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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: Lathe tool geometry for threading aluminium
06/01/2016 09:48:51

I agree with Hopper, the backgear is only going to drive the motor train if it is engaged for hand powered threading on my lathe. I would disengage the backgear and leave the drive pulley on the spindle unlocked so the motor was not able to drive the spindle, much safer when a crank handle is sticking out of the back of the spindle and no effort going into manually turning the motor.

Martin

Thread: Recommended material suppliers
05/01/2016 21:40:54

No, Speedy Builder5, he works for a Peterborough engineering company but they have a small workforce embedded in the place I work. He has to buy his materials through the Peterborough purchase department but what we are doing is not a formal setup. He has a regular requirement to supply a short piece of 1/2" diameter phosphor bronze so just wants to cut a piece off a bar with a hacksaw and file it flat on the ends. Almost all the machining done in the place I work is now done on CNC machines and anything else is put out to sub-con. The last manual machining department was closed last year. Add on the £70 an hour labour cost for in house work and you can see why he wants to use an informal system to keep his costs down.

I am buying the 1/2" diameter personally and so keep the larger diameter personally. He has already paid out for the large diameter bar but gets what he wants without any further cost reducing its diameter. I get the large diameter bar for the cost of the small diameter bar. Hope this makes more sense now. 

Martin

Edited By Martin Connelly on 05/01/2016 21:47:20

Thread: Emco Compact 5 Motor Problem
05/01/2016 20:00:00

Can you mount the motor on electrical isolators to see if that stops the fuse from blowing? That would confirm if there is a short to earth from the motor. If you put a low wattage incandescent lamp in series with the motor to restrict the current you will also find out if the fuse is blowing due to an internal short in the motor.

Martin

Thread: Recommended material suppliers
05/01/2016 19:45:09

I've just ordered some pb102 phosphor bronze from Maccmodels. Some one asked me today to turn a 350mm length of 26mm diameter pb102 down to 1/2" diameter. I had to check twice that I had heard him correctly. He has to buy from approved suppliers for his stock material and he asked for 1/2" diameter and got the 26mm at the price for 26mm bar. I said it seemed stupid to throw 3/4 of it away as swarf. We struck a deal instead, I keep the 26mm diameter bar and supply him with two lengths of 200mm x 1/2" which is what I have ordered. It saves him from having to pay for the machining (some bottles of beer in my case) to get the size he wants and I get a nice piece of raw material.

Martin

Thread: Warco BH600G Modifications (clutch, gears, 3 phase)
05/01/2016 18:33:17

Use a pound coin. It is very similar to aluminium bronze and the only part that needs to be in the correct material is the face in contact. There are plenty of forgeries in circulation so if you use one of those you are not breaking any law if you destroy it.

Martin

Thread: Who can regrind a shaper way?
05/01/2016 14:35:37

Any chance of scraping the surfaces yourself? I've never done any myself but I see a lot of posts where people claim it is easy. In this case the hard part is ensuring squareness of the finished surface to an existing surface if there is no adjustment in the machine's design.

Martin

Thread: Thread cutting and Change gears
05/01/2016 14:30:33

They can be used as idlers. Idler gears can be any size but they need to be a size that allows a set-up. If you have pre-owned lathe then there is a possibility you do not have a full set of gears and the duplicates can be used instead of idlers listed on a change gear chart that are missing from what you have.

Martin

Thread: Time for a name change?
05/01/2016 11:56:23

Good call Duncan, CNC is just another tool.

Martin

05/01/2016 11:47:22

Roy, most of my work on my CNC modified Smart and Brown and Rong Fu mill is done without a program. I go into the workshop and switch on the power to the laptops and machines and then do the same sort of thing any manual operator will recognize, set up a workpiece, set up the tooling. Work out the tooling position relative to the workpiece to know how much to move it to get the desired result, check the result as the work progresses. The difference is that I cause the tool to move by instructing the motion through the CNC program manual data input instead of by turning handles. No time spent programming at all for basic machining.

Martin

05/01/2016 11:31:14

There is a halfway point in home CNC between fully manual and fully CNC. I think a lot of home machinists who have CNC will work this way.

I made my machines CNC for times when CNC allows me to do things that are hard or possibly impossible to do without CNC. A lot of the time I use them with MDI (manual data input). There is not a lot of difference between turning a handle 1mm by hand and telling the computer to turn the handle 1mm.

What I get from CNC on the lathe is never having to mess about with change gears anymore. I can cut imperial threads or metric regardless of what gears I have or the leadscrew pitch. I can chose a feed per revolution and if it's not quite right I can try a bit more or a bit less on the next pass or even during the pass if it is long enough. Want to turn a bar down taking a lot of passes or bore out a small hole to a large hole? I can use a wizard and let it do the bulk of the work and take over for the manual input when I approach target dimensions. Recently I was asked to make a bellmouth for a carburetor intake **LINK** . It required an elliptical curve on the inside and a circular curve on the outside. I spent some time working out the maths equation for the coordinates for the cutter to follow then wrote a small program for the lathe. No sitting down with a PC and just putting a DXF into a CAM program. Formed the complete curve inside and out with a 6mm button tool without pausing between start of the curve and the end of the curve.

On the mill I can do a similar thing, use MDI to treat it like a manual machine with input through the keyboard instead of turning handles. Does winding a handle manually from x=100mm to x=200mm take more skill than telling the computer to move the table 100mm from 100mm to 200mm? I can tell the spindle to move down at a rate of 0.05mm per revolution to a specific depth when drilling a hole and tell by the sound and swarf coming off if it should be faster or slower feed. Does it really mean I have less skill than someone who is doing the same thing by winding a handle? I have still chosen the rpm of the spindle to suit the cutting tool the same as anyone working without CNC.

CNC does not de-skill someone, it just changes the skills used for achieve an end product. How much computer power is used to get to the end product will vary from person to person but for what I do it is only a small step away from manual machining. Hobby machining is a very wide spectrum of ability and processes.

Martin

Thread: Stirling Engine : Laura
05/01/2016 10:35:02

Make a stiff card radius gauge to check against if you are going to manually make the radius. It does not need to be a perfect curve as it going to be in the bottom a test tube that is probably not a perfect hemisphere anyway. It just needs to look good in the tube.

Martin

Thread: Warco BH600G Modifications (clutch, gears, 3 phase)
05/01/2016 10:27:01

Screw cutting up to a stop is going to be a case of immovable object trying to stop an irresistible force. Something has to give way and if you are lucky it will be a drive belt slipping. If you are unlucky, which is more than likely, you will strip a gear of some teeth, break a drive key, distort a shaft, damage a mechanism, break your half nuts or the leadscrew. All of these are considered bad and so not something to be taken lightly. Due to the high reduction required to reduce the carriage speed for fine screw cutting it has a lot of force trying to move it along the bed. Even using a handle and turning the shaft by hand you may not be able to feel the resistance of a carriage stop. My lathe has a shear pin in the leadscrew drive for when this happens and it is not the easiest thing to access and replace but it is considerably better than damaging something that is not designed to give under load (bust it once by inattention).

Martin

Thread: Fly Cutting
02/01/2016 23:40:18

The link to the photo clearly shows a ground tipped tool for flycutting. The text refers to cutting a slot with an end mill mounted in a collet. This is not flycutting with an end mill.

Martin

Edited By Martin Connelly on 02/01/2016 23:40:56

Thread: Casting brass or bronze
02/01/2016 10:37:59

UK HSE state that drinking milk does nothing to prevent metal fume fever. Milk is sometimes suggested for ingested metal based poisons but I have not been able to find definitive research on the subject of milk for the prevention of metal fume fever.

Martin

Thread: Fly Cutting
02/01/2016 10:13:42

Use a lathe bit in the chuck. I use a 6mm button tool in a flycutter for some work and the basic flycutter bit is ground like a lathe tool. There may be a need for some paper or card to be fitted between the chuck and the tool to increase friction.

Martin

Thread: Boxford VM30 Milling Machine Motor
02/01/2016 09:59:19

Get a vfd that is big enough to suit this motor and a larger motor as well. A 2kw vfd will drive anything smaller as well and you may want a larger motor in the future or to drive a different machine with the vfd.

Martin

Thread: Casting brass or bronze
02/01/2016 09:45:16

DMB, I tried to find evidence for the use of milk as something for welders to use as an antidote to welding fumes some years ago (for where I work) . I failed to find any research, do you know of any that exists, I came to the conclusion at the time that it may be an old wives tale but I would love to be sure one way or the other.

Martin

Thread: something simple!
31/12/2015 14:25:08

If what you have is like mine then there is a clamp screw on top that needs to be released and a pin in the disk at the collet end that needs pulling out. There is a retaining ring at the other end that may need adjustment to stop it binding on the body of the indexer. There are videos on improving the squareness of the Base that may help if you find them.

Martin

BasementShopGuy did the videos I am thinking of. 

Edited By Martin Connelly on 31/12/2015 14:31:12

Thread: First day on milling machine
31/12/2015 11:27:11

Andrew, I said maximum metal removal rates are for production environment, not that people should not know what they are or work close to them. I just think that that is something to work on after the basics of feed and speed are understood. These are suggestions for a beginner to consider after all.

Martin

Thread: Gloves
31/12/2015 10:32:25

Gloves seem to direct splinters into my skin so I just have bare skin when using the lathe and mill. I was taught it is better to lose a bit of skin than a finger or hand. I keep rolls of paper towel handy to remove gross contamination and wash frequently.

Martin

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