Hi!
I decided to publish the first part of this project. Let's start with a video, please bear with me as this is one of my first videos ever - there are some passages that are not sharp because the autofocus on my Canon SX20IS didn't properly adapt - probably because the zoom level was to high - I will have better equipment for the next part.
Sadly it seems bb-html-tags are not allowed, so I can't embed the video

But here is the link:
https://sendvid.com/3ylq89h0
(I did decide against using YouTube for a reason)
Please do not share the video without my little corresponding write up as a couple of things have to be explained - if anyone wants to share it at all.
Let's start with a closer look at the "delinquents". From left to right: FAMAG Bormax (profi), PROJAHN, BOSCH diy (China), FESTOOL Zobo
All 4 share common ground - 15 mm outer diameter. (Continuing with this project, I'll have digital calipers to get numbers.)
FAMAG
PROJAHN
BOSCH
FESTOOL
Length
Now the "fun" part starts. If you watched the video you already know that for this very first encounter I used a Bosch Professional GBH 2-26 DFR - it's an SDS-Plus rotary hammer of almost 3 kg - used with a rapid exchange chuck (with collets) instead of the SDS-Plus chuck. It goes approximately 900 rpm. Why did I do that? I wanted a genuine first impression with a drill I had laying around. No fine tuning and tweaking for best results - simply straight and true.
I didn't give it any test shots. I removed the Forstner drill bits from their packaging and off we went.
Quiet obviously a machine like that is not made for this kind of work. It is too heavy and tolerances are anything but tight on a rotary hammer with exchangeable chucks. BUT it is still realistic because if you look at all the different trades many use this kind of rotary hammer for a lot of different jobs - and at some point might end up needing to drill a hole trough a beam for piping, cables or whatever with it.
Now if you watched the video you saw that the FAMAG drill bit went in and out pretty smooth but not perfectly clean. It created very fine shavings and generated not much to no heat.
Then I went on with the PROJAHN. What a difference. Not only was it a lot slower, cut worse and I really had to push it into the material, but also it created much larger shavings that stuck to the drill bit - that lead to heat build up and finally to a burnt smell and burnt hole.
The BOSCH is pretty similar to the PROJAHN speaking of its edges/geometry. It also cut slower than the FAMAG, with much larger shavings and a similar result of material stuck to the drill bit - also I had to push harder. Again heat built up and the result is the same.
I then went for the FESTOOL. Larger shavings than the FAMAG but it cuts as fast and smooth into the material. But: because of the larger shavings and it's edges/geometry material does stick to it when you push to hard and forget to clean the path. So the end result is again pretty much the same - a burnt smell and a burnt hole.
Now we're getting to the next part of the video when I drilled into the edge of my wooden post at an angle. Again, please keep in mind that I'm working with a machine that comes very close to 3 and a bit kilograms. So I started in reverse order beginning with the FESTOOL drill bit and as expected it went in smooth as silk. When pulling out I didn't pull completely straight and the corner of the drill bit caught the material - which resulted in a big chip. You'll notice that this time I drilled kina "once more with feeling" and as expected the FESTOOL drill bit did not clog/overheat.
Going on with the Bosch - it's back to what I wrote in the first part. More pressure, not so smooth cuts and clogging.
Then the PROJAHN. Which did not clog this time but slipped on the second run. From all the bits it was the hardest to cut with, the saw horses wiggled just a little and it slipped. Pretty much because it has the shortest centering tip from all of the drill bits.
Last I went with the FAMAG and again it performed very well.
Then I gave the FESTOOL a second run because I wanted to see if I would create another chip. I didn't. I also re-confirmed that by pushing just a little to hard the drill bit clogs immediately and overheats.
The first video ends here.
To take it to the max, I put the 3 mm drill bit into the center opening of the FESTOOL Zobo and went through the complete 70 mm of my wooden post. Pushed it down really hard without cleaning the path - and I created a nice clog. Why did I do that? I wanted to see if the bit - despite the burnt smell and burnt hole - would create a smooth cut. It did. And for the record, I went in from one side for approximately 67 mm and then turned the wooden post to remove the last 3 mm. Cutting ability is really excellent on the Zobo.
Now let's take a closer look at the holes. Starting with FESTOOL. Cleanest cuts in the line up - right down to the bottom of each hole. Sadly one big and a small chip after pulling out. I will further experiment here.
BOSCH: Cuts suitable for general construction work, require aftercare. No chips during the angled cuts.
PROJAHN: Rather rough cuts, short centering pin leads to slippage. Bigger chip on angled cuts. General construction work on a budget. (Cheapest drill bit in the line up at well below 10 Euro-Bucks

)
FAMAG. Not as clean as the FESTOOL but close. Little chip on the angled cut, rather rough entry on all holes.
PROJAHN: While cleaning the drill bits I noticed that one edge of the drill bit had a small but very noticeable dent.
What can I say? I had a blast - and I want to continue this as I don't feel up to drawing any real conclusions yet. Drill press, lighter drill and more solid setup will be next. Then I will also publish some tables and charts from my measuring results.
What definitely can be said is that even new out of box drill bits lead to noticeable varying results - sharp and new do not guarantee a clean cut.
Kind regards,
Oliver