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Timleech
03-16-2011, 11:11 AM
I had to make a special 1/2" dome nut for an engine oil filter the other day, the original had gone missing years ago and a plain nut fitted, which leaked enough oil to be annoying.
1960s British diesel, all threads on the engine are BSF, except for this 'bought-in' oil filter which was obviously finer. Must be UNF, plenty of it in use here at that time, so made a neat job of a nut to fit. Spindle measures a few thou shy of 1/2".
Went to the vessel today to swap to the new nut, while the crew were doing an oil change, bl**dy thing wouldn't screw on.

Brought the whole thing back here to measure properly, the thread is 19 tpi (UNF is 20, BSF is 16).

Then after scratching head a bit as to what to do (no 1/2" - 19 taps in the house), noticed the male thread wasn't cut to full depth. Light bulb came on, 1/4" BSP is 19 tpi, and about 0.54" major dia.
Grabbed a 1/4" BSP tap, ran it down the existing nut (sorry guys, no time to make a new nut!), job done ;)
There's plenty of engagement length, it's not a sloppy fit, should be plenty strong enough, but why do (did?) manufacturers bother??

Tim

John Stevenson
03-16-2011, 11:35 AM
Not special at all. Oil filter - lube system - oil pipes - pipe threads - gas threads ?

Come on man get your act together .............:rolleyes:

Richard Wilson
03-16-2011, 12:17 PM
Brought the whole thing back here to measure properly, the thread is 19 tpi (UNF is 20, BSF is 16).

Then after scratching head a bit as to what to do (no 1/2" - 19 taps in the house), noticed the male thread wasn't cut to full depth. Light bulb came on, 1/4" BSP is 19 tpi, and about 0.54" major dia.
Grabbed a 1/4" BSP tap, ran it down the existing nut (sorry guys, no time to make a new nut!), job done ;)
There's plenty of engagement length, it's not a sloppy fit, should be plenty strong enough, but why do (did?) manufacturers bother?? Tim

I've got a British made lathe c1945 (a William Findlay 'Electrolathe') which has fine threads for the adjustments on the leadscrews and feedscrews. It puzzled me for ages, because the diameters were strange. Eventually after some research I found they were electrical conduit threads.

Richard

Timleech
03-16-2011, 02:06 PM
Not special at all. Oil filter - lube system - oil pipes - pipe threads - gas threads ?

Come on man get your act together .............:rolleyes:

Yes but it's 1/2" diameter, and it's not a pipe fitting, it's the central bolt, the thread is clearly cut to partial depth (probably with a pipe die).....

It's a big filter, the pipe threads are probably 1 1/4" BSP

Tim

Jaakko Fagerlund
03-16-2011, 03:11 PM
I've got a British made lathe c1945 (a William Findlay 'Electrolathe') which has fine threads for the adjustments on the leadscrews and feedscrews. It puzzled me for ages, because the diameters were strange. Eventually after some research I found they were electrical conduit threads.

Richard
You mean the PG (Panzergewinde)? And that has been made "old" by replacing the standard with a 1.5 mm pitch metric threads :) Oh the fun with these threads...

RWO
03-16-2011, 03:58 PM
I've got a British made lathe c1945 (a William Findlay 'Electrolathe') which has fine threads for the adjustments on the leadscrews and feedscrews. It puzzled me for ages, because the diameters were strange. Eventually after some research I found they were electrical conduit threads.

Richard

Sounds perfectly reasonable on an "Electrolathe" ;)

RWO

John Stevenson
03-16-2011, 04:06 PM
I've got a British made lathe c1945 (a William Findlay 'Electrolathe') which has fine threads for the adjustments on the leadscrews and feedscrews. It puzzled me for ages, because the diameters were strange. Eventually after some research I found they were electrical conduit threads.

Richard

Richard,
Are you sure it was a leadscrew and not a length of flexible conduit ? :)

sansbury
03-16-2011, 06:26 PM
but why do (did?) manufacturers bother??


I have a theory that certain operations happen because somebody said, "the print doesn't say, so just grab any old (tap/bolt/shaft/etc) that works," and the one that gets grabbed becomes the standard. That's the great part about having a lathe and mill: there's no such thing as an unavailable replacement part, just an excuse to buy the cutting tool or attachment you need to make one yourself :D

Paul Alciatore
03-17-2011, 12:28 AM
19 TPI has got to be about as non standard as you can get without using pie.

Who even has gearing for that thread? I have a full set of gears for my SB, including three compounds and some extra gears not usually included. I have created a chart that shows all possible threads that it can cut. I can do 19.2 TPI, 19.33333 TPI, 19.5 TPI, and several really odd values starting with 19 and with infinitely repeating decimals. But I just do not have any combination of gearing that will do 19 TPI. It is a prime number and I assume you would need a gear with either 19 teeth or a multiple of that (38, 57, 76, etc.).

Does anybody have the ability to cut 19 TPI without making or buying such a gear?

On the other hand, it is fairly close to 1.333 mm: 1/19" = 1.337mm which is certainly well within the accuracy of measurement. Guess what, I have four different combinations of gears that can cut that. The simplest is 32 - 60 with a 100 - 127 transposing gear between them. (8 TPI lead screw). So it is probably a combination of English and metric.

The only possible reason I can see for this is to prevent third party replacements. Inch OD makes you think English measure. Nobody thinks about metric thread. So a special gear is needed to make a special tap which is needed to make a special nut. Not many will copy it. More sales for the OEM.

form_change
03-17-2011, 03:20 AM
My lathe has 19tpi on the gearbox plate and I think Tim's does too.

Michael

Peter N
03-17-2011, 03:26 AM
Does anybody have the ability to cut 19 TPI without making or buying such a gear?

.


Yes :D

http://www.btinternet.com/~p.neill/Coffee/Metric_2.jpg


http://www.btinternet.com/~p.neill/Coffee/57TGear.jpg

Timleech
03-17-2011, 04:10 AM
19 TPI has got to be about as non standard as you can get without using pie.

Who even has gearing for that thread? I have a full set of gears for my SB, including three compounds and some extra gears not usually included. I have created a chart that shows all possible threads that it can cut. I can do 19.2 TPI, 19.33333 TPI, 19.5 TPI, and several really odd values starting with 19 and with infinitely repeating decimals. But I just do not have any combination of gearing that will do 19 TPI. It is a prime number and I assume you would need a gear with either 19 teeth or a multiple of that (38, 57, 76, etc.).

Does anybody have the ability to cut 19 TPI without making or buying such a gear?

On the other hand, it is fairly close to 1.333 mm: 1/19" = 1.337mm which is certainly well within the accuracy of measurement. Guess what, I have four different combinations of gears that can cut that. The simplest is 32 - 60 with a 100 - 127 transposing gear between them. (8 TPI lead screw). So it is probably a combination of English and metric.

The only possible reason I can see for this is to prevent third party replacements. Inch OD makes you think English measure. Nobody thinks about metric thread. So a special gear is needed to make a special tap which is needed to make a special nut. Not many will copy it. More sales for the OEM.

19tpi is normal for UK lathes, as 1/4" and 3/8" BSP use it.
All three of my lathes can do it 'straight out of the box'. Two are CVA 10EE clones, I think I'm right in saying that early CVA lathes must have copied the 10EE box slavishly and didn't include 19 tpi, (John?) later versions did.

Yes I have dealt with mixed metric/inch threads, this one I'm sure is basically a BSP thread. Laziness or perversity from the makers, I think.


Tim

franco
03-17-2011, 04:39 AM
Quote:
Originally Posted by Paul Alciatore

"Does anybody have the ability to cut 19 TPI without making or buying such a gear?"

Yes, my Chinese 13x40 will cut 19TPI. A lucky find in a friend's box of junk of an old but unused 76T spare 16DP gear for a long gone sickle mower blade sharpening grinder allows me to cut 19TPI on the old change gear lathe too.

Re unexpected threads, recently I removed the cylinder head from a 1940s British JAP 2S stationary engine. The head bolts looked too fine for BSF - surely not UNF on such an old British engine? The threads turned out to be 5/16 x 26TPI 60 degree British Cycle. Reasonable I suppose, considering the extensive use of JAP engines in older British motor cycles, but not what I expected on an engine usually used of fire pumps and similar applications.

franco

.

Timleech
03-17-2011, 04:53 AM
Quote:
Originally Posted by Paul Alciatore

"Does anybody have the ability to cut 19 TPI without making or buying such a gear?"

Yes, my Chinese 13x40 will cut 19TPI. A lucky find in a friend's box of junk of an old but unused 76T spare 16DP gear for a long gone sickle mower blade sharpening grinder allows me to cut 19TPI on the old change gear lathe too.

Re unexpected threads, recently I removed the cylinder head from a 1940s British JAP 2S stationary engine. The head bolts looked too fine for BSF - surely not UNF on such an old British engine? The threads turned out to be 5/16 x 26TPI 60 degree British Cycle. Reasonable I suppose, considering the extensive use of JAP engines in older British motor cycles, but not what I expected on an engine usually used of fire pumps and similar applications.

franco

.

A while ago I was asked to find a nut for a big old Lucas headlamp, the type which fixes to a spherical seat for adjustment. Ones I've seen before had a tubular brass clamping bolt through the seating, to allow the cables to pass down the middle, but this one had a solid bolt with a fine thread. Assumed without studying it that it would be 1/2" UNF, in fact it was 1/2" x 26 - whether cycle or Brass thread I didn't discover, it's UNF now, as I didn't have 1/2" tap among my 26 tpi stuff ;)

Tim

ed_h
04-07-2011, 09:18 PM
1971 Triumph motorcycle. Petcock bung on the fuel tank. I wanted to pressure test the tank and needed to fit a hose barb to the bung. I've got an inch thread pitch gage set with over 50 pitches in it and none of them fit, but it looked to be between 18 and 20 tpi. No metric pitches fit either. Finally verified 19 tpi by using the 38 tpi gage.

Turns out it is a standard 1/4" BSP fitting, but unless you know what to look for, it's hard to find in a thread listing.

Must be another example of that British odd-ball thread fetish they have.

jugs
04-08-2011, 04:37 AM
1971 Triumph motorcycle. Petcock bung on the fuel tank. I wanted to pressure test the tank and needed to fit a hose barb to the bung. I've got an inch thread pitch gage set with over 50 pitches in it and none of them fit, but it looked to be between 18 and 20 tpi. No metric pitches fit either. Finally verified 19 tpi by using the 38 tpi gage.

Turns out it is a standard 1/4" BSP fitting, but unless you know what to look for, it's hard to find in a thread listing.

Must be another example of that British odd-ball thread fetish they have.

British with odd-balls :eek:

thread fetish !!!!!

just because you can't cope with 55 or 47

Next you'll be saying we drive on the wrong side of the road :p

john
:)

Tel
04-08-2011, 07:42 AM
The ML7 Gear Calculator give 52 different solutions to cutting 19 tpi on the Myford, using the standard change gears.

http://www.duncanamps.com/metal/software.php

Circlip
04-08-2011, 08:25 AM
Next you'll be saying we drive on the wrong side of the road



That's the problem with bringing British bikes back from over the pond, nobody wants the RHD kit after conversion.

Regards Ian.

Tel
04-08-2011, 06:05 PM
Getting RHD bicycle clips is an even bigger problem.

jdunmyer
04-11-2011, 04:07 PM
The Chinese 7X lathes can cut 19tpi.

My LeBlond cannot, however.