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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: 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

Thread: Vfd update
02/02/2019 16:53:59

The white paste is heat sink compound. Added at manufacture to keep the chip cool by assisting heat transfer to a heat sink.

Martin C

Thread: Chester Craftsman Lathe
02/02/2019 15:48:45

In the thread milling on the craftsman lathe I put a link to the manual. Parts 278 and 279, described as gears, are drawn with different tooth profiles. They are both keyed onto a short stub shaft on the tumbler assembly.

Martin C

Thread: Cut a slot in round stock
02/02/2019 15:38:07

img_20170329_181417.jpg

This photo shows a supported and clamped overhanging workpiece which is the way to do what you wanted. A hard collet block held by hard vice jaws gives poor grip as you found. A piece of paper between the block and the moving jaw may have helped. Putting milling cutters in lathe chucks can have similar issues.

The other thing that is a problem is the lack of material at the sides of the slot. If you think of a twist drill as a twisted ribbon you can understand hiw easily it can deflect. In this case as soom as one side is weakened enough the drill will be pushed that way by the forces acting on it. A stiff stub drill or spotting drill would have helped but a 3 or 4 flute milling cutter would be stiffer so better.

Regarding plunge cutting with milling cutters even centre cutting ones do not go in as easily as a drill. One way to improve on this is to ramp the tool into the workpiece. This is easily done with CNC but is possible when manually operating a mill. It requires lateral movement of the workpiece as the tool is lowered into it. Since you needed a slot it was possible in this case.

Martin C

Edited By Martin Connelly on 02/02/2019 15:39:12

Thread: Milling on the Chester Craftsman
01/02/2019 16:21:35

Adrian, the relative with the lathe in Boston also has a small mill. If he is willing to sell the lathe it may be possible to sell both machines as a package. I will see him Sunday and ask about them. Both together for less than you were planning to pay for a new lathe should be possible. That would solve the problem of fitting a milling slide to a lathe.

Martin C

Thread: Testing for isolation
01/02/2019 15:45:48

I've got a non contact voltage indicator (Iso-Tech IVP-1) and would recommend them for anything to do with mains voltage electricity.

Martin C

Thread: Fitting a Reversing Switch to a Motor on a Myford Lathe
31/01/2019 20:16:38

No whine on any I have used.

Martin C

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