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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: Modification to an ebay sourced electronic controller
28/05/2017 19:31:25

If you have no joy from the suppliers you could try a 470k pot and modify it with some conductive paint on the track to give a 90k range over about 50 degrees.

Martin C

Thread: Gear drive problem
27/05/2017 11:48:31

Duncan, turbochargers for boat, train or ship engines go to multi megawatts. Same type, just a different size.

Martin C

Edited By Martin Connelly on 27/05/2017 11:50:10

27/05/2017 08:20:21

Duncan, the reported question does not mention either steam or turbine disks, the use of the work rotor makes me think of a car's turbocharger turbine. The turbine disks on a gas turbine may be spinning in the region of 15000 rpm at a lot higher temperature than a steam turbine. Doubling the disk diameter would probably result in a design that could not take the stresses unless the rpm is reduced. What seems like a simple question on a test paper could have a complex answer. I think people who had done the course would know what the expected answer would be based on coursework covered.

Martin C

26/05/2017 09:27:42

I would tend to discount the massive gear solution as it does not seem logical to have a first stage that reduces the rpm followed by such a massive increase in rpm at the second stage. However maybe this silly solution was what was required to test if the person being tested really understood the calculation process for the gears.

Martin C

26/05/2017 08:13:12

I think it is 12 teeth. The question regarding the ratio is should it be 1:12 or 12:1? If it is for a threading solution for a lathe gear train then 1:12 may make sense. If direct drive gave a tpi of 1 then the calculated gear train would give a tpi of 12. If you are looking at the ratio of input rpm to output rpm then 12:1 would be the correct ratio.

Martin C

Thread: Chucks
22/05/2017 05:48:07

If you have the option of a 3 jaw with soft jaws as well they can be very helpful for some jobs. You may not need them for a while but if you do then you may find yourself buying a second 3 jaw chuck if the first one does not have them as an option.

Martin C

Thread: Screwcutting Crashes -
13/05/2017 09:37:08

I have a micro switch mounted on an aluminium block that clamps on to the lathe bed and can easily be repositioned to suit collets, 4 jaw or 3 jaw chuck as appropriate. It is a home switch for CNC and a limit switch at the same time. It has saved me from crashing bits together a number of times when using manual data input to move the carriage around.


Martin C

Thread: Simple Cad Drawing start-up.....
13/05/2017 09:16:18

When we got AutoCad at work some years ago it was supplied with a nice thick manual. I worked my way through the tutorials in the manual and found it easy to work with as a result. I often see work done by people who did not do this and as a result do not use model space and paper space (now layouts) correctly. This was long before 3D cad was affordable for most people and YouTube didn't exist. I would recommend trying to get something with a good tutorial to get you started, YouTube may have plenty of tutorials but they may be of variable quality if they are not official releases.

CAD is an excellent tool when you get over the initial learning stage otherwise very few people would bother with it. A big screen always helps as well.

Martin C

Thread: Warco WM280V Metric or Imperial
04/05/2017 14:17:03

Maybe it's a mid terrace and the bolts go through two or three neighbours' properties as well.wink

Martin C

Thread: P-Power hacksaw
02/05/2017 14:04:03

Only cut big partswink

Martin C

Thread: Chester Super lux
02/05/2017 13:58:38

I have had a look at the Super Lux spindle relative to the table. With the table wound fully towards the column the spindle centre line is just about in line with the edge of the table, this is with a DRO mounted on the back of the table. Winding the table as far as it will go away from the column the spindle centre line is only over the third tee slot in the table.

Martin C

02/05/2017 11:48:56

The Super Lux I measured is in an industrial workshop used by a number of people and has been in use for a number of years. The only issue is that since it has to comply with PUWER regulations the safety guard must work and the plastic it is made of is not very robust. It has been replaced a number of times due to the table being moved with a power feed and a vice catching it.


PS, nearly forgot that the knob that is used to engage/dis-engage the fine feed fell apart but was easily replaced with an off the shelf al. alloy one.

Edited By Martin Connelly on 02/05/2017 11:50:08

02/05/2017 11:32:56

The 18" figure is the table to spindle nose distance before any tooling is put in place. Do you need 18" under the tool? It may be possible to extend this distance with a spacer piece as 628 owners often do but it would not be as simple as the 628 version, you would need something about 7" x 11" x whatever height you needed under the column.

Martin C

Thread: Unrecognized gauge marked "PERLES"
02/05/2017 10:10:52

EGA, seed pearls in jewelry are going to be about size 1. If you want even sizes then a gauge is needed.


Martin C

Thread: Making a small profile tool.
02/05/2017 10:04:23

About 18 months ago there was a thread where pre-insert threading tools were discussed. This is an alternative to the tangential tool design above that may be worth consideration. The tools discussed look like this.


It should be quite easy to produce a disk in gauge plate with the required profile, harden and temper it then sharpen the cutting edge. You can make a profile tool to create the disk by drilling a piece of gauge plate near an edge then cutting half of the hole away followed by hardening, tempering and sharpening. The advantage of this is only one tool body is required and a selection of discs could be made over time as the need arose. Larger radius disks may need a half profile tool to cut each side separately.

Martin C

Thread: Weird mill problem.
01/05/2017 22:40:58

If you are moving 15mm based on the scale on the handwheel then moving back 15mm based on the handwheel scale what you have is backlash. The point of the DRO is to allow you to make movements using the DRO not the handwheel scale. Backlash is not usually a problem on a lathe as you only work from one direction.

Is this what you are doing?

Martin C

Thread: Unrecognized gauge marked "PERLES"
01/05/2017 18:34:32

Bead, pearl,  stone gauge.


Martin C

Edited By Martin Connelly on 01/05/2017 18:35:06

Thread: Which is the best diameter for an ML7 Leadscrew.
30/04/2017 18:44:44

With a bigger diameter the load on the thread surface will be over a larger area. Perhaps this reduces wear.

Martin C

Thread: Boring head then fly cutting - OK or naughty step
30/04/2017 18:38:53

It is said that the proof of the pudding is in the eating. If you have an acceptable result it falls under the "more than one way to skin a cat" category.

Martin C

Thread: metric thread on my imperial lathe
30/04/2017 08:51:41

As you cannot reverse the motor the safest option until you have used the lathe for a while is to do as Hopper says and disconnect the drive to reduce the force required to manually wind the tool back to the start position. As an alternative to turning the chuck if you can devise a suitable hand crank for the left hand end of the spindle it would be an easier job. If you Google lathe hand crank there are lots of hits that will show the idea and lots of reasons to make one. Just remember that it should not be in place when the motor is engaged and started.

Martin C

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