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Member postings for Martin Connelly

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

Thread: Milling machine clamps
19/11/2021 12:58:28

I bought my mill used and it had two 1/2" UNC clamping sets with it. It did allow me to shorten some of the studs to between the as supplied lengths without ending up with not enough for a complex setup. Having lots of step blocks allows them to be used for more roles when clamping such as setting up a nice solid stop or two for multiple parts with the same setup. I have never used the stud couplers though.

Martin C

Thread: Wanted - Brass tube bending
15/11/2021 13:38:34

I have seen another method used in brass instrument tube bending. After the initial bend form is made the part is put in a mould and ball bearings are pushed through to push the tube into the mould walls. The first ball is to maximum size and subsequent ones are slightly under size so they fall out easily.

Martin C

Thread: Feed trip electronic
12/11/2021 19:08:54

Tony P 1

I would have to say that a two motor ELS setup is far more work than a 2 motor CNC setup. I have looked at what is involved with making and programming an ELS and it is not an easy task. Since you can use turning wizards with Mach3 there is no need to learn CAD/CAM or Gcode to use it.

This video shows what is needed for Mach3, most of it is shared with and ELS and the old second hand laptop is perfectly adequate and cheap. The only thing missing for threading is a suitable sensor which costs a few pounds on the internet.

In Mach3 to cut a thread with the threading wizard you input start diameter (or radius if that is how you have it set up), end diameter (radius), pitch, start z value (position along the bed), end z value, spindle speed, pass depth, final pass depth angle over which the tool is retracted and number of spring passes. You can set the infeed angle, minimum pass depth and some other parameters in the settings to suit your usual needs. A mini remote keyboard makes a good pendant.
No need for a gearbox or change wheels. Metric and imperial threads can be cut.
Martin C
Thread: Run out on bar
12/11/2021 08:36:18

I think most of the answers on here were not related to the stated problem of "run out at the end of the bar", not at the chuck.

Martin C

11/11/2021 08:48:28

To those who use them regularly it is well known that if you take something out of a 3 jaw chuck and replace it it is nearly impossible to get it back in the same position without some fiddling about. The issue here is that there is friction between the chuck jaws and the bar, the chuck wouldn't be much good without it. At a small angle from the centre line the friction forces will be higher than the forces trying to line up the bar along the spindle centre line. You will find examples on line of people mounting a bearing in the tool post to push on bars to line them up, you will also find examples of people tapping then into line after clamping. If you put the bar in the chuck but not fully tighten it you can position a tool in the tool post and move it close to the bar and than turn the chuck by hand to see where it needs moving back towards the centre. Light taps with a suitable mallet, copper drift or machinists hammer can be used to improve the runout. Once it is in the best position you can tighten the chuck fully.

Martin C

Have a look at this video about 3 minutes in. Its in a collet but the principle is the same. Some adjustment is required to achieve a low runout.

Edited By Martin Connelly on 11/11/2021 08:52:28

Thread: Book Your Covid Booster! Errr, How? Where?
10/11/2021 18:46:45

It's probably the NHS not the Government, and that's why it worked.

Martin C

Thread: Single point tool to cut an internal 5/8-10 LH ACME thread
10/11/2021 14:48:10

I think a second tap will have full thread for part of its length. Since this is not for a blind hole there will be no problem pushing a second tap all the way through to cut the thread to full depth. Undersize threads can occur with ring series tap sets for tapping hard material if you don't use all taps in the set but I think one described as a second tap would not be a ring series tap. You could ask the suppliers to confirm this is the case.

Martin C

Thread: Clamp Sets - Thread Type?
08/11/2021 07:51:21

I have metric pitch, Whitworth and UNC thread gauges. I checked my kit before ordering some 12" x 1/2" UNC studs.

Martin C

Thread: GPS as a low-speed Speedometer
07/11/2021 15:16:23

The readings are not continuous and the accuracy is not to a fraction of a metre so it doesn't seem odd to me. If you got continuous readings every 0.1 of a second and the accuracy was also 0.1 of a metre you would have a much smoother graph if it was plotted. If you got two readings 0.1 second apart and the position accuracy was 5m too far north for the first one then 5m too far south for the second one it would think you had travelled 10m in 0.1 seconds, equivalent to the 100m sprint in 1 second. When you add the irregular readings to poor positioning the average over time and the distance travelled will be about right but for short times or distances you can expect bizarre results to pop up on the screen.

Martin C

Thread: Music on TV Programmes.
04/11/2021 13:35:18

I think some of the issue are that the speakers in flat screen TVs are not great for sound quality and that there are some variations in the sound transmission between mono, stereo and 5.1 surround sound. I know that at the moment with my setup the sound level volume varies when switching from an SD channel to the same broadcast in HD and also between different channels with the same definition.

Martin C

Thread: Thread dial indicator
03/11/2021 10:13:44

Message me and I will send a copy of something I wrote about understanding the threading dial (pdf)

Martin C

This is the album with the jpgs of the pages but it is a bit hard to read as a jpg Album thread

Edited By Martin Connelly on 03/11/2021 10:35:56

Thread: Time code Updates with clock change
01/11/2021 09:20:44

My watch and other RC clocks had changed by 8am GMT on Sunday as well.

Martin C

Thread: Spur gear diff rotation.
31/10/2021 15:02:53

The second shaft will go clockwise. It is easier to consider the case where the cage is stationary first and what is labelled as fixed goes anti-clockwise at rpm X. Then you will see that shaft C goes clockwise. In order to then see the case where the first shaft is fixed everything else has to go clockwise at whatever rpm X you imagined the fixed shaft to be going in the first case plus what it was doing in the first case. So the cage is rpm X plus zero clockwise and the output is clockwise amount plus rpm X.

Martin C

Thread: Choice of collets
30/10/2021 11:02:27

Ahem, see post at 09:45

Martin C

30/10/2021 09:45:00

Here are a few things to consider.

If you use a collet directly in the spindle you need some way to lock the spindle to be able to tighten and then loosen the collet otherwise you may be on here at some point in the future asking about spindle locks.

If you get an ER collet system be aware that some collet holders do not have spanner flats on them. Same issue as above. It is easier to make sure you buy them with suitable spanner flats as otherwise you may have to add some by grinding or machining.

It takes a reasonable amount of torque to close down an ER collet so that it doesn't slip but you can buy replacement nuts with built in bearings that make it a lot easier to close down the collet and they don't try to twist the collet as you do so.

With ER collets don't use hook wrenches on the nuts, apart from wear and tear you are likely to skin some knuckles at some point. A properly designed wrench to suit the nut is much better and allows better application of torque. It should be noted that sizes such as ER16 can be supplied with different types of closing nut, some are simple hex nuts but others are slimmer with finger slots and are usually supplied with a matching wrench.

According to some professional machinists on YouTube ER collets are a consumable item. I have not destroyed one yet but then I don't apply the torques they use in CNC for machining to machine parts with huge value that I don't dare scrap off.

The self locking collet systems such as Clarkson, Vertex etc. require a threaded shank tool but there is nothing to stop someone with a lathe from threading a Ø16 ER collet chuck shank to suit and so adding the option of a small ER chuck for use with them. It is also something that can easily be done with the shank of insert milling tooling to allow their use with these systems. I have also made a Ø16 hollow shank for one of these that holds a Ø10 edge finder (with a bit of Loctite for extra security). If an edge finder is not sufficiently accurate for your needs a holder for a DTI is an easy project.

Martin C

Thread: A question about traction.
29/10/2021 08:58:55

There must be some deformation between the rail and the wheel due to applied pressure, steel is not infinitely hard. For a given weight on a wheel a smaller wheel will have a smaller contact area so more deformation will occur as the pressure is higher. The actual friction force will not increase as that is dependent on both pressure and area so I can only imagine that an increase in traction is due to a either a greater deformation taking place with a smaller wheel or the increase in pressure effectively cleaning the rail surface better.

Martin C

Thread: Smart & Brown Questions
27/10/2021 15:20:21

I made a 127 tooth gear out of aluminium plate as a hobby machine will probably not wear an aluminium gear out in a hurry. A 95 tooth gear should be relatively easy as the 127 was about as large a disk as I could easily turn in the lathe. Since then I have converted my model m to CNC so I have the gears but never use them. However I have kept all the parts removed and all the gears to stay with the lathe when it moves on.

I still have the cutter and I have a suitable disk of 10mm steel plate so I will have a go at the 95 tooth and if it looks ok I will let you have it, It would just need a few washers either side to space it nicely. Then you can cut the 19tpi and 38tpi threads it is for.

Martin C

Thread: Lathe Drilling
26/10/2021 18:51:15

The process of accurate drilling came up some time back but was not talking about tailstock drilling, it was about basic drilling or milling machine drilling. Using a centre drill is the wrong thing to do as the angles are all wrong and the outer edges of the drill will contact the workpiece first and cause wandering. The use of a spotting drill with an angle greater than the standard drill point should be used, so for a 118° drill the spotting drill used should be 120° or more. This will guide the drill into the centre before the edges contact the workpiece and cause wandering. You can test the effectiveness of this by using a turning tool to produce a 120° recess and using a standard 119° drill in it.

Another thing you can do is use a stub drill to start the hole at the desired diameter then follow up with a jobber drill. Standard jobber drills are like a twisted ribbon and can flex a lot.

Martin C

This thread covered this subject

Edited By Martin Connelly on 26/10/2021 19:01:19

Thread: Advice from the photographers.
24/10/2021 08:16:49

I have a Canon scanner with a slide and negative carrier. It has a backlight set into the lid for this. Trying that I found it was too grainy (and slow). What I ended up doing was using the slide scanner backlight and a digital camera supported on a bean bag set to macro. It gave much better results and muck quicker. As above just some cropping required. Some of the slides I copied were 110 not 35mm.

Martin C

Thread: Collets for Myford tailstock
23/10/2021 17:58:52
Power tapping with a tapping head. The knurled ring allows the torque at which the clutch slips to be adjusted. If tapping a blind hole for instance the part holding the tap will start to rotate rather than strip the threads. I did a test on the other end of the plastic to set the torque high enough for it to tap in plastic and drive back out, if I left it at that setting it would not tap metal.
Martin C
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