Unfamiliar screw thread
Unfamiliar screw thread
(OP)
Our customer is asking for a 0.668-20 UN 2B thread to be machined int a part. The thread is not to be coated. He insists it is not really an 11/16-20. There does not appear to be a metric equivalent, either. Any ideas where I can get info on this?





RE: Unfamiliar screw thread
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RE: Unfamiliar screw thread
Plug in 0.668 and chug away.
I'd suggest getting your customer's signature before you commit to any tooling.
RE: Unfamiliar screw thread
Harold
SW2010 SP3.0 OPW2010 SP1.0 Win XP Pro 2002 SP3
Dell 690, Xeon 5160 @3.00GHz, 3.25GB RAM
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RE: Unfamiliar screw thread
0.668 - 20 UN-2G - 1 Start
c/w 45 Degree End Chamfers
External Diameter Internal Diameter
Major Dia. 0.667/0.658 Minor Dia. 0.614/0.625
Pitch Dia. 0.634/0.630 Pitch Dia. 0.636/0.641
Minor Dia. 0.608/0.606 Major Dia. 0.668/0.671
Measure the Pin over 0.029 diameter wires for a pitch diameter of 0.673/0.678 (3 wire measure).
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: Unfamiliar screw thread
When it comes to chosing major diameters to suit pitches there are tables of drecommended diameters for the pitches listed, however since this is not UN (your cutomers ahs said so) then these tables don't apply but could guide you.
I have faced this problm with my customers ona numebr of occasions, usually this problem occurs from them buying foreign equipment. The Japanese are notorious for defining thread of a non standard nature (which is frowned upon in the EU if not banned. When the aprt of the equipment fail they have to choose between manufacturing their own (cheaper) or buying in from Japan (expensive) then they find there is no standard for the part. The most dangerous thing the customer can then do is to parce out the thread without defining the standard, over time different copanies make the parts and the standard starts to drift. Over the years they get a whole bacth of parts that don't fit.
The first thing to do if you are makng the nut is to ask your custmoer if you can emasure a range of components. By doingbthis you will identify the major diameter of the male part. If you are amkign th emale thread thenyouhave to ask for the female part to measure. Once you have a table of results with the variations you can then design a thread table to make a tap.
In your case the tap wil be around 17 millimetre, not a huge obstacle and you cna then define your table to suit this tap with the normal tolerance and clearance for this effective diameter.
before designing this table you need to be up on thred forms and tables. A tap manufcaturer willa ssist you. It is quite easy once you have determined:
1. the thread form
2. the pitch
3. the effective diameter male and female, all other sizes come from these.
In your case it is realtively easy, you have:
1. the thread form (UN)
2. Pitch (1.20")
3. within 1.6 thou the major diameter (17mm)
You give the minimum of information and it seemes it has to be dragged out of you like pulling a tooth but if you were more open we could be more specific. I find the same story with most enquiries, there is limited information, and no mention of quantities or cost considerations. I have yet to recive a thanks for the dozen or so answers I have listed.
This thread could be a 17diameter x 1.75 pitch metric thread, but only if the cusotmer has mesured the pitch wrongly. There is almost 2 thou difference in the pitch. Go see your customer and measrue the pitch for your self. Keep your knowledge under your hat and solve the problem and earn your company years of work. Tell the customer and they may well put the work out to someone else.
RE: Unfamiliar screw thread
RE: Unfamiliar screw thread
1. the thread form (UN)
2. Pitch (1.20")
3. within 1.6 thou the major diameter (17mm)"
The pitch is what??
Software For Metalworking
http://closetolerancesoftware.com
RE: Unfamiliar screw thread
Harold
SW2010 SP3.0 OPW2010 SP1.0 Win XP Pro 2002 SP3
Dell 690, Xeon 5160 @3.00GHz, 3.25GB RAM
nVidia Quadro FX4600
www.lumenflow.com
RE: Unfamiliar screw thread
RE: Unfamiliar screw thread
2. Pitch (1.20") ... Obviously a typo ... should have been 1/20"
metalonis and lumenharold,
It's just the B which indicates the internal aspect. The 2 refers to the class of tolerance.
RE: Unfamiliar screw thread
Harold
SW2010 SP3.0 OPW2010 SP1.0 Win XP Pro 2002 SP3
Dell 690, Xeon 5160 @3.00GHz, 3.25GB RAM
nVidia Quadro FX4600
www.lumenflow.com
RE: Unfamiliar screw thread
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Unfamiliar screw thread
Software For Metalworking
http://closetolerancesoftware.com
RE: Unfamiliar screw thread
Thanks everyone for your input.
RE: Unfamiliar screw thread
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?