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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: Time for a name change?
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

Thread: Loctite - Can I warm it up, move the joint and let it cool again?
31/12/2015 10:11:06

Loctite sets chemically not by cooling. This implies it is not a thermo setting plastic so once the bond is broken it cannot be remade.

Martin

Thread: Feedshaft worm lubrication
31/12/2015 10:07:08

Power feed shafts do not spin at high rpm so will not sling the oil out of the trough so not a lot of topping up required, no grease sounds sensible.

Martin

Thread: First day on milling machine
31/12/2015 09:59:49

There are theoretical values of maximum material removal for given power but they are best kept in production environments. What you should be concentrating on at this stage is getting correct speeds and feeds for you setups. You need to keep the chip thickness in the correct range. This involves considerations such as number of cutting edges on a milling tool, the spindle rpm and material. You do not want the tool to rub as it just reduces it's life. Spindle speed is the same as drilling speed for tool diameter. Work out feed rate for a chip thickness of 0.05mm for example and time yourself feeding to see how you compare, no need to be cutting metal when doing this. This is assuming you are working manually. If you have power feed find out the relationship between speed setting and feed rate.

Make sure you understand the difference between conventional and climb milling and the importance of minimal backlash for climb milling.

You may not be planning to use CNC but if you load Mach3 and set it up for milling it includes a wizard for calculating feeds and speeds for given materials and cutters. There are probably others available.

Martin

Thread: Boxford goes crunch! Now refuses to turn.
31/12/2015 09:20:43

Oil on gears is less likely to form a grinding paste than grease on gears. Is there a Boxford recommended lubricant for these gears?

Martin

Thread: How can I tell if a carbide tip is worn?
30/12/2015 11:25:16

I have a broach cutter (trepanning cutter) with 55mm diameter. I mount these cutters in an ER32 collet mounted in the tailstock. The standard length is good for 25mm thick material but working from both sides increases this. I would use this to remove the core then finish with a substantial boring bar. For spindle speed I use a drilling feed and speed chart. When using hss tooling the drill speed for a 60mm drill is about the same as the spindle speed for 60mm turning, double for carbide. This is a starting point and can be tweaked if required. I have a 3 phase vfd so setting a suitable spindle speed is a case of nearest gearing then speed up or down to get best results. The feed per rev is also relevant to turning, the larger the diameter the larger the feed per rev should be. This keeps chip thickness more constant and pressure on the cutting tool similar at different diameters.

Martin

Thread: Fusible Plugs
29/12/2015 10:47:09

Lead has a higher melting point than eutectic solder (60 40 mix) so may be a consideration.

Martin

Thread: Question: mounting slitting saw
29/12/2015 10:43:25

I have seen arguments both for and against keys in slitting saws. The view of some people is that if no key is used then in the event of the saw being grabbed it will slip on the arbor so will not be destroyed. It does assume manual feed rather than power feed so operator response is rapid. I have no view to push either way regarding key or not but thought I would let you know the use of a key with slitting saws is debatable.

Martin

Thread: What did you do today (2015)
27/12/2015 19:13:27

Bri, if you have a single phase motor with a start coil and start capacitor then the start coil only starts the motor running in the chosen direction by supplying a suitable torque for a very short time. The run coils then maintain the motion. To reverse the motor the start coil gives an initial torque in the other direction. These start coil torques are quite small and of short duration so will not be sufficient to stop a running motor and force it to rotate in the opposite direction. You must allow the motor to stop before choosing the reverse direction. It is a characteristic of some single phase motors.

Martin

Thread: New precision chuck for milling machine
27/12/2015 17:19:20

I second Vic's comment. Most problems I have seen with big drill runouts is due to bent arbors. New arbors are quite cheap and swapping out an old one for new on your drill chuck may cure the runout. Most of the ones I have sorted out have been bent by people at work swinging a radial arm saw so that the chuck or drill bit in the chuck clouts a solid feature such as a vice. They then put everything away without telling anyone so the next person to use the chuck has to get the problem sorted out.

Martin

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