Here is a list of all the postings John McNamara has made in our forums. Click on a thread name to jump to the thread.
Thread: Facing parallel between centres. |
13/09/2020 06:56:28 |
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. 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. 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 |
Thread: Mystery Object ... This one has me beat |
12/09/2020 07:32:31 |
Yes I know this is a segway... assuming the part is a survey mark 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. |
Thread: Mechanisms in modern engineering design Artobolevsky |
14/01/2020 12:50:44 |
Hi David George. |
14/01/2020 05:40:39 |
Hi All Regards Edited By John McNamara on 14/01/2020 05:41:00 |
Thread: MSMEE Exhibition Melbourne Video |
07/10/2019 07:28:53 |
Hi All Regards |
Thread: Machine alignment using low cost electronics |
22/09/2019 08:28:16 |
Hi All This project keeps getting better. Regards
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Thread: Anthropocene |
22/09/2019 04:54:39 |
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. Regards |
Thread: CRT Free! |
14/09/2019 09:32:27 |
Drill a hole in it! |
Thread: Machine alignment using low cost electronics |
06/09/2019 16:25:03 |
Hi Michael
|
01/09/2019 11:05:11 |
Hi All Regards |
Thread: Equity release! |
31/08/2019 11:02:06 |
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. 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 |
Thread: Machine alignment using low cost electronics |
28/08/2019 03:58:52 |
Thanks Michael I responded with an email. |
27/08/2019 01:28:53 |
Hi All I Bumped this post because there are some worth wile changes. There is an executable version available, A Jar file so you will need the current version of Java installed. Regards PS: Edited By John McNamara on 27/08/2019 01:32:56 |
24/08/2019 12:55:12 |
Hi Andrew "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. 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 The colour image is converted to grey-scale by the software. I will keep working on this project. Edited By John McNamara on 24/08/2019 12:59:40 Edited By John McNamara on 24/08/2019 13:06:43 |
24/08/2019 10:24:42 |
Hi All I stumbled upon the following post on another UK forum. "DIY laser leveling using webcam and laser level." The poster provided a link to the software source code on Github I obtained repeatable accuracy of 0.039mm (.0004" Regards |
Thread: Hieroglyphics on a Wehlen & Co clock face |
13/08/2019 09:21:46 |
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? |
Thread: Black Oxide coating |
12/08/2019 08:59:25 |
Hi All One of my treasured books. Howe does an outstanding job describing formulas on metal and wood finishing. Regards
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Thread: Colchester Bantam gear spline profile? |
09/08/2019 09:42:56 |
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. The flat belt driven black japan finished lathe second photo down. **LINK** Edited By John McNamara on 09/08/2019 09:44:16 |
Thread: DIY Epoxy Frame based CNC MILL |
08/08/2019 10:57:35 |
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. Once the table is made It will be installed and tested in a similar manner. |
07/08/2019 14:30:35 |
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 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. 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
Edited By John McNamara on 07/08/2019 14:32:01 |
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