Actual hole size for 3-1/8" instrument?

[Chappyd]

I'm making a CNC program to cut my panel out at work this Staurday. I have 4, 3-1/8" instruments to cut holes for, but I only have 1 of them in my hands. It's a pictoral pilot from TT. Using dial calipers I get the OD of the area to fit in the hole to be actually 3.140". I have an old tach from the Mooney, and it measures 3.115". What do you guys cut these hole too? How much room to leave for clearance from varying instruments?

Thanks.

[jsharkey]

Originally Posted by Chappyd

I'm making a CNC program to cut my panel out at work this Staurday. I have 4, 3-1/8" instruments to cut holes for, but I only have 1 of them in my hands. It's a pictoral pilot from TT. Using dial calipers I get the OD of the area to fit in the hole to be actually 3.140". I have an old tach from the Mooney, and it measures 3.115". What do you guys cut these hole too? How much room to leave for clearance from varying instruments?

Thanks.

Not sure what size hole it cuts but the female and male dies on my instrument punch set measure 3.125" and 3.116" respectively. All 3-1/8" Instruments fit great. Leave room for paint - but 3.14" seems big.

Jim Sharkey

[Kevin Horton]

When I cut my panel I noted that the actual size varied from instrument to instrument. If you are going to make all the holes the same size, you might want to wait until you have all the instruments in your hands.

[Webb]

I just calipered the flush mount hole that came with my Dynon unit. I used it as a pattern for drawing holes in the panel.

After cutting, don't forget you will sand smooth and it may get a smidge larger.

All instruments fit great and most of mine are 3 1/8. Suggestion, use your hole cutter on some scrap and test. That is what I did and I have a scrap piece with 3 holes in it till I got it right.

You don't want too tight so you can easily install and not chip paint off.

[Chappyd]

Thanks for the info guys. I can change the hole sizes in the program to fit. I can make the TT hole 3.170, to allow for paint. The rest I'll go 3.140 to allow for paint. Not using a hole saw, the cnc mill will use a .250 rough end mill to rough the cut outs, then a .125 carbide endmill making 2 passes around all the contours. From panel blank to having all the cutouts should be about an hour. Overkill, maybe but I have access to it so I may as well use it

I'll post a before and after shot and how long it took.

Thanks again

[trib]

Also keep in mind that half of your holes won't end up being round, they'll have the bumpout for the knob for adjustments.

[kentb]

I cut my holes with a fly cutter. The first hole I cut just a little undersized figuring that I would us a file after the cut to get a perfect fit. Big mistake!

I could not keep the hole round with the file. By the time the instrument fit in the hole there were small gaps in the side at some places. You have to be looking for this mistake very carefully to see it, but I know it is there.

The next hole I cut with the fly cutter I made sure that it was just a little bigger then the instrument and it came out perfect.

Kent

[Chappyd]

This is kinda what I had in mind when I started. I posted it on the -7 forum, but it didn't attract a lot of interest. When I posted it I had all the gear in house already. I actually put a lot of thought and deliberation into what I bought, some choices were made by desire, some by $$$$$$. The layout is what works for me, mostly by my experiences in the planes I've flown in my 500 hrs. and what I think I want. I spent a lot of time looking at all the panel pics. Boy there sure are a lot of different ones, probably 5000 + The mock up was very helpful when sitting in the plane. Everything is well within reach and easily readable. Cockpits are really pretty cozy after all.






Well I went off to work Saturday morning and set my panel blank up on our CNC milling center. I had to set it up twice, becuase the travel across the table was only 30". Took me about 3 hours, as I really took my time, didn't want to make a bad cut. It came out great!! It really was/is a bigger part of the project than I had envisioned at first. Drawing up the design in Mastercam took me sometime, with a lot of rearranging and fine tuning placement of stuff. One thing I didn't realize right away is that Van's .dwg file has the extra 1" along the bottom, the piece that's bent back.





After I got the initial brackets mounted, I installed the trays and popped everything in for a quick look. I'm rather happy with it so far. One of the best parts of building the plane is envisioning what I want in my mind, and then being able to create it.



It's kinda hard to make it out in the pic, but the equipment is a TruTrak EFIS, TT pictoral pilot auto pilot. The radio stack is the air gizmo for a 495/496, PS Enginnering 9000ex, Garmin SL30, ICOM A210, and a Narco AT165 tx. The engine monitoring will be the Dynon EMS 120. There's still a couple of small holes I'll have to put in, but the machine was sitting there between jobs on a Saturday.

[Webb]

The fly cutter worked great and was inexpensive. Go slow. Piece of board under kept pressure and the cutter didnt' hit the drill press table. Using it in a hand drill is a no no. I also had one of those that you turn and the cutter was the drill bit. It didn't work worth a flip on the practice scraps. Use a little oil too.

As I said earlier, I practiced on scrap until I got a hole I was happy with and then cut the panel (and held my breath). Cutouts for instruments were done with a file.

Take one of your instruments to use as a gauge for fine tuning the hole.



And call me old fashioned but I wanted a standard six pack instead of glass.