Member postings for old mart

If the crank pin was running in a radial slot, the stroke could be adjusted

That leadscrew pitch of 3.15mm looks a lot like 8tpi which is 3.175mm.

I have seen dial indicators with changable gearing between the leadscrew and the indicator, but have never known what their function is.

During the last couple of weeks, I have been making internal threads of 2.5mm pitch and have to leave the leadscrew engaged. I find that it is just as easy that way, stopping and reversing the spindle as it gives me time to think about the next setting, backing off and making the next depth of cut. The Smart & Brown model A has proved very easy to change spindle direction, and quicker than when I was cutting 40tpi today and waiting for the threading indicator to turn through 24, not 4 divisions as on Myfords. If I was doing lots of threading, I would bother to learn the proper way to use the threading indicator.

With most keyed chucks, you can open up the jaws and put a drill bit in the lathe chuck to drill through the body of the chuck. There is a short cavity between the chuck and the end of the arbor. Then you can remove the arbor with a parallel punch. Your method of fitting the chuck to the arbor should work, just withdraw the jaws first to avoid damaging them.

While the motor in your modern mains powered electric drill will be double insulated and not require an earth cable, machinery motors either single or three phase are not double insulated and must be earthed and an eathting point will be provided.

Edited By old mart on 02/02/2022 19:12:50

Very useful if you are milling using cutters of 6mm and below for small projects.

Before skimming the front of the backplate, I would always fit and refit it to the spindle at least 6 times to settle it down.

The important parts which affect the fit of a backplate are the squareness of the rear face which contacts the face of the spindle and the threads which are normally 60 or 55 degrees. The tightening up of the threads centre the faceplate and the square end contact does the rest. The so called "register" does nothing at all, except on the rare spindles with a square thread which cannot self centre.

I have had these over the years and have a stock of o ring material. I find that not all superglues will bond the material sucessfully. When I worked in aircraft instruments, we had one of those tiny watchmakers lathes and the leather belts were about 5/16" diameter and past their best. I substituted some rubber tube using the newfangled superglue and we had very good drive belts

A sleeve for the spindle-backplate? I run backplates with up to 0.020" clearance and down to 0.0005", they all repeat exactly the same.

Edited By old mart on 31/01/2022 21:36:28

Just in case it is not generally known, the Vertex Posilock uses the same collets as the Osborn Titanic II in the smaller sizes up to 16mm.

Strange coincidence, I have a book from the library, Branch line to Minehead, by Vic Mitchell and Keith Smith which mentions this. Plate 49 shows a train on a single track curve near Doniford Bridge Halt. There is mention of "concrete monuments (short posts spaced about 20 feet apart on the inside of the curve) at the ballast shoulder helped staff to return the track to its correct position after speeding trains moved it towards the sea". Not exactly a high speed line, either.

I would turn up a small plug for the central bush with a small centre or spotting drill hole in it to use a pair of dividers to get an accurate gear diameter measurement. To get the exact number of teeth, I would scribe a circle to match the od of the gear on some card and mark the teeth positions in stages around it.

If you can get a complete gear made, two quadrants could be made from it and the welding heat would not have to be near the teeth.

 And, by the way, welcome to the forum.

Edited By old mart on 29/01/2022 18:57:03

Edited By old mart on 29/01/2022 18:58:36

Looking at the rail surface, they are either very new, or the line is very little used.

I had a good look under the drill mill before deciding to make the nut assemblies for the X and Y. The X still has about 100mm space either end when at the limit of travel, so this doubling of the nut length will not do any harm. The Y axis nut is restricted towards the rear, but there is plenty of room at the front side, so the front nut will be displaced towards the winding handle.

The 2.5mm Trapezoidal inserts arrived the other day and the first 2 nuts are made as well as the X nutblock. Getting the pitch was straightforward, instead of the original 120 idler gear, the Smart and Brown model A has a double 127/125 and driving in that order turns a 10TPI set in the Norton gearbox into 2.5mm exactly. To save money the body is a block of aluminium. One nut will be Loctited in place and the other is screwed in with a 40tpi thread. The flange of the screwed nut will have axial holes in it for adjusting in situ, and there will be a spring loaded clamp to prevent it turning by itself. reversing the motor while threading is easy, I stop before changing direction, it gives time to back off and/or advance the cut depth.

We have a couple of pristine Jacobs small chucks, one 5/16" and the other 1/4", I believe they are JT1 tapers. One has a MT2 and the other is on an R8. The 1/4" will hold a no80 drill easily, and probably smaller and the body is much shorter than the common 1/2" chucks.

Edited By old mart on 27/01/2022 21:40:31

It could easily be a special made for a particular job. I have a box of specials at the museum, from the toolboxes left to the museum. If very unusual sizes were specified, a firm would add the tooling costs to the quote and a specialist would make it.

The NSVT may be a code for the job it was used on and nothing to do with threads.

 The threads on the tap look like a multi start on my screen, probably an optical illusion. I would 56tpi to look like rings turned. I turned a 40tpi on a 1.26" diameter today and I cannot detect any helix angle by eye.

Edited By old mart on 27/01/2022 20:35:53

Here it is, in good condition and the MT3 tanged socket is undamaged.

Edited By old mart on 27/01/2022 20:23:08

If you intend to scrap it, please grind or file a bit out of that "swaged" end to put us out of our misery.

I found the one at the museum, it has a MT3 socket in it. The body is about twice the length of the one pictured.