Unusual thread

Threads are never the nominal size when measured, but usually several thou less. A 6BA thread is nominally 0.110ins but usually measures 0.106ins, which is quite a bit less for such a small thread. Your rod could have been prepared smaller to facilitate cutting the thread. The Asme thread of 0.268ins x 18tpi. would seem to be the only one near. Modolit

Again, thanks for the replies. The six candlesticks are now polished and back in the church, behind the security alarm system. I will next be handling them in about 11 months time.

I thought it very unlikely, with them being in an English village church and possibly dating from the Victorian refit in 1892, that I would have to think metric or USA threads, but probably Mad Mike is right; oversize die, use any material to hand etc.

I can't find ASME threads in my M/C Handbook 17th Edition (1964) but no matter, they will be there.

The steel rod is rough and oval and I suppose it could have expanded through corrosion to 0.258-60". Perhaps it could it be old enough to be wrought iron with inclusions that have allowed damp in.

Thanks again.

I have an old "die plate" I suppose it is, Made from hard steel with a forged handle. This has 24 threads, look like Whit. form, the largest is about 5/16 dia. the smallest is broken off but could be 1/16 ". This is just to show the variety of threads in use, in I guess about 1900.So the candlestick could be threaded with the nearest suitable size.

Merlin,
Sorry my input is late but I ran a brass shop in the 60s and would confirm that even then the tools and methods were "simplistic", to be kind. Threads were chased in brass wherever possible, one TPI for all, 26 TPI irrespective of size. Many of the tools were home made from hardened carbon steel as this was adequate for brass on slow machines or for hand cutting.
Short of a deep clean I can't put my hands on the split die block that was used to thread iron tie rods like the ones off the candlesticks, but it was after the style of the sketch below.

Being split dies it would be an easy matter to take 5/16 whit (18 TPI) and produce home made taps in carbon steel to near 1/4 dia x 18tpi (perfectly capable of tapping into brass) and then using the same dies, a little tighter, to thread the tie rods. Soft iron nuts would be similarly made with a carbon steel tap.

There was no sophisticated measurement or concern about British standards let alone Metric or American. Parts were required to "fit" and interchangeability was low on the priority list and the candlesticks .bear witness to the fact that they can stand the test of time OK.

The 50s/60s was an interesting time to enter an Engineering career, fortunate to be trained in modern methods but still able to see the traditional approach in the peripheral industries and then grafting onto that skills from both a toolmaker father and smithy grandfather.

PS SHMBO is unhappy to think your church brasses only get an annual treatment . There is a weekly rota for polishing in our church! A bit OTT to my mind.

Bob D

Well, that is interesting.

The rods are ovally and nominally 1/4" all the way.

I have the threads hand tight but this year two of them had siezed in the candle-holder at the top, due to water leakage I supposed. I dismantled one of them and looked at the thread from about arms length and knew, with all my experience, that it must be, could only be, 1/4" Whit.so I died it down for 1/2" just to clean it up. All my Whit tackle is scrounged second-hand so it was no surprise that it was a bit stiff going down. What was a surprise was that the candle holder had then become a sliding fit, touching hardly anywhere.

I didn't have much time so a few turns of PTFE tape filled it up well enough to last another uneventful 11 1/2 months.

I too am surprised that the shine on the 22 brass items lasts so long but the church isn't used much and there is no evidence of bat urine stains. There are always some stains and I use a buffing m/c to remove the pits. To be able to safely reach the nooks and crannies I completely dismantle the candle-sticks.

I think that the few parishoners are so pleased to have someone to do the job that they are willing to accept my annual interest. The church is in clean country air. To do them weekly seems unnecessary although it would catch corrosive droplets before pitting began. Is your church sponsored by Duraglit?

I would like to know more about the manufacture of church brass accesssories, if that is what they are called. The large altar cross is stamped 'Cox, London' a well -known name I think, but the vases and sticks are not marked.

Do you know of any literature on this?

Very many thanks.

Merlin,

I'm no expert in church metalwork and furniture but I did spot this archive with catalogues of church equipment. Two are UK names, albeit old catalogues and you might find your candle stick illustrated amongst them.

**LINK**

http://archive.org/details/churchartinmetal00armo

Our "sponsor " is Brasso which gets into every nook and cranny but does not get polished out every time and then builds up a yellowly green scale in the recesses.
The answer seems to be a Karcher wash every so often to force the dried on crud out of the inaccessible spots.

Another source of info would be your Diocese Architects office. They should keep up to date catalogues of suppliers

Bob D

Are we too obsessed by our DROs, micrometers and digital calipers and using nice clean BDMS?
A victorian brassworks would have considered a dimension holding 8 thou accuracy to be high precision. Their lathes wouldn't have had dials at all and the workers would have measured dimensions with calipers against their wooden rulers though the forman would have perhaps had a precious brass rule marked in 64ths.

------

I was thinking along those lines

If you wanted to crank out a quick medium thread on a 6TPI leadscrew

20 on the head, 60 on the leadscrew, voilla 18TPI

Or with 8 TPI use 20/45

simples!

edit:

I do it myself all the time because 16 to 18 tpi is a doddle to cut and tidy up on a manual lathe

Edited By Ady1 on 18/12/2012 12:36:06

Thanks.

The reason that I go to the trouble of dismantling the six candle sticks, although it might seem slightly obsessive, is that, apart from buffing into the corners, in the long term it is easier to do that than to faff about with an old toothbrush. Actually, no-one would notice much but I get some satisfaction out of doing it properly, as I see it. It is my only claim to fame in the village. The worst part of the job is cleaning down the horizontal surfaces in the workshop afterwards - the black dust and fluff from the buffing make a lot of mess.

I use Duraglit because it doesn't leave the dried remains that you mention.

You have just reminded me that I want to find out why the twisted ('barley-sugar' tubes are called 'olivers'.

The reasons that I mentioned the o.d. of the rod were that I wanted to submit all available dimensions to the forum and that I expected the grotty thread to be undersize which would could have meant an original diameter of possibly0.280" i.e. heading for 7mm.

Thanks

Merlin,

Do you think that the name Oliver is another Cockney slang based on Oliver Twist?.
The alternative name for the book is after all " The Parish Boy's Progress "

BobD

I also had a type of split Die ( very similar to R Dodds [above] ), but the threaded "teeth" were cut into the top moving piece (there were3 of these) and the bottom was a "V" shape that the bar rested in.

This was used by my grandfather, who was a Coachbuilder/Cabinet Maker, to cut threads onto wrot. ironwork for coaches/carages and oftain on bars that held together tall turned hardwood candlesticks.

As a child I was allowed to "help him" in his workshops - His favourite phase being "cant you keep the nipper out from under my feet!!" - any way I remenber that the distances of the "teeth" were 1/8, 1/10, and 1/12 of an inch as measured on his boxwood bench rules. - As far as I can remember the pitch used was "best for material" and used on any diameter.

I also remember that nuts were formed by forging a lump (square) of red hot metal with a hole in it, directly onto the threaded bar that that had been cut.

I might add that his measuring items were boxwood rules, calipers and deviders.

The metal rod is proberbly a bit of wrought iron, forged round by the Blacksmith. Ian S C

Hi Ady,

Why do you say that lathes from that era, even in a brassworks, wouldn't have dials?

Regards

Terry

You have just reminded me that I want to find out why the twisted ('barley-sugar' tubes are called 'olivers'.

I second the Olver Twist theory!

Neil

because dials were a non essential refinement. Until recently I had a lathe from 1900 advanced enough to have power facing but no need for dials. **LINK** newer than this and not restored.

One of the "hardest" lessons learned (by me) , while learning on a hardinge superprecison cnc (0.0001 mm resolution )..you can compensate for toolnose radius, thermals,and programme to a tenth of a micron but what you get still depends on the old problems..workholding,tool "sharpness and hence push off amount..even variations of coolant delivery ..so dials..Ha..get yer mike out and see what youv'e got...

Admittedly dials help estimate cut (OR a DRO for that matter)

Edited By jason udall on 20/12/2012 01:20:39