Model Engine Maker

Supporting => Boilers => Topic started by: Smudger on July 16, 2018, 01:47:22 PM

Title: Help with Boiler Construction
Post by: Smudger on July 16, 2018, 01:47:22 PM
Hello all help please my first post on this section having just joined the group. I am about to start to make a small pot boiler and have a number of books and forums to call upon for my research. I do not have a metal lathe and looking for alternative methods to make the boiler bushes. I do have a wood turning lathe and I am considering an attempt to make the boiler bushes on the lathe. The plan is to buy material as near as possible to the OD I need and then turn down the last section using my lathe with metal lathe tool cutting tool. I think it will be possible to cut the internal threads on the lathe and donít see a problem with that. Can anyone see any problems with my idea ? Any advice greatfully received.
The boiler size will be about 2 1/2 OD and about 4 inches tall. My reading material is Tubal Cain and  Stan Bray, Making simple model steam engines.
Thanks for reading
Title: Re: Help with Boiler Construction
Post by: b.lindsey on July 16, 2018, 02:07:59 PM
Smudger, while I am not one of the experienced boiler makers on the forum and can't speak to the technical details of that, the use of a wood lathe for metal work could be problematic. Immediate questions that come to mind are what type of chuck does it have? Does it have a cross feed? What kind of tool post is available?  A picture of the lathe might help but in the long run, if you are serious about doing metal work, even a smaller import machine designed for metal work would be a good investment. There is plenty of help here for selecting a machine as well.  Not wanting to rain on your parade at all, but safety and accuracy are both concerns in metal work. I am sure others will have opinions as well.

Title: Re: Help with Boiler Construction
Post by: Smudger on July 16, 2018, 02:18:59 PM
Thanks for the reply Bill. No cross feed on a wood lathe Fully award and take your point on H and S. I note there are a number of posting on You Tube of people using wood lathes for metal turning. If my calculations are right I would be trying to remove about 2 mm dia of material at a length of 6 mm this would be brass or bronze and would be free hand using a static tool post.
Title: Re: Help with Boiler Construction
Post by: crueby on July 16, 2018, 02:22:59 PM
For boiler bushes you want to use bronze, not brass. Bronze would be pretty tough to turn that way, but probably could be done with very light passes, would take a while, and getting tight tolerances would be tricky.
Title: Re: Help with Boiler Construction
Post by: Ian S C on July 16, 2018, 02:27:20 PM
Hi Smudger, If you have the means to hold the metal in your wood lathe, a wood turning scraper will turn down a bit of brass / bronze quite easily for boiler bushes.
Ian S C
Title: Re: Help with Boiler Construction
Post by: Jasonb on July 16, 2018, 02:47:25 PM
As Ian says a scraper type tool used for woodwork is not that different from a "graver" which is a hand held metal working tool so quiet doable, I use my woodworking scrapers to do freehand metel turning.

If you have one of the woodturning 4-jaw chucks you may well be able to use that if it will close down enough, drilling and tapping using  a tailstock chuck is no different.

While it is good to aim at a specific size for the step in the bush it does not have to be too accurate so keep to the large side of what you are aiming for and the holes can easily be adjusted with a round file, you want a small gap for the solder to flow.

Infact there is no real reason to turn a step on a boiler bush they can also need threaded externally and the hole in the copper threaded to match which will hold them in place until soldered, so you would only need to face off the short lengths.
Title: Re: Help with Boiler Construction
Post by: Smudger on July 16, 2018, 03:26:46 PM
Thanks everyone for your input. Will have a practice and let the forum know how I get one.
I have a number of chucks so that won’t be a problem.
Title: Re: Help with Boiler Construction
Post by: Alyn Foundry on July 16, 2018, 04:41:28 PM
Hello Smudger.

Greetings from a fellow North Walien.

I acquired my first metalwork lathe in my early 20's. This hadn't stopped me from building small oscillating steam engines from a very early age.

My father had mounted to his bench a pedestal grinder, this had a stone on one side and a medium sized
" Jacobs " chuck on the other. With this rather simple apparatus I made many parts using a flat file and the tool rest. For pistons my method was to use varying grades of files starting from coarse to fine and finishing with different grades of emery cloth.

The old saying of " necessity is the mother of invention " springs to mind and I'm looking forward to reading of your progress. My old friend Vincent was forbidden by his father to buy a metalwork lathe so he built his own!! That homemade machine went on to restore his " K " type National Gas engine and build his first model IC engine, the Retlas.

Let nothing stand in your way, Progress, ..... Powell's of Wrexham's slogan.

Cheers Graham.
Title: A modified wood lathe for metalwork
Post by: Smudger on September 17, 2018, 10:35:33 AM
On my last post I promised I would get back to let you know how I got on turning on a wood lathe.
I had in my drawer a flat plate that fitted into my tool post. I opted to buy a small cross slide and tool holder. I decided this was much safer than trying to turn freehand using wood turning lathes. So for a small financial layout I have purchased a number of lathe accessories and I am pleased to report that I have managed to make my first boiler bushes including cutting a 1/4 x 40 ME internal thread. A problem I have at the moment is chatter. I have kept the stock short in the chuck and ensured that the lathe tool is dead centre. The cuts are very fine. I am struggling with parting of at the moment. The stock is 15 mm dia turned down to 12 mm I have been unable to part all the way through so I have resorted to fininshing with a hack saw.
Photos attached.