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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: Mystery Tool!
25/11/2019 15:56:47

Is the spiked thing for curling off butter pats?

Martin C

Thread: Tapping a nylon hole.
25/11/2019 15:53:33

A helicoil tap for M10 may cut the thread to the required size if you have one. It is the same pitch but larger diameter than a normal M10 tap, test it on something first or only cut partway into the hole to ease the pressure.

Martin C

Thread: 1P 240V Lafert Motor In Colchester Student Lathe - Wiring Help
25/11/2019 15:49:35

Could be start coil. Possibly a timer and relay to cut it off after starting instead of a centrifugal switch. Are there remote mounted capacitors?

Martin C

Thread: "Mystery" Tool
24/11/2019 21:49:36

Back stop for short lengths in a chuck so you can machine to length easily. Very useful if you need a number of parts turning to the same length. I put a collet in the spindle and put a length of pipe or tube in the collet to do the same thing.

Martin C

Thread: Holding screw-end end-mills/slot-drills
18/11/2019 18:39:15

If you haven't got a ball bearing nut for your ER25 get one and increase the clamping effect with the same torque you are using now. Put on the recommended torque and keep the tooling and collet oil free before fitting and tooling doesn't pull out.

Martin C

Thread: Aircraft General Discussion
18/11/2019 16:46:25

Thanks, your link does mention Summit Air as operators of two of them. Stall speed of 69mph which is why it seemed to be travelling very slowly (flaps down in photo).

Martin C

18/11/2019 16:13:20


Spotted this flying caravan today, well it is boxy and as slow as a caravan (I was outside and had time to go in and get my camera). It seems to be a Ledcor/Summitair aircraft but they are based in Canada's Northwest so it seems out of place. Does anyone recognise what it is or know where it is based?

Martin C

Thread: 3 phase motor
17/11/2019 14:09:43

Old Mart has touched on an important point. The rpm of a three phase motor depends on the number of poles it has. To swap a single phase out and three phase in it is best to know the rpm of the current motor before assuming a straight swap will give the same resulting speed range.

The nominal speed of a 2 pole three phase motor at 50hz will be 3000rpm. Double the poles and it drops to 1500rpm, triple the poles and you get 1000rpm. It should be possible to get a suitable motor to swap in but it may not be the one you have.

Martin C

Thread: Screwcutting on the lathe
17/11/2019 13:57:27

Has this lathe got back gear? One where you operate a lever to engage the back gear and then disengage normal drive by means of a pin or lever or something similar? Failing to do disengage normal drive when in back gear locks the drive on the lathe quite effectively.

If you only have speed control of the motor to change speeds then low rpm probably gives low power. If this is the case then consider a spindle crank, these have been discussed a number of times in past threads.

Martin C

Thread: Ornamental Turning
17/11/2019 13:37:09

J. H. Evans wrote Ornamental Turning in 1886. This is now available in paperback form (1993) so you may be able to find a copy.

Martin C

Thread: Positioning bushes for welding
17/11/2019 13:29:43

Welding and accuracy are somewhat mutually incompatible. The weld pool freezes at a high temperature and all the way from freezing to room temperature it is contracting and creating stresses. These stresses will distort the fabrication to some extent. Fabrications for tools and jigs have to be stress relieved after welding and before machining as a result. No matter how accurately you position them for welding expect some movement away from the ideal position.

Martin C

Thread: Star to Delta
15/11/2019 12:04:40

A reading of 44 ohms between any two terminals in the connector box of a star connected motor means each winding is 22 ohms. If the motor was in delta then the 44 ohms reading would be from a coil resistance of just under 30 ohms due to 2 in parallel and one in series being 15 + 30 roughly. Since the aim is to change from star to delta this means the coils are 22 ohms.

Martin C


Failed the fastest finger first challenge!

Edited By Martin Connelly on 15/11/2019 12:06:28

Thread: To pin, or not to pin
12/11/2019 19:43:24

There is always the risk that you will machine something that gets hot and the heat transfers to the joint. That is when you will find out how well Loctite works when it is hot.

Martin C

Thread: Slitting saw
12/11/2019 19:38:26

When I was at work I arranged the regular sharpening of 300mm (when new) cold saw blades. We waited until we had more than 20 then sent them off. It worked out quite cheap per blade that way. They were done on a CNC sharpening machine because the previous system used before that, which pushed the blade around by means of a pawl ratcheting around the teeth, tended to produce eccentric blades after a few sharpenings. It seems to me that if you have a Dremel mounted on a CNC mill with a 4th axis you could easily sharpen these blades (with a suitable dust extraction set up). I might have a go and see how it works out

Martin C

Thread: Rapidor Power Saw
06/11/2019 20:01:45

A few things can cause this, too fast a feed putting pressure on the blade (or too much weight if it is not a controlled feed), blade not taut enough, blade blunt or blade clogging up. These all cause the blade to distort and result in cuts going off to one side or the other. Unusually the material can cause problems if there are internal hard spots or stresses. Worn or loose blade guides on a bandsaw can cause this, if it is a powered hacksaw then material trapped between the blade and the saw where it is mounted can also cause blade wander as the blade is not correctly positioned relative to the hinge point.

Martin C

Thread: Cutter Advice for silver steel Micro machining
02/11/2019 19:20:11

Chris, reading your original post I get the impression that you think aluminium inserts are made of aluminium. This may not be the case but if it is I would like to point out that these aluminium inserts are carbide ones designed and made to cut aluminium. They will not wear any more quickly than other carbide inserts.

Martin C

Thread: Could anyone let me know what these are
19/10/2019 19:07:30

If the flat topped tool is a metric or imperial length (measured to a reasonable tolerance) it may be a height setting pillar for items that are quite tall when clamped to the machine bed.

Martin C

Thread: VFD Instructions
17/10/2019 17:28:14

Paul, if you have a 1.5kW motor that is not fully loaded it will seem like a small motor to the VFD. It would be a poorly designed VFD that could only be used with fully loaded motor running at max rated power.

Martin C

Thread: What is the way to put these holes in the right place?
08/10/2019 19:39:29

Dovetails are measured with cylinders to avoid problems like this. Do you have any silver steel or other ground rod that could be used against the angled face to allow more accurate measurement?

Martin C

Thread: Issue 286 Spot drills
01/10/2019 08:10:13

Is the theory of larger angles for spotting drills matched by something similar for centre punches? I have bought centre punches in the past that have been supplied with quite a blunt point ground on them. It may be that they are intended for drill positioning purposes where sharply pointed ones are not or that they are for larger drills with a wider chisel point.

Martin C

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