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Member postings for John Purdy

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

Thread: Stuart Turner No.9 Slide Valve
09/04/2020 18:35:31


I've sent you a PM.


Thread: A free ride to hospital
13/03/2020 17:19:03

Yes it VERY DEFINITELY can happen, I know from personal experience as it happened to me. Unbeknownst to me, my son had ground of the heads of a number of aluminum pop rivets on my 1" belt sander. Later while fairly aggressively grinding the sawn edges of some angle iron, a large bright white fireball engulfed the sander, my hands and the front of my shirt. My hands suffered fairly sever burns with the skin hanging off the heals of both hands and the ball of my thumbs. The front of my shirt was smoldering. I lost most of my mustache and eyebrows, My face looked like I had a good sunburn ( except around my eyes which were protected by my glasses). and the workshop was full of white smoke. Luckily the burns weren't quite bad enough to require plastic surgery. As has already been said, essentially what you have made in the grinder is thermite with the mixture of aluminum dust and the iron oxide from grinding steel, ignited by the hot sparks. After it happened I wrote it up in ME (09 Mar 2001) as a warning to others. I have pictures of my burned hands somewhere. My son has been educated and I now leave the side cover off the belt sander and brush out any residue on a regular basis. Also never use it on aluminum!


Edited By John Purdy on 13/03/2020 17:23:24

Thread: Looking for ME 3942
22/02/2020 18:02:54


I've sent you a PM.


Thread: Unimat Fretsaw set up
26/01/2020 17:48:10


When I use mine I set the blade guide 1/16 - 1/8" above the work. This provides good support to the blade but allows you to see what's going on. It's not actually used as a work hold down (that's the job of your fingers!).


23/01/2020 18:50:11


If you attachment looks like this, the rod is just a guide for the blade. The blade is not actually fastened to anything at the top but just slides in the slot in the rod which acts as a guide. The tube on the rod is fixed and serves to retain the blade in the slot. In use the rod is moved down to just clear the work and is clamped to the frame at the top with the large knurled thumb screw. It is also orientated with the slot to the front so the cutting pressure pushes the back of the blade against the slot.



Thread: Scaling the Eureka
10/01/2020 18:40:35


The issues of EIM that had Brian Wood's articles in were June and July 2019. I've sent you a PM.


Thread: Machine reamers
08/01/2020 18:04:19


I'm in BC and I get mine from either KBC Tools ( or Travers Tools ( Both have Canadian warehouses and are reasonably priced. They both have large free catalogues.


Thread: Myford super 7 oiling
04/01/2020 23:21:52

I find the brass seals quite well with just moderate pressure applied to the nipple. I would be concerned with the softer material wearing quite quickly as I have found even the brass wears over time. I have made 3 ends over the last 20 or so years as I find the small dia. end tends to get damaged. I feel that one advantage of this type as opposed to the one that seals on the outside of the nipple is that as the sealing ball is pushed back by the small end and not the pressure from the oil can so not nearly as much pressure is required from the oil can.


Edited By John Purdy on 04/01/2020 23:23:29

Edited By John Purdy on 04/01/2020 23:24:44

04/01/2020 19:50:54

The Myford oil gun is (or was), as you were thinking, an inverted cone to theoretically seal on the outside of the oil nipple but I found that it did exactly as you envisioned, putting oil everywhere but in the nipple where it's wanted. That's why I made the one shown which seals against the sides of the small hole putting the oil in the nipple where it's wanted.


04/01/2020 18:53:01

The small ones are oil nipples. I found the easiest way to oil them is to make an end for a standard oil can like this. The small end fits in the hole in the end of the fitting pushing the small ball back and has a small slot filed across it so the ball doesn't seal it off. (the pictures are in my album)dscn3201a.jpgdscn3201b.jpg


Edited By John Purdy on 04/01/2020 18:54:01

Edited By John Purdy on 04/01/2020 18:55:00

Thread: 5" gauge boiler rod stays
29/12/2019 20:12:59

Reference your question about BOC tip sizes, I had the same problem when reading Alex Farmer's book as to the best of my knowledge BOC equipment is not available in this country so quoting tip size numbers means nothing ( my equipment is Liquid Air). But through a post to this forum a couple of members were able to measure their equipment and provide the following actual tip sizes:

BOC tip size     diameter      closest # drill size
#1                    .6mm                 74
#3                   .8                       68
#5                 1.0                       61
#7                 1.3                       55
#10               1.4                       54
#13               1.6                       52
#16            1.8-1.9                    48
#25               2.0                       47
#35               2.4                       42

There is also a chart of equivalent tip sizes for a number of manufacturers here:
Hope this is of some help to you

Edited By John Purdy on 29/12/2019 20:15:42

Edited By John Purdy on 29/12/2019 20:19:09

Thread: Any users of the 'ModelEngineersUtilities here?
03/12/2019 18:58:18


When you open the program and select one of the functions (say "cutting speeds" ), does it work normally, no black boxes?

I have just downloaded it (again) to my W10 laptop and installed it exactly the way you describe above and it still does not work. When any of the functions are selected (say "cutting speed" as Thor selected) all I get is a couple of boxes listing inputs ( one is "materials" and the other is "calculate" ) but the rest are just black boxes. I would sure like to know how you get it to work properly on your machine.

It also does the same thing on my W7 platform when installed as above.


Edited By John Purdy on 03/12/2019 18:59:07

02/12/2019 19:28:43

I have it on two computers a Win7 and a Win10 and so far have only used it for drill sizes for tapping and it seems to work OK for that. But I just tried some of the other functions and I get the same as Hans, a lot of black boxes where input data should be. I had it on an XT machine and all functions worked OK.

I've just downloaded it from both sites listed in the above posts and it does the same thing. It does not matter which folder I unzip it to or if I unzip it as administrator, the initial screen comes up fine but when any of the functions are selected they come up with a number of black boxes.


Thread: DRO problems
29/11/2019 22:58:01

Just over seven years ago I installed a Newall DRO on my Taiwanese VMC. It consists of a DP700 readout and two Spherosyn encoders on the X and Y axis. Up to about two years ago it has performed flawlessly. But then every couple of months or so one of the display readouts jumps exactly .5000" up. It seems to happen whether the table is being moved or not. It's always an increase of .5000", never anything else. If I reset the display to it's former value then it reacts normally till it does it again a couple of months later. I have swapped the cables on the display and the error appears to follow the encoder, but I'm not positive, I wasn't keeping a log of when it happened. I have now been keeping a log and in the four times it has occurred since Jul last year it has always been the Y axis display ( the cables were not switched). The next time it happens I am going to switch the cables and see what happens.

Has anyone else experienced this fault?

Over the last year I have sent two emails to Newall's tech help via their web site but have never received a response.

Edited By John Purdy on 29/11/2019 22:59:40

Thread: ME Beam Engine
14/11/2019 18:13:49


There is currently a build series running in ME on building the ME beam engine. It started in issue #4603 17 Jan 2019. Latest installment was part 10. You might find some useful info there.


Thread: What's this please?
01/11/2019 18:01:21


As Alan says its part of a dial indicator unit, specifically for converting a rear plunger dial indicator to a DTI type of indicator. The mounting rod on the dial indicator is held in the 1/4" hole by the thumb screw and the rocking lever is adjusted to rest against the plunger on the dial indicator. The other end of the rocking lever then functions the same as the lever on a DTI.

If you go to Travers and search for their part # 57-051-196 (Starrett  part # 196A1Z) you will see a picture of it.


Edited By John Purdy on 01/11/2019 18:08:55

Thread: engine tightness
12/10/2019 18:37:11


I have just completed a ST#1 (see my post of 21 Aug. in the "work in progress" thread) and it turns over with some drag which I put down to the ring friction in the bore, but I wouldn't call it tight. It uses the supplied ST rings and are fitted with an approximate 3-4 thou gap. During initial testing I assembled it without the rings and it that state it just spun over easily and if the flywheel was given a good spin it would coast for 2 or 3 revs. Try assembling yours without the rings and see how it goes, it may be just the ring to bore friction that is causing the tightness. How thick are your rings? The ones from ST in mine are .0955 thick, which are by all accounts considerably thicker than optimal. The wall pressure may be higher than optimal. I found that I could remove the rings without disassembling the whole top end by removing the the top cover, and with the piston at TDC the nut could be undone and the top half of the piston unscrewed. Lowering the crank to BDC then left the rings in the top of the cyl. and could be removed. With the crank back up at TDC the piston could the be re-assembled. I must have done this a half dozen times!


Edited By John Purdy on 12/10/2019 18:40:52

Thread: Red Wing build article
01/10/2019 17:53:28


I've sent you a PM.


Thread: Boiler plans
28/09/2019 17:18:53


Tubal Cain did a series on the building of a 5" shop boiler in ME starting in Vol. 144 #3591 18 Aug. 1978. You might find it useful.


Thread: silent whistle
21/09/2019 19:58:20


I forgot to say the one I made is a bell type and is quite small. The bell is 1/2" dia by 3/4" long with an overall height of about 1 5/8".


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