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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: Alternative to PC based Cnc controllers
14/09/2016 10:39:29

Further to the Mach3 threading bug. I think the problem is that the threading macro tries to go to the tool changer and so switches to machine coordinates for the move. If you have not got the machine coordinates set they may be very different to the user coordinates. The easy way to set the machine coordinates is to home the X and Z axes. This does require home switches on the lathe but a lot of people probably never fit them as they can seem unnecessary. I experienced this bug when I first tried using the threading wizard but as I have fitted home switches and now have the machine coordinates set as something sensible I do not have alarming and seemingly random moves to a tool changer taking place.


PS I also think you can switch off the tool changer option somewhere but I may be mixing this up with Mach3 on the mill.

Edited By Martin Connelly on 14/09/2016 10:41:25

Thread: Press fit bush
13/09/2016 18:28:34

Loctite it to avoid tensile forces in the cast iron.


Thread: Can a Drill be a Mill?
13/09/2016 13:35:24

The important difference between a drill and a vertical milling machine is the drawbar that is fitted to the milling machine. Without a drawbar the cyclic loading on a morse taper will cause it to loosen and fall out with the forseable consequence of damaged workpiece. If your drill does not have a morse taper it probably still has a Jacob's or B type taper into the chuck.


Thread: old 13A plugs
11/09/2016 13:27:13

Ed, search the net for plugs type G and you will find a lot of countries use these plugs.


Thread: Stepper drive for a Lathe Cross Slide. Issue No.246
11/09/2016 13:22:05

Yes, z axis positive direction is away from the chuck. X axis positive is towards the operator for a front tool post.


Thread: 2MT taper tooling
11/09/2016 09:19:54

The shanks on drill arbors are usually soft down the core. Get one with a tang, cut the tang off and drill and tap to suit your needs.


Thread: Things to save from a CRT TV being scrapped
09/09/2016 13:00:15

Save your back, get someone else to take it awaywink


Thread: Technique Required to Make Accurate Backplate
09/09/2016 09:41:21

Is the blemish raised? If so it needs to be flush or lower than the rest of the register face. I would consider stoning a small area to remove a raised blemish an acceptable way of repairing it. If it is lower than the rest of the register it should cause no problems.


Thread: Running several 3 phase machines
09/09/2016 09:34:27

Some of the older properties in my village are supplied by power cables on poles that look similar to telegraph poles. They can get 3 phase power to their houses for quite a low cost compared to properties with underground services. The poles carry 3 phases plus neutral so it is a relatively easy process to connect the other two phases and a suitable meter (unlike digging holes in the ground). If I had this as an option I would give it serious consideration.


Thread: Pros and Cons of the ER collet system
06/09/2016 18:32:47

I think that under large radial loads a tool near the bottom of a collet's range may deflect into the spaces where the collet is not touching the tool (or workpiece if used for work holding). If the tool matched the collet size this will not be happening but I wonder if it is possible for the tool to push parts of the collet away from the split if enough force is applied. This would be more likely if the collet holder and collet were both lightly oiled and have a smooth finish.


Thread: Tangential tool holder
04/09/2016 10:05:08

The best one is one that you can make, fits your machine and does what you want. Only you can design this tool. Here's my own design.



Thread: Is CNC cheating
03/09/2016 10:49:18

As stated a number of times in this thread cheating means breaking rules where rules exist, presumably in competitions. It seems to me that as tooling has evolved from basic to CNC the rules also need to evolve alongside the tooling and the follow on from that is that the judging needs to keep up with this progress. I think anyone who has put a great deal of time and effort into designing, drawing and CNC creating a part for a competition entry only for it to be marked down because of the CNC would rightly be annoyed. The judges in modern competitions should have an understanding of CNC manufacturing to be able to make sensible decisions to judge between work done with different methods.


02/09/2016 10:27:04

A short time ago I made a part using the manual data input (MDI) of Mach3 to do the work. I thought it would be interesting for all the manual machinists to look at the half-way house of CNC that is MDI so wrote up the process with a parallel commentary of what a manual process would entail for comparison. I think it would help some of the people who may be interested in dipping their toe into CNC but are daunted by talk of 3D CAD and CAD/CAM/CNC with POST processing and all the other abbreviations that can be bandied about. It may also enlighten some of the people who think CNC is just pressing a button and sitting down to wait as to what may be entailed. Due to the limitations of this forum there may be some loss of quality in the prints.

cnc mdi 1.jpg

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cnc mdi 6.jpg

cnc mdi 7.jpg

cnc mdi 8.jpg

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cnc mdi 13.jpg


Thread: Steampunk
31/08/2016 18:35:50

Lincoln Castle hosted a steam punk event this past weekend, not for the first time.


Thread: What to get: Imperial or metric
30/08/2016 13:07:49

Warco offer this machine with DRO fitted. If you went with that option that would make the discussion simply one of are you going to cut more threads using TPI or metric pitch and if you know get the one with the leads crew that matches your needs.


Thread: Boxford TCL 125 stepper motors. Worn out?
30/08/2016 13:01:30

If there is a lot of heat build up then the magnets may be degrading. I think I have seen 70° as the maximum working temperature for some stepper motors. This will be the temperature at which either the insulation starts to degrade or the magnets suffer or any adhesive used in the assembly fails. If the step and direction inputs are easy to connect to I would think about replacing the motor and its power supply. You could also consider a hybrid servo stepper as they can be used like an ordinary stepper motor but can give an error signal if steps are lost. The Leadshine three phase ones give a good torque in a small package but unless you can change the value in the software you need to match the steps per rev to what you already have.


Thread: Dovetail cutter.
30/08/2016 08:47:59

Ray, your post regarding clearances was posted not long before mine and since I did not refresh the page with your posts on before my post was submitted I had not seen it. If I had I would have modified my post to make clear that the comments regarding positioning of the inserts and back edge rubbing was only relevant to inserts with little or no back rake for anyone who was thinking of making their own tooling in the future.


Thread: Boxford TCL 125 stepper motors. Worn out?
29/08/2016 16:57:52

What are the stepper motor specs, what power supply and controller have you got, do the motors get hot in use? There are probably other questions that will need an answer but we need to start somewhere.


Thread: Dovetail cutter.
29/08/2016 16:46:49

Further to my post yesterday I have taken a photo of my little hogger insert cutters. What can be seen with these cutters is that the cutting edges are not aligned on a diameter through the centre. As Muzzer stated the inserts must be ahead of this line by at least half their thickness. If you measure the distance from cutting edge to opposite cutting edge on your cutter the dimension may be less than the dimension of the trailing edge to trailing edge of the inserts. If this is the case then the trailing edge will rub.


Thread: Technique Required to Make Accurate Backplate
28/08/2016 23:04:32

You can have swash on the back face even if it is flat. Since the thread in this case was cut with a tap not single point threading there is a chance the thread is not normal to the machined back face. Putting the plate onto the spindle reversed then skimming the back face ensures the thread is normal to the back face and eliminates the risk of swash. If there is swash then there is a possibility that the runout will vary depending on where the backplate is pulled up to.


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