Thread identification

Left field question: I'm trying to identify the thread in a flue/drain brush. This has a female connection, in brass with an o/d of 22mm. The minor dia of the thread, measured with a caliper, is ~15.1mm and my 7 tpi Whitworth gauge appears to be a perfect fit. That's very coarse for the diameter, according to my tables, so what have I got? ( I can't measure the male connection as the rods are in another country, but I believe the set was UK-sourced). British Standard Sweeping Thread? Adrian

I bet even Tracey Tools would struggle to find a tap for that. A wonderful thing for saving money though!

Neil

Hi AB658, The following info. is approx. The male end of our drain rod: Thread crests 18 mm dia. Crest to crest = 0.14 in. which is close to your 7 TPI. My thread gauge is closest at 3.50 metric. What is it you want to do? Regards, Bear..

My old bamboo set is compatible with my new plastic set at 3/4in x7tpi. Maybe you have 7/8 x 7tpi. Is the 22mm you measured the outside of the female sleeve?

It might have originated as a thread used on turned wood items, like candlesticks, thence into brass equivalents and so tothe brass fittings on rods.

You may get a clue as to what thread you have there by studying some of the sweeping statements made by some on here ---------- Rik

Lots of info here

MichaelG.

But it does not give the thread sizes, I looked at it last night.

Given that the male part of these rod threads have quite a rounded crest its quite poissible that if the male were measured it would be 3/4x7tpi and its just that the female has a more V shaped valley which makes it look like 22mm

I've just been out to measure mine, 18mm od male, pitch difficult thru' wear but near 2.5 mm. the male thread is very sharp point, unlike the old bamboo ones which had a very round thread, like a bottle thread. I suspect there is a big variation between makes but the thread is now so short ( 2 or 3)that we get away with it. I know I've had to file some to fit other rods, but still work ok.

Thank you all. More info: I want to sweep the flue of a log-burner that has a 150mm (I think) flue with 2 x 45 deg bends in a length of about 5 metres. Our friendly UK sweep has given me his old set of thin rods (he now uses the super-expensive flexi rods) and an 8" brush. This proved too big and I brought the brush home again to source a smaller replacement. I would like to be sure that the type I'm looking at will fit the rod set that is currently 1300 miles away; I only have the female end of the 8" to go on to define the requirement. And yes, Bazyle, 22mm is the outside of the sleeve. Adrian

You will know that log burners make a lot of tar. A soft sweeps brush won't shift this. Depending on the type of flue/ liner get a wire brush and/or buy or make a scraper ( this where the subject comes on topic)! I make them using a spare rod for the screw fittings, but I reckon as long as the dia. is right a small file will make it fit.

Forty years ago my father-in-law lent me his old set of rods to clean our chimney. I still remember his warning, "keep twisting clockwise as the rods go up the flue - it keeps everything together". He even tied a clothes line to the brush in case it fell of. He was that tight he couldn't bear the thought of loosing a thing. In the end he did though, he died on the bog and his missus copped the lot!!...................

................. but I digress. Soot acts like weightlifters resin - you can really get a good grip as you twist and push. So good in fact that I twisted an amount of skin from the palms of both hands - very painful. I have never swept a chimney since.

Rik

I only swept our chimney once. Set up the wet'n'dry vac witha board taped to the fireplace.

Advice - make sure there are NO leaks in your dustbag before trying this.

'nuf said?

Neil

They are standard fittings for everything an amateur will encounter. An eight inch brush is fine for a six inch flue as it goes in twisted and you keep twisting clockwise on the way in and again still clockwise on the way out. An extra hard twist as you reverse it helps compress it.

AB658

It would appear that 7 tpi is correct for the "Universal" fitting

DRAIN-TOOLS.COM lists rods and attachments, here

... and adapters from "Universal" to "spring steel" fitting, here

MichaelG.

As a result of the generous advice received I have ordered a 7" pp brush with a ball on the top (for the bends) and an adaptor to connect it to the now likely universal 3/4" x 7 tpi rod connectors. Stove specialists recommend 7" for 6" flues and mine is single skin, galvanised, so the thought of getting a bigger one stuck or forcing joints apart in a system buried in the non-accessible ceiling cavity gives me severe palpitations (above & below is reinforced concrete....). Why am I bothering? The stove installers wanted €150 for an hour's drive to do it. Adrian

Glad to see you are DIYing it. I'm amazed by the number of people who think it is difficult and as a result don't often get the chimney swept.

As a general note for others reading this - the black plastic rod sets sold by eg Screwfix these days are crap. Made of wobbly rubber. Find a blue set in a car boot sale if you can't find one in a shop. The wobbly ones do have their uses but not for sweeping chimneys.

When I was faced with sweeping log burning flues, the most successful tool was a hefty chain with coarse bolts through the links to break up the tar. I was lucky in that I could do the work from the chimney top. The amount of junk that shifted was quite impressive.

Brian

Never had any problems* with my wobbly black ones, for chimney or sewer!

Neil

*with rods, not the vac...

My tool for breaking up the tar is a home made "basket" welded up from 12mm x 3mm black bar to a sleeve ,bolted to a redundant brass socket. A bit harsh on thin steel flues, best advice is have a blaze up once a week, to stop the formation and build up of tar. Should follow my own advice, I've had two flue fires, one nearly serious and the roads were blocked by snow.