Member postings for The Mad Professor

Sorry this is a bit late. The change gears for the Pools Special are indeed 24dp. The back-gears are 16 dp. The set of change-wheels that come with the lathe originally were 2 x 24, 27, 30, 33, 36, 42, 57, 60, 90, and 96. Note that they increment in 3s rather than 5s like the Myford, so there aren't any thread cutting tables published other than the one on the lathe headstock.

There was an additional set that had 60, 66, 78, 84 teeth to allow 26 and 28 tpi threads to be cut. There was a metric conversion gear with 127 teeth. This allowed a large range of metric threads to be cut. Although the 127 tooth gear does seem to be enormous, it does fit onto the leadscrew, where it needs to be located to cut all metric threads.

I have a set of thread-cutting tables for the Pools Special, so could upload them for you (if I can work out how to do it!).

Kind regards.

Thanks John, I knew that someone "out there" would have a copy of the sheet available! All I have to do now is get some laminations of the right size (available from ASCO - https://ascocomponents.co.uk/ ) and off I go!

Kind regards,

The Mad Professor.

Many years ago (at least 20?), RS used to issue paper "datasheets" on their products. One such product was a transformer kit. This had a pre-wound 240 volt primary winding and space for a secondary of your own choice. They no longer offer this product (EU regulations?). Does anyone have a copy of the original datasheet? I have no idea of the Datasheet Number but the RS Stock No. was182-9925. Can anyone help or do they have access to the old red/brown binders of the datasheets?

Thanks.

Howard is correct - I removed the taper pin which allows the back-gear selector lever to be pulled off. There is a bush axially pinned to the shaft which needs to be removed first - not easy with 90 years of congealed oily muck holding it in, but once this is removed, the spacer grub screws can be slackened off and the shaft then slides out to the left.

The back-gear bobbin is on a steel tubular shaft which runs on the eccentric steel shaft. Not a good idea running steel on steel - hence the desire to put in a decent method of lubrication. The eccentric shaft is located in the lathe bracket by the bush, which isn't obvious under the muck, but once cleaned it can be pulled out to the left.

Many thanks to all contributors.

Hi Clive,

Thanks for the advice. Clearly I need to have a little poke about and look at it carefully, but it would seem that your advice is spot on. When I've finished machining the job I'm on, I'll have an investigation. The back-gear bobbin is definitely on an eccentric, which is probably located on to the shaft with a grub screw accessible through one of the spacers which also have grub screws. It will need a good look to find the pin or screw.

I have a 4" Pools Special lathe, 1934 vintage, so no manuals available at all. Has anyone "out there" ever dismantled the back-gear mechanism so that the back-gear countershaft can be removed from the lathe? I want to fit a decent lubrication point and need to get the shaft out to end drill it for an oil nipple. I am reluctant to just go at it without any prior knowledge as it seems that an impossible situation is present, in that the spindle on which the back-gear cluster rotates appears larger in diameter that the holes in the headstock casting supporting it and there does not seem any way that I can withdraw the spindle.

You either know what to do or you don't...

Thanks

Hi David,

Thanks for this - I think I'll go the whole hog and machine them from steel - I think that I might have a problem machining the existing washers flat. I managed to balance the first grinder using Picador flanges, and I too, have a similar vibration problem on the latest grinder I have - hence the need for proper flanges.

Thanks to all for the advice

The Mad Professor

Thanks - I thought as much. Its making my own I think, to get the wheels to balance better than the pressed steel ones fitted to the grinder as supplied.

Years ago, I bought a couple of pairs of Picador diecast aluminium flanges for use on bench grinders. They were 2 1/4" diameter, 1/2" bore and 5/16" thick with a 1/16" deep recess, 1 1/2" diameter. These were a much better bet than the steel flanges supplied on typical cheap bench grinders today. Internet searching for these reveals little - only a website listing Picador Engineering in Grimsby, (103 Louth Road, Holton, Grimsby, DN15 8QJ). None of the links on the page works. Does anyone 'out there' know whether these flanges are still available, as it wastes valuable workshop time making two sets for the latest bench grinder that I bought? Alternatively, does anyone else supply them?

Many thanks

In 2008 or 2009, there was a free pull-out drawing of Martin Evans' Boxhill locomotive. Does anyone know which issue it was in? I have all the issues and all the plans but I cannot locate which issue it was in orginally. I cannot locate it in the ME index on Colin Usher's Web pages. Can anyone help?

Thanks

Just a little warning. If you use silver solder, use the lowest melting point you can, a zinc-free solder, or use a special stainless steel grade of solder, such as Argobraze 56 (usual disclaimer). If you silver solder an austenitic stainless steel at about 700 deg C using a zinc rich solder, it is likely to crack due to zinc embrittlement. Remember Flixborough?

Edited By The Mad Professor on 26/07/2012 09:14:23

Edited By The Mad Professor on 26/07/2012 09:15:13