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Member postings for Hugh Gilhespie

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

Thread: What type of steel to use for the 1/4 inch axles ?
14/06/2014 13:17:39

Hmmm, a pion vice is going to be a bit small -

"Abstract

The pion radius has been measured by direct scattering of 50 GeV negative pions from stationary electrons in a hydrogen target. We find the square of the radius to be 〈rπ2〉 = (0.61 ± 0.15)fm2."

cheeky Hugh

Thread: COLCHESTER STUDENT HEADSTOCK ADJUSTMENT
08/06/2014 09:56:20

Hi Everyone,

More interesting responses that I thank you for. It gives me more to ponder on - I haven't actually attempted the headstock alignment yet so all information is welcome.

Some points that might help clarify:

1. The lathe is mounted on a fairly hefty concrete slab

2. The jacking feet allow it to be set level with a reasonably similar torque on all six feet.

3. When it is level. it cuts a pronounced taper - 4 thou in six inches

4. By 'unlevelling' the front tailstock foot the taper is reduced to less than 1 thou in six inches.

5. At this point, the rear tailstock foot is no longer touching the ground.

6. This was a training lathe - for London Transport - so has had the usual knocks and bangs but is not badly worn - as far as my inexpert eye can tell.

7. It seems entirely possible to me that the apprentices being trained were shown how to adjust the headstock as part of their training so it's misalignment isn't a great surprise.

Regards, Hugh

04/06/2014 09:27:50

Hi,

That was a great response, many thanks to everyonefor the information. I will have a go at setting the lathe true this weekend and - hopefully - report a successful outcome.

Thanks again, Hugh

03/06/2014 13:06:56

Frank in France,

Many thanks for your reply. I was hoping for info about using the 'screw jack' to set the headstock true as I am a bit worried about clouting the chuck - I know you said GENTLY TAPPED but even so it can't be good for the bearings and they cost a fortune to replace. If all else fails I will go this way but surely somebody must have experience of using the 'screw jack' and can tell me if I need to remove the gear banjo to do so?

Regards, Hugh

01/06/2014 09:39:58

There have been a couple of interesting recent threads on Colchester lathes and there are clearly some very knowledgeable owners on this forum. Unfortunately although I am a Colchester Student owner I am definitely not very knowledgeable and I would like some help about how to adjust the headstock to make the lathe cut true.

Some background. The lathe is a Student 1800 and has six feet. The lathe was relocated into a new workshop at the beginning of the year and one of the first projects in the new shop was to make a set of screw jacking feet that make it straightforward to level the lathe. This was pleasantly successful and so the lathe was duly levelled. I used a Hilger & Watts clinometer that I bagged from fleabay for not very much at all - I can thouroughly recommend these. Not only do you get a very sensitive level but with a bit of basic trig you can actually calculate how many turns are needed for the raising and lowering.

My feet use M20 x 1.5 threaded bar which is readlily available and since this thread is used in automotive applications, sets of taps are also easy to find and fairly cheap.

Anyway, back to the main story. I got the lathe nicely level but when I did some test cuts with a length of 1.5 inch steel bar it was still cutting a taper. About 4 thou over six inches which was too much. So I looked at the manual for the lathe with a view to using the headstock adjustment to set the lathe true. To be honest, I chickened out. It wasn't at all clear to me how to access the adjuster without what looked like some serious dismantling.

So, Plan B was to set the cut true by adjusting the feet. Harold Hall's website has a very clear set of instructions for this and by following these I did indeed manage to reduce the degree of taper to less than one thou over six inches which I could live with. BUT - a big but too - to get the degree of adjustment needed the lathe is a long way from level to the extent that the rear foot at the tailstock end is now completely off the ground. This surely can't be right and so I really do need to learn how to use the built in adjuster. Then hopefully I can have both a level lathe and one that cuts true.


Could someone who has used the headstock adjuster please give me some details about how to do it? I think that you need to remove the banjo to access the adjuster - if so is this difficult and are there any issues when you put it all back together ?


Thanks, Hugh

Thread: Chamfering on the lathe
24/05/2014 20:24:43

Colin,

This is the toolpost on my Student

chamfering 1.jpg

24/05/2014 19:28:08

Colin,

The QCTP came with the lathe when I bought it. It is a Dickson type and I believe it is size T2. It is a pleasure to use and particularly as I was lucky enough to buy a goodly number of tool holders from an ex-employee of Colchester lathes along with some other goodies, including the reat tool post that I use for parting off with an upside down tool.

I will try and post a picture of the QCTP.

Regards, Hugh

23/05/2014 19:57:30

Jason - I like your method. I have tried this with an old carbide insert with a 90 degree point - i.e. two faces at 45 degrees but it wasn't terribly successful, just not sharp enough away from the tip I think. I am STILL working on the Worden tool grinder I started 4 years ago and hopefully when I finish it I will be able to grind form tools including one like the one you are using.

Les - I moved house in late spring last year and have only just got a workshop back so everything has been on hold for about 18 months. I got as far as completing all the electrical side of my cross slide drive project but stalled on the - in theory - simpler stuff to design and make the mechanical components to drive the cross slide handle. It is on the ever growing Things To Do list and I am motivated by having a lovely new workshop - ex stone barn but now fully insulated and with a new roof, concrete floor, etc that is a pleasure to work in.

Hugh

23/05/2014 17:21:38

I would be very interested to know how other forumites set up for chamfering on the lathe. I find it a bit of a struggle and it usually takes me a couple of tries until I have a set up that lets me access the edge of the piece I am turning without either hitting the chuck or running out of travel on the cross slide or top slide. I am using a Cochester Student lathe with a QCTP and the method that I usually use is to set the top slide over to 45 degrees with the tool post pointing towards the chuck, fit a tool with a 9 mm circular insert and chamfer on the far side of the piece with the lathe running in reverse, using the top slide to move the tool past the edge of the work and backing the cross slide until the tool starts to contact the work. I can't help feeling there must be an easier way so all suggestions gratefully received.

Hugh

Thread: Microstepper drivers
01/03/2012 19:31:45

Hi Ralph,

I have recently built a drive for my lathe top slide based around a 2M542 controller from fleabay. They are microstepping and the number of microsteps is selectable - I used 8 microsteps giving a total of 1600 pulses per revolution of the motor.

I haven't any other experience but this driver worked fine, was relatively cheap and seemed to be quite well made with good specs, i.e opto-isolated inputs and adjustable current limiting.

Regards, Hugh

Thread: New website editor
17/02/2012 10:12:26

Word 2007 on Vista Home Premium typed directly into Word

Posting from IE version 9 on Windows Vista.

Thread: Another broken tap thread
26/01/2012 21:09:10
Sid,
 
For ISO metric threads the formula to calculate the percentage engagement is:
 
percent engaged = 92.38 * (major diameter - pilot diameter) / pitch
 
So, for M6 x 1 using a 5 mm pilot drill gives 92.38 % engaged.
 
Most people recomment around 70% so, using a 5.2 mm pilot would give
0.8 * 92.38 = 73.9%.
 
The formula is from Machinerys Handbook by the way.
 
Regards, Hugh
Thread: Radiant Superheater Types.
18/12/2011 16:24:35
Hi mgj
 
I wonder if the advantage of the spear point design is because it minimises the loss of cross section in the flues? Two 5/16th od tubes have about 20% less cross section compared to a single 1/2 inch od tube. Of course, if the flue diameters are much bigger it probably won't matter.
 
Regards, Hugh
Thread: Cadmium, simple test for?
16/12/2011 20:51:23
To answer Paul's question. Test, yes, simple -no. Details here.http://pubs.acs.org/doi/abs/10.1021/i560126a027
 
Regards, Hugh
Thread: Top Slide Self Act?
08/12/2011 21:19:36
I used a PIC simply because I happened to have one - that and a complete ignorance of what was involved. Having got a bit further down the road I think Neil & Skarven are right, to get where I want to I should have started from a different place. Still, it is proving a very interesting journey and I am getting close to an exciting bit - hooking up the stepper motor and optimistically seeing it rotate, realistically trying to work out why it isn't rotating.
 
The Amtel chips do look nice though!
 
Regards, Hugh
06/12/2011 17:41:16
Hi Billy
 
But to answer Hugh's question-all you need to step a stepper is an oscillator driving a counter which then sequences four transistors, costs a few quid. You could feed a standard stepper driver board with pulses from a 555 timer or whatever. No processor needed.
 
Well, yes and no! In a spirit of gay abandon I decided that I would make my own controller. I am now struggling up the near vertical learning curve for PIC assembler programming. I also foolishly decided to try and make an all singing and dancing controller - I think that I will have to drop the dancing though. So far I have a PIC driving a 4 line LCD display that lets you input the lathe speed, desired feed rate and to set a jog rate. I wanted to make it so that you can programme the travel distance as well but have decided that is a step too far.
 
With the lathe rpm and target feed rates set, the PIC then outputs the correct pulse rate to drive the motor. I chickened out of all the stuff about high power mosfets and bought a chinese driver board so all my little PIC board needs to do is send it the pulse rate and a couple of control signals.
 
It has been fascinating doing the programming - I have some experience of Z80 assembler but that was over 20 years ago and now the procedure is so much easier with the Microchip MPLAB IDE - all free too.
 
I have made a small start on the mechanical side and fitted a timing pulley to the top-slide handle but I didn't want to go too far until I was sure that I could cope with the electronics.
 
Regards, Hugh
Thread: de-scaling steel boilers
05/12/2011 20:44:50
Hi Kerrin,
 
I am also one of the guys who has done boiler cleans. I was chief chemist and bottlewasher for 3 out of the top 4 boiler cleaning companies in the UK over the last 30 years. It is a funny industry, the names change but by and large the people stay the same. I worked for Atlas Products and Services, Redland Industrial Services, Costain Industrial Services, Brambles Industrial Services.... I have worked almost all of the old CEGB stations in the UK as well as many of the newer combined cycle stations. When we were Costain Industrial Services we pioneered the use of HF for in-service chemical cleaning in the UK. However, with the break-up of the CEGB, in-service cleans became much rarer and most of our work was pre-commission cleaning all around the globe.
 
Nice to hear from someone else who knows about boiler cleaning.
 
Regards, Hugh
28/11/2011 21:40:26
A quick ps
 
DON'T use ammonia in copper boilers. Good for steel boilers only.
 
Regards, Hugh
28/11/2011 21:26:02
Hi Jason
 
A couple of drops of household ammonia in the water will jack the pH up to a safe level and will be beneficial to the boiler. Somewhere around pH 10 would be ideal. I would avoid any non-volatile water treatments as without using a lot of blow-down you risk getting a lot of deposits building up. Ammonia won't cause any deposits and is perfectly safe to use, although a bit niffy when concentrated. The other advantage of using ammonia is that it makes draining and drying the boiler after use less important. You won't get any rusting when the water pH is 10 or over. Still some risk in the head space above the water level though so for long term storage draining is best.
 
Regards, Hugh
27/11/2011 20:12:44
Dave,
 
Lovely thought but water makes it own ions, hydrogen ions (plus) and hydroxyl ions (negative). These can't be removed from the water. What can be removed are impurities such as calcium ions, magnesium ions, sulphate ions, chloride ions, bicarbonate ions - the list is endless. The way that deionising resins work is by swapping nasty impurity ions with nice hydrogen or hydroxyl ions so the water is ionically balanced but without any impurities.
 
Regards, Hugh
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