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Thread: measuring threads accurately
02-18-2012, 03:53 PM #21.... a new thread micrometer from Mitutoyo or Brown & Sharpe is about $1000 if you include a range of anvils. Try to find used tools that weren't actually used...
I've cut plenty of threads in various forms but not qualified to discuss thread measurement, yet; so this "thread" and information is very much appreciated. Especially enjoying apestate's discourse.
I will say that before I was outfitted so luxuriously, the fast and dirty way to compare OD threads was over wires, any near-size wires (or same size drill bit shanks), so long as the thread being cut came out the same as the measurement over the same wires on the thread being compared.
02-18-2012, 04:48 PM #22
Usually for common sizes internal I will order a gauge, it is pretty cheap if you order ahead and people bring it in. For odd sizes I usually make them or ask the customer for one. It usually takes an hour or two to make a good gage, so for the common sizes it is very reasonable to purchase. For external I use wires, you can also use thread mic's for "V" threads.
Like many here Gagemaker is great for checking with a "gun" style mic, but they are usually only for bigger threads like 2" (50mm) and bigger. Sometimes it is enough to make them from threat heights of Acme threads if you know and trust your inserts (always check thread form if you do it this way). Gagemaker also has great software for thread specs.
It is always a hard thing to decide what needs to be done. I usually charge a bit more if I need to make/buy gages, I have quite a few gages on my shelf gathering dust, so make sure you are paid for your time and efforts, unless they are for sure going to give you the repeat job and not just when they can't get it done on time.
02-19-2012, 08:43 AM #23
I've found that I can buy a thread gage (OD set or ID) for less than I can make one and have any certainty that it is correct. The cost of the time in making a gage out of good material and inspecting it to ensure it is correct has always been greater than I get them for through my supplier. I get a decent discount off catalog prices from Bass Tool in Houston, who supplies me with Meyer, Vermont, or Pennoyer Dodge stuff.
I have made quite a few in an emergency, but I'm not keen on it! The aspect that bothers me is making a gage on the same machines that I will be making the parts on is suspect.
I typically buy the appropriate gage set, but I also have a OD thread mic set for external stuff - and insist that both are used. For internal threads I will use an indicator to check the thread crests for taper as well as using plug gages. This is in conjunction with always using the full form threading inserts.
02-19-2012, 09:08 AM #24
As you want to make an inside thread that's a perfect fit for the cusomer's part, why not get such a part from him to use as the gauge . ?
02-19-2012, 02:23 PM #25
However the prints from most of the top names are just about identical.
When making these one does need to realize that their checking methods vary.
Sandvik's inspection is tough as nails, no doubt about that. They are very hard to please.
You should realize that a fair amount of this work is outsourced.
The shop that ground your Sandvik full profile threaders may also be making them for Seco, Kennametal, Valenite, and others.
Single point toppers are relatively easy, lots of room to play.
It's nailing the seven tooth APIs that separate the men from the boys and pushes your measurement capabilities.
02-19-2012, 02:30 PM #26
02-19-2012, 02:44 PM #27
02-19-2012, 03:00 PM #28
02-19-2012, 03:33 PM #29
First off plug and ring gauges don't "measure" anything, they simply tell you if you are within the tolerances or not.
Pitch diameter is the diameter to measure and for a M56x1.5 (if not otherwise specified) the tolerance is 6H. In numbers the pitch diameter tolerance is min. 55.026 and max. 55.238. A tolerance of more than 0.2mm (0.008") should present no problem.
Take a look at http://www.f-m-s.dk/3,00%20pages2-15.pdfand for even more Screw thread types
As already suggested I'd use a full form thread tool to cut.
I'm sending you a PM and you can see even more
I sent you an email - not a PM.
Last edited by Gordon B. Clarke; 02-19-2012 at 03:45 PM. Reason: email
02-19-2012, 04:05 PM #30
02-19-2012, 05:13 PM #31
They only job out finishing operations.
The originators of this tool were a nice size operation here in Detroit on 8 mile known at the time as the best in world at pressing intricate details.
As I said there can be no argument as to Sandvik's quality. They did not get to where there are by making and selling average quality stuff.
02-19-2012, 06:34 PM #32
02-21-2012, 03:24 AM #33
It's not that what you write is incorrect but you'd be more at home in a technical school teaching theory that working on real threaded components.
We're dealing here with measuring a simple straight forward fine metric thread and it's far from rocket science.
Measuring threads is both simple and inexpensive. Try clicking on my name (Gordon etc.) and looking at my website. External threads for 1/4" have a reasonably large pitch diameter tolerance (around 0.004") and a 2" thread is around 0.01". The pitch diameter tolerance on internal threads is usually about 30% more than for external.
The pitch diameter tolerance for the thread in question is 0.008" so what's the problem?
02-22-2012, 03:38 PM #34
Thanks to All for the info Guys !
I called the Customer and requested he sent the Male Part which he had no problem with (just shows that sometimes its best to ask rather than struggle by when he just had a male part sat on his desk ready to send)
@ Gordon , Thanks your stuff looks good and i will be in touch shortly as i am interested in buying.
I actually used a full profile sandvik insert and tried the method suggested to turn to the mean minor diameter and when i tried in the sample it was perfect so that was a good call , but i was glad to have the sample as when running quite a few you never know if the insert starts losing its edge and push off occurs , you just have that piece of mind of trying the male part in before removal from chuck .
Thanks All TB
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03-01-2012, 07:09 AM #35
I'm just going to add this as the "apestate" way of thinking might scare people into thinking that making correct threads is complicated.
The closest I can come to thinking about how to make a "perfect" thread is by measuring pitch diameter and using a GO thread plug or ring gauge.
This lets you know where the thread is with regard to the tolerance and the gauge lets you know that the thread profile is OK.
In a pinch you can also use a nut or bolt to check thread profile as long as you measure pitch diameter. You can even make your own gauge if you measure pitch diameter and the cost of a real gauge seems a bit over the top.
Again, it surprises most just how big thread pitch diameter tolerances are.
I made this table long ago but it gives a good idea of just how big "big" is
0.10mm = 0.004"
And to those wanting to know more
To get from mm to inches just divide by 25.4
05-07-2012, 02:12 PM #36
I just talked to a guy that did threading overload work for Air Research/Garrett/Allied Signal in Phoenix in the 1960's through mid 90s. He recommended this company's product line for internal thread checking:
Internal Gages, Internal Gage Frames, Internal Gage Fingers, Internal Gage Stands: MTG: Carson City, Nevada
05-07-2012, 02:53 PM #37
Using a "nut" or "bolt" to make a good external or internal thread can be very dangerous as 1) you don't know where it is with regard to tolerance and 2) the part being made is almost always a much tighter fit than need be. A nut and bolt should be easy to screw together, not a "tight" fit. A tolerance is there to be used.
Cut the thread pitch diameter as close as possible to the middle of the pitch diameter tolerance and probably the only thing you need to be on the look out for is a worn or broken threading tool.
05-07-2012, 03:02 PM #38
Oh, I guarantee this stuff isn't cheap.
05-07-2012, 03:32 PM #39et a high quality (recommend sandvik) full profile insert. Bore the hole out to about 0.1mm under the min. minor diameter of the internal thread, then start threading. Carefully increase the thread size until you hit the mean minor diameter.
I wouldn't trust this unless you're diligent enough to keep a close eye on your tool tip quite often.
02-18-2013, 04:39 PM #40