Member postings for old mart

The tilting vise would be useful for small component milling, but adds quite a lot of flexibility and has its limitations.

Having a mill which has both spindles adds to the cost of tooling and you need to be sure that none of the special parts needed to utilise all the functions are missing when you make the purchase. Don't be fobbed off with statements like "you can easily get the part that's missing".

Never mind about the microcockup, S O D, next time its my turn.

Pistons fitted to petrol and diesel engines are never turned round, and are also tapered and if anybody tried to measure one to a 2 micron tolerance they would get a different reading each time.

Edited By old mart on 07/07/2019 11:44:25

The Tom Senior light vertical we are refurbishing has a quill with 2 1/2" travel as well as the knee movement. The same head is also fitted to some of their more advanced models which have a horizontal spindle as well. The downside of the quill, is that most of them only have MT2 spindles, although the horizontal spindle is BT30.

I am going to modify our quill to use R8, not exactly straightforward, but doable.

As already mentioned, the "lathes UK " site is the best place to research the many types of mills available to meet your requirements.

There are several suppliers of discs and rings for sale on ebay, just like F W B's example. If you look at the picture, you will notice that the cut is started inboard of the diameter, which may be a problem. The example shown would probably clean up to your required diameter. The thickness might not be enough if you want 15mm finished. I have bought several rings which saved a lot of machining, you just have to look through the whole lot for the sizes required.

Martin, we had two Gazelle helicopters privately owned in Royal Navy colours at the museum the other week for the Weston Super Mare air show. I watched as they took off in formation from our field. A year or so ago, a Gazelle was visiting and had an engine fault. They changed the engine the next day, it took an hour. 

When I was a kid, on holiday every year at Shoreham, I frequently watched Tiger Moths doing aerobatics over the airfield.

Edited By old mart on 06/07/2019 21:50:19

Great idea John, wish I had thought of that myself. I will try to remember it in case I ever need it.

Years ago my firm had some apprentices and I had one practice tapping using small taps. Nothing like actual practice on scrap metal to learn. I got him started on 5/16" and gradually worked down in size. When I gave him a 6BA, he took a little longer, but ended up with a nice thread in 1/4" steel plate. When he gave me back the tap, I realised that I had mistakenly supplied him with a plug tap. He did well not to break it.

We don't sell the titanium, if I'd found steel ones, they would have been equally useful at the time. They, and 8/10mm ones were originally used in Westland Lynx gearboxes, but were replaced by steel which is superior. Having a large stock of them saves me having to make them myself.

We kept concentrated sulphuric acid in glass carboys, in straw, within a steel frame. There was no health and safety then. And nitric, hydrochloric, and glacial acetic acid.

I found some square headed 5/16 BSF screws on ebay to replace the SHCS on the four way toolpost. Why, you ask, well the front and rear saddle lock screws, the left and right stops and the travelling steady all use them and one spanner is more convenient. The spanner is a 1/4" drive double square socket pressed onto a shaft with a sliding tommybar.

I haven't seen any 5mm square head screws unfortunately.

As soon as you use posidrive or phillips in an electric drill, it becomes normal to have to throw away the bits after every dozen screws. I always buy my pozidrive #2 bits in boxes of 25 at Screwfix. They are made of "S2" steel, whatever that is.

The square drive screws are excellent, although I personally favour torx.

Read my post again. 10 microns is less than 0.0005". 0.0005" is equal to 12.7 microns exactly.

One micron is a millionth of a metre, or one thousandth of a millimetre.

One thousandth of an inch is 25.4 microns.

Hydrofluoric acid will attack glass, many years ago when I worked in electroplating, I intentionally put a 10% HF solution in a glass bottle, left it overnight, and when it was rinsed out, the immersed part of the bottle was a couple of mm larger diameter. HF is stored in lead or polypropylene. Sulfuric acid, H2SO4, will not attack glass, the sediment must have some other explanation. Be afraid, always, when handling conc sulphuric acid, I got one drip on my hand once and was rinsing it off under running water within a second, too late of course.

I have one 9" faceplate fixed to a steel 1 3/4" x 8 backplate of about 3 1/2" diameter. The backplate was bought cheap on ebay, I have no idea what it was originally intended for. It is fixed by six double diameter studs, 6/8mm diameter, the 8mm in the plate. Unusually, the studs are titanium, ten a penny in an aviation museum.

The ci with the inclusion was sold to me as meehanite continuously cast by a reputable company, I would have no idea if it was something else.

I have micrometers capable of measuring microns, but it is extremely difficult to get repeatable results at this scale. When I was working in a firm making parts for aircraft, there was rarely any requirement for drawings to call up tolerances of less than +- 10 microns, that is less than +- half a thou.

Those people who like to boast and have deep wallets can buy themselves a Mitutoyo digital micrometer with a tenth micron scale.

I remember quite a few years ago that certain cans of beer had a plastic widget in the can pressurised with nitrogen that caused the dissolved CO2 in the beer to form a fine froth when the can was opened.

Two examples are Boddingtons, and John Smiths extra smooth, still available. Somebody must like the stuff, they are not CAMRA members.

I made a 6 3/4" backplate out of a piece of meehanite which started at about 200mm. There was a hard bit on part of the OD about 1/4" deep, just like an interrupted cut. I was glad to get through it, and doubly glad to have a variety of TNMG16 inserts. I drilled and tapped the CI to fit on a faceplate and did the od and face so it would fit in a four jaw for the rest of the turning. The mess was incredible, despite having magnets set to catch the cast iron dust.

If I ever have to do something like that again, I will try to get a piece of SG iron.

 I bought a 160mm ci blank from a well known supplier for a 160mm chuck and it was under size. It would have cleaned up at 152mm, but I left a bit uncut at 155mm. I contacted the supplier, who immediately refunded my money and said keep it. I reckoned that the three 8mm rear mount screws would be too near to the edge for comfort, so I simply drilled and tapped for six 6mm screws to hold the chuck instead, they could be on a slightly smaller pcd as well as being smaller diameter.

Edited By old mart on 04/07/2019 23:15:37

The extra length of thread is now cut. I had contemplated turning the compound to 14.5 degrees, but it makes things more complicated when using an existing thread for lining up. I had to adjust the traveling steady several times as the brass pads wore rather quickly. This was despite frequent deburring with a super fine file. I started with 0.006" cuts and gradually reduced to 0.002". I had to double the leadscrew speed and set 10 tpi to achieve 5 tpi pitch.

As the centre part of the leadscrew is worn more than the ends, I have had to match the wear by setting the sides of the insert to just rub the worn parts and then continue over the less worn areas. I am hoping to get consistency over the entire length. Doing the other end of the leadscrew requires even more concentration. Lining up on the centre threads, backing off the tool, coming off the end of the thread with just enough to use a small live centre instead of the fixed steady, and then guessing how much of a cut to take. Then starting at the end and remembering to back off the cut before disengaging the leadscrew.

Soft jaws were bored to 3/4", so I can hold any part of the leadscrew securely and accurately.

Running the leadscrew at double the speed puts a lot of strain on the geartrain, so for safety during the operation, I have replaced the safety link pin in the system with a solid one. There is a greater danger from the shear pin failing during a cut than there is of my crashing into the chuck.

It has been waiting all these years to get you.

Years ago, I couldn't be bothered to pick up a pair of scissors and ripped a couple of layers of bubble wrap in half. I damaged the tendons in the rear of my left elbow so badly that it took a year to heal.

As lasers have been mentioned, I will describe how the laser on the museums round column is set up.

The laser is one of the cheap gunsight types which has the flexible remote squeeze switch in place of the push button type. It is mounted parallel to the centres of the spindle and column. The beam reflects off a window 10 to 12 feet from the mill and back to a white mark painted on the end of the laser body. This should give an increased accuracy. The beam is about 8mm diameter in this distance. I don't know whether a higher quality laser would have a lower beam dispersal. I must try putting a mirror on the window to see if things improve. It is easy to find out the best way of tightening the head clamping bolts to give the minimum and consistent deflection of the beam. With care, accuracy of +- 0.001" is easy.

I tried mounting the laser tangentially to the head as there was a 60 feet sight line to a wall, thinking that it would be better, and it was useless. With hindsight, the shortcomings are obvious.

 Here is the ebay number for the type I bought. The remote squeeze switch and the mountings included made it easier to fit and use. Only the red was available when I bought it. 283044776422

 Filling up the bores of round column drill mills has been tried many times with generally disappointing results. In theory, filling up the bore with scrap metal and pouring in a liquid epoxy should improve the resonant frequency just by adding mass, the stiffness would not improve much.

Edited By old mart on 04/07/2019 21:44:47

Edited By old mart on 04/07/2019 21:54:24