Why are gear tooth gauges so ridiculously expensive?

Industry can’t get away with paper cutouts and 3d printed plastic. I’m an airline pilot, and years ago there was a DC9 whose windshield blew out because the maintenance team used screws that were literally a couple thousandths too small. But it resulted in the Captain being sucked out of the plane (fortunately he lived to tell the tale). I get that as hobbyists we are not in industry, and close tolerance isn’t that big a deal, but I like the idea of ”doing it as the pros”, and as such I have been patient and purchased Starrett from ebay. So while I agree with everyones position above, and I support doing things in a “cost effective” manner, I also maintain the ideal of doing the best that I can. When I look at the work I do, and can see that it is to tolerances greater than spec, I am proud, and the extra $60 doesn’t matter...... how much does proud cost? That is for each of us to answer; I’m also proud when I manage to save $60 by clipping coupons, lol. Cheers lads, no disrespect, just my 2 cents.


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Moderatemixed said:
Industry can’t get away with paper cutouts and 3d printed plastic. I’m an airline pilot, and years ago there was a DC9 whose windshield blew out because the maintenance team used screws that were literally a couple thousandths too small. But it resulted in the Captain being sucked out of the plane (fortunately he lived to tell the tale). I get that as hobbyists we are not in industry, and close tolerance isn’t that big a deal, but I like the idea of ”doing it as the pros”, and as such I have been patient and purchased Starrett from ebay. So while I agree with everyones position above, and I support doing things in a “cost effective” manner, I also maintain the ideal of doing the best that I can. When I look at the work I do, and can see that it is to tolerances greater than spec, I am proud, and the extra $60 doesn’t matter...... how much does proud cost? That is for each of us to answer; I’m also proud when I manage to save $60 by clipping coupons, lol. Cheers lads, no disrespect, just my 2 cents.


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I'm not sure anyone is saying to use a paper cutout or 3d printed gauge to check tolerances (or steel ones for that matter), and one wouldn't use screw pitch gauge for that either. But if I have a worn buggered up gear in my hand and am trying to determine which gear cutter to use (or buy) they are very useful ... and plastic works for me. The gears I deal with most (not that I deal with them often) are from 4-8 dp and can be either 14 1/2 or 20 PA. So, for most gauge sets I have seen ... I would need 4 sets, 2-5 DP and 6-80 DP in both 14.5 and 20 PA. I'll keep printing them on my 3D printer.
 
Many long years ago, I was explaning to a co-worker how mass production worked. Since we both were in the electronics field, I related the story of ICs, specificly the 7400 TTL chip. When they first came out, they were expensive. Very expensive. Later, the price came down. Over the years, as more complex ICs came to be, they got so cheap they weren't worth the profit on the shelf space. You had to ask for one, in dozen lots~~

What it came down to is the manufacturing costs. The first 7400 costs $300 K to make. The second one costs 37 cents. The thousandth one cost 3 cents. And got cheaper from there.

Gear guages fall into that same catagory. Only they never got much beyond the first stage.

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Hello from Belgium,
For my pension, i did by me a WMW ZFWZ 250x2.5 Gear cutter.
20190626_204145.jpg
DSCN0775.JPGI am leurning the differences in Module and diametral pitch gears.
Now i am on the question of the pressure angle:
most 20° pressure angel today.
15° or 14.5° for older gears (before 1920?).
25° or 30° fot high torque loaded gears.
To control those differences i did saw the different gear tooth geauges.
Last month i did find a Mutitoyo PJ250B profile projector on my way(home).
With the magnification lens of 10/1 i want to figer out the difference in pressure angle.
By trying to proceed this way:
I have a hobbyist licence off Fusion360 with the app/schipt GF Gears installed.
I want to make some smaller pignons for speedcounters of DKW-SB bikes.
My gear WMW cutting machine kan machine up to Module2.5 gears.
The hight of a Mod2.5 tooth = (2 x Mod) + (Clearance(=0.2xmod))
So that is maximum (2.5 x 2)+ 0.2x2.5 = 5.5mm
A tooth of 5.5mm hight projected 10x bigger on the screen of the profile projector,
must be good vissibel on 55mm hight?
When i draw the profile off on tooth in Fusion360 10times bigger an print it
on a transparant scheet to put it on the screen of my projector?
When i make two scheets, one on 15° pressure angle and one on 20° pressure angle,
it must be possibel to figer out the pressure angle of the gear?
I think that solution must worck in my situation?
DSCN2079.JPG
 
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Today i did started to print out some caliper plates to measure.
But as i am in Europe we have Diametrale pitch and Module.
I want to be able to control pressure angle of 20° and 14°30 for the older stuff.
For the range from Dp2 to Dp5 and from Dp6 to Dp 32 i need two caliper plates;
So that means in total 8 different caliper plates to print.
Thee of theme are already done, the rest is for next week in the fab-lab.
When i have a look on the printed plates to see some differents
between 20° pressure angle and 14.5° pressure angle on a big Dp2 dent:
The Dp2 Pa14,5° measure a little bit larger ( mm) on top of the dent
and measure a little bit smaller ( mmm) on the base of the dent
 
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When i have a look on the printed plates to see some differents
between 20° pressure angle and 14.5° pressure angle on a big Dp2 dent:
The Dp2 Pa14,5° measure a little bit larger ( 10mmby Pa14.5° and 8.7 by Pa20°) on top of the dent
and measure a little bit smaller ( ( 14.7mmby Pa14.5° and 15mm by Pa20°)) on the base of the dent.
difference PA.jpg
On a big teeth of DP2, you have to look good, to se to see the difference between a Pressure angle of 14.5 Degrees ans 20 degrees.
To for tooths smaller than let us say Dp12, it will be difficult to see the difference on that printed measuring plates........
When i work with the profile-projector and a magnification of 10 by 1 the difference in thickness, caused by the pressure angel,
must be 10 times more visible i suggest ?
We will make everything ready for some measurements to find out that possibility of visual measurement with the profile-projector.
 
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