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Member postings for old mart

Here is a list of all the postings old mart has made in our forums. Click on a thread name to jump to the thread.

Thread: Cast iron - 160mm dia
05/07/2019 19:18:25

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.

Thread: Corrosion or Stale Oil (in joint face)?
05/07/2019 19:10:32

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.

Thread: Square Headed Screw Supplier
05/07/2019 17:17:00

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.

Thread: Phillips vs Pozidrive and portable drills
05/07/2019 17:04:20

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.

Thread: Microns ...
05/07/2019 16:55:13

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.

Thread: Corrosion or Stale Oil (in joint face)?
05/07/2019 16:44:26

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.

Thread: Cast iron - 160mm dia
05/07/2019 16:16:37

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.

Thread: Microns ...
05/07/2019 16:01:52

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.

Thread: Curious
05/07/2019 15:46:37

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.

Thread: Cast iron - 160mm dia
04/07/2019 23:01:34

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

Thread: Start of Tom Senior refurbishment.
04/07/2019 22:43:09

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.

Thread: Old Plastic - of all the stupid injuries
04/07/2019 22:02:18

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.

Thread: How to use a round column mill
04/07/2019 21:19:37

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

Thread: Corrosion or Stale Oil (in joint face)?
01/07/2019 20:30:33

I shouldn't worry about the stains, you might try rubbing them with wire wool and wd40, but not anything more abrasive.

When I first took the Smart & Brown model A spindle out, I took the whole head off the bed and the staining made by the soluble oil was amazing. It very likely had been undisturbed in 70 years. The joint surfaces got a minimum clean and lined up perfectly when it was bolted back down. I now know how to remove the spindle, it takes ten minutes.

Thread: How to use a round column mill
01/07/2019 20:05:19

Could the metal guide strip on the column be loose? Without a fine feed on the quill, the only way to move slowly in the Z axis is with the wheel at the rear. Are any adjustments possible to the fit, such as a vertical jib strip?

 In your first picture, behind the 11 on the rule is a plate which looks like it is a pointer. Can the column be rotated in the base? Is it tight?

Edited By old mart on 01/07/2019 20:10:22

Thread: Thread Bare
01/07/2019 18:03:48

Studding in metric fine may be hard to obtain, if there is sufficient wall thickness, then helicoils are much easier.

Check out ebay listing 173833058997.

 Michael Gilligan's post shows a source, but it is very expensive for only 25mm lengths.

Edited By old mart on 01/07/2019 18:08:59

Thread: How to use a round column mill
01/07/2019 15:19:40

Could we have more pictures of the mill? Possibly a name and there may be more info on the "lathes UK " site.

Thread: Modding a fixed steady
01/07/2019 15:12:01

That is very similar to the fixed steady I bought to use on the Smart & Brown model A. A base was made to fit the bed of the lathe. The reason I bought it was that original ones cost an arm and a leg. The shortcomings were exactly the same and I shortened the original fingers to allow 100mm stock if required. I also made a set of fingers with sealed ball races to span 14-80mm. It is certainly sturdy enough to be useful. With the use of a mill, making the fingers is easy.

If the original fingers are shortened, they will not reach smaller diameter stock, unless an extension is made for them.

Thread: How to use a round column mill
01/07/2019 12:45:56

Round column mills don't usually have an alignment strip. They clamp the head securely and rely solely on the quill for Z axis. Whether yours can be used moving the Z axis depends upon the fit of the rectangular strip stopping any tendency for rotation. This could be verified using a dti when the head is free to move up and down to see if the head can be rotated on the column. More than 0.002" movement would be too much.

Thread: Snail Problems
30/06/2019 20:19:39

When I was small, spending summer holidays with my aunt and uncle, I was given a bucket with salty water in it and searched the front garden for snails. I found hundreds. When I was even smaller, my mother found me chewing away on snails which I had picked out of a stone wall.

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