Aerospace fittings questions

The Academy
1

Good afternoon Everyone!

On the 131LM fitting; D1 is shown as +.00/-.002 X 118 ± 5 degrees
I get the 118 degree chamfer; do I understand the diameter to be 0.430 and therefore trig out what the OD of the chamfer would be? How am I to know the ID if the spec is the actual OD? Thanks in advance for your assistance on this!

Respectfully,

Frank Stanek

2

Hello,

The 118° in D1 does not apply to any chamfers on this part.

You didn’t ask but I hope this helps.

Interpretation… Sometimes it can be difficult to see what ‘Should Be’ from what is given. In the area of Ø D1 we have dimensions and GDT.

131LM Snip

From the part view and text here is what I think the B/P is trying to say.

  1. Ø D1 (.430) +.00/-.002. with drill point angle 118° ±5°.
  2. Depth of hole is length L1 (1.685) ±.030 AND the diameter along the length of the hole is Ø D1 (.430).
  3. Position Tolerance within Ø .005.
  4. Parallel within .002 to Datum –A–.

What I think the B/P Should Be saying. This is not a criticism or a critique of the material that TITAN and the Team have put together. They are doing a great job of providing free education to the community. I’m just here to learn and grow.

  1. Ø D1 (.430) +.000/-.002 THRU. Drill point angle should be omitted because drill point angle IS NOT a part feature. Should be included only if the hole making process IS dependent on the drill point angle to make the hole.
  2. Length L1 should be omitted to control depth because hole IS Thru. Given Length L1 (1.685) is also longer than the actual hole length (1.590). If length is used to control minimum hole diameter depth then the length should be dimensioned on the part so that we know which end of the thru hole it applies to.
  3. Position Tolerance given has incomplete location Feature Control Frame. It is missing DATUMS like |A|B|C| or |A|C| or |A|B| meaning we do not know WHERE to measure the position from.
  4. In the B/P, I read Datum –A– to be the left hand side of the part or the top of Port AS5202-08. The hole orientation cannot parallel to Datum –A–. Datum –A– should be changed to an OD or ID or even Thread Pitch diameter to run along the axis of the part.

LD

1 Like
3

Good afternoon!

Thanks for the reply! I took it that the chamfer should be 118, however the diameter MUST be bigger than the .430 dia of the hole. I am used to that spec on medical parts.

Also, it wasnt that the spec to datum A is wrong; I believe it should be a perpendicular symbol. Then that spec is valid.

But you see the same things I did then! I greatly appreciate your time and response.

Respectfully,

Frank Stanek

4

Looking at the spec and not the entire drawing, I was assuming (yeah, wrong thing to do) that the call out was for the tap drill for that part. I see there is an entire specification for the threads and ID of threads. Not sure what the 118 deg is referencing to the thru hole.

5

Good evening Stephen!

I am very familiar with this type of spec; see it A LOT with the parts we make here. It is specifying the chamfer between the ID and the face. HOWEVER; if we use the .430 spec that is the LARGE diameter of the chamfer. Hence we have no other data with which to come up with the ID. IF the ID is .430, then we can trig it out and measure the chamfer dia by illuminating or back lighting it on a comparator. That was why I was asking for clarification. I am in the process of programming these parts out if I have off during this shut down over the corona. Also, as L replied; there is a mistake on the GDT form. Can not be parallel since the two are perpendicular to each other. That one is also used quite a bit here, I took the leap of faith on that from this side. I do not have the print next to me, I will have to pull it out and give what I think would be a useful spec on that print based off of what we see here. The .430 would be a separate spec with the +.000 -.002 and the chamfer would have another dia on the next line with the chamfer details. I will have to see if there is an example I can freely cut n paste to share with everyone.

Respectfully,

Frank Stanek