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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: Milling around with bits
16/04/2021 17:49:27

Do you understand the difference between climb milling and conventional milling, it sounds like you may be climb milling on a machine that is not suited to it (juddering). There is a guide that can be reached from the home page but here is a link anyway.

Why climb mill?

Also as Ian said aluminium and its various alloys can easily clog up the flutes or stick to the cutting edge which causes problems. The fewer flutes the better with these metals, you can get special cutters with one flute but mostly two works ok, three at a push and avoid 4 flutes. Use polished cutters not coated as well. As soon as the cutting action starts to change stop at a convenient point and check for build up on the cutter. Some people suggest paraffin as a lubricant for aluminium but the smell is quite strong and you probably don't want a build up of flammable fumes in a workshop.

There are rules of thumb for cutting depth based on the tool diameter and you should learn about speeds (rpm) and feeds (thickness being cut by each pass of a cutting edge) to avoid either rubbing or overstressing the tooling and machine. There are online calculators to help with feeds and speeds.

Martin C

Thread: High Temperature Air Source Heat Pumps for Domestic Heating
13/04/2021 14:02:14

The outside units are able to detect ice build up and go into de-icing mode. Mine iced up once this winter when I left it on overnight due to the predicted low temperatures with wintry showers and you could hear the change in the pump when it went into de-ice mode at about 07:30. Returned to normal after about 10 minutes. I also have an app on my phone that controls the unit so I can set schedules for how I want it to work. There is also an energy consumption report that does days, weeks and years so you can compare day to day or year to year as well as telling you what the consumption of electricity has been in the selected period. Yesterday it used 13.8kWh. Last week it used 117.3kWh. I do not have a full year's figure yet. The highest month was January when it used 855.9kWh, by March it was down to 508.7kWh. I use the scheduling to switch it on at a high temperature in the morning when off peak rates apply then back the temperature back down when normal electricity rates apply. This was the only source of heat used, about 170m², no back up required but I do have 2 electric towel rails. Hope these figures help.

Martin C

Edited By Martin Connelly on 13/04/2021 14:02:33

Thread: 24mm end mill for 16mm collet?
12/04/2021 15:01:54

I would consider one of these Ø24mm Hole Saw Cutter High Density Carbide Teeth for Stainless Steel Metal available for about £10 when searched for on line.

As an alternative at a higher price Ø24mm Rotabroach mini cutter and matching arbor.

Rotabroach mini cutters

You need the RA118 arbor for cutters over Ø21mm.

Rotabroach are more expensive but are made to accurate diameters.

The pipe fitters where I used to work used them on 316L stainless pipes in preference to drills.

These types of hole saws are better for sheet metal than drills when the diameter is a multiple of the thickness as is the case here.

Martin C

Thread: Laptop with a SD card slot
12/04/2021 14:37:56

I have an old router plugged into my home network (via powerline adaptors) that is configured just as a switcher. I have plugged a Wavlink network USB port into it and a 4 way USB hub into that and can run USB memory sticks, USB printers and USB external hard drives on it. I have not tried it with external CD but have just tried a USB SD card adaptor and that works fine. The Wavlink server allows plugged in items to be connected or disconnected so I leave the external 4TB drive disconnected most of the time as it slows printing down if it starts indexing. This is using a Windows 10 laptop.

Martin C

Thread: Horizontal Bandsaw Problems - -Advice Please.
07/04/2021 13:47:07
This video shows a blade tension gauge in use and explains how it works. The interesting thing is that it is all based on the blade length change due to correct tension. So in theory if you know the length of your blade and the required tension you could calculate how much a tensioning screw of a given pitch needs to be turned to go from the taking up slack position to fully tensioned. It will not be as accurate as a professional gauge but should put you in the correct ballpark for blade tension.
Martin C
07/04/2021 07:59:35

I have fallen foul of the overtightened guide rollers and ended up with a distorted and prematurely snapped blade so don't feel too bad about it, you are not the first and probably will not be the last.

Tension is sufficiently important that industrial machines often come with means of setting it correctly and it is usually a lot higher than you would expect. I have seen them with hydraulic piston tensioning operated by a screw driving a piston in a pressurising pump and a gauge with a narrow pressure band marked on it. I have also seen screw operated ones with parallel stacked Belleville springs where the operating screw has coloured bands on a collar and there is a pointer on the frame to line the bands up against. As the tension is increased the springs compress and the screw and collar moves to the point where the pointer indicates correct tension. Where they were not fitted with an inbuilt system like this you bought a band tension gauge to check the blade. A gauge like this is probably not cost effective for occasional home use but a saw in regular use that is having blade changes weekly benefits from getting the tension right. If the blade does not twang when plucked it is probably too slack.

Martin C

Edited By Martin Connelly on 07/04/2021 08:03:36

Thread: Home Made Rear Toolpost Issue
05/04/2021 15:44:01

Have a look at this Youtube video from Winky's Workshop. Interesting how much difference the chuck overhang causes. Collets always make parting off easier as well.

Martin C
Thread: Probem with soft limits mach3 turn
03/04/2021 08:21:58

I use a clamp on limit switch for negative Z axis moves. The option of using collets or a chuck makes a fixed one problematic as mentioned by John. I use this for homing/limits once the setup is done so that any error or overnight shutdown can be recovered from with minimal effort. You could easily mount fixed ones on the X axis and moveable ones on the z axis and then not worry about soft limits, just need to remember to set them up after things like chuck changes.


Martin C

Thread: Electric Smart Meters
01/04/2021 17:33:50

The big lie regarding end users saving money is exposed here. Suppliers-charged-14p-day-rent-smart-meters.

Martin C

Thread: CNC - What's the Problem?
01/04/2021 16:13:17

Want to create a nameplate? F-engrave is free. I've also just downloaded Estlcam 11 (another free program) to have a play with. It loads a DXF file (available from plenty of CAD programs) and creates the Gcode program for the part and also simulates the program running. Just an few examples of the useful free programs available.

I use Mach3 on old laptops running XP that were going into the WEEE waste at work if I didn't salvage them. I have external motion controllers so an old computer works fine. On the lathe I use a wireless mini keyboard as a pendant control. I have a wireless pendant with MPG (manual pulse generator) for use on the mill because it has two more axes than the lathe.

You can download and run Mach3, F-engrave and Estlcam onto a windows 10 computer and play with them to see what can be done without knowing any Gcode and without buying any hardware.

Martin C

01/04/2021 07:57:48

"How much fun is it to push a button?"

It's more fun than constantly cranking handles. Wasn't that used as punishment in prisons at some time in the past?

There are a lot of people who are part way to just pushing a button with DROs being a common addition so having a bolt circle option available. Then there are all the ways people have added motor drive to the lead screws so they can just push a button. An ELS is just short of CNC on a lathe.

You can use CNC machines in MDI mode (manual data input) where you use it just like a manual machine but instead of cranking handles you just instruct the machine to move to the required position at a given speed. Not all CNC is create a program, set everything up, press a button, remove finished part.

Martin C

Thread: Vehi cle Tax Scam
30/03/2021 08:26:36

Ways to spot a scam email.

It will be a general text that can be sent to anyone without raising questions of why have they sent me this obviously wrongly addressed email.

It will not include your name or address or vehicle details or tax details or your sex (eg Mr or Mrs) or postcode or dates or the last two digits of a bank account they are referring to or anything else that makes it a personal email specifically aimed at you.

Anything that is not explicit in who they are addressing to can be ignored even if it is from the DVLA, police, HMRC or any other organisation. It is no different to an advertising flyer sent to "the occupier" at a property. It's a good reason to have an email that does not have both your first and last name for the scammer to pick out.

Martin C

Thread: Rubbish Milling Finish in Aluminium
29/03/2021 08:42:29

Look at the size of Jason's chips and then at yours. Jason is feeding fast enough to be cutting, I think you are feeding too slowly and probably rubbing as much as you are cutting. Plus the other points regarding sharp tools and fluid to help. Find a speed and feed calculator on line and learn how fast to turn the handwheel for the suggested feeds. For a 3 flute cutter Ø5/8" with rpm at 600 you need to be feeding in at about 3.5" (90mm) per minute as a starting point then adjust feed up or down to suit the actual conditions. For a 2 flute cutter the feed would be 2/3 of that required for a 3 flute cutter, 60mm/minute.

Rubbing produces heat that can cause the aluminium to become tacky and help it stick to the cutter which adds to poor finishes.

Rigidity of workpiece holding is also very important. Looking at your picture the vice has serrated jaws. To me this makes it look like a drilling vice and not a milling vice which usually have smooth jaw faces. if it is not a milling vice that may also contribute to a poor finish.

Martin C

Edited By Martin Connelly on 29/03/2021 08:46:30

Thread: Removing a J2 arbor from a drill chuck
27/03/2021 11:23:48

I have managed to get them out of the chuck with a suitable sized open end spanner after wedges failed by splaying out. The arbors are soft centred so last resort is to cut them off and drill out. They are a cheap throw away item so not a big deal. Just size the drill to the smallest diameter of the J2 taper. Once the centre is gone the pressure on the face of the taper usually gets reduced to the point where the remains come off with the drill.

Martin C

Thread: Care of morse tapers
26/03/2021 08:08:39

From the steel construction industry:

The corrosion of structural steel is an electrochemical process that requires the simultaneous presence of moisture and oxygen. In the absence of either, corrosion does not occur.

Martin C

Thread: Endmill smear of metal
22/03/2021 07:55:23

Often beginners overspeed and under feed. Set the speed (RPM) correct for the material and tool (diameter and tool material are taken into account as well as the number of cutting edges) and feed fast enough to make chips not filings.

There are plenty of feed and speed calculators on line but using Andrew's speed of 2500 rpm and a 3 flute cutter you need to be feeding about 50-60mm/minute. If it is a 2 flute cutter then feed at 2/3 of this and a 4 flute cutter feed at 4/3 of this. If you are turning handwheels find how fast you have to turn a handwheel to achieve something like 50mm/minute (2"/minute) feed and it may surprise you.

A tool that is rubbing not cutting will spend a lot of time rubbing its cutting edge off compared to a tool that is fed fast enough to cut. If for example you were being overly timid and were feeding at 5mm/minute the cut would take 10 times as long and so the tool will suffer 10 times as much wear doing the same job.

Martin C

Thread: Flat bottomed hole with a boring bar - technique?
18/03/2021 10:16:57

Regarding the direction for boring I usually do the direction of movement away from the centre line for diameter and in from the open end. This makes sure the forces from cutting material are always pushing the tool back against the leadscrews. I would do this part by leaving a small machining allowance on the bore and the depth then take a final pass starting with the tool outside the part, moving the tool from the centreline side out to the final bore setting, move in to final depth and then move toward the centre line. Withdraw the tool.

Martin C

Thread: Brass facing finish.
18/03/2021 07:47:48

This happens a lot with round bar stock and I have often wondered if the production methods resulted in a non-homogenous material that triggered this sort of result.

Martin C

Thread: Making hexagon nuts on a rotary table & mill.
17/03/2021 15:21:28

How about this as well. ER chuck on a rotary table. Does not even need accurate set up if you only cut on one side of the stock and the stock is oversize by a small amount. Drill, tap and use a slitting saw to cut off.


Martin C

Edited By Martin Connelly on 17/03/2021 15:27:09

Thread: RH vs LH threads
14/03/2021 09:28:59

I don't know if it is the case with all modern cranks but I agree with David on this, when the pedals were the screwed in type they came marked LH and RH on both the pedals and cranks on ones I changed out.

I recently re-did the preload on my mill's spindle bearings and I have a written note on the mill saying LH threads and an arrow to the top nuts. I remember the first time I tackled the job I was puzzled over my inability to get the top locknut loose. There was no visible thread to give a clue so when it finally dawned on me that it was LH I put the note on to make sure I didn't go through the same head scratching in the future. Once again this makes sense from the point of is it tightened in normal use? With the potential for intermittent cuts causing vibration it seems to me that the importance of the nuts tightening in use rather than loosening is quite high.

Martin C

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