Member postings for Trevor Wright

Lloyd,

Have always parted off by hand feeding, you get a feel for the cut throught he handwheel.

Squealing usually occurs when the workpiece is spinning too fast - chatter when parting will usually wake the neighbours and look like a ploughed field.....

Keep the revs down, lots of lube (WD40 works well) and try hand feeding.

Trevor

No matter how rigid a machine tool or boring bar is there will always be some form of spring and retracting the tool will always cut metal.

Even on industrial machines if a tight tolerance was required I would always cut to within 0.1mm of size, 2 spring cuts, measure then take the finish cut.......and probably another spring cut to finally hit the required size.

Using the spring to take a back-cut will usually leave a better finish as you are cutting with an edge of the tool that is still sharp, and is less likely to chatter as the tool is being pulled rather than pushed.

Trev

Another extinguisher story.....

Went to pick the spare up from under a shelf without realising that it was the only thing holding the shelf up......lots of heavy steel off-cuts on the floor and me dancing like John Travolta.........

I use the CO2 bottles for my hobby, building fighting robots (RobotWars) - a full bottle fed into a 100mm diameter ram will generate 2 tons of lift, and have had burst discs go on hot days so I have an image of Stub trying to switch it off.......

Trevor

Edited By Trevor Wright on 31/10/2012 12:59:01

Would go for the steam engine, but without the blast furnace there was no quality steel for the boiler, without the lathe the cylinders could not be bored. Without Iron ore and coal in the ground the blast furnace was pointless.....without power the the lathe would not turn.....

To me the industrial revolution may not be a machine in itself, but as a whole it happened because of all the above mentioned factors and the world changed for ever.........for good or bad......

Waiting to be shot down........

Trev

Went many times as a child and the place was vast, went again 6-7 years ago and it was a shell of it's former self.

The Rocket was there (but it is not yellow) as it is the original, and Babbage was at the side, only found it by glancing sideways when reading about the Rocket.

The ground floor is the best part of the museum, I was really disappointed with the rest. I know the old musuem was a real rabbit warren but there were thousands of exhibits, including the Kitty Hawk and Logie Bairds first camera, where are they now?

had a reprap Huxley from Easter, took 2 weeks to assemble and wire up, 3 weeks to suss out the computer speak and set up the laptop and about 10 weeks to get repeatable results....

That said, it is the most amazing piece of kit I have used to date.....you are only limited by the size 140x140x140mm and your cad programme - "Tinkercad" designed for kids but accurate to 0.1mm is brilliant, was using Solidworks originally but is too sophisticated for the Huxley slicing software.

We took on a CNC programmer/operator recently with 15 years experience in the trade - he cannot work a manual machine.........I kid you not.....

I am a skilled miller/fitter/turner according to my indentures, but my current company re-defined me as a skilled precision machinist - sorry, but don't they work sewing machines?

As an apprentice there was no guarantee of a job at the end - there was - but there were 400 apprentices out of 2500 staff at any one time, could you see that happening now?

A 4-jaw self centre-ing chuck will not hold bar that is not round - material that is supposed to be round but isn't, most stock bar that you will buy from suppliers - causing it to rock from side to side. We bought one at work and scrapped 3 jobs before the chuck was found to be the problem. It is still sitting on the shelf unused now.

3-jaw selfcentring will grip well and if in good condition hold true, soft-jaws can be trued for each job as needed - highly recommended.

If you want to grip a bar tightly then an independant 4-jaw is the best - a pain to set running true - but is more versatile in the long run if you are not in a hurry.

Trevor

The biggest problems were that there is another gearbox between the change wheels and the leadscrew which gives another gear combination set - and is different for each selection lever. Also the recommended output gear of 30 teeth cannot be driven from the 120 tooth gear because the 127 gear hits the output shaft.

It was only when I recognised patterns of multiple tpi that it was possible to select a ratio to give a coarse pitch, work out the change wheels, and use the gearbox selections to acheive the other pitches.

Hope that makes sense.......I agree with the calculations above, unfortunately, the practical applications of the calculations are not physically available.

Trevor

Hmmm table was spaced out when I wrote it, still, it is just about understandable.

Trevor

Murray, you are correct in that I do not have a manual, but me being me, I like to figure things out for myself.

Anyway, most of the above posts are reccomending the gears that I found did actually work. Here is the table I created;

Pitch... Lever/Pos..... Changewheel sequence...... %age error

3 ...........C6................. 35--127/100--57 ...................0.2%

2.5 ........C6................. 30--127/100--57 ...................3%

2.25 ......C5 .................30--127/100--57................... 0.2%

2 ...........C4 .................30--127/100--57 ...................0.2%

1.75 ......C1 .................35--127/100--57 ...................0.2%

1.5 ........C1 .................30--127/100--57 ...................0.2%

1.25 ......B6................. 30--127/100--57 ...................3%

1 ...........B4 .................30--127/100--57 ...................0.2%

0.75 ......B1 .................30--127/100--57 ...................0.2%

0.5 ........A4 .................30--127/100--57 ...................0.2%

Apart from the 2.5 and 1.25 pitches I would say that all the settings are as near perfect as you are likely to get.

Trevor

Edited By Trevor Wright on 25/07/2012 21:33:13

Thanks Keith, programme sitting on my desktop as I type, enough combinations to keep me busy tomorrow night.................

Trevor

Having bought a MK1 Bantam for the garage I am ready to screw-cut metric threads.

I have hit a brick wall when setting up the changewheels - I can get within 1% of true pitch but cannot mate outer threads with tap cut inner threads without making the thread sloppy.

All my calculations are way out and am ready to ask for help........

I have all the change wheels including the 127 tooth gear but cannot get the right combination - can anyone help with links to where I can get the information? Or have done it themselves and can post a photo of their setup?

Trevor

have machined a lot of Titanium in my time, mostly grade5, and on serious machines, would not recommend it as a material for engine blocks and Ti-Ti rubbing is an absolute no-no.

Have recently cut plate with an angle grinder, the fire aspect that was mentioned earlier was not an issue. In fact it cut better when the plate glowed red.......the sparks are ridiculously hot though and burnt a hole in my trousers and jacket......

Tapping is a nightmare unless you use cobalt style taps and drill at least Ø5.3mm for M6. Work hardening is not an issue but heat transfer is. Titanuim absorbs heat slowly so your cutting action will cause the immediate area to swell and expand and will "grab" your tool with a heart-stopping squeal. Don't try to force it - instead, go and make a cuppa and by the time you return it will be loose enough to retract.......then get another tap......

If you burn a drill out in the metal you are stuffed. The work hardening mentioned earlier is akin to a chilled casting. Cut low revs, feed hard and plenty of lube, pecking every 2-3 seconds maximum.

Have fun.........

Trevor

I am surprised by the last comments, have had these on the machine for several months now and had no problems, agreed, I do not use coolant, but that makes the machine easier to clean and maintain. If any lube is required a squirt of WD40 is more than adequate. In the last few weeks have been machining gear and bearing mountings, and 1/2" Ali plate, so it has not been idle.

Trevor

Photo link;

**LINK**

Trevor

Chris

Have fitted Allendale read-outs to my Clarke mill-drill, they are just electronic vernier scales but without the anvils.

Total cost £75 for X and Y axis and work superbly. I am extremely impressed with the quality and the accuracy.

Will post photos later, am at work atm.

Trevor

Dan, are you looking for the pins or the internal mechanism? the pins can be bought new from RDG tools

I am looking for a 127 tooth change gear for my mk1 bantam, can anybody point me to a supplier.?

Failing that, what gear form are the gears? I can buy a standard gear and fit a splined inner.