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Member postings for Pat

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

Thread: Tempering Salts
19/07/2012 18:21:12

Hi Andy - Never ever raise any oil to boiling point as this is a fire hazard as the fumes given off will be above the liquid oils flash point. I only posted the oil method of drawing the hardness down as this does not need any special equipment other than a suitable source of heat and a container. Olive oil and many others edible oils smell very good where as mineral oil is not good and is probably poisonous.

The domestic oven is ok but in my experience the temperature need to be watched all the time as the oven themostats are not precise so the temperature wanders up and down quite a bit. I use an industrial glass / mercuary thermometer that is in a protective steel tube. The oils are from the supermarket or the local deli.

Regards - Pat

18/07/2012 15:38:36

Hi Andy There are alternatives to salt for the lower teperature tempering of previouly hardened parts . For example for light straw simply use olive oil. It starts gently smoking at 190C to 200C and the smell is OK but there is a fire risk if heated to its boiling point arround 300C. Other oils can be used SAE30 oil could also be used but the fumes are not good.

As these oils vary a bit it is advisable to measure the temperature  of the actual oil you have.

Here is a link to some other oils and their smoking temperatures. **LINK**

And here is a better link to kitchen edible oil smoke points

http://en.wikipedia.org/wiki/Corn_oil#cite_note-chef-5

 

Regards - Pat

Edited By Pat on 18/07/2012 15:39:24

Edited By Pat on 18/07/2012 15:43:09

Edited By Pat on 18/07/2012 15:58:20

Thread: Casting aluminium without a furnace?
25/06/2012 17:53:23

Hi jason

Thanks for that link the digitising probe looks interesting. As I understand the process there is an eletric micro furnace with cruciple included in the kit. The domestic microwave is used to melt the wax from the investment plaster cast and vaporise any remaining wax. The metal is then melted in the supplied electric furnace and poured into the mould. This process is for small parts so should suit some model makers.

Regards - Pat

Thread: tapered points
20/06/2012 01:31:41

Seen tools very similar to those in the picture except they had wooden file handles on the short end. They were used to assemble thin aluminium sheet metal parts into a former and to get the reference holes to line up with the reinforcing rings prior to drilling additional holes for riveting. They were called podgers and had similar square sections on the shanks to make removal easier. The full diameter of the slow taper was the diameter of the reference holes and were filled after removal from the former after inspection. The inspectors would be check that the reference holes were correct. This was in the aero space industry in the 70's. Regards - Pat

Thread: Fitting Digital readouts (DRO's) to Clarke CMD10 mini mill.
19/06/2012 17:12:39

Hi Chris

These small mills come in a variety of different configurations and there are several factories in Tiwan and China making them. So not only do they come in different colours but they eminate from different places as well and to make the mix even wider some importers have them badged and made to their own specifications. What I am trying to put over is that just because they look similar there can be differences in the castings and the clearances between the moving bits.

Here is a link to a site showing DRO scales fitted toa Seig X2. This mill has a tilting mast but the X and Y axis arrangements would be similar .

**LINK** Amadeal and ArcEuro have the scales but you would have to improvise your own brackets as per the link but the dimensions may be different. You could also search the CNCZone for X1 + DRO

Hope this helps - Regards - Pat

Thread: Mini Mill belt drive conversion
02/04/2012 16:37:01

Hi John

I found a suitable Vee belt as a sewing machine spare in a shop that specialises in the repair of domestic sewing machines. I think it was from a Toshiba sewing machine - it is vee section with polturathane covering. All I did was take a bit of paper with the correct diameter circle drawn on it and a bit of card with the correct angle. The belt is very flexible and designed for small diameter driving pulley of similar diameter as used in the design by Hoss. Not sure about the exact profile as I worked from the belt and a pulley from a dead motor. The advantage of a vee belt is that it acts as a clutch of last resort but a HTD toothed belt should also be as silent.

I have not completed mine yet as I want to get the Z axis drive for CNC sorted first. I have in mind moving the motor to the control box side so that the ball screw can drive down the centerline of the rack.

Hope this helps - Pat

Thread: A one cylinder Stirling engine
26/08/2011 02:44:58
Hi Andy
 
At first sight this appears to be a type B Stirling engine which has been made in a rather elegant form. This illustration is from the Wikipedia site. The fingers round the glass tube are the cold end and the heated end IMHO is that nearest the flywheel and this gives the nice pictorial design in the photos posted by Andy.  A first class exhibition model.  However a movie would clinch the identification as being a re-jigged class B Stirling engine design.
 
And in diagrammatic form belowjust reverse the connecting rods to get the configuration shown.File<img
 
However looking at the photos posted the rather thick bar that runs from one end to the other is out of kilter with the rest of the mechanical design so is this type A making use of a heat pipe as I can see the dual connecting rods in the pictures?  
 
The more you look the more fascinating so I hope some one has some ideas or may be purchases one!
 
Regards - Pat

Edited By Pat on 26/08/2011 02:56:20

Thread: Pinning
26/08/2011 02:05:06
Peter - I agree with Steve Garnet - best to use taper pins and the associated taper reamer and drilled hole. That way the pin is a good fit and can easily be removed and refitted for maintenance or assembly purposes. Both pins and reamers are available from suppliers specialising in clock makers tools and materials. In the bigger sizes roll pins are good if you must use a plain drilled hole. Normal engineering practice for the holes for parallel pins is to use reamed holes to ensure a good fit. The taper on a hand reamer can in an emergency be used to good effect with care.
 
Regards - Pat
Thread: digital tv switchover
20/08/2011 21:18:26
Hi Gordon
 
Might be '7E EUTELSAT W3A' which is at that magnetic bearing and elevation for mid Scotland.
 
Good luck - Regards - Pat
20/08/2011 19:51:54
Hi Dick
 
As far as I am aware there is little impact of frequency on the design of the dish. The diameter to depth is mainly a function of the mechanics of illuminating the horn of the LNB. This is very different from an astro telescope where the aim is to bring the wave to an actual focus. The LNB has an active area of approximately 10mm square.
 
The frequency (low GHz) is important when the dish is perforated or formed from slats. If the holes are too big or the slats the wrong dimensions the surface ceases to act as a reflector and the dish becomes transparent. The long range radio fraternity use very high gain aerials to get extra long range communications under ideal (freak) conditions. For reliable satellite reception a few extra dB are required to cope with rain clouds (10 dB is typical) but other wise the signal is reasonably constant as there is little weather in the path from the satellite. To get a reasonable signal to noise ration the gain required is low because the aerial is looking into space and is thus not picking noise from man's activities which involve the use of electricity.
 
To see how all of this influences the design and construction of a 2 meter dish draw the thing out to scale and pick the way the dish gathers the beam and projects it onto the LNB as this is the best way I know of showing how the various LNB feed arrangements work. Regards - Pat
20/08/2011 19:14:14
Hi Gordon
 
Commiserations over your poor internet speed. Think the satellite service you are signing up to is at 39.0 degrees East and for the North of Scotland 14 degrees elevation or 15.5 degrees further South.
 
Good luck for high speeds soon. Regards - Pat
 
 
20/08/2011 17:06:44
Hi Dick
 
If you are going to make your own dish. An easy method is to use a large block of high density foam plastic that is friable.  i.e breaks into crumbs when rubbed. Make a spade cutter out of a bit of sheet material to the correct parabolic shape. Plunge the cutter into the foam with care and a light action as the cutter is large and the cutting edge less than rigid! I have made 1 meter diameter dishes this way but 2 meter may be too big. Lay up horizontal tinned copper wires at 5mm intervals and press down into the foam and secure. Leave all wires 100mm too long to permit soldering to the edging tube. Bend and solder cross wires to complete the mesh and bend a hoop of copper tube to make a neat edge when soldered in place.
 
Remove all traces of the foam by what ever method appeals. Result is a dish with minimal visual impact good performance (provided you have kept to the profile) and low windage. The windage is important as the angle subtended to the satellite is very small which means that wind rocking the dish can become an issue particularly in exposed situations.
 
A previous contributor has given a good link to a site that shows how big a dish is normally required for any given location / satellite.
 
Just check the price of a suitable metal sheet against the cost of a commercial dish as the sheet of metal may be very expensive by comparison. Try and use a better quality LNB if you are on the fringe of the service area.  But do check the satellite operators site for recommended dish sizes along with the stations broadcast on each of the transponders to make sure you are going to get the required entertainment!
 
For Gordon,s benefit just enter Astra in to Google to list the services provided by the transponders on Astra 2 I think 2D is correct but this is from memory so please check - however since they are all on the same satellite it only comes into play when starting up the receiver.  Note the 2D transponder is beamed at the UK.  
 
 
 
Good luck - Regards - Pat

Edited By Pat on 20/08/2011 17:07:59

Edited By Pat on 20/08/2011 17:23:10

20/08/2011 11:06:49
Hi Chris and others
 
Here is a simple way to set up a dish using two sheets of paper.
 
1. Go to http://www.dishpointer.com/ enter your location Blogtown, Blogshire, UK and this will show your district on a map. It opens with a US location!
 
2. Use the map to locate the dwelling on which the dish is to be mounted.
 
3. Select the Astra 2 satellite ( The other satellites have different services so make sure you select the correct one as the angles are very different!)
 
4. Check the box on the map to show obstructions.
 
5. Use the obstruction point to pick the best location on your building or garden for the dish and increase map scale to maximum magnification. This is also an indication of how far up the wall you need to mount the dish. This is simple trigonometry but the method described below is so simple and is probably quicker.
 
6. Check that you can achieve sufficient height to clear the obstruction. Move the marker corresponding to the dish around the property and select the best location. Now for the elevation check you do this by measuring along one edge of a piece of paper the number of units from a square (90 degree) corner. Mark this edge HORIZONTAL Now measure from the same corner the height of the obstruction using the SAME scale! Now fold the paper along the line joining the two points measured earlier on adjacent edges. This is the elevation for the dish above the horizontal.
 
7. From the printed map fold along the line of the surface from which the dish will be mounted. Then fold along the line to the satellite. This is the angle of or the dish when mounted on the wall. Just make sure you do not turn the paper over!
 
8. From the point on the building on which the dish is to be mounted use the Second piece of paper to show the direction of the satellite as an angle from your selected mounting surface. Note this avoids any problems with a compass pointing at local metal work etc. Then use the first piece of paper to check there is a clear view of the sky - no buildings - trees or other objects by sighting along the paper. Use the second piece of paper to check and re check that the view of the sky at the elevation angles given by the two bits of paper is clear - then - and only then mount the disk brackets. Where obstructions are found the at the angles required for free sky view the dish position selected is too low. It is possible to use the elevation angle to calculate the height above ground level but I have not found this necessary in practice as a quick check by sighting is so easily done from the ground and ladder as necessary.
 
9. Tweek the mounting adjustments on the dish to get the angles for both elevation and bearing from the mounting surface. Nip the adjusting screws and chek the signal strength monitor on the receiver set up page for the Astra 2 satellite (There are various letter suffixes which indicate which transponder you are tuned to be it Freeview or Sky this only affects the tuning range of the TV or set top box not the dish position. If the signal quality is not sufficient then move the dish on its adjustments but check first that it is properly aligned to the bits of paper.
 
10. If the paper angles have been adhered to as well as plotted accurately then no tweeking should be necessary. I find this method is quicker than using the meter compass and can save a lot of debate on positioning in sensitive locations!
 
Just make sure the dish is mounted where it will not be disturbed.
 
Also for most LNB the leads should come out of the bottom for the correct polarisation and the fine tweeking of the angle is done using the signal strength meter either in the TV or STB or a separate meter if available.   
 
Regards - Pat

Edited By Pat on 20/08/2011 11:09:58

Thread: Numbering - automatic adding to each post
04/08/2011 16:58:53
Hi David
 
You have illustrated my point in that you have used up a load of extra lines in the thread. You could have just posted:-
 
In response to post no 1 my response is:- No just use the quotes feature and paste in the appropriate lines
 
The problem comes when there are many pages in the thread and people start to add quotes and then add in their comments without using anything to indicate what is a response against just a few lines of the original post as a quote.
 
Just an observation - Regards - Pat
04/08/2011 10:54:07
Hi David Clark
 
At some time could you try and get the automatic numbering of the posts with in a thread given a number as this would make referring back to earlier comments much easier.
 
Thanks for pushing for the much improved digital publication for MEW.
 
Regards - Pat
Thread: hole size for tight fit
04/08/2011 10:32:45
Simply use a hand reamer having pre drilled the hole under size. Use the tapered portion of the reamer to slowly open up the hole trying the fit on the motor shaft as you go. Stop when the motor shaft just enters the hole being reamed being careful to ignore and radius on the end of the motor shaft. The small taper on the hole should ensure a nice press fit.
 
Use the hand reamer not a machine one in the lathe tail stock chuck is ok but turn the work by hand not under power as you only want to remove a smidgen of metal. I would use 'Locktite' or similar rather than grub screws unless removal at some future date is envisaged. as this will not add extra out of balance to the motor shaft.
 
Do not use a taper reamer as these are designed for use with matching taper pins not to bring the hole to a dead size. Check the motor shaft size against the reamer's designated size as the motor shaft may already be under size to suit stock pulleys etc.
 
Regards - Pat
 
PS a boring bar for a 6mm hole is very delicate. 

Edited By Pat on 04/08/2011 10:34:10

Thread: Cutting oil
02/08/2011 13:36:58
Hi Garry
 
Plenty of suppliers on ebay - just type in Neat cutting oil. I like the water miscible oils but this is a personal choice and is also dependent on material being machined as well as the feed rate and the cutting tool being used. There are also mist cooling systems - flood cooling as well as dabbing with a brush or drip can - explore all and make your choice an informed one.
 
Regards - Pat
Thread: Milling drawbar
14/07/2011 21:50:05
Hi John Coleman1
 
Can we have a repeat of your post as your design for a self releasing draw bar sounds good.
 
May be I am looking in the wrong place as the last post in the thread 'milling collet arbour jammed in milling machine' is June 2010.
 
Help please - Regards - Pat
 
PS found post as June 2010 and have pasted it here:- 
 
Julian,
"Been there, done that"
My long-term solution as follows.
Trapped nut system works like a dream - try it!
I made new drawbar with nut just touching top of mill spindle, remove, cross-drill + pin.
Large AF hex bar bored out to fit over top of mill spindle and locked on to it with 3AAllen key grubscrews.The rest of it drilled right thro` clearing size for drawbar thread. Make new smaller AF nut, taller than standard, fit  on top end D-bar + wind down to just touch top of large AF nut, cross-drill + pin.
John  

Edited By Pat on 14/07/2011 22:04:09

Thread: How to clean a bandsaw
14/07/2011 15:18:23
Hi Folks
 
I use white spirit when I am not going to immediately continue to machine or work the parts in some way as white spirit contains oils that help prevent further corrosion. This is of importance to me for machinery during a strip down or cleaning prior to assembly. I have never had the need to remove the oily film other than in preparation for painting where I have always used the thinner/cleaner for the paint process being used.
 
Paraffin on the other hand is a fuel and is refined so that it contains little or no corrosion preventative free oil. If you store paraffin in a steel tin it soon rusts out the bottom even with the cap in place. The same remark applies to petrol as a cleaner but there is a real risk of explosion of the vapour in the confines of a workshop. I do not know how diesel performs as a cleaner as I hate the smell!
 
The likes of Jizz - Gunk and industrial detergents are good but require post treatment to keep rust away. There are numerous small parts washers at bargain prices if you have a lot of this sort of cleaning to do. They have the advantage of a pumped supply of fluid which is reused after filtering. I use mine as a lathe and mill coolant system and only fill with cleaning fluid when needed. Being a one man band I don't need to do both at the same time.
 
Regards - Pat
 
PS John - you might consider the parts washer approach if you need to supply coolant to the saw during cutting of heavy sections.  Draper - Screwfix and other do cheap (£40 ish) parts cleanrers comprising a small tank and pump. 
 
 

Edited By Pat on 14/07/2011 15:21:33

Thread: Something to ponder 02
14/07/2011 10:40:57
The problem with microscope sub stages manipulation is one of vibration. As most if not all microscope use is under stable temperature condition the effect of thermal expansion during can usually be ignored provided the mechanism has the ability to absorb large changes in the design of the slides and other moving parts. Some stages have to operate under vacuum as well as at various temperatures as part of the observations of the specimen.
 
Cam and lever with a small electric motor are the normal methods of motion control. The speed of traverse is normally very slow as the field of view is restricted so it is all too easy to loose the subject if the movement is too rapid. A large reduction in the gearing between the motor and the cam is often provided by a double or triple sun an planet coaxial gear box as part of the motor drive. The lever and cam mechanism being arranged to provide quick initial centring of the specimen.
 
On optical quality mechanisms it is often a good idea to use a very viscous grease specially formulated for this type of use. This gives a nice action by damping the vibration as the parts move. Unfortunately the use of vacuum often precludes the use of lubricants necessitating dry film and/or sintered bearing surfaces with external to the vacuum chamber motors etc.
 
The use of motive forces that involve impulses require that the impulse is applied as a balanced force to avoid vibration which is the bugbear of the high power microscope.
 
The use of pneumatic / hydraulic manipulators is common to isolate the manipulating tool from the operator. These mechanisms use the operator in the feedback loop OR have some very sophisticated means of providing tool point position for feedback in the servo loop.
 
Hope this helps - Regards - Pat
 
PS Yet again define the total movement - the accuracy of placement - speed of movement - any rapid movement requirement - environmental conditions as vacuum and temperature are often critical to microscope stages.  Contamination issues also arise which may require special attention as parts may need to be removed for sterilisation in some nasty fluids.  
 
PSS The use of a piezo material as a beam that can be deflected using an applied voltage is well known but has very limited movement and would need to be part of a dual stage motion in a practical implementation unless the specimen is pre located by other means.  The use of other materials might be more amenable to experimentation as a DIY project two materials come to mind electroactive polymers and memory alloy.  The latter is available in short lengths and is used for nano bots and toys but the movement is small and there are hysteresis effects to be accommodated.

Edited By Pat on 14/07/2011 11:10:15

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