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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: Dovetail cutter.
28/08/2016 19:29:35

I am curious about the back edge of the inserts. They look to me like they will have a larger radius than the cutting edge and as a result will rub. Is there any sign of this?

Martin

Thread: Technique Required to Make Accurate Backplate
28/08/2016 19:21:03

After cutting the thread on backplates I have made I mounted the plate backwards on the spindle thread and skimmed the back face. This makes sure the back face does not have uneven contact that may cause runout if the backplate is screwed on more sometimes than others. Have you done this?

Martin

Thread: Acceptable wear on leadscrews and nuts.
26/08/2016 11:56:00

It can be argued that wear and backlash on the carriage lead screws is not a problem since you are likely to be approaching the work piece from only one direction and should be checking progress as you go. There are lots of factors that affect the resulting diameter when turning down to size as well as lead screw wear, such as workpiece deflection, tool tip wear, tool tip height (if it is not quite right) and depth of cut.

Wear on the screw cutting lead screw will show up as uneven threads but only if you are cutting long threads. It would take major wear to produce noticeably uneven pitches in a thread that is only 6mm or 1/4" long. If your intention is to make your own long lead screws with good precision then wear in the lead screw will be a problem.

If there is enough wear to make you thing the half nut threads are likely to shear then replace the half nuts otherwise I think you can use it and not worry unless you need to do a long thread that requires precision. Does the lead screw have the option of swapping it end for end as some lathes do to put worn sections where they are least used?

Martin

Thread: Compressor only works for one cycle
25/08/2016 14:06:41

Are the fins on the top of the cylinder getting hot to touch? Sounds like a thermal problem rather than electrical. Heat soak may be causing loss of clearance somewhere in the compressor.

Martin

Thread: PCNC770 - The Wait Is Almost Over....
18/08/2016 09:56:06

Oh look, someone caught their long sleeve on the wrong switch.

Martin

18/08/2016 08:35:47

I can give you bad press for the publicity photo, those sleeves look far too long and baggy for safety to me.

Martin

Thread: Decoding Abbreviations on a Technical Drawing
17/08/2016 15:04:21

Here's another abbreviation for applying to note 1 on the drawing. WTF

Martin

Thread: Lathe backstop
17/08/2016 14:58:34

My recent requirement for a backstop was for 6 spacers. I put a 3/4" collet in the spindle and a piece of 3/4" tube in that. Mounted the chuck over the tube and cut the parts to length. It helps to have a lathe whose collets have a through hole and a draw tube for pulling them in.

Martin

Thread: bsf thread
17/08/2016 14:43:34

Funny old world! Last week a colleague asked me to make a 3/8 BSF hex head bolt for his brother's old motor (don't know any more than that). They had tried to find one that did not require the purchase of lots of them. I found one that was too long but had a long enough plain section to cut more thread on. Cut off the excess then cut the thread on the lathe and polished the finish with a die nut. He was very happy and at some point I am sure he will be helping me with something I need.

Martin

Thread: Old Boxford Lathe
15/08/2016 11:35:49

Before you put any grease in the grease nipples make sure they are not oil nipples.

Martin

Thread: Deep throat drilling, a quick lashup machine
15/08/2016 10:28:53

What sort of hard drive had a linear slide in it that was big enough for this? Or was it from a removable drive mounting?

Martin

Thread: VFD drive for a pond pump?
12/08/2016 14:51:09

If you choke off the flow from a centrifugal pump the impeller starts to stir the some of the fluid instead of moving it through the pump. As a result it does less work so the speed increases and back emf rises. The power requirement is a function of mass flow through the pump, the rate of change of momentum of the fluid is equal to the force that causes the change. Just keeping the same bit of fluid spinning does not change the momentum of that fluid so zero rate of change no force required (apart from friction losses). Think of the note change on a vacuum cleaner when the suction is blocked off, it will rise as the motor spins faster.

Martin

12/08/2016 11:06:35

What you have sounds like a shaded pole motor. The speed of rotation is linked to the frequency but since it is a single phase motor you cannot drive it with a 3 phase VFD. The VFD would see an imbalance in the output and shut off due to a perceived fault. BobH's solution may be a better option.

Martin

Thread: gopro hd hero b
11/08/2016 14:44:17

You don't need wifi in the workshop. The camera connects to the pad (or smartphone) by wifi directly not through any other network so you can use it in the middle of nowhere if necessary. It is also far easier to change settings using the app available for the operating system on the pad/phone (eg Android) than working through the menu system on the camera with a very small LCD screen.

Martin

11/08/2016 14:30:24

They do not have viewfinders so aiming them is a bit hit and miss. You can connect them by wifi to a tablet to see what it is looking at though. As a person who makes things (an assumption since you are a member of this forum) you could probably make some sort of clip on sighting system if you wanted to. The field of view is quite wide as well.

Martin

Thread: Setting Up a Workshop Special
11/08/2016 14:10:03

Maybe a list of reading material could be compiled, I am sure the members could come up with some useful suggestions.

I would suggest Model Engineering: A Foundation Course by Peter Wright as a good starter for a complete novice.

Model Engineer's Handbook by Tubal Cain also has a lot of useful information in it.

Martin

Thread: Aircraft General Discussion
11/08/2016 14:00:29

Hth, there is very little room for error when you are flying a display close to the ground. Also if there is any mechanical failure you have no room to recover and consider what to do next. There are also more birds near the ground for a bird strike. In order to entertain the crowd aircraft are flown close to the limit of what they can do safely. Displays put more stress on an aircraft than the boring but safe patterns flown by passenger aircraft. Finally human error. Set the local air pressure at ground level wrong on your altimeter then fly into the ground that is twenty feet higher than you thought.

Martin

Thread: Bronze Bearings
11/08/2016 13:00:13

The halves should be split before boring and shimmed when clamped together for drilling and boring. You may know this already but I did not think it would hurt to make sure.

Martin

Thread: is this motor suitable for a milling machine
11/08/2016 12:51:47

The 17.8 amps may be inrush current when first switched on as capacitors are charged, these inverters have quite high capacity ones inside. The current draw when running will depend on the motor and load but should be proportional to the load the motor is taking. I would give it a go and see what happens. If it trips a circuit breaker then reset it and try again, if it is capacitors being charged then once they are full the inrush current will drop off.

There is a possibility that the maximum current given is for an inverter with a motor matched to its maximum output and set up to run at startup. Most default to not running at startup but if you have one set up in a factory where power trips regularly you may want automatic restart when power is restored.

Martin

Thread: Setting up a rotary table with chuck
10/08/2016 11:02:11

As Martin K says above centre the RT then mount the chuck. There are plenty of YouTube videos showing this.

**LINK**

Martin C

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