5/16 - 18 UNC -2B DEPTH 0.375 . In this 0.375 is the depth of the thread tap or depth of the drill ?
5/16 - 18 UNC -2B DEPTH 0.375 . In this 0.375 is the depth of the thread tap or depth of the drill ?
Mike Agan wrote:
thread
Functional thread.
Michael Miller wrote:
Mike Agan wrote:
thread
Functional thread.
Minimum functional thread
Moderate amount of thread.
I've seen it as FTD (full thread depth)
Hi ,
Thanks for the answer .
If 0.375 is the thread depth then what should be the depth of the drill. ?
See Machinery's Handbook. It depends on the tap (bottoming vs plug).
Debananda Shrma,Sahu wrote:
Hi ,
Thanks for the answer .
If 0.375 is the thread depth then what should be the depth of the drill. ?
Deep enough to get the threads in and also fulfill the desired design intent.
In short, depends. Sometimes you want a blind hole, sometimes you don't. Bottom tap, straight flute, or spiral tip tap? Thread mill, formed threads or cut threads? What kind of tool are you using to put the hole in?
Well you get the picture. The design dictates what the hole can and can't be. The rest is left to whether available tooling can make the hole or not.
Here's a pretty good description of what I'm talking about. If you can define the hole in a way that both meets the function and can be manufactured with tools your manufacturer already has, then it's a win win. You can't compromise your design though to just be able to use existing tooling...although it helps to know whether something can actually be made or not :-)
Frederick Law wrote:
Minimum functional thread
Moderate amount of thread.
I would think to make that a minimum you would have to have a Min or other expression next to it. Otherwise it is the depth of the functional thread to the tolerance expressed.
So if the call out is .375 and the tolerance is +/-.005 then the thread depth would have to be .370/.380. Having had the unhappy experience of attempting to try prove to a bunch of Aerospace people that said depth of thread where with in the ridiculous tolerance they had on their prints, it was always +/- unless it was specified otherwise.
Not saying that that is correct as I've never actually seen a standard on it, but everyone I know assumes +/- even some dork making me prove that a thread depth is with in +/-.005....yeah, that really happened....lots of times unfortunately. To be honest I often times took the "Well I'll lie about and see if they can prove me wrong" approach.
Is there a tool for measuring thread depth with that level of accuracy?
1-6BG786M wrote:
Is there a tool for measuring thread depth with that level of accuracy?
Nope. It's a classic example of "right until proven wrong."
Michael Mille wrote:
Scott Perman wrote:
Is there a tool for measuring thread depth with that level of accuracy?
Nope. It's a classic example of "right until proven wrong."
Why would you say that??? These types of thread depth gages have been around for decades and there are dozens of others.
Thread Depth Gage | Emuge Corporation
https://www.google.com/search?client=firefox-b-1-d&q=thread+depth+gage
+/- 0.005" ? Repeatably? a strong-armed (willed?) QC guy could easily fudge that.
Only one of the items you posted claims it can check thread depth to +/-.005 or less. The other that is a direct link is +/-.02, which while still difficult in the real world is at least reasonable.
I would not doubt that the gage itself has an accuracy of two, but in order to create a thread that could be checked, repeat ably, to .002 you would have to put it in a hard material, grind the threads and do it with a special end that had some sort of thread stop.
As Michael Miller stated you could make that think read whatever you wanted even if it included a torque limiter of some sort.
M. B. wrote:
... These types of thread depth gages have been around for decades and there are dozens of others.
Matt Juric wrote:
... As Michael Miller stated you could make that think read whatever you wanted even if it included a torque limiter of some sort.
Again, these types of gages have been around for a long time.
https://www.multimaticproducts.com/features/
http://personalpages.tds.net/~tdsign/mph.htm
Leader Wireless Digi-Speed Motorized Thread and Depth Gage | Willrich Precision Instruments
M. B. wrote:
Again, these types of gages have been around for a long time.
https://www.multimaticproducts.com/features/
http://personalpages.tds.net/~tdsign/mph.htm
Leader Wireless Digi-Speed Motorized Thread and Depth Gage | Willrich Precision Instruments
No one is saying you CAN'T check thread depth. I'm saying you can't repeat ably check thread depth to "/-.005 on a typical thread cut tapped hole. +/-.005 on a 1/4-20 screw is +/-36 degrees of a turn. Total tolerance less than 1/4 of a turn. I don't care what kind of tool you're using but there are so many variables that could effect a 1/4 turn of a screw that realistically checking to that tolerance with any level of confidence is near impossible and unquestionable unnecessary.
To make matters worse in order to meet even a CPK of 1.3 you'd have to have a mean of zero and max deviation of +/-9 degrees.
So even if you actually managed to check the hole repeat ably with in the +/-.005 you'd never be capable and if you're not capable in your ability to inspect something there's not way you can prove capability of the feature.
I didn't see anywhere on any of these devices that said "You can check a threaded hole depth +/-.005". Just because you have a tool that can inspect something does not mean that tool is capable of checking that thing to any tolerance and capability level.
A thread gage with precise thickness and depth gage.
Scott Perman wrote:
Is there a tool for measuring thread depth with that level of accuracy?
I suspect one could be made what what we did was to take a "Go" gage for that particular thread and screw it in until you couldn't screw it in any more. Essentially if it wasn't considerably deeper and not shorter than the called out thread depth it would always magically be in tolerance :-)
The parts that we were working on were an actuator in a helicopter for the military. The company that designed the actuator really had their heads stuck when it came to tolerances and understanding of function. However since it was on the print we HAD to meet the spec.
That project was such a cluster and so poorly designed I'm quite afraid to fly these days :-)
The "norm" is specify minimum thread for the load required without stripping the thread.
Machine shop usually tap more instead of less.
I had a bunch of re-threading to do long time ago because the CNC lead out make last thread not spiral.
It was a short thread to begin with.
Frederick Law wrote:
I had a bunch of re-threading to do long time ago because the CNC lead out make last thread not spiral.
It was a short thread to begin with.
Unfortunately I've been there myself. Had a project with a bunch of holes where the drill depth was called out shallow. The operator(s) broke one tap. So instead of asking to drill deeper or going to a flat bottom they tapped ALL the holes shallow. Something like 500 holes we had to have people go back and tap deeper by hand.
Frederick Law wrote:
I had a bunch of re-threading to do long time ago because the CNC lead out make last thread not spiral.
It was a short thread to begin with.
Man this is reminding of all the really crappy things I had to do over the years for simple mistakes.
When I was designing gages for automotive we had a part that they punched with a particularly tight hole undersize. Don't ask me how the gage department got stuck with this, apparently we were the only ones that knew how to accurately use a plug gage.
We had two or three bins, the large, 4ft X 4ft ones filled with these parts that were probably only 4-5" long. THOUSANDS of them. Me, one of my co-workers and my boss sat there over a weekend gaging that one hole on every part and then reamed them out by hand if they were small. Metal Slivers, Blisters was not my best weekend.
Get a copy of Machinery's Handbook and keep it just to the left of your keyboard. Reach for it every time you have one of this type of questions. (Yes, thread gauges are included.)
(Plug taps - AKA: Gun-plug taps)
I've got a depth micrometer accurate to .0001" for measuring drainage ditches.
^^ Same logic.
thread