cjensen

cjensen

Well Known Member
just finished countersinking for the #8 screw dimples on the spars, and they came out pretty good, but they are not PERFECTLY smooth. it's like there are tiny little particles on the countersink cutter that are preventing a nice silky smooth finish. they are the right size, but i wondered if i should get a new cutter to smooth these out, or just leave 'em.

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these are all the same countersink hole. whatcha think?
 
It looks to me like there was nothing behind the material for the pilot to ride in. If you look at the perimeter of the machined area it is not round, but kinda squared off here and there. This happens when the cutter starts to chatter around in the hole. I'm not sure what, if anything, needs to be done to correct it though. If it were me I'd probably run the countersink around the hole a couple of turns by hand to smooth it out and call it a day.
 
Steve is right,you could clamp a soft 2X4 under so the pilot steers in the wood,I had the same problem on my 8 wings and orther places but the soft wood solves the problem

J?rn m?ller
RV8 205hours
 
Chad-
Mine looked pretty similar ... are you using a single fluted cutter or one with 3 blades?
I chose not to worry about it.

Thomas
-8 wings
 
Chad,

Your picture shows a fine countersink:

csink1.jpg


I found that my cutter prefer low speeds. I use a cordless electric drill on slow speed. It seems to come out well.

Tell me, what did you use? How fast were you turning the cutter? Many people prefer high speeds. It probably doesn't change the end product, though. It is just user preference.

;) CJ
 
I'm wondering if some of the perceived distortion is due to the angle at which the photo was taken - it is not directly above the hole.

I agree about the single flute cutters - you have to make sure the hole is clean, if it clogs with shavings then it won't cut deep enough and sometimes even digs a groove in the surrounding material (ask me how I know this!)

Thomas
-8 wings
 
Tribal Knowledge

cjensen said:
...................are not PERFECTLY smooth. it's like there are tiny little particles on the countersink cutter that are preventing a nice silky smooth finish...............whatcha think?
Click to expand...
Often times, an open non-piloted countersink as typically used on composites or plexiglass, even a deburring bit such as the one illustrated will not only polish out minor surface imperfections in the countersink, but can sometimes enhance the "roundness" of the hole.
weldon20cs20bit506gb.jpg

Rick Galati RV-6A "Darla"
 
thanks for the responses so far guys...

to answer a couple of questions about the pics...shoulda clarified a little better in the original post-

i used the vans method to the "T" by installing nutplates first, then running a new #30 cutter into the hole using the nutplate as a guide.

the cutter is a 3 fluted from ATS. they actually started out very nice and smooth, then as i got to the second spar, they started looking like this. that's why i'm wondering if these things dull...but after such short use?

i didn't think to use boelube on the cutter-that would help i'm sure!

i was using my air drill at full pull of 1800 rpm and smooth application of pressure.

there a few distortions here and there, but most are round.

i'll splash some boelube on the cutter and run a few. i just wanted to make sure it doesn't look like i'm dealing with potential problems down the road...
 
I think they do dull reasonably quickly - I noticed a pretty significant difference just in doing the spar. Plus, that anodized spar is harder than untreated Al.

Thomas
-8 wings
 
Do it in two steps. Take half of the material out on the first pass on all the holes, and then do a final adjustment and take the rest out on a second pass, perhaps with the new, sharper cutter. This will minimize chatter and decrease the likelihood of getting "halos" from the material scratching as it's cut out. Also, I would highly recommend LOW speed with high torque. See RVator of last year for process of countersinking. BTW, your's look OK from my perspective. It's a stressful task, I remember, but don't sweat it too much. Good luck.
 
rudi,

i was actually going to do it the way you describe. i bought the #19 and #28 countersinks from Cleveland, but for some reason, the #19 countersink was too big for the #19 hole i drilled :confused: :confused: whatever...

since that didn't work out, i just went with vans method. it worked fine, but my cutter became dull towards the end.

i did use a pilot-less cutter/deburring bit to smooth some of them out last night without removing too much material by hand. worked out fine, and they are still .370 wide.

movin' on...
 
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