Drilling stainless firewall *HELP*

[Siarti]

Just my two cents...Sorry for bumping...

High speed steel is good for anything from wood to titanium, why titanium you ask...its beacuse the high speed steel takes te heat where carbide will cause work hardening and snap a drill very fast if the piece gets warm. Their are alot fo variables on this one but high speed steel is a great general purpose steel for drilling/milling


Cobalt~ cobalt is a very tough material but extremely brittle and when mixed with HSS it creates a very tough drill second only to carbide good for everything from wood to harder steels

Carbide~ there are many different types of carbide with micrograin carbide being the toughest and couple this with coarbonitrate titanium and other titanium coatings and you have a very formidable drill that is capable of drilling most any material, Concrete drills use carbide tips and hardened steel bodies with the carbide brazed on the body, this provides a very tough drill that can take the pounding and not chip out. Carbide drills are usually 3 times heavier than HSS

Diamond~ Diamond is used for cutting concrete and for holding tight tolerances in high speed machining of aluminum and softer metals, When i was at 3M they actually invented a machine that makes industrial grade diamonds, it was so efficient that GE asked them to stop producing diamonds. The Machine that looks like a alien bomb still sits in a dusty room to this day at 3M's center in Oakdale MN. Diamond or diabide is coated onto drills and adds a very thin layer of diamond buildup that last a long time in abrasive conditions. Diabide cannot take heat and the coating crumbles off when cutting harder metals.....its kind of a bummer we can use diamond on our cutters but cant cut anything hard. Also industrial diamonds are used on concrete blades and are visible by little black dots and raised dots on the blade.

Drills come in many different sizes and qualities with chinese drills leading the pack of cheap disposable drills that dont hold an edge very long, so is true for carbide and cobalt drills, you get what you pay for..usually if you go to JandLindustrial.com theylists all their tools as either import or domestic. Machinists know the difference between import and domestic tooling` Import tooling wears out too fast but is a great substitute when setting up a production job where you may break a tool or 2.

Also drill technology has come a long way, companies likeAllied offer a psade drill that takes a insert made out of micrograin carbide and coated for the application. these drills are sweet but arent for your average consumer. Here is a little info if you are going to sharpen your own drills at home

1. 118 degrees is your standard drill tip angle
2. 135 degrees is usually used on a split point drill where you are not using a center drill to start the hole.
3. Keep in mind the relief on the top of the drill and on the side!!
4. Drills usually are only sharpened 8-10 times in a machine shop as the inner web gets thicker and is tapered the drill looses alot of efficiency
5. Drills are also prone to the side flutes wearing, it is possible to resharpen a drill and it may look good but not leave a good finish in thehole or leave a galled or reduced diameter.
6. Remeber that you can sharpen a drill back to spec but if you spin the drill in your chuck youve probly damaged the shank and the drill will not hold a on center rotation with a damaged shank.


good luck with your drills guys and if your hand drilling with a old drill make sure your bracing yourself or slow down at the end of the hole

[psalter]

Dan and I used a cobalt bit slow speed on a cordless drill pressing hard with a wood backer on the other side. We did not use any oil or water. We were through pretty quickly.

If the hole was going to be larger, started with the #30 and went up from there.

[GlenNJ]

I found another way to put the holes in the sides and bottom flanges of the stainless steel firewall. I tried the usual way first (#40 cobalt, cordless drill set to low speed, cutting oil, a lot of pressure), and burnt up 2 new drill bits with no holes. I probably should have pushed harder, but I was afraid to push to hard and have the #40 drill bit snap. I broke out my Whitney hand punch and put the 3/32" punch in it. With the firewall in place, I carefully circled holes with a sharpie at the top and bottom of the sides, and the middle of the bottom fuselage pieces. I took the firewall off and center punched the holes. The Whitney punch had no problem blowing holes through the stainless. I clecoed the firewall back in place and circled the rest of the holes. I removed the firewall again, center punched, then hand punched the holes. This was much easier to do then drilling for me, and the firewall fit perfectly.
The trick with doing this technique is to take your time when center punching the holes, making sure you are exactly centered. My Whitney punch has self entering guides on the male dies which will line up with the center punched hole. Of course when center punching, make sure you have a block of wood behind the stainless steel. It took me less than 2 hours to do what would have taken me a week to do at the pace I was going. The pictures shows my punch resting on the firewall clecoes.

Glen

[jamesmil]

I use a product called "BOELUBE"to lub drill bit,s when drilling stainless steel or any other hard metal. Got it from ACS, in 2003 when building a rv7 and have used it to build a rans s7s and a Kitfox model 7ss. Works great and goes a long way.

[woolleys]

I have found that starting with a #40 after you have center punch the location gets a quick penetration. Up drill with a #30 and then go to a good step UNIBIT. As Tony has said go slow, especially with the UNIBIT and it should cut through nicely.

[Tony Spicer]

Sean,

Small point, but be sure to apply as much pressure as you can muster before pulling the trigger. If it doesn't start making chips immediately and pop thru in 2-3 seconds, you'll just end up work-hardening the SS. My drills all come from McMaster-Carr and I use no cutting oil. http://www.mcmaster.com/#standard-drill-bits/=ythdd5

Tony

[Lowrider]

I'm no expert but a cobalt bit and center punch the hole first then very slow with the bit. After about 10 seconds of SLOW drilling, dip the bit into some water to cool it. I never use oil but I suppose it might help. with a cool bit, continue drilling. The center punch is a PIA but it gives the bit something to bite into. Above all else, don't let the bit get hot or it is ruined and don't let the bit run above maybe 300 rpm. I did about 90 holes in my firewall and it seemed to take forever.

If anyone else has a better idea please post because SS is a pain to drill. GOOD LUCK!!

[Seansull]

Hi Everyone,

I am having a hard time getting my firewall match drilled. I am using Avery cobalt #40 drill bits with "off the shelf" Home Depot cutting oil. Further, I'm using my cordless drill on very low speed with quite a bit of pressure. After monkeying with this for well over an hour, I have one hole and about 6-7 trashed drill bits.

My question for those who have already completed this step.....

Exactly what brand, type of drill bit did you use?
Exactly what type of cutting oil did you use?

Any help on this would be fantastic!

Thanks!