duo doweller DD 40 P

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leecab

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May 21, 2014
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          I use my DD 40 P for edge drilling timber slabs, then join them.
          13,500 rpm is way too fast for drilling a pair of 12mm diameter holes in tough Australian hardwoods.
          Mafell keeps recommending applying more hand pressure when drilling, but that doesnt work at all.
          Does anyone know of a reliable variable speed controller that can be plugged into, and not be loosing too much torque?
 
  Thanks Michael,
                        I thought of that, it could help, but changing bits every time would be a pita.
 
Buy another DDF40 or 2 more. That way you can have one with 5mm, 8mm and 12mm No bit changing needed... [big grin]
 
In all seriousness though.  Have you looked at something like this Im no electronics wizard but it seems like it might work.  Says it doesnt work with AC capacitor start motors.  Once again not an electronics wizard but I think thats usually larger type motors than whats in the DDF40 for what it costs its probably worth a try. 
 
  Thanks Afish,
                    I have ordered a similar one to try from eBay and expecting it very soon.
                    I note that it is not to be used with an "ac capacitor start induction motor"
                    Tried getting info from mafell about this topic but they don't want to talk about it for some unknown reason.
                    Love to hear from an owner who is electronically literate.
 
An old machinist told me about a drilling technique he called a wood pecker drill. The idea is to drill a little bit then retract the bit. Repeat as necessary. I’ve tried that with Ipe wood using my DD40 and it worked. I found that exerting too much pressure with the DD40 results in burned drill bits. Those bits are very expensive.
 
never heard it called wood pecker  :) but peck drilling is pretty standard method when cnc drilling.  Its typically good practice all around. helps the bit clear the chips faster, less heat, less breakage, longer bit life.
 
afish said:
never heard it called wood pecker  :) but peck drilling is pretty standard method when cnc drilling.  Its typically good practice all around. helps the bit clear the chips faster, less heat, less breakage, longer bit life.
Click to expand...

[member=73094]afish[/member] summed it up nicely.  [big grin] 

It's commonly used for CNC metal fab equipment and it's referred to as peck drilling. While designed for the metal fab folks, it can be used to great advantage for woodworking, especially for extremely hard woods (and I'm not talking about maple or ash), or for woodworking when drilling deep holes. Deep hole depth in metals is considered to be when you drill over 4X the diameter of the drill bit. For wood you're probably at the 8X -12X diameter for depth. 

The idea for metal working is to drill the hole at something a lot less than the 4X drill bit diameter depth, then stop the bit, break the metal chip, raise the bit to the metal surface where the chip is removed and then plunge down again to resume drilling the hole. This is extremely important when drilling aluminum as the chip is "stringy" and if not removed it can pack around the drill bit and lead to drill bit breakage.

However, a different situation exists when drilling stainless. Most stainless steels "work harden" which means that ANY additional heat added to the drilling process will create an extremely hard drilling surface that will prevent the drill bit from penetrating the metal surface. The only thing that will happen is that you will burn the drill bit and blue the stainless.

Pecking allows the drill bit to advance at a rapid rate to penetrate the metal surface and then withdraw thus avoiding adding any additional heat to the material that would "work harden" the metal.

So how is all of this related to wood working?

I use peck drilling for wood working all of the time, let's say a 1/16" drill bit through 6/4 maple...that'd give a diameter to depth ratio of 24X.

Another situation is deep cutting cedar with a hole saw, if you don't clear the swarf the accumulated saw dust will start to smoke.
 
leecab said:
  A very interesting read thanks Cheese.
Click to expand...

Thanks for that [member=34467]leecab[/member]

For a quick background, I started in metal working for motorcycles, cars and firearms. At some point that became a natural transition to woodworking and I've been 70% entrenched in woodworking over the last 50+ years. It's such a natural transition and I promote it constantly because what works or doesn't in metal also applies to wood. It's just a difference in Janka hardness.  [big grin] [big grin]

 
Metal workers invariably make great woodworkers. So much overlap really!
Just road tested the $30.00 eBay speed control unit.
Using the woodpecker method I'm now producing shavings instead of powder.
Still the holes are black, but I tested using Australian grey gum which is extremely hard.
Tomorrow I will do the same test but try my unused 12mm bits instead of my hand sharpened 12,2mm ones.
If they perform the same then its not a sharpness issue.
 
leecab said:
Metal workers invariably make great woodworkers. So much overlap really!
Just road tested the $30.00 eBay speed control unit.
Using the woodpecker method I'm now producing shavings instead of powder.
Still the holes are black, but I tested using Australian grey gum which is extremely hard.
Tomorrow I will do the same test but try my unused 12mm bits instead of my hand sharpened 12,2mm ones.
If they perform the same then its not a sharpness issue.
Click to expand...

Wait, im a little confused. 
1. Did you tryout the speed controller ?
2. If so did it work to slow down the the RPM ? 
3. Or was this strictly a peck drilling test?
4. How deep are you drilling typically?
5. Are you using a dust extractor?  Its been my experience that the DDF40 should always be hooked to some type of vacuum assist DE (more cfms the better).  The ddf40 is more difficult to plunge than say a domino.  2 drills vs. 1 cutter, plus a domino cutting a slot makes it easier to clear the chips since there is extra space around the bit, less surface contact/friction etc.  With a drill bit the land of the bit is in constant contact with the material especially with deep holes. If the flutes get clogged this only exacerbates the problem causing more friction and heat. 
6. You didnt mention using re sharpened bits.  While I have no idea of your sharpening skills or sharpening equipment I will say its been my experience that any cutter that has been attempted to be re sharpened by anyone other than a professional sharpening service "typically" more harm than good is done to said cutter. So, this is very likely causing some of the issue.

 
It's kind of funny that the guys with similar backgrounds seem to end up in the same threads.
I too started as what you would call a manual machinist. They didn't call it that back then though, because cnc was in it's infancy.
I worked for Sandvik in the Coromant division, making T-Max and Trepan drilling heads. I was manually cutting angled and radiused holes, strictly with a DRO. They called it "blind pocket milling". This is certainly done with multi-axis cnc equipment today, (assuming that they still make them)but was un-available at the time (1981)
They did have 2 Bridgeport vertical mills that were cnc, but they only used them to cut the insert pockets in the removeable holders that the drill heads used.
They also had a nc lathe that actually ran off of a paper tape, which was generated remotely. All you could really do on the machine itself was establish the X and Y origin. It was really cool at the time though, because it could cut "4 start" threads.
There were also a couple of smaller "screw machines" that could do that too, but on a much smaller scale.
The plant was moved out of state and I didn't follow.
My car tinkering/street racing got me in the door as a mechanic, where I learned to weld, then progressed into motorcycles and working in a bodyshop.
The woodworking was just an extension of DIY from homeownership. When the bodyshop owner moved, a friend got me into the cabinet shop where I have been for the last 18 years.
They got a 4' x 8' flat bed cnc machine a few weeks after I started there and the whole thing came back to the beginning.
I didn't have anything to do with running it back then. I assembled cabinet parts that came from it for the first few years though, working up to the large custom units that I do today.
 
leecab said:
Metal workers invariably make great woodworkers. So much overlap really!
Just road tested the $30.00 eBay speed control unit.
Using the woodpecker method I'm now producing shavings instead of powder.
Still the holes are black, but I tested using Australian grey gum which is extremely hard.
Tomorrow I will do the same test but try my unused 12mm bits instead of my hand sharpened 12,2mm ones.
If they perform the same then its not a sharpness issue.
Click to expand...
afish said:
leecab said:
Metal workers invariably make great woodworkers. So much overlap really!
Just road tested the $30.00 eBay speed control unit.
Using the woodpecker method I'm now producing shavings instead of powder.
Still the holes are black, but I tested using Australian grey gum which is extremely hard.
Tomorrow I will do the same test but try my unused 12mm bits instead of my hand sharpened 12,2mm ones.
If they perform the same then its not a sharpness issue.
Click to expand...

Wait, im a little confused. 
1. Did you tryout the speed controller ?
2. If so did it work to slow down the the RPM ? 
3. Or was this strictly a peck drilling test?
4. How deep are you drilling typically?
5. Are you using a dust extractor?  Its been my experience that the DDF40 should always be hooked to some type of vacuum assist DE (more cfms the better).  The ddf40 is more difficult to plunge than say a domino.  2 drills vs. 1 cutter, plus a domino cutting a slot makes it easier to clear the chips since there is extra space around the bit, less surface contact/friction etc.  With a drill bit the land of the bit is in constant contact with the material especially with deep holes. If the flutes get clogged this only exacerbates the problem causing more friction and heat. 
6. You didnt mention using re sharpened bits.  While I have no idea of your sharpening skills or sharpening equipment I will say its been my experience that any cutter that has been attempted to be re sharpened by anyone other than a professional sharpening service "typically" more harm than good is done to said cutter. So, this is very likely causing some of the issue.
Click to expand...
 
to "wait I'm a little confused"!
    My unit is the 13500 rpm DDP40 1000w.
    I used the cheap speed controller and it did slow down the rpm maybe 40% I'm guessing though.
    With slower rpm and I think less torque now I was able to effectively use the hard push technique recommended by Mafell.
    I eliminated burning of the holes.
    Holes were drilled to 27mm deep.
    I set up the dust extractor for this operation and it does make a difference.
    The fast plunge was more effective than the woodpecker method.
    The sharpening of my bits was just a touch up on the inside with a fine half round fine diamond file.
    Drilling with just 1 bit greatly eased the effort,
    I am pleased I can now dowel the hardest timber slabs together with less effort and better results.
    The speed controller is a great addition to the super fast DD40P.
    Oh, I lost 1 of the dowel bit grub screws. Are they a standard item or exclusive to this tool?
 
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