many years ago, T 640x480 webcam came from the junk bin. Now 1080p camera modules are dirt cheap some under 20 dollars

The colour image is converted to grey-scale by the software. 

I will keep working on this project.

Regards
John

Edited By John McNamara on 24/08/2019 12:59:40

Edited By John McNamara on 24/08/2019 13:06:43

Hi All

I stumbled upon the following post on another UK forum.

"DIY laser leveling using webcam and laser level."
Link:

The poster provided a link to the software source code on Github
It creates a Gaussion graph of position, I tested the software using a crude test setup.

I obtained repeatable accuracy of 0.039mm (.0004" and I am sure that can be improved with a better setup....... remarkable.

Regards
John

Hi Sam

I know that modern watch faces are often Pad printed. (As well as billions of bottles and the like) It works well on curved surfaces.

I also read somewhere that this process goes back 100 years?

I wonder if the raised text might have been done by this process or a similar process.

Here is a Search that revealed a few good links......
**LINK**

Regards
John

Hi All

One of my treasured books.

Howe does an outstanding job describing formulas on metal and wood finishing.
Also high precision toolmaking in general from an old school manual perspective.

I bought mine many years ago. for the tech info, The gunsmithing part is secondary.

**LINK**

Regards
John

Hi

My first lathe was a vintage Colchester it was a version of this one. I was very sad to let it go due to lack of space.
It used splined centers for the change gears.
That looks like a very nice set in good condition. There should be a 127 tooth Gear.

The flat belt driven black japan finished lathe second photo down. **LINK**

Regards
John

Edited By John McNamara on 09/08/2019 09:44:16

Hi all

I test fitted and aligned the X axis saddle that carries the Z Axis today. Those following this post will remember I set the gantry yesterday using a 0.01mm dial indicator set against two bearing blocks. With the carriage in place I was able to use a straight edge allowing me to test the full travel of the carriage. there was a 0.005mm error in the height. No problem, I tweaked the height of the gantry casting to reduce this to less than 0.001mm along the full travel. Remarkably this was better than the accuracy I obtained setting up each rail individually, that was using 1 bearing block. The saddle is mounted on 4 bearings. Averaging must have worked in my favor. I am very pleased with the result.

Testing the X Axis travel height.

This photo shows testing the X axis travel near the tool in the horizontal plane.
Remarkably no adjustment of the alignment done yesterday was necessary.
The indicator moved less than 0.001mm

Once the table is made It will be installed and tested in a similar manner.

Regards
John

Hi All

Now that the rails are attached I have reassembled the cross member and test aligned it. This is not going to be the final assembly, there is further steps to go that will require it being disassembled again.

As the photos below show I have test aligned the components using the linear bearing sliders reference points. I wanted to test the alignment system built into the machine. As noted earlier in this post there are built in adjustment screws to enable the cross member to be set parallel and perpendicular to the to the rails that will support the table. I had no trouble aligning the reference points to .01mm on the dial indicator if it was the final assembly I would have used a .001mm indicator. The rails are already aligned to +-.001mm to my straight edge.

As you can see I have used a Moore & Wright precision square sitting on a parallel bridging two linear guide bearings.

The linear guide bearings have a ground reference edge, this has been used to check the height using a dial indicator siting on a steel block to increase the height resting on a linear guide bearing. (The assembly was moved alternately to the left and right rail until the zero point on the indicator was the same for both sides)

The height adjustment is made using the two vertical jack screws on the top of the cross member, you can see a T handle and hex key if you study the photo. There are also 4 jack screws to set the gantry to perpendicularity to the table guide rails. see the two Allen keys I left in position. I have also marked the various points referred to with arrows.

Also as noted earlier in this post once the machine is finished I will fill the small gap between the columns and the cross member with metal filled epoxy. **LINK**
The jack screws will have done their job. I do plan to do the first cutting tests without the epoxy in place. That will be an interesting experiment. It will significantly reduce the vibration damping of the cross member. It will be interesting to see how much?

Reflecting on the design of this machine and in particular the way the rails for X,Y,and Z are all located on flat planes that are generated separately and the way the rails were easily aligned to very high accuracy makes me realize that the the biggest errors will be caused by my scraping and lapping of the bearing support plates. Before assembling the machine I will revisit the lapping and try to improve the accuracy I documented earlier in the post. I guess this is being obsessive but It will be worth the effort. Unfortunately all the geometric errors, temperature effects, deflections due to gravity and vibration etc will be compounded, Time will tell what the final result will be?

Regards
John

Edited By John McNamara on 07/08/2019 14:32:01