Member postings for old mart

I can understand why the design has not lasted.

Check your shed for old newspapers, their time has come. **LINK**

A lot depends on the length of the cut, that is the thickness of the brass. Using the flutes close to the plain shank if possible makes the cutter stiffer and stronger for its diameter compared to using the tip. You will have to look at the cutting edges on the sides to see the point at which they run out. Its common practice to keep a cutter that is blunt or badly chipped at the end for cutting with the less used sides to get a bit more life out of it.

It would be risky to, for instance, for a 6mm cutter to be used to make a sideways cut in 12mm thick metal all at once, the forces might be too much even for brass.

Edited By old mart on 18/03/2021 21:00:09

When I bought my laptop, it had a 1tb Seagate hard drive which was quickly replaced by a Samsung EVO850 500gb SSD. That speeded up the boot somewhat. Another feature of laptops is that they are normally configured to run slower when on battery power to make a charge last longer. That can be disabled at the expense of shorter times between recharging.

Anyone fancying Linux would find Ubuntu to have a similar desktop and be quite easy to migrate to.

Edited By old mart on 18/03/2021 15:49:02

At the museum, we have been left toolboxes often over the years and I have a tin with all the special taps in it. From buttress tap sets to 40 tpi micrometer pitch and everything in between. Tap manufacturere will produce any size and pitch to drawing and they usually end up in a toolmakers box and surface many years later. Amongst the specials are pre plating sizes with + 0.003" or similar, they need to be kept well apart, or binned in case they get mistaken for standard sizes.

I went to Specsavers twice, once to benefit from two pairs for the price of one, but when I wanted safety glasses, they would not play ball. I had to have one pair of ordinary ones. I still have two pairs of Boots glasses from about 25 years ago, they are superior to Specsavers.

I thought I had produced another of my typo's, but looking at my post, it says 0.01mm.  Now I see that the size was down twice, of course I meant 0.01mm both times.

Mitutoyo make a digital micrometer that measures down to 0.0001mm, seems rather difficult to ever get the same reading twice with one of those.

Edited By old mart on 17/03/2021 20:45:35

Regarding digital micrometers, it is easy to be too worried about the repeatability and the actual dimensions involved. I worked making aircraft parts for many years and looked at thousands of drawings. 99% of those drawings did not specify tolerances tighter than +- 0.01 microns. And aircraft parts are more closely inspected than most things. Any parts deemed critical have all their origin, heat treatment, dimensions and finish checked 100%.

A micrometer that has graduations of 0.01mm will give all the needs of general measurement, and one calibrated in 0.001" can be read easily to 0.0005" or better.

I had 3 digital Mitutoyo micrometers, and sold them all last year, I can still manage my metric and imperial mechanical mics.

There is one thing to be aware of when using a long travel DTI in a horizontal plane, they can sometimes stick slightly, as their preferred attitude is with the plunger vertical. It would pay to double check the contact when extending.

Back in the early 70's when I was fitting central heating, the preferred flow was in at the bottom and out at the diagonally opposite top for the best heat output. That rarely happened in practice.

I wouldn't be surprised if your live centre turned out not to have any seals fitted, there is not much room for swarf to enter through the rear.

Try the grease method, take out the 6mm bolt and replace it with a grease nipple and gently pump grease through. The grease will work its way through all the bearings until it emerges at the back.

I would leave at least 1 1/2" clearance between the OD of the chuck and the lathe bed. The Smart & Brown model A can use a 9" faceplate, and the biggest chuck that is used is 6 3/4" diameter. That size is only used occasionally as it is heavy and takes up a lot of length. The chuck is a Pratt with serrated jaws which comes in handy for precision work, as it is intended for soft jaws.

I would get a 160mm, they are much bigger than a 125mm, and easy to get hold of.

Edited By old mart on 15/03/2021 16:03:28

You can probably buy lengths of hexagon brass of the right AF for BA sizes. I have used the rotary table to make lots of custom nuts and bolts, but never as small as BA. You will need a method of getting the spindle exactly in line with the table axis. I cheat a bit and put a test bar in the RT centre Morse taper, and close the jaws of a three jaw scroll chuck gently on the bar before tightening the chuck down. Then I use an optical tool in the spindle to centre the end of the test bar. That gets me to about 0.002" tir which is good enough for most work.

If you make your own out of old drill bits, it would be best to make them as short as possible to increase their stiffness.

Bronze does not contain zinc so it is better able to withstand the corrosive affects of sea water. I was surprised to hear that a propellor shaft would be made out of a copper alloy, most likely bronze of some sort, they tend to have a more coppery colour than brass.

Welcome, Julian, we all mean well. despite the occasional typo. As you are interested in improving your lathe, I wonder if you have come across this site which could be useful;

**LINK**

The ad I saw on ebay had a choice of sizes for slot fillers.

In theory, the thermostatic valve should be on the flow side, but it will make very little difference in practice.

I googled 82 degree countersink and got lots of hits. Five flute countersinks were easy to get hold of and would be my choice. Practice on a spare piece of brass to get the optimum speed which should be slow to minimise chatter.