Member postings for Martin Connelly

John, if you are using a full sized 102 key keyboard then (with windows at least) some available sub and superscripts and symbols are easy to do. For example if you hold down the Alt key, press 0176 on the numeric keypad, then release the Alt key you produce °

Alt 0216 gives Ø

Alt 0176 gives °

Alt 0177 gives ±

Alt 0178 gives ²

Alt 0179 gives ³

0185 ¹

0188 ¼

0189 ½

0190 ¾

I never found anything for a negative to precede a superscript number or a square root symbol by typing.

So some of your equations are doable, R²+h²=(R+r)²

Martin C

Ronald, the Gcode for a curve is quite simple, you tell the controller where the tool is starting from, where the tool will end up (as either X and Y coordinates on a mill or X and Z on a lathe) if the path is clockwise or anti- clockwise and either the radius you want or where the centre of the curve is.

Typically this would look something like this:

g01 x15 z-1.5 (go to the start point)

g02 x15 z1.5 r12 (travel in a curved path to the end point with a radius of 12)

g02 or g03 determines if the path is clockwise or anticlockwise.

There are variations in different controllers so this may not be quite the way that Les would set it up.

Martin C

I used to do this type of thing but without the beam underneath. We lifted a large load at one set of lifting points at one end just enough to get it to rotate and recorded the weight from the crane and the distance from the fulcrum point to the lifting point. Then repeat with a set of lifting points at the other end and also record the distance between lifting points. Off hand I can't recall if the known total weight was included in the calculations but I think not, we had a program on a programable calculator to calculate the distance to the CoG from one of the lifting points and marked it on the load. We also, very occasionally used four load cells under a load to calculate the vertical height to the CoG. This required lifting one end of the load about 300mm higher than the other and recording the weight at each load cell and the distances between the load cells. Then repeat with the other end raised higher by the same amount. With the two calculated CoGs you could do a scale drawing and where the two lines of CoG crossed showed how high it was. I've probably still got all the relevant PC files somewhere.

An added extra to the program on the calculator was that it could be used to work out the number of links required for the spreader beam chains to get a correctly balanced load with the first lift and also if any leg on the lift was exceeding its WLL

Martin C

Edited By Martin Connelly on 07/01/2023 16:27:19

The question of maximum diameter hole you can produce before starting with a boring bar depends on how much material each drill is removing if you start small and step up to final size. Trying to drill a Ø25 hole may be possible if you can go up to it in many steps whereas trying to cut it with just a Ø3 pilot hole will probably not work. There is also a chance, if the material is not too deep, of cutting a large hole with a hole saw or broach type cutter (my preferred option, it produces less waste and a useable solid plug). Also blunt drills will not get you to the maximum size you can cut with something sharp.

Martin C

Dogma.

Assuming cutting between centres:

With a perfectly set up lathe the tool will be on centre line and the distance of the tool tip from the rotational axis of the bar being cut will not change from one end to the other. The result, if there is no deflection and no wear on the tool tip, is a perfectly cylindrical bar.

If the tailstock centre is higher or lower than centre then the correct cutting height will only occur at one point along the rotating bar. As the tool moves away from this point the effective distance from the rotational axis to the tool tip will increase slightly. So where is the tool set up to the correct height?

If at the headstock there will be a taper that increases in diameter as the tailstock is approached.

If at the tailstock then it will increase in diameter as the headstock is approached.

If in the middle then the diameter will increase either side away from the centre.

The last case is the nearest to a barrel but in an inverse way as it is narrower in the centre than at the ends.

This tapering effect is only noticeable at small diameters and long parts, it decreases as the material diameter increases and for most people making a long thin part will probably require a travelling steady that will negate a lot of these issues. This is making a mountain out of a molehill that will make virtually no difference to the majority of work done on a lathe. The horizontal error on a tailstock can cause far more error and that is what needs to be concentrated on. With a suitable dumbbell setup bar you are setting the tailstock over to the point where the readings at both test points on the dumbbell are the same. This will negate any small height error in the tailstock as you would be moving the actual tailstock horizontal position to the point where the axis of rotation distance to the tool tip is the same at both ends which is not necessarily on the exact horizontal centreline of the axis of rotation. The height error is thus accounted for and so irrelevant.

Martin C

Looks like something to hang under a table saw or a conveyor belt. As you say, such roles have now been superceded by VFDs which can be operated remotely and do not wear the same way this style of speed control will.

Martin C

Neil, I have seen a video, probably on YouTube, of a lathe with a very rapid X axis being used to cut polygons under the control of Linux CNC.

Martin C

Here is one 

Edited By Martin Connelly on 04/01/2023 08:32:36

Modern cameras, phones included, put orientation information on the photos. Sometimes all you can do is open it in a photo editing program, rotate it then re-save the correctly oriented picture, maybe with a new name. I once spent some time looking through a load of photos, rotating some as I went. When I left the photo viewing program all the ones I had rotated were back where they started because I had not saved them in the new orientation.

Martin C

+1 for what Mike Poole said. The natural speed of a 2 pole motor at 50Hz is just under 3000rpm. Change the non-rotating stator windings to 4 pole and you have a motor with a natural speed of just under 1500rpm, 6 pole - 1000rpm. Since the rotating part does not differ in any way 3000rpm should not be a problem for a modern motor. Additionally if the motor is rated for 60Hz as well the maximum should be closer to 3600rpm. I have limited my lathe to what is on the original speed plate because it has plain bearings and chucks usually have a maximum rpm and I don't know what it is for mine so, better safe than sorry. I have done the same for my milling machine, The belt table gives a maximum RPM based on the original motor and pulley system. Not knowing what the limiting factor is I keep it set up so that with the belt option I use for everything I do I can increase the frequency of the motor over 50Hz but it is limited to what the original max rpm was. I don't fancy a big cast aluminium pulley bursting from too high an rpm even if it is in a metal cover.

Just be aware that increasing frequency too much may also reduce the current as the current in the motor coils will decrease as they are inductors. They are often optimised for around the 50/60 Hz frequency.

Martin C

The recent thread on making change wheels Thread 184394 contains a link to GearDXF. If you have a suitable CAD program you could use this to cross check a couple of button based tools from both sources against the required thread form to see what matches best.

Martin C

My Machinery's Handbook chapter on screw threads goes from page 1256 to page 1382. This is followed by sections on measuring screw threads then cutting screw threads. The writing is very small but there are charts and figures in amongst the writing. The point is that a comprehensive list of all screw threads would be a very large download so it is more usual to either refer to a book or find a web page with the information you want and print off a chart or make your own and print that off. If you want a small reference book then the Zeus booklet is a useful workshop reference. There have been threads referring to it in the past so a quick search using the home page search will bring up details on it, but don't get ripped of by high priced re-sellers, it should be quite a low price. It may not cover model specific screw threads so may not suit what you want. Different issues have different contents as it evolves, as well as screw thread details earlier ones had log tables and trig tables but now these tables have gone (due to calculators) but other things like CNC Gcode commands have been added.

Martin C

Hand soap is likely to cause corrosion in some combinations of wood and metal due to it not being PH7 (neutral) and including water in it. I have seen this myself so I would avoid soap and stick with wax or some other plain lubricant.

Martin C

There is a recent thread about making a faceplate for watchmaking that links to a YouTube video. In it there is a short segment where a tool of the style you are after is shown being made. Thread 184361 so it is probably worth a look if you have not already watched it. It is nearer the end of the video than the beginning if you don't want to watch the whole thing.

Martin C

I have the 13 part BBC radio adaptation of the Lord Of The Rings. It is on cassette but I copied it onto my PC because cassettes are not a great format for repeated listening or future use. My experience of audio books is, unless you know the book well to start with, you have to concentrate to hear everything, any distraction and you have to go back to an earlier point and start over. As such I don't think I would ever try listening to one when working with machine tools.

Martin C

There is no problem threading with Mach3 on a suitable machine. The main issue is with some of the lathes it is used with. Mach3 requires just one indexing pulse per rev. It uses this pulse to synchronise the start of the z axis motion and to set the correct feed rate for the required pitch. If you have a lathe with an underpowered motor or you are too aggressive with depth of cut for the available power the resulting reduction in RPM throws the calculations done by Mach3 off. If you are threading on a lathe with plenty of power for the work being done then Mach3 can cut threads without issue. Trying to use a lathe with electronic speed control at low speed and with no back gear for example is likely to fail.

Martin C

As more home machinists take up CNC it may be the case that the lower demand for castings has made the suppliers go for cheaper options that have reduced the quality. With low numbers of parts it may be a better option for the suppliers to find someone to CNC large parts, like the beam, from solid.

Martin C

Andrew, I am a hobby machinist so I would not particularly say my friend out-sources to a machine shop but in effect that is what he does. Most of the music boxes he restores are European so generally the screw threads are small metric standard but there are some unusual threads occasionally appearing. The last thing I did for him involved making some Ø7x1.1 Lowenherz form screws (once I had identified the thread form). Not something you will easily find dies for and an unusual pitch as well. These were not part of the music box mechanism but were for holding the case to the main frame.

You can see the sort of music boxes he restores if you search for "Antique Mandoline Piccolo Music Box by Paillard, c. 1880".

Martin C

The easiest option if you only have a small number of thread sizes you plan to do is buy some suitable dies and make a tailstock die holder. There are plenty of plans and videos on this tool. I don't know if a Unimat threading attachment allows left hand thread cutting. If it does not then once again a tailstock die holder with a suitable die would be the best option. The other options of going down the ELS or full CNC route would probably be overkill for this small lathe with a small, specific, need. I have a friend who does restoration work on music boxes with a Unimat and this is his method. Anything bigger or odd I do for him.

Martin C

I have always considered the Dickson style tool holder to be over constrained. This is because two parallel vee shaped mountings are always going to be fighting each other if there is even the slightest error, damage or contamination and the lack of adjustment for the piston pull in. This all adds up to a holder with poor repeatability of positioning. If I was making my own tool holders to fit one of these tool posts I would only make one vee and leave the other side smooth with a threaded hole for an adjusting screw to allow proper pulling tight by the piston. It would mean you could only use the tool holder in one direction as the vee should be near the cutting point but in favour of making your own would be easier to produce. I would also try putting a gap down the centre of the vee to effectively make it a three point mount on the tool post.

Martin C

The only diagram I could find for this controller did not show what the outputs are doing and did not show a recommended connection to a driver. I thought it may be a recommendation from the controller paperwork. The worst that can happen is nothing. The connections for the driver module show either the +ve terminals commoned together and connected to Vcc or the -ve terminals commoned together and connected to the ground terminal. In the absence of proof one way or the other try the wiring as shown. If it doesn't work then look at the driver module diagrams and try them instead.

Martin C