Member postings for Hugh Gilhespie

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 〈r_π²〉 = (0.61 ± 0.15)fm²."

Hugh

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

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

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

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

Colin,

This is the toolpost on my Student

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

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

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

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

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