Drill Doctor or cobalt bits
 

I need to either buy a drill doctor and keep sharpening my high speed steel bits or buy some expensive cobalt bits for drilling steel. Any advise appreciated. I see a 29 piece cobalt drill bit set at Harbor Freight that looks interesting. Anyone own that and want to comment on the quality?

Cobalt bits are great, but not the Harbor Freight variety. I have given up buying anything from them that has a cutting edge i.e. bits, snips, chisels, etc. Even with good quality bits, I use my Drill Doctor all the time to touch them up.

Jim Berry
RV-10

Fastenal drill bits
 

Diamond, fastenal outlets keep good qulity industrial bits in a case at the front counter. You jus open the lid and pick what you need. They will drill stainless ( @ slow rpm with pressure and cutting lube)

Drill Doctor
 

I have a Drill Doctor in my shop that is collecting dust. I was never able to make it work (or felt that it worked) well enough to justify buying it.

I would suggest getting the common drill bit sizes that are used in a RV project

#40 and a #30 for 3/32" and 1/8" rivets
#28 (or #27) for size 6 screw
#19 for size 8 screws
#12 for size 10 screws and AN3 bolts
1/4" for AN4 bolts

A package of 10 of each sizes listed above are probably all you will need to do an entire build for any of the RV types. As you get further into it, you may find you need something else.

For larger holes invest in a reamer or the cheaper alternative a "step" drill. Large drill bits don't work well in thin aluminum or (4130 steel or SS), they tend to rip holes rather than cut.

Personally, I like the piloted double margin drill bits that Pan American tool sells. The hole quality they produce is on par with what you get with a reamer. The drill bits and reamers that Pan American sells are high quality. My only complaint with Pan American is their shipping charges tend to be higher than other tool providers like Brown, Avery and Cleveland.

Drill Doctor - Don't Waste Your Money
 

Ditto what James said. I couldn't make the Drill Doctor work for small drill bits (#30 and #40), so I resorted to just buying the HSS in lots of 10 as I needed them.

Good list. I have found the long reach #30 and #40 to be very helpful in getting the drill away from the action. One each is enough. Especially in working in the upper forward fuse for avionics/wiring. My HF step drills actually work pretty well. I turned down the drive shank on one to fit my angle drill.

BTW - I have a Drill Dr too, and it sharpens maybe 3/16 and up pretty well, below that new ones are best. The only thing that would be better than the Dr is a professional sharpening machine. It is the best sharpener I have used and I have tried many in the last 5 decades including by eye against a bench grinder.

Another negative on the Drill Doctor
 

The biggest waste of $90 I ever made. Spend your money on lots of good quality #30's and #40's and throw them out when they start to get dull.

The best way to sharpen #30 and #40 drill bits is to hold them firmly between thumb and forefinger as you make an underhanded swinging motion in the direction of the nearest garbage can. Release the bit at the apex of the swinging motion, with practice you can launch the bit with a graceful trajectory into the can with one attempt. ;)

Underhanded? Seriously? Like girls softball?

Personally, I throw anything under 3/16 at my hanger mates Piper Cub. Five step drop, Manning goes deep to Thomas.... Broncos beat the SeaTurtles 51-3 in New York!

It's remarkably difficult to penetrate that fabric with a #40 bit!

Hey, is there a good sharpening machine out there, one which won't break the bank?