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Member postings for Alan Charleston

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

Thread: At last - no more chattering when parting off!
07/10/2019 08:11:25

Hi,

Came across this solution to chattering when parting off on youtube.

https://www.youtube.com/watch?v=lboJ95ZlvV0

Go to 58:26

Regards,

Alan

Thread: Glass cutting
27/08/2019 07:04:51

Hi Ken,

I'm not sure using a cut down bottle is such a good idea. Bottles are usually made from soda lime glass which doesn't handle thermal shock well. The glass will get hot from the lamp flame and if a bit of water gets onto it it will likely shatter.

You would be better off getting in touch with a scientific glassblower who should be able to supply you with a length of borosilicate (pyrex) glass of the right diameter and with the ends flame polished to take away the sharp corners.

Mind you, I thought miners lamps had copper or brass gauze around them to prevent methane in the mine atmosphere from igniting.

Rehards,

Alan C.

Thread: Dehumidifier project
30/07/2019 07:02:00

Hi,

I assume you want to dehumidify the atmosphere around your machines to prevent condensation and corrosion. If that is the case all you need do is to raise the temperature a few degrees hotter than the surrounding air to keep the relative humidity less tan 100%.

I used to run a steam generator which was sometimes hard to start due to condensation in the electrical control gear. I fixed it by putting a heated towel rail on the ground underneath it. It didn't take much electricity to run, was designed to run continuously and stopped water from condensing on the generator.

Regards,

Alan

Thread: Guess the Chemical?
28/07/2019 06:53:20

Ethanol?

Alan

Thread: Threading Problems on Colchester Student
18/06/2019 10:02:29

Hi,

The idea isn't mine. I picked it up from this YouTube video.

https://www.youtube.com/watch?v=HXt4TWa382Q

He shows how to do it very clearly. I've used it on a bunch of different threads and it's never failed.

I think the reason it works is that by engaging the half nut on the same thread dial number when reversing, it engages on the screw at the same point as when it disengaged going forward i.e. it's the same as not disengaging the nut but stopping and reversing the lathe.

Regards,

Alan

18/06/2019 07:22:06

Hi Stephen,

You don't need to keep the half nut engaged when cutting a metric thread on an imperial lathe if you have a thread dial fitted. The procedure to follow is:

After setting the tool to cut the correct depth, start the lathe in the forward direction and when the thread dial reads 1, engage the thread nut.

When the tool has advanced to the end of the thread, disengage the half nut and turn the motor off.

Withdraw the tool to clear the work.

Start the lathe in reverse and when the thread dial reads 1 engage the half nut.

Run the lathe in reverse until the tool clears the work.

Turn the lathe off but leave the half nut engaged.

Set the tool to the new depth and start the lathe in the forward direction.

Repeat till the thread is cut to size.

This method is useful because disengaging the half nut stops the tool a lot quicker than waiting for the lathe to run down giving a more accurate stopping point.

I don't know if it makes much difference, but the half nut on my lathe also has a bit of play in it and I always grasp the apron handle when starting a cut to apply a bit of force resisting the movement of the saddle and making sure any backlash is taken out of the half nut - don't get too enthusiastic though, a gentle pressure is what I aim for.

Regards,

Alan

Thread: Quicksilver
05/06/2019 07:29:27

Hi,

Clive is quite right about using nitric acid to clean mercury. I used to use it in a lab to determine the bulk density of porous fertiliser granules by measuring the force required to submerge them in a pool of mercury. The mercury required frequent cleaning and this was done in two stages.

The first one involved setting up a filter paper in a funnel and piercing a small hole in the bottom. The dirty mercury was put in the top and the mercury went through the hole while the foreign bits and some of the oxide was left on the filter.

The semi cleaned mercury was then put in the bottom of a Buchner flask and covered with dilute nitric acid. A bung fitted with a length of glass tubing was put in the top of the flask such that the end of the glass tubing was below the mercury. A vacuum was then applied to the side arm of the Buchner flask and air drawn through the mercury. Initially it just slopped from side to side but when the mercury was clean, it separated into a myriad of beads.

Most of the dilute nitric acid was decanted off (down the drain - this was 50 years ago) distilled water added and the process repeated 3 - 4 times to clear the rest of the acid from the mercury.

After decanting off as much of the water as possible the mercury was then dried by blotting it with filter paper. It came out bright and shiny.

We also used sulphur on mercury spills - the idea being to convert volatile elemental mercury to a non-volatile sulphide.

Regards,

Alan

Thread: Boxford Screwcutting box / Leadscrew binding
14/03/2019 05:17:28

Hi Andrew,

If you want to get the gearbox off you'll need to slacken off the bolts holding the headstock in place and slide it forward which will reveal the cap screws holding the gearbox in place.

This is not easy as the front bolt holding the headstock down is really awkward to get at and there's very little room to swing a spanner between the sides of the bed. I ended up buying a good quality 15mm ratchet ring spanner to get it out. Due to the restricted swing available, it needs to have a fine ratchet action so a cheap one won't do.

Regards,

Alan

Thread: Machining cork!
05/03/2019 05:02:07

Hi Maurice,

Moulding a silicone bung sounds a good idea. If that doesn't work try a scientific supply company. Rubber bungs are made from a small end diameter of a millimeter or so to huge (>100mm).

Regards,

Alan

Thread: metal spinning small bells
23/02/2019 05:24:07

Hi David,

You may have a problem trying to spin a bell. Whenever I've tried spinning brass I've found I need to keep annealing it to get it to flow evenly. I suspect annealed brass will be fairly dead as far as ringing goes so you are more likely to get something to ring by turning it from either a hard brass or bronze. Phosphor bronze may be a good candidate as it is hard and readily available in short lengths for bushings.

I actually have some brass which rings really well. It is 1" dia. and came from an old set of door chimes. Two different lengths were suspended from wooden plugs driven into the ends of them and a solenoid mounted between them hit first one then the other with a wooden striker giving a ding - dong noise. You might find some of this material in a junk shop.

Regards,

Alan

Thread: Quality issues with a SIEG SX2.7 mini mill
20/02/2019 05:43:53

Hi,

I have an SX2.7 mill and it has a peculiarity I'm not sure is a fault or not.

If there is a drill in the chuck but the mill is not turned on, and the quill is lowered using the handle on the right until the drill hits the work, it is possible to continue turning the handle a bit (say 2 degrees) until it comes to a hard stop. It's like the rack and pinion is really loose and a spring is used to keep the pinion at one end of the rack on the quill. This results in a tendency for the drill to suddenly drop a bit when the pressure comes off and grab when it breaks through the bottom of a hole. Is this normal. I did try to pull it apart to see if I could see what is wrong (if anything) but with the electrics in the handle to enable power tapping (a truly useless complication) I chickened out half way through and put it back together while I still could.

When I first got the mill, it came without the little bit of brass between the locking screw and the quill so I couldn't use it as a mill. The local supplier got onto Seig and as the part only weighed a few grams I expected them to mail the bit. No - they waited until they had a container full for the supplier - so it was about 3 months before I got it.

The other problem with the mill is the lack of oiling points. Unlike the SC4 lathe I was silly enough to buy which seems to have had a shotgun involved in the decision where to put the oilers, the SX2.7 only has one oiler - on the bushing end of the x axis screw for the table. It's really awkward trying to get the ways a screws lubricated.

Regards,

Alan

Thread: Anyone fitted a DRO to Sieg SC4?
10/02/2019 05:08:38

Hi Jim,

Rather than fit a DRO you may want to consider making a bracket to screw on the rear of the carriage and a DTI. DTIs are quite cheap through AliExpress and seem to be accurate.

sc4dti1.jpg

sc4dti2.jpg

Regards,

Alan

Thread: Filing A Curve
28/01/2019 06:47:43

Hi,

I was watching the video posted by Jason of the guy making a ring from a couple of brass nuts. I noticed he was filing the ring by starting with his left hand high, and following the curve with his left hand dropping as he pushed forward. This seems to be the usual procedure for most if not all of the people I see filing curves which is not surprising as it is the natural way of doing it.

When I was taught workshop practice at the Tech however, the tutor went to a lot of trouble to stop the class doing it that way. He taught us to start a cut with the left hand low, and to raise it as the file was pushed forward. There was a lot of muttering about it initially, but once the technique was mastered, it seemed to give better results, although this may have been because we were getting a lot of practice in filing.

Is the way I was taught the "correct" way or doesn't it matter which way it is done. The guy making the ring certainly ended up with a nice curve.

Regards,

Alan

Thread: The Diamond Tool Holder
21/01/2019 05:23:11

I've had a diamond tool holder for years and I love it. The surface finish I get on steel for general turning has improved no end.

I'm not great at grinding tools so in the past I've cut threads on the lathe using cutters with no top rake. The surface finishes were usually poor and needed finishing off with thread nuts to be useful. I was aware from their videos that the diamond tools could be used to cut threads but couldn't see how to grind them. I e-mailed Gary at Eccentric Engineering and he was kind enough to grind both 55 degree and 60 degree threading tools for me. They work brilliantly with the metal peeling smoothly off the work and giving a beautiful surface finish even on steel which is of dubious quality.

After seeing what the tools look like, and practising grinding them with key steel on the jig that came with the holders, I found it to be quite easy to do.

Regards,

Alan

Thread: nylon gib strip grub screws?
15/01/2019 04:58:37

Hi Peter,

Would wrapping a grubscrew in teflon tape give the same effect? You may need to roughen the thread surface by gripping it hard in a pair of pliers to stop the teflon slipping and experiment with the number of turns of tape but it should be possible to end up with a screw which is resistant to vibration turning.

Regards,

Alan

Thread: First attempt at threading on a bantam - all didn't go well
12/01/2019 05:24:44

Hi Mark,

If you can source or make a thread dial, you can use the half nut to stop the carriage even if you are cutting an imperial thread on a metric lathe. The method is as follows:

1) Engage the half nut when the thread gauge reads 0.

2) Disengage the half nut at the end of the thread and turn the lathe off. Back the tool off.

3) Start the lathe in reverse and engage the half nut when the thread gauge reads 0.

4) When the tool is clear of the work, stop the lathe, leaving the half nut engaged.

5) Reset the tool and start the lathe in the forward direction.

I made a thread gauge out of PVC for my old imperial Boxford lathe and turn metric threads quite happily using this procedure.

Regards,

Alan C.

Thread: Minnie Traction Engine
05/12/2018 05:08:46

Hi,

I've been casting around looking for a new project and thought I might like to give the "Minnie" traction engine a go. The snag is that the book by Leonard Mason is jaw droppingly expensive. It's no longer published and second hand ones go for upwards of $US100.

It was published by Model & Allied Publications (MAP) which over the years has morphed into Special Interest Model Books Ltd. I E-mailed them and asked if they would consider publishing it again. I received the following reply:

"We don’t have any plans to republish that particular title and in any case I would not know how to reach the author in order to clear the rights."

If anyone knows where Leonard Mason or his literary heirs are, you may wish to contact them and suggest they look at republication. Given the high price the used copies command, there's obviously a demand for it.

Regards,

Alan

Thread: Stepper Motor Identification
30/10/2018 01:26:12

Hi Joseph,

Thanks for putting me right as regards the motor resetting itself to the nearest step each time it powers up. I thought what I was doing was OK because I set the motor to run with 4800 pulses which resulted in the stepper motor rotating 3 times and the business end of the dividing head rotating 9 degrees which is what is needed for a 40 tooth gear. I set the head up to start at 0 degrees using the indexing pin, then went through the process of turning the Stepduino on and off 40 times. The indexing pin slid smoothly into the plate at 0 degrees, indicating an accurate process. The reason it worked, is that 4800 is divisible by 8 (the number of microsteps) so the rotor stopped at a full step rather than halfway through a step. My method would probably work if there was no microstepping, but the accuracy of the system would be less.

As far as the confusion regarding the steps/revolution is concerned, that was my fault. I could have set the steps/revolution to be 1600 (which is true) and the number of revolutions to be 3, but instead I set the steps/revolution to be 4800 (which is not true) and the number of revolutions to be 1 (which is also not true) but which also results in the stepper motor turning 3 times.

As far as the duration of the pulse to the motor goes, Dave had an ON time of 2 microseconds and an OFF time of 100 microseconds. I believe this gives a speed of about 375rpm. I found the motor was easily stalled. I wanted to reduce the speed and hence the acceleration at start-up and to increase the torque so I increased the ON time to 500 microseconds. The torque was much better and the speed went down to about 60 rpm. I ran the motor through 127 iterations when connected to the dividing head and the motor temperature didn't go up so I'm assuming I'm not damaging anything.

Hi Dave,

I loaded your first sketch into the Arduino and hooked the motor up to the dividing head. I set the head up to start at 0 degrees using the indexing pin, then applied power to the Stepduino and let it run until I counted 127 iterations. The indexing pin slid smoothly into the plate at 0 degrees so it looks like your solution works a treat.

Thanks for your latest sketch. There is a "Buttons" tutorial in an Arduino kit I've got so I'll work my way through it (again!) and see if I can get one to work with your sketch.

I'm really greatful for the help you've given me.

Regards,

Alan

29/10/2018 03:13:35

Hi,

Thanks for all your comments.

I'm not worried about plugging and unplugging the motor as the way I have it set up is that the power to the stepduino and motor is only on when the button is pressed i.e. the power is off, the button is pressed which supplies power, the motor advances the set number of steps, the button is released and the power is off again. I like this way of working as I can do as many teeth as I want then leave it and come back again the next day and continue where I left off. I'm not sure if that applies to the other programmes that are around.

I wasn't aware that each time I put the power to the system that it will restart at the beginning of a full step. I'm not sure that this matters however. As long as each pulse produces the expected rotation, and the number of pulses are correct to give the rotation required, I don't think it matters whether the new rotation restarts from the same stage during a step or from the beginning of a step.

Thanks for the sketch Dave. I put it into the Stepduino and it seems to make the motor rotate about the right amount. Is it supposed to stop after 127 iterations? I set a microscope above the pulley to see if it would return to the same point after 127 turns but it didn't stop. I'll have a closer look at the sketch and see if I can figure it out. I slowed it down to about 60 rpm by putting a 500 microsecond delay for the pulse HIGH time. This gave a much higher torque.

Regards,

Alan

28/10/2018 07:06:07

Hi,

Thanks for all the comments. I don't think lost steps are a problem. I've reduced the speed to about 60rpm to reduce the acceleration when starting each step and the registration pin on the head engaged the built in indexing plate at 0 degrees before and after 40 steps of 9 degrees each.

If I was confident of programming the Arduino I think I'd follow Duncan's approach and calculate the number of cumulative pulses for each tooth as the gear is cut, subtract the total for the previous tooth and round it to the nearest integer.

Alas I'm not. I have tried for years to get my head around programming the Arduino but I've got a teflon brain that nothing computer oriented will stick to. I'm in the frustrating position of understanding enough to see what can be done but not being able to do it.

That's one of the reasons I'm keen to stick with the simple solution I outlined in my last post. I take the point that it's probably not wise to do all the residual pulse correction on consecutive teeth but rather spread them out over the whole tooth. I can do that by using the two outputs from the Stepduino as I outlined earlier. I need some way of easily swapping between the two outputs as the gear is cut. My first thought was to have a plug from each of the outputs and switch the motor plug between the two at regular intervals throughout the cutting operation. It would be better however to have a rotary switch between the controller and a single plug. The operation of the switch would need to carry out the operation shown in the photo.

switch.jpg

It would need to switch the 4 wires of the motor between the 4 outlets from controller one and the 4 outlets of controller two. I don't know what the name of such a switch is which makes it hard to find out where to get one. Can anyone tell me?

Regards,

Alan

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