Member postings for John McNamara

Hi All

I have seen this design before but this is a great image as a working start for anyone who would like to build one.

The video also has some wise words at 21 minutes. and a good family history of 3 generations of a metalworking family.

**LINK**

The scroll in a 3 jaw chuck has to have a small amount of lateral clearance within the chuck body or it would seize up. this creates a small and unavoidable radial error that grows as the chuck gets older.

Try this; put a piece of ground stock in the chuck using one of the tightening points. Mark it with an A using a felt pen. Then check the concentricity of the ground stock with a dial indicator. Note the max high and low amounts and points for A using the felt pen on the chuck body. Now repeat this for the rest of the tightening points.

You will find that the noted points are not all in the same position. most likely one of the drive points will give the least run out. this is because no scroll chuck is perfect, when you drive the scroll from one point on its side it is pushed laterally by the angled drive gear inside the chuck. this may increase or decrease the total error in the system.

Some machinists take advantage of this phenomenon and mark the drive point on their chuck that gives the least run-out error.

Unfortunately there are other errors in the chuck mechanism the scroll itself and the teeth on the back of the jaws also are not perfect; different diameter workpieces may give differing results.

For normal 3 jaw chuck work I do not worry about small errors, however if doing a long run of the same part that requires high precision it may help to find the best drive point to use to reduce error.

All this can be avoided by using a 4 jaw chuck and a dial indicator however the three jaw is a great time saver.
 

Edited By John McNamara on 24/06/2022 00:51:06

Greetings From Melbourne Seamus.

Regards
John

Hi All
Iron Twist Drawn using standard AutoCad
Method:
Drew a spline and dragged it into a 3D shape. A bit fiddly.
Extruded a circle over the spline line
Drew the base profile using a closed polyline.
Swept the base profile
Time about 20 minutes.

Thought I would add some cotton just for fun

FreeCad Cad Cam (Completely open source.)

Hi All

This 2 hour video gives a very good perspective of the various commands and features of FreeCad
**LINK**

The presenter at the JOKO Engineering You tube channel has made many other videos on FreeCad**LINK**

As far as I know this is the only Free CAD CAM option available with a feature set approaching Fusion360

Cotton reel drawn with plain Autocad
About 7 minutes work I am getting a bit out of practice.

Hi All
A quick ramble from a grey haired machinist.

A spring clean in the UK with a new broom, maybe a good thing, Model engineering or as I prefer to call it DIY Home shop machining is changing. Like it or not Automation is coming. While there will always be traditional hand guided precision toolmaker level machine work. CNC Automation is here to stay.

I have always wondered why ME and MEW focussed so heavily on Hand work. There must be a balance. The magazines need to increase their readership in order to prosper. MEW needs to change. They must embrace new technology. CNC Machining, CNC Plasma cutting, 3D printing, CNC routing . Essential for the up and coming around 30 something younger readers.

Once you get over the shock of new tech you will find that all the hand skills learnt over a lifetime are not lost at all, they are needed to run that new fangled CNC widget. You are still dealing with different materials, cutting tools, feeds and speeds etc.

Before I press the send button on this and no doubt ruffle many feathers, a bit, but not, like the new duckling as painted in Alfred Noyes poem, please take the time to consider where our special hobby is heading?

Tn this case the duck needs to survive just like the magazines. Change is a good thing if it is balanced.

Regards
John

PS:
A while back I posted in the MEW forum under "DIY Epoxy Frame based CNC mill" Regrettably not finished due to life's pressures, I will get back to it as soon as my new home workshop shed is built. Waiting on the council approval, fingers crossed it is soon.

This thread alone has had over 62,000 views on this forum and counting. 62K views shows there is genuine interest in CNC from this forums viewers in this sort of machine build.

When we moved into our house about 45 years ago it was derelict, a brick Victorian with bad everything except the cracked walls. ! Yes it even had a council notice served on it. that it could not be re-let, The previous owners were terrible, the worst kind of landlord. Anyway for a youngish couple like us then it offered opportunity, and years of work restoring it.

There was a lean-too at the back that was in slightly better than the front, at least there were no holes in the floor.

It was here we slept for the next couple of years. however when we moved in there were another occupants, In the roof there were possums. About the size of a medium size house cat these critters like the protection of the roof space. I gather they have an appetite for certain physical endeavours, All know is they make a lot of noise when engaged. In due course I was able to close of the holes they used and we had a little peace.

But then there was the scratching and scurrying noises with the occasional squeak. A rodent!

Evicting Mr Ratty was not possible, there were too many holes. It became quite annoying having retired for the night, he would swing into action. "Squeaking and scampering everywhere" (Walter De La Mare described it so well).

Anyway one night I could hear him in the next room It was actually a walk in cupboard about 1.8m square. I knew with the door closed there was no exit. So in I went and closed the door. I was armed with a broom. And so the battle started. I had no Idea how fast a rat can move. and yes they really are aggressive when cornered! Fair enough too I was on his turf and he was defending it. Sadly a story like this has to conclude with an outcome and yes after maybe 15 minutes of me shifting boxes and Mr Rat darting and lunging, the broom minus the head which had broken off settled the argument.

I was never happy about that argument, I guess you do what you have to do is the right rebuttal.

Having now moved to the country I See rats and mice in the fields from time to time. I wonder if they know I am a killer?

Our country garden is also home to many Antechinus a pouched Marsupial About the size of a large Mouse. Most times I go for a walk I will see one. The live on insects mainly. The Males have a very short but happy life, a few weeks, adding to the gnome!

Cities within cities within cities.

Hmmm Windows 10.

Overall It works well in an evermore Microsoft centric sort of way, you can turn off all the back to base stuff it asks you about when you install it hoverer it periodically nags and nags asking you to turn on this or that "Feature".

I did an update from Windows 7 to 10. not a new installation.

It did an OK job of transferring most but not all the software I use.

It installed my licensed Non Subscription version of AutoCad 2021, Revit and 3D Studio and two versions back. However previously installed earlier versions did not work. Yes this is in accordance with Auto desk's licencing policy, however they all worked with windows 7! This may be a problem for other users with older versions. I guess it calls home while Transferring.

I still use Microsoft Office Pro version 2003. including MS Access That transferred successfully.

However hardware gremlins that have caused me a lot of grief.

I have an HP 42" Designjet 500 plotter and a Xerox Office printer. Both are connected to a separate Windows 7 PC that is connected to the network. I can print a pdf created in Autocad if i transfer the files to the PC then print it from there The same applies to Microsoft Office Word Excel and Access programs.

I can also print to both printers over the network from another windows 7 PC. But not windows 10.

The problem is my printers are old in age, they work perfectly! The windows 10 drivers will not communicate. Not having direct access to the plotter in particular is a real bugbear. It would be very expensive to replace. There is a lot of discussion on the net about HP driver issues. with windows 10. I have had a couple of goes at sorting out the problem using various "fixes" posted on forums but to no avail. Somewhare out there there may be a workaround... Fingers xxx

Anyone with older hardware should check, they may need to keep an older Windows 7 PC to run it.

Regards
John

I have specified dozens of skylights. Recently I have been involved in construction. I have always used Velux, some types open some are fixed, manual or automatic.

In my view blinds are essential to keep out summer heat, Velux supplied blind kits are likely to be half the cost of having a local blind company make one to fit a skylight. Depending on the area insect screen as well if they open.

Take note that the roof angle has to be considered, not all types will not work with with all angles. check the angle first.

Cutting the opening to fit a skylight is easy, Velux supply flashing kits for most roof types. The local Velux sales office should have a list of installers. for DIY You can download very detailed installation instructions.

Light? Don't over specify check how much you actually need. Beware of creating a heated greenhouse!

I have no connection with the Velux company.

Edited By John McNamara on 11/12/2021 06:21:58

Good find Michael G

From the first Scientific American link you posted.
If this image is from the Antikythera find it appears to show a larger fragment. Maybe it is an assembly of found pieces? However even if it is it may enable a more precise centre point to be derived, Even if just a "feature" arc is used if the holes are not visible. it might improve the accuracy of the calculations for the hole circle. By knowing the radius of a feature arc and then measuring the distance from the feature arc to the hole circle arc, a more accurate radius for the hole circle might be obtained. I firmly believe that the mechanism was accurately made with true concentric circles.

Maybe there is a better copy of this image available?

Slideshow Link

Regards
John

Hmm

Maybe oysters... But then again, maybe not.

Happy birthday Bill

Cheers
John

Both Browne & Sharpe and Pratt and Whitney made similar machines.

**LINK**

Many companies made similar machines

An assembled photo might help identify it.
Are the parts numbered?

Vintage machinery.org have free downloadable documents from that era. the best site I know of for old US metalworking machines.

**LINK**

Hi Drewt

I should have made it clear in the last post I made that all the arcs placed with the three point method were positioned on the end circle centres. The two "feature" arcs were positioned entirely by eye.

The centre of the hole(s) arc was positioned by eye as seen below. I tried to visually pick the visual average centre of all the holes.

The circles around the holes were also positioned by eye, prior to placing the arc. Reviewing the placement used it looks about right, Improving it would not significantly affect the placement of the arcs. and the the all important radius that assists us in calculating the number of holes.

I am surprised how much the the centres of the hole arcs and the two feature arcs deviate in the tests. There is significant error, they should line up better, assuming the creator had a half decent compass. It is clear the device was created by master craftsman. They would have had high quality compasses and tools.

For me that only leaves distortion, the centres should align a lot more accurately. was this distortion physical? The result of unknown forces over time? Or could it be possible that the X-ray scanning methods introduced error. I know the imaging was done in slices, were they truly planar to the mechanism? Could there be some form of spherical distortion of the scanning beam?

I would really like to know more about the scanning method. what was the accuracy and linearity obtained particularly over the entire area of the objects. The fine detail is good but that is not all we need.

See enlarged images below

Edited By John McNamara on 16/11/2021 13:42:14

Edited By John McNamara on 16/11/2021 13:43:29

Hi Nealeb

The link below may possibly interest you?
Gearotic is a suite of tools used to create all sorts of gears standard and exotic!, Clock escapements, Bolts and and other parts.

Developed by Art Art Fenerty and Bob Landry, Who created Mach 3 CNC.
It is not free and costs 120 US dollars. (For a lifetime licence with free updates forever)

**LINK**

I have no connection with the company apart from having bought my copy maybe ten years ago and updating it as new versions come along. What I can say is it works well. a bargain if you have a use for it.

Hi All

When I started this project I had no idea that having got so close to a finish, Life pressures would push it into the background.
I am also astonished that this post has been viewed about 57000 times.

Clearly I have a debt to repay the interest received with a completed project.
My sincere apologies for the delay.

My workshop is now moved to a new temporary brick garage and hopefully soon I will have 3 phase power. I need the lathe to make some of the parts. I want to build a new shed later this year. But at least I can work in the temporary garage.

At the moment I am bench testing the XYZ drive system. Will post a description soon.

It will be interesting to see if there is any change in the alignment of the mill, having travelled on a truck about 60 kilometers crane on, crane off etc. The columns and crossmember are only bolted, as noted in the post they were to be set in epoxy then bolted to final alignment.

Regards
John

Hi All

Thank you Drewt for the image, I am not exactly sure who to acknowledge regarding its copyright. However I wish to acknowledge that it is.

More testing and again differing results!
I have been using Autocad to work on the image, I did not select any centre points when placing the true circular arcs. I just used the three point arc method. I am confident the method is accurate.

To me the results all point to distortion.

How many holes? So far the tests have suggested a lower number certainly not 365 is the most likely?

Regards
John

Firstly I never repost but this is an important lesson. apologies.

Just because it looks all right? You better look very very very carefully.

We recently bought a new house. An exciting time. The usual thing we paid a nominal deposit on the day pending payment of the full amount a couple of days later. Having looked at a number of properties with the same estate agent we knew several of the sales staff and the name of the sales office accountant who had properly handled the initial deposit.

All good so far.

A couple of days later we received an email telling us the bank account details for the rest of the deposit, The email used the logo and office details of the agency together with the names of the sales agent and the details of the amount owing. However, there was one difference. the bank account details had changed to a new account number. Apart from that it looked like the initial deposit email.

Luckily this triggered an alarm in our minds. It was then that we also noticed a difference in the web address, so we phoned the agency to check the validity of the email. They were shocked! They knew nothing of the infiltration of their computer. And yes! it was a scam.

I later found out that this bank account number was indeed a genuine Australian bank account number. The Police told me that this is the norm. However, any money paid into that account would have been whisked out of the country in seconds.

What had happened is that the estate agent’s office computer system had been hacked. The hackers had gained access to the records of current sales taking place at the time and were able to construct bogus documents to use against current transactions. With all the correct names and logos in place.

We were lucky, the small discrepancies triggered that essential check phone call. Had we not done that we would have suffered a substantial loss. As I understand it another client did not notice. and was snared by the scammers net. I don't know if they were compensated. I suspect not.

As a consequence, the estate agent shut their offices for several weeks while a new system was put in place.

We made the payment in person at the estate agents bank after checking the credentials of the account with the bank manager.

In Australia Property is now settled by computer, not like in the past where the conveyancing Layers for the parties concerned sat around a table. and exchanged documents.

Our lawyer who conducted the final settlement told us that many lawyers and other businesses that handle cash had also been hacked in a similar way. She told me that in spite of automation they always telephone other parties verbally and only use account numbers obtained verbally having confirmed that there is no possibility that the party on the other end of the phone is a scammer.

While the settlement is normally done by a layer in Australia the deposit is usually just done personally, typically about 10%, a substantial amount of cash to loose.

The event also triggered a long investigation by our two banks not because we were affected but because they were trying to set up defences to counter this sort of activity, however in my discussions with them I gleaned that as soon as the cash is out of the country it is almost impossible to recover it.

Naturally we had put a stop on all our bank accounts immediately, We did not know what sort of information the scammers had.

Just because it looks all right? You better look very very very carefully.

Hi All

Using the second set of observations I made shown in green I calculated 355,83deg. This used the larger fragment with no visible cracking. I guess this larger fragment offers the best approximation accuracy available.

The method used was to visually place small circles over the “points” then apply an arc over the circles using eyeball best fit analysis.

Can we assume the points were holes? If they are holes I would be very interested to know if the “silt” mentioned previously by Drewt contained iron, particularly at the bottom of the holes? Maybe this would suggest pins protruding that might suggest a pin gear.

Getting back to the method. I would like to try it on the best available known image. If available online I would appreciate a link. I will repeat my test using this image.

I am somewhat confused by the apparent inaccuracy of some of the points, I firmly believe that a person capable of constructing this mechanism will have been capable of better hole placement.

Maybe we should ignore certain outliers from the calculations. Local corrosion might possibly have moved the apparent hole in the substrate.

Additionally, there is the possibility of larger (not visible) cracks deforming the substrate.

I look forward to a retest on a better image if found.

Edited By John McNamara on 13/11/2021 00:09:54