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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: Older/cheaper lathes
07/03/2019 08:42:31

Beware of a good paint job, clean and shiny looks good on a screen but can distract from mechanical state underneath.

Martin C

Thread: Lathe screwcutting
07/03/2019 08:35:09

You have said you are set up for a metric thread and are using a Boxford lathe which I think has an inch based leadscrew. This is the situation where the threading dial does not work and the best advice to follow is to leave the half nuts engaged to avoid multiple start threads.

Martin C

Thread: Aircraft General Discussion
28/02/2019 22:52:10

Glad to hear you made it. I saw them after they left Cranwell but they were disappearing in the low cloud as they passed.

Martin C

28/02/2019 14:14:12

Tornado flight details

**LINK**

Martin C

28/02/2019 08:15:53

Marham are planning to have a 9 Tornado formation fly to Cranwell and back today. The aim is to fly over Cranwell at 15:15hrs. This is all dependent on the weather, yesterday would have been perfect, today may not be so good.

Martin C

Thread: Anyone have a Clarke CL250MH (Sieg M1)
24/02/2019 16:18:55

Lead screw length may not matter as there is a lathe bed preventing it being lowered too far. Regarding solid versus hollow, the rigidity is a function of diameter more than wall thickness. A solid bar adds weight but doesn't increase rigidity very much. Adding mass may increase damping.

Martin C

Thread: Pensions
21/02/2019 17:01:38

According to a financial advisor I spoke to recently managed funds are earning about 4% per year. For the privilege of managing these funds the manager tajkes 3%. Where I live at the moment rental income from property runs about 5% and your capital doesn't get used up. Buy to let looks like a sensible option but doesn't suit every investor.

Martin C

Thread: Lead Screws
19/02/2019 21:36:18

DRO may be a cheaper option.

Martin C

Thread: Stepper Motor Controls
18/02/2019 17:42:43

The main reason for using the microprocessor with a shaper (as I see it) is to synchronised the movement to the shaper stroke. I imagine there will need to be a sensor to detect when the cutting stroke is complete and only move the workpiece on the return stroke. It may be possible to use a simple interupt on the enable signal of the simple system using a pulse generator but the variable number of steps per stroke that could result may marr the finish.

Martin C

Thread: Plus or Minus
17/02/2019 22:59:31

The CNC convention John gave is based on the idea that if you forget the minus in front of a number the tool will move in a safe direction, doesn't quite make sense when boring or cutting away from the chuck though.

Martin C

Thread: Y axis problem
14/02/2019 19:23:38

At 10mm/min feed you are rubbing not cutting. Something around 200mm/min would be more typical for this combination of tool and material. Does your version of Mach3 have the feeds and speeds wizard? If so use it to ensure you are cutting not rubbing. Load on stepper motors will increase if you try to push a rubbing tool into the work piece.

Martin C

14/02/2019 18:14:39

In certain situations you should avoid using the radius format with G02 and G03 as it can cause problems according to the Mach3 programming notes. Small errors due to rounding of coordinate values can cause large variations in the path the cutter takes.

Martin C

Thread: How do I adjust the quill?
10/02/2019 12:25:03

Pi times diameter times angular slop divided by 360.

Martin C

Thread: Fly cutter bits
07/02/2019 18:27:19

Just one additional thing that you should keep in mind, the cutting point needs to be further from the centre of rotation than the other low corner in order to avoid rubbing unless it (the non cutting corner) is higher than the uncut face you are removing. If you buy a fly cutter you will probably find that it holds the back face of the tool on the centre of rotation to help with this. It also means that it is easy to have a tool with negative rake if it is not ground to take this into account.

Martin C

07/02/2019 16:10:21

I use small lathe insert tools a lot of the time so similar angles to lathe tools work fine.

Martin C

Thread: Division Master (Stepper Motor Dividing)
07/02/2019 16:03:25

This thread **LINK** mentions the required accuracy of dividing plates so may be of interest.

Martin C

Thread: How to model the mechanism of a Taylor Chuck?
04/02/2019 20:58:07

Create a helical line that tapers then sweep a triangle along it. You can do it in AutoCad so I expect other CAD programs will have something similar.

Martin C

Thread: Myford Vm-f
04/02/2019 14:34:33

Ah, but when you are bending you are lifting your own upper body weight.

Martin C

Thread: Chester Craftsman Lathe
02/02/2019 17:57:16

You want Grizzly manual for G9249 it has a clear picture of the drive train. Easily found online.

Martin C

grizzly-g9249 

 

Edited By Martin Connelly on 02/02/2019 17:58:54

02/02/2019 16:58:49

It may be possibkecto find the equivalent lathe on grizzly.com in the USA. They have usually got better manuals than the UK.

Martin C

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