Member postings for Martin Connelly

Search for "Imperial Double Coil Spring Washers Thackery" on Ebay.

Martin C

Are you sure it was not a ferritic stainless steel. They can look like mild steel and be magnetic but tough to work compared to the real thing.

Martin C

I think it would be worth looking at a Joe Pieczynski YouTube series on making a single cylinder steam engine for an overview of the general process.

Part 1

Martin C

From the standard AT1, AT2, AT3 data sheet. TA common, TB Normally open, TC normally closed. 250VAC 5A/30VDC 3A

You will have to check with a multi-meter if this is triggered by starting the motor and stopping the motor.

Martin C

PS The data sheet shows the relay as optional. Out of curiosity I searched for images of the terminals. There are a few showing TA, TB and TC as solder pads on the board next to the UVW outputs. You will have to investigate for yourself if these are connected to a relay and need either wires soldering to them or a small socket/plug needs adding.

Edited By Martin Connelly on 11/04/2023 13:37:24

I have tripped an RCD on a circuit that has been isolated at the MCB by cutting through a wire and shorting the neutral to the earth conductor. As Willem says there is enough voltage in the neutral wire to drive the RCD into tripping. The neutral return has a small but non-zero resistance. Current still flowing through this resistance follows Ohm's Law to produce this voltage relative to earth on the neutral wire. The original live to neutral short probably produced enough heat to remove more of the insulation that had degraded. This allowed the second fault of neutral to earth shorting.

Martin C

Neil, I use chuck soft jaws frequently and see Jason has also used them in this build which I feel should be mentioned as well. They are good for ensuring parts are mounted concentric for second operations and also with the machined faces in the correct plane without a lot of checking, adjusting and repeating. They are also good for firm holding without marking the gripped surface. They really save time when there is more than one part with the same diameter to be gripped for second operations.

Jason, I am curious about the soft jaws in the chuck used for milling the ellipses. Were they milled to suit in the mill or just left as they were from when they were on the lathe?

Martin C

Is the lathe useable at all? If so you could bore the spare oversize to fit a plug in it and re-bore to the correct size. Another option would be to use some drink can to shim the pulley. It may take a few layers as the wall thickness of cans I have measured is 0.1mm. Try a few other things like oil cans, you may find a more suitable thickness.

Martin C

I've got the earlier Brother Pt-PC printer but have to use it with a no longer used laptop with XP on it. I can run the software on later machines but it needs a serial port and trying to get a serial port to work via USB will cause hair loss. When the tape cartridges are used up it will become WEEE.

Martin C

I have managed to snap an M2.5 insert screw when using a 2 insert Ø16 end mill at a depth of 7.5mm in steel. It was an original and probably not the best quality as the head was rapidly showing signs of damage in use. I swapped out the other screw as well when I replaced it. Based on Jason's post I was probably pushing it a bit too far on depth.

I thought I was going to have a job getting the remains out but as soon as I touched it with a small engraving tool in a Dremel it spun out.

Martin C

A 10:1 gearbox will take your 3Nm torque close to 30Nm torque (some friction losses) and will cost about £60. This is a cheaper option than a new motor and driver and will out perform just about any stepper motor without a gearbox. It is certainly something that should be considered when speed of operation is not a factor you need to consider but raising some weight is. I use this combination on my mill for raising/lowering the spindle without any spring or gas pressure assist.

Martin C

You can buy in line speed reduction gearboxes for most standard stepper motor sizes. If you buy a stepper that turns out to be underpowered then adding a gearbox is a relatively minor mod that will increase the available torque at the expense of speed. I would not think speed is that important for raising and lowering the Z axis.

Martin C

I had some Bilofix when I was too young for Meccano

Martin C

If you put the tube at an angle of 20.91° to the horizontal then the two angles you need to cut are 60° from the vertical plane that goes through the tube centreline. It should be possible to make a simple wooden jig to allow them to be marked out like this.

A chop saw with a tilting head set to 30° off vertical and horizontally rotated the 20.91° will also make this cut but cutting steel may be an issue however cutting a wooden saw guide/marking out jig should be easy.

Martin C

As Robert points out the voltage of a true sine wave AC supply is usually given as an RMS (root mean square) value. For 230V mains this means the peak voltage is the RMS voltage multiplied by the square root of 2, 325V. For a 380V RMS true sinewave the peak voltage will be 537V. For a VFD where a circuit chops the voltage to give an approximately sinusoidal voltage it would be likely that the peak is close to 500V. Without a load to feed it is possible that there are smoothing capacitors on the output that are charging to this peak voltage but not being allowed to discharge and so reach 500V and stay there. As the peak of a 380V AC supply is over 500V I would not worry about connecting a 380V motor to this VFD as they are built to take this voltage.

RMS is the voltage of an AC supply that has the same output power as a DC supply at that voltage. A 230V RMS AC supply will cause the same heating effect in a 1kW heating element as a 230V DC supply. It is based on the area between a sine curve on a graph and the line passing through the centre of that sine curve. For an AC voltage that line is usually the X axis. This is how the square root of 2 ratio of peak to RMS is mathematically derived.

Martin C

Short video showing the effect of residual stress in cold rolled steel that is only machined on one side.

The latest version of Autodesk's (free to use) Trueview will open all of Autodesk's DWG files to look at them, print them and convert them to older versions. This will allow older programs to open newer files but may need careful scrutiny to ensure nothing is missing or changed due to the conversion.

Martin C

I think the only thing I ever really checked on my 6" Eclipse vice was the fixed jaw's perpendicularity. That is easy to get right with a bit of shimming and/or stoning between the vice body and the jaw. Then, as suggested above by Mike, that is your reference surface for all future work. When I put a 123 block on parallels and pinched it with a roller between the 123 block and the moving jaw both parallels had the same feel of resistance to sliding out so I didn't go further than that. Across the vice bed has always been fine based on the results of surfacing both sides of a workpiece. It could be argued that if you have a well set up fixed jaw then for a lot of jobs one parallel is all that you should use, the second parallel just helps with positioning the part in the vice before it is tightened (a third parallel helps position a roller in this situation).

Don't overtighten the vice either, this will always move the fixed jaw relative to the base as nothing is perfectly rigid except in mathematics.

Martin C

If the only part of the cutter being used is the bottom 1-2mm then surely for a lot of the work an insert cutter would be a better option. No sharpening, just rotate the insert or throw it away and replace it if damaged. I know this is no good for things like plunge cutting and narrow slots but an all round course should cover insert milling cutters anyway.

Martin C

Mag base with some rigid plastic sheet with a small overhang at the top gives flexibility. I just aim to keep the chips away from the operator's direction to reduce the area to be cleaned up.

Martin C

Not something I do a lot of but CNC so always power fed when it is done.

Martin C