Metal lathe? Peterborough area?
- Thread starter pe2dave
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Inspector
Nyuck, Nyuck, Nyuck!
If you can't find someone to make the point for you look for a bolt that fits the thread that isn't threaded all the way to the head. Cut the head off and chuck it in a drill and present the spinning bolt to a bench grinder. It won't take long to shape it. You can clean up the marks with sandpaper.
Pete
Pete
pe2dave
Established Member
Good idea... but where to find imperial bolts Pete! Sure I don't have any lieing around.
Inspector
Nyuck, Nyuck, Nyuck!
You're asking a guy in a land that won't let go of the imperial system. 
I suspect that given the 5.5mm diameter = .216" = No12 fastener size it would be quite hard to find even here as it isn't a common size. If you can determine what the thread actually is I have no problem sending you some if I can find them. https://www.icscuttingtools.com/pdfs/screwthread-guide.pdf I checked my old tap and die set and only have the 12-24UNC size and I have never used them in the almost 45 years I've had the set. Chronos have the dies if you can find the silver steel to make one.
I am curious as to why the upper one has the slot shaped to kick it over on an angle. Is it to trail the point when scribing circles on sheet metal?
Pete
I suspect that given the 5.5mm diameter = .216" = No12 fastener size it would be quite hard to find even here as it isn't a common size. If you can determine what the thread actually is I have no problem sending you some if I can find them. https://www.icscuttingtools.com/pdfs/screwthread-guide.pdf I checked my old tap and die set and only have the 12-24UNC size and I have never used them in the almost 45 years I've had the set. Chronos have the dies if you can find the silver steel to make one. I am curious as to why the upper one has the slot shaped to kick it over on an angle. Is it to trail the point when scribing circles on sheet metal?
Pete
pe2dave
Established Member
@Inspector guessing the thread is ...?(help anyone) some older imperial UK thread. I don't have the tools
to measure pitch etc.
The brass inserts are not quite in 'square'. I've slimmed it down, now fits. Except. I now need a pencil
<7mm diameter, a 'slim' golfers pencil.
UNC? Dunno. Whitworth sounds much more likely (but a guess). British Standard Whitworth - Wikipedia
I'll pull the other one and *try* to measure pitch and depth.
to measure pitch etc.
The brass inserts are not quite in 'square'. I've slimmed it down, now fits. Except. I now need a pencil
<7mm diameter, a 'slim' golfers pencil.
UNC? Dunno. Whitworth sounds much more likely (but a guess). British Standard Whitworth - Wikipedia
I'll pull the other one and *try* to measure pitch and depth.
Ttrees
Iroko loco!
Should this be a one time deal, and you decide to try as Inspector suggests, (the finer wheel works much nicer)
Might it be a sloppy enough fit for a metric thread to work...
worth trying again if not happening, with a damaged thread re chased with a cheap tap and die set
from the middle isle of liddles
(which includes a pitch gauge)
pe2dave
Established Member
pe2dave
Established Member
Ttrees
Iroko loco!
@pe2dave
I ain't one to talk about tapping or die-ing threads as my track record isn't great on strange materials,
not to mention cast isn't something I've ever attempeted to tap.
Having bought a bag of brass threaded inserts from the states for converting unservicable guitars with doweled in neck joint to bolt on neck (have some in the workshop to check, IIRC the same size)
Little did I know it would be difficult to get nice allen head bolts for the job, so a case of...
if you've only got a hammer, everything looks like a nail.
Not being used to any engineering toolery, and being ignorant in my youth, I used some blackened hard bolts to convert them into metric, didn't mind wrecking one, worked well in the end.
It was certainly a bit of effort to do, can't say if a tap woulda been better or not,
and might be a bad idea on something cast, should it crack.
(my inserts were machined from bar stock)
I was only suggesting should you be able to see if a metric thread could possibly be a nice fit without a wrench.
Tom
I ain't one to talk about tapping or die-ing threads as my track record isn't great on strange materials,
not to mention cast isn't something I've ever attempeted to tap.
Having bought a bag of brass threaded inserts from the states for converting unservicable guitars with doweled in neck joint to bolt on neck (have some in the workshop to check, IIRC the same size)
Little did I know it would be difficult to get nice allen head bolts for the job, so a case of...
if you've only got a hammer, everything looks like a nail.
Not being used to any engineering toolery, and being ignorant in my youth, I used some blackened hard bolts to convert them into metric, didn't mind wrecking one, worked well in the end.
It was certainly a bit of effort to do, can't say if a tap woulda been better or not,
and might be a bad idea on something cast, should it crack.
(my inserts were machined from bar stock)
I was only suggesting should you be able to see if a metric thread could possibly be a nice fit without a wrench.
Tom
Dave T
Member
If you are happy to put it in the post to Essex, I can do this for you. Send me a pm for the address.
Dave T
Dave T
pe2dave
Established Member
A new thread?
;-)
This youtube video helped me understand the differences and how to measure threads. UK bias perhaps.
I've tapped into it. Dieing to get a thread gauge
(Sorry, couldn't resist)
;-)
This youtube video helped me understand the differences and how to measure threads. UK bias perhaps.
I've tapped into it. Dieing to get a thread gauge
(Sorry, couldn't resist)
John Hall
Established Member
If 6mm is a sloppy fit, it’s probably 1/4” BSF….BSF…British Standard Fine, and BSW..British Standard Whitworth are the common imperial threads used on tools and engineering along with BA…British Association, UNF and UNC…Unified national fine and course….BSF bolts are easy to get hold of on EBay, but you’d need to confirm it first….Just cut the part threaded bolt to length, put the threaded end in a drill chuck and turn the point against a grinder or file
Last edited:
J-G
Established Member
Overall that might be useful to someone with some existing knowledge (so that they can ignore the obvious errors) but there are a few bad referencies - close to the end he suggests that BSPT & NTP threads are interchangable !!! He does then say that the flank angles are different but doesn't make it clear that that fact alone makes them non-interchangable. Even PTFE tape wouldn't help to make a gas-tight joint with such a marriage.
On the difference between Whit & Unified or Metric he made no reference at all to the easiest way to decide which you have - - - BSW, BSF etc., as well as having a 55° form, also have rounded crests & roots whereas Unified & Metric, with 60° form, have flat crests & roots.
pe2dave
Established Member
Thanks for the kind offer Dave.
I may take you up on it!
I need 5.5mm mild steel (the only stuff I have is 1mm too big, and it's hard work taking it down on a pillar drill / file).
I've made an informed guess it is UNC 12 (or UNC 7/32) from diameter / thread count.
I've yet to decide if I'll be bored to tears putting a point on it + if it's worth buying a die + diestock!
Option (bit ashamed) epoxy in some smaller stuff and 'point' that.
I'll pm you if I may.
John Hall
Established Member
Looking closer at the last pic I would say it’s BSW…and probably 1/4” if the 6mm is a sloppy fit. UNC would fit…
pe2dave
Established Member
Possible John.
24 tpi, 5.5mm diameter body of the point?
BSW 24 tpi 7/32matches though. Tapping drill is 4.5mm, seems to match?
(Why is nothing 'easy'
)
J-G
Established Member
There is no 7/32 BSW in the BS 84 : 1956 standard -- There is a 'non prefered' 7/32 dia. in the BSF series at 28tpi.Possible John.
24 tpi, 5.5mm diameter body of the point?
BSW 24 tpi 7/32matches though. Tapping drill is 4.5mm, seems to match?
(Why is nothing 'easy'
That does not mean that the thread couldn't be 7/32 x 24 Whitworth - it's just not BSW!
Why do you state the diameter in mm but the pitch in TPI ?? Is the diameter of the thread really 5.5mm? (0.21653") or is it 0.216"? - which might indicate a N° 12 UNC which is 24 tpi even though 0.216" is the nominal dia. in fact a N° 12 UNC thread is more likely to be smaller than 0.216".
7/32" is in fact 0.21875" so it would be reasonable to assume that this is nominally a 7/32" thread but at 24 tpi would be a non-standard.
It seems unlikely that it is a metric thread since the rare occsion that 5.5mm dia. is listed in a 'Standard' it is only in the Fine pitch series at 0.5mm - 24 tpi could be a mis-measure of 1mm but never 0.5mm!
At 24 tpi it also cannot be 1/4" Whit. form - BSW is 20 tpi and BSF is 26 tpi - and 5.5mm OD would be very much undersize.
pe2dave
Established Member
There is on the chart I have.
OK. Understood. (guess) it's 50-100 yo?
I counted the tpi... I can't count in mm
I measured in mm.Yes, according to my micrometer.
#12 UNC was my first guess. I lie. 7/32 UNC was my first guess. Since tracytools don't do that size, I settled on #12
as the best guess so far.
Not impossible?
I agree. Age would tend to agree with that conclusion (apart from which I can't measure the pitch accurately enough)
I didn't suggest it might be (according to the table I have).
YMMV
Dave
J-G
Established Member
No - John Hall did (Reply #16) I just tacked that on the end as an afterthought
Do you not have a 'Thread Pitch Gauge' ? The difference between 24tpi and 1mm is palpable with well made sets. If you have one such as shown in the referenced Video then maybe not as muchpe2dave said:
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