Unknown Drafting Symbol - Half-Filled Circle X

holows88 · Jul 16, 2020

Hey there y'all,

I've hunted through my Machinist Handbook. I've scoured the internet. And yet, I can't figure out what the heck this symbol on the drawing I'm working off is.

Engineer is retired and customer is unaware. Part is an aluminum hatch cover. The symbol is near, but not quite in the center of the part I'm making (off by about 0.071").

Anyone know what the heck it could be?

Thanks in advance!

guest · Jul 16, 2020

origin

***The message you have entered is too short. Please lengthen your message to at least 10 characters***

AJ H · Jul 16, 2020

Sometimes that's used to reference the origin

eKretz · Jul 16, 2020

I've also seen that symbol used to denote a reamed hole, but usually it's with the "cross hairs" aligned vertically and horizontally. Usually for a dowel pin.

DDoug · Jul 16, 2020

Start surface (usually not machined)

Tyrone Shoelaces · Jul 16, 2020

eKretz said:
I've also seen that symbol used to denote a reamed hole, but usually it's with the "cross hairs" aligned vertically and horizontally. Usually for a dowel pin.

When I worked on marking out that was the symbol we used for a reamed hole. You blued or whitened up whatever it was you were marking out, scribed out your reamer drill dia circle, then your reamed hole dia circle. Then you dotted the quadrants with a centre punch. Last thing to do was to scratch out two sections of the circle in the blue with your scriber, just like the illustration, to signify to the driller that it was a reamed hole and not a drilled and tapped hole. As you say the crosshairs would be aligned vertically and horizontally.

Regards Tyrone.

boslab · Jul 16, 2020

I looked and wondered what the hell a hydraulic motor symbol was there for, ok minus the lines, it’s not a drg symbol I’ve used geometrically but who knows what iso symbols appear each day!
DDs start seems poss,
Mark

eKretz · Jul 16, 2020

Tyrone Shoelaces said:
When I worked on marking out that was the symbol we used for a reamed hole. You blued or whitened up whatever it was you were marking out, scribed out your reamer drill dia circle, then your reamed hole dia circle. Then you dotted the quadrants with a centre punch. Last thing to do was to scratch out two sections of the circle in the blue with your scriber, just like the illustration, to signify to the driller that it was a reamed hole and not a drilled and tapped hole. As you say the crosshairs would be aligned vertically and horizontally.

Regards Tyrone.

Eggsactly! It seems to be kind of old school, the newer guys don't seem to use it anymore.

R. Dan · Jul 16, 2020

It's an origin symbol, often the center of a round part.

ripperj · Jul 16, 2020

It’s also used to mark center of gravity

Sent from my iPhone using Tapatalk Pro

theperfessor · Jul 16, 2020

If it was done on a CAD system it is probably the Center of Mass/Gravity generated by the CAD system and not suppressed during printing so it shows up on the print.

DDoug · Jul 16, 2020

theperfessor said:
If it was done on a CAD system it is probably the Center of Mass/Gravity generated by the CAD system and not suppressed during printing so it shows up on the print.

I've NEVER seen that.

Mtndew · Jul 16, 2020

I've seen it be the Datum, and also a symbol for dowel holes.

Scottl · Jul 16, 2020

Also sometimes used as an alignment mark for artwork such as applied graphics including silkscreen lettering etc.

However, in that case there would never be less than two.

kenton · Jul 16, 2020

BMW on the side of a hill.

vmipacman · Jul 16, 2020

We use that symbol as the CG (center of gravity) of part. If its something that is lifted with a crane or winch its even more likely.

morsetaper2 · Jul 16, 2020

ripperj said:
It’s also used to mark center of gravity

Sent from my iPhone using Tapatalk Pro

This, what ripperj said, denotes position of CG

UncleFrank · Jul 17, 2020

In this context I'd say CG. Datum pts would be rotated 90deg and have slight extensions on the ctr lines.

Bobw · Jul 17, 2020

I just did a part that had a bunch of symbols similar to that.

I found my answer in the notes.

This quadrant blacked out meant
a .293 hole. That quadrant blacked out was a .359 hole.
Those 2 quadrants blacked out meant a .3125 on assembly.
Those other 2 quadrants blacked out was a .375 on assembly.

Did you dig through the notes?

Glock34 · Jul 23, 2020

Spiderman.

Unknown Drafting Symbol - Half-Filled Circle X

Aluminum

guest

Guest

Hot Rolled

Diamond; Mod Squad

Diamond

Diamond

Titanium

Diamond; Mod Squad

Cast Iron

Stainless

Cast Iron

Diamond

Diamond

Diamond

Stainless

Cast Iron

Diamond

Cast Iron

Diamond

Plastic

Similar threads