Member postings for Jim Guthrie

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

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Thread: Drawings / Artcles
25/07/2012 23:03:36
Posted by John Besley on 25/07/2012 22:00:04:

Hello Jim

is it possabile to send me a copy of the article and plan so i can weigh it up, I am looking to build a "Mammod" type as this would fit in with my 7/8ths scale garden railway

John,

I'll fire the scanner up and I'll need your email address. smiley

Interesting that your railway scale is not far off 1" scale, and a Minnie might be closer to correct, or a half size Allchin at 3/4" scale. smiley Cherry Hinds built a half size Allchin so no pressure there. smiley

Jim.

25/07/2012 14:08:28
Posted by John Besley on 23/07/2012 20:49:17:

Many thanks where can i find the back numbers from ME4142

John,

I had a quick look at the traction engine in ME4142 and I don't know if you would like what you see. It is representative rather than realistic and is very similar to a Mamod style engine - the main difference being the "proper" slide valve cylinder. The boiler is a simple pot type and its outer sheet diameter is well over scale diameter.

I think the problem with modelling a working 1/2" scale traction engine is the boiler size - a half size Minnie would give a boiler diameter of 1.25" which doesn't give much capacity if you have an internal flue. You would probably need a very good feed pump arrangement to keep things going for a reasonable length of time.

Unfortunately I don't have all the articles in the series. i think it was around the time when the delivery of the ME was very spasmodic and I missed quite a few issues.

Jim.

Thread: Will electrical 'multicore 'solder adhere to brass ?
24/07/2012 10:35:04
Posted by Terryd on 23/07/2012 21:37:37:

If you are going to use propietary fluxes Laco is a good one. Will clean the metal as you solder. But again, a good scrub afterwards is essential.

I have used Templers Telux flux on brass, nickel silver and steel for the past few years and there are no bad after effects of oxidisation. You do need to wash off the work if you are going to paint it, but can leave it if no further treatment is required.

http://www.gwneale.co.uk/telux.html

 

Jim

Edited By Jim Guthrie on 24/07/2012 10:35:56

Edited By Jim Guthrie on 24/07/2012 10:37:16

Thread: Travelling Steady Question - Speed 10 / ML10 Owners
16/05/2012 15:45:11

I agree with Tigertrev. I've just checked mine which is a genuine Myford one bought way back in the 1970s and it has a part threaded hole - top end - with a reduced shank bolt in the hole which is retained in the item unless you want to unscrew it.

Jim.

Thread: Shell CY2 oil for Centec Vertical head
28/03/2012 15:46:33

Posted by Andy Belcher on 27/03/2012 21:56:31:

Before stripping your VH, I would try the proper oil. If it still leaks, then do the head and all you have lost is a bit of oil.

The previous owner of my Centec warned me of its tendency to leak from the lower bearing of the vertical head - normally depositing the oil in a horizontal line across the user's anatomy when the machine was in use. smiley I don't know if he meant just the machine I now own, or whether that applied to all Centec vertical heads, but I got the impression that it was a general Centec fault. I shall try the thicker oils mentioned in earlier messages to see if I can cut down the leakage. My machine doesn't get very heavy use at the moment so the leakage isn't a major problem.

Jim.

19/03/2012 17:25:27
Posted by Andy Belcher on 19/03/2012 10:07:35:

Thanks Jim,

That will save a lot of work!

I have got a lot of setting up to do as it is part refurbished.

If you would not mind helping a bit further;

What size pulley is on your motor? I have got a 1425 rev motor to go on it.

What oil do you use in the gearbox?

I have got the Mk II vertical head; what holds the spindle in the horizontal section? Mine just slides out towards the vertical head with nothing on the pulley end to retain it. Is it just the VH gear that holds it in place? But then there is nothing to tighten the bearings. I have not looked too far into it yet but I would have thought there should be retaining rings both ends.

Thank you very much for your time

Andy

Edited By Andy Belcher on 19/03/2012 10:10:46


Andy,

I've just popped out to the workshop to check out your questions.

 

In the size of the motor pulley, I can't be of much help. My motor is sitiated in the top of the stand and you can't see the back of it where the pulley is. I felt round the back and a rather inccurate measurement might be four fingers width of diameter.smiley To get an accurate measurement I would have to strip the motor out and I'm not to keen to do that at the oment. smiley

On the horizontal shaft, mine is retained in position at the rear by the drive pulley for the vertical head and two nuts. I've posted a couple of pictures to my web space to show what's there. The first shows the pulley and nuts in close up. http://www.sprockets.myzen.co.uk/Centec01.jpg The next shows a wider shot with the pulley and belt tensioner on the vertical head being shown. http://www.sprockets.myzen.co.uk/Centec02.jpg

For oil, I use what I use on my lathe head bearings - which is probably a bit light for the gearbox and gears in the vertical head. I reckon a heavier grade gear oil would probably be better and could reduce the leaks from the bottom of the quill on vertical head.

Jim

Edited By Jim Guthrie on 19/03/2012 17:26:51

Edited By Jim Guthrie on 19/03/2012 17:28:32

19/03/2012 09:06:42
Posted by Andy Belcher on 18/03/2012 20:34:13:

Oh, and I found a reference on how to remove the knee...it goes up and off the top of the dovetails.

Andy,

You don't need to lift it off the top of the slides, just loosen off the gib screws and take the gib out and it will pull straight off the slides to the front. The gib is quite thick which means that the gap in the knee way is greater than the width of the top of the slides.

Jim.

Thread: cutting polycarbonate disc
08/02/2012 08:37:14
Posted by capanab on 07/02/2012 22:58:56:
I need to cut some 56mm diameter polycarbonate discs from 2mm thick sheet, with no hole in the middle.
Have so far tried
- hole saw in bench drill. - teeth get very quickly clogged up , bit like sawing mdf.
- fretsaw/piercing saw - pretty tatty edge , which takes forever to sand down to anything remotely respectable.
- lathe face plate , - difficult to make a tool that cuts cleanly without clogging up.
 
teenage daughter came home from school and dismissed my attempts saying I needed a laser cutter like they have in D+T.
 
useful suggestions welcome.
 
 
I cut perspex on my milling machine and I use carbide cutters and get an axcellent finish. Perhaps using a new - i.e. very sharp - carbide tool might give good results in a lathe.
 
Jim.

Edited By Jim Guthrie on 08/02/2012 08:38:18

Thread: Power switch for Myford ML speed 10
22/11/2011 09:10:53
Posted by Mike Gibbs on 22/11/2011 08:26:24:
Very many thanks to everyone. I have ordered the unit from Axminster Tools, and it should be here tomorrow.
 
The overload protection on my ML10 is a slightly slack setting of the countershaft so that the belt slips on very heavy loads. I can't remember when I had to adjust it tighter.
 
Jim.
Thread: machining conn./coupling rod ends.
12/10/2011 23:14:47
Andy,
 
A method I have used some years ago on the coupling rods for a Gauge 1 loco was to mount a spigot on the vertical slide which fitted the bearing hole on the coupling rod. With the milling cutter in the chuck, mount the coupling rod on the spigot and feed the coupling rod down onto the milling cutter using the other end of the coupling rod as a lever to rotate the rod on the spigot to form the circular end.
 
I think I got the idea from the Model Engineer many years ago. It does look to be a bit dodgy but it does work - you just have to be very careful. You need a lock nut and washer on the spigot to hold the coupling rod firmly and you have to apply very light feeds. You would normally have to position the spigot above the milling cutter to give you sufficient angular movement to do an end in one setup. If you feel the coupling rod is not long enough to give sufficient control, you can clamp another length of metal to it to give additional leverage.
 
Nowadays I have a milling machine and a rotary table and I would use them in preference for the same job.
 
Jim.
Thread: Vectric 2DCut and Mach3
09/10/2011 18:49:09
Nigel,
 
Have you got the post processor definitely set to Mach2/3 mm (or inch)? The choice is in the drop box immediately above the Save Toolpaths button. I've been using Cut2D with Mach 3 for the past year and it has always worked well with no interface problems with Mach3 on a KX1 mill.
 
Jim.
Thread: Milling - what do i need
12/09/2011 13:31:04
Posted by russell on 12/09/2011 05:22:56:
Apart from the mill itself, what else should i consider as a minimum to be generally useful? A vise? clamp kit? face cutter? Rotary table?

Russell,
 
Apart from what others have recommended I would add a good shop vacuum cleaner to clean up the table and surrounds. It migth not work too well if you will intend to use a lot of cutting fluid, but for dry cutting it makes cleaning an easy process. I got a cheap, bagless model from a chain store in the UK for about £30 and I wouldn't be without it now.
 
Jim.

Edited By Jim Guthrie on 12/09/2011 13:31:23

Thread: beyer peacock iom steam locos
25/08/2011 08:53:01
Posted by david johnstone 2 on 25/08/2011 07:50:47:
Hi
Does anyone knoe if plans, kits or parts are available for the beyer peacock isle of man steam engines as i would like to build one. Scale is not important but nothing too large.

 
Dave,
 
The actual Beyer Peacock plans are online from MSIM - here
 
 
If you select "Beyer Peacock" in the Collection Name drop down list then put "Isle of Man" in the Object Summary box and press search you should get three drawings and five photographs. The online images are quite small but you can get large scale drawings from MSIM, either on paper or a large JPG file on CD. A few years ago, the drawings were about £20 each as a file on CD and could be a bit more by now.
 
Jim.

Edited By Jim Guthrie on 25/08/2011 08:54:21

Thread: end mills, how many flutes?
21/08/2011 18:55:16
Posted by Clive Hartland on 21/08/2011 16:18:05:
This all depends on what you are cutting, side cutting or slots.
Two flutes will cut just fine but if cutting slots then it will sometimes cut oversize. With four or more flutes the cuts are balanced on both sides of the cut and it does give a better finish.
I always understood that two flute cutters were more accurate in cut width when cutting slots.
 
Jim.
Thread: GETTING CNC WORKING
25/07/2011 13:37:55
To add to the other reply, Mach prefers to work through a built in parallel port in the PC. However built in parallel ports have not been common on PC motherboards for a few years and the option is to use a plug-in board to provide the parallel port. And not all plug-in boards will work properly with Mach. I use a plug-in board with Mach3 and it took a bit of fiddling around to get ti to work, but once set up, it has worked perfectly.
 
Maybe you should log on to the Mach support forum for help. There is very good help there.
 
 
Jim.
Thread: Extending X capability of KX1?
22/07/2011 14:58:32
I've just found out that the Seklema Multimat I have does not have a very good tolerance on thickness - just in case anyone else is contemplating using it on a milling machine. I had changed my methods of referencing tool height this week. previously I had set the tool level from the top surface of the styrene but that had given some problems due to the variation in thickness of the styrene sheet. So I started refernceing from the base of the material and I would use thicker sheet and surface it down to the required thickness before milling out the details.
 
But I had been getting poor results with depths of cut apparently all over the place. I've been double checking Mach and the KX1 to see if something in them was causing the problem. I hadn't even considered the Multimat until last night, when I put a steel rule flat on the surface and ran a clock gauge in the spindle along it and found a 15 thou variation in about six inches. When cutting I had been setting tool height at the edge of the Multimat with a piece of metal of known thickness, then moving into the material and mat to do the cutting.
 
I had assumed that the Multimat would have had quite close tolerance if it was to be used for engraving. The unused bit I have has a variation betwee 2.25 - 2.80mm when measured round the edges with a caliper. I've sent a message to the makers via their web site to see whet the tolerance should be.
 
Meanwhile, back to low tack double sided tape. There are so many cut through holes on my work that I don't think a vacuum table might work.

Jim.
20/07/2011 12:37:47
Posted by Clive Hartland on 20/07/2011 09:57:36:

I did note that you were using an adhesive underlay but only offered the vaccuum method as a viable alternative.
The machining marks indicate that the cutter lip is picking up and and carrying a bit of plastic which is stuck on the cutter face. This is much like the build up on a lathe tool.
It might help if you use a single lip cutter as it runs cooler.
A continuous air jet can keep things cool.
Clive,
 
Sorry - I misread your message about the vacuum holding.
 
However, I don't want to get too involved in doing this job. I intended to use the KX1 for other purposes and only ventured into the styrene cutting as a "wonder if I can do this" project. I agree that vacuum holding would be better but that would involve me in a lot more work than I really want to do. The extension plate is already pushing me into areas that I didn't originally intemd to get into. I've got a fourth axis rotary table here which was bought for my original intentions which hasn't been used in anger as yet, and I would like to start work with it.
 
Jim.
20/07/2011 09:41:17
Posted by Andrew Johnston on 18/07/2011 23:57:25:Ok, I understand why your depths of cut are shallow. It's interesting to note your step over values. They seem very small to me? If I'm facing a flat area or pocketing out I'll use a step over of between 70 and 90%, to make full use of the cutter. This is true for both plastics and metals. To a first approximation I'm not sure that the step over will have much effect on the finish. I think that feedrate is probably the most important factor?
 
Andrew,
 
Just did some more experimenting yesterday with feeds abd stepovers cutting 1mm styrene sheet. The maximum stepover I could apply was 50% - that's all that Cut2D will let me apply. I worked a 5mm cutter up to 480mm/min with 50% step over and started getting tool marking - not too much but still enough to require finishing with sanding. I am assuming that the reason for this is that the styrene is flexible and the Multimat holding it down to the table can also be compressed so that the work might be deflecting under the tool when the pressure of cutting increases. I've started backing off to get the good surface finish.
 
Also, I can't work out why I still get untidy cuts with the 1mm cutter. I tried a new one yesterday at various speeds and I still get the rags of swarf left attached to the work if it is only cutting on part of its width round a part. It cleans up quite easily, but it's annoying. I don't get vthis problem with any other cutter.

Jim.

19/07/2011 11:49:38
Posted by Clive Hartland on 19/07/2011 09:06:50:
Have you considered a vaccuum table to hold down the styrene you are machining?
You could make a table exactly the size you require and again using pegs relocate for the next step of macining.
A good vaccuum machine would give all you all the suction you require.
The table will have to have a lot of small holes drilled in it where your workpiece sits.
I do believe these sort of vaccuum tables are available commercially.
 
Clive
 
Clive,
 
As I mentioned at the start of the thread, I am using a product called Seklema Multimat to hold the styrene sheet on the table. The product is designed specifically for engravers and is double sided with both sides "sticky". I think it works on the same principal as the tax disk holders on a car windscreen - a very smooth, slightly tacky and resilient surface which holds flat sheet very firmly. I've had no movement at all when using it. I started off using double sided tape, but the adhesive was too strong and parts tended to get distorted when trying to prise them off the tape. The Multimat releases the parts quite easily - just pick up one corner with your finger nail and the rest peels of with little effort.
 
 
It is a bit expensive - a square foot cost me about £65 (inc VAT) but that should last me for some time. My first piece on the machine is still in use on the first side used, even with one or two slightly deep excursions with the cutters on a few occasions.
 
Jim.
19/07/2011 08:37:27
Andrew,
 
The people at Swindon were good. We agreed on one of their offcuts over the phone but they said they would double check that it was there and phone me back - which they did. The only slight hang up was the operation of their card machine which seemed to be tied in to their VAT reporting on their accounts and required some apparently involved setup entry to work for my payment. But it was all very pleasant and a nice day for a drive.
 
I've been doing further experiments with feeds and stepovers and increasing values and the results so far have been good. The only problem I am having is with one particular 1mm cutter which is leaving a lot of rag ends still attached to the cut. I suspect it has been blunted or chipped but I need some sort of microscope to check it out. My eyes and my binocular viewer are not good enough to see if the cutting end is OK. It is my last 1mm cutter so I'll order up another couple to try some alternates.
 
Jim.
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