drill bit for mortice.

[timothy thorpe]

hi guys, thanks again for all your help!! heres somethign i was wondering. what is the best drill bit for the mortice. brad point or standard. thanks

[achduliebe]

Tell you the truth, there are three that I have used. I have used a brad point, this is the one that I use most often. I have used a forstner bit and I have used an end mill, well the end mill was used to clean up the mortise after using another bit.

However, most often I use the brad point.

[Nick]

Brad point here too.

[KurtHuhn]

5/16" precision ground forstner bit here. I also dressed the cutting edge to make a nice tight fit on the delrin that I use.

[bvartist]

5/16" precision ground forstner bit here. I also dressed the cutting edge to make a nice tight fit on the delrin that I use.

Ditto. I've tried regular and brad point bits, but I get a more precise mortise with the forstner, critical when using delrin.

[jeff]

It honestly does not matter. If you prefer a brad point, then use it. Standard jobber bit? Use it. I use a jobber bit and then bring it to size with a reamer. I've tried an end mill before, but they are so precise that any fluctuation in temperature and humidity will cause the fit be off. In one climate it will be perfect, in another it will just fall out, and another will find it so tight as to crack the shank when removed. Essentially, you need some play or slop in order to have a good fit across environments. A jobber bit will be just fine.

[bvartist]

Jeff, does the reamer you use flatten the bottom of the mortise? Curious how you deal with the "cone" shape at the bottom of the mortise left by the point of a jobber bit.

David

[StephenDownie]

I use both precision ground forestner or a pilot point bit depending on the circumstance. The Pilot points make it really easy to center the draught hole in the center of the mortise:


The Pilot point drill bits are cheap, give a flat bottom to the mortise and are accurate enough to fit Delrin with no problems. I generally use the Forestner bits for counter sinking stems into the shank. Both are invaluable in the right situation.

[jeff]

Jeff, does the reamer you use flatten the bottom of the mortise? Curious how you deal with the "cone" shape at the bottom of the mortise left by the point of a jobber bit.

David

I've modified one of my reamers to flatten the bottom of the mortise, but this isn't necessary. If you do this, you'll need two reamers, one unmodified and one modified. Enlarging the mortise with a modified reamer will mar the mortise walls pretty badly and won't track properly in the pilot hole. To be truthful, you really should not worry about the "cone" at the bottom of the mortise. Just put a corresponding angle on the tenon and you will eliminate the gap.

[ArtGuy]

I used a brad point bit for a long time and then switched to a jobber bit. I have found that Irwin bits are readily available and are an accurate diameter. I also don't worry about he cone at the bottom of the mortice. Most of my pipes have an airway with a slight uphill angle so I carve a slight ramp there anyway.

Also, another critical tip for those usuing delrin and have trouble getting a snug fit.... Do not back out the drill while drilling the mortise. Do it in one motion and you will get a more accurate diameter.

[KurtHuhn]

Also, another critical tip for those usuing delrin and have trouble getting a snug fit.... Do not back out the drill while drilling the mortise. Do it in one motion and you will get a more accurate diameter.

Really? I've found that backing out the bit and clearing the chips actually makes for a tighter fit since you're not rubbing that stuff against the walls of the mortis. I'm using a forstner bit, so that may be the difference.

See, ask a dozen pipe makers how to make a pipe, you'll get a dozen different answers....

[bvartist]

Really? I've found that backing out the bit and clearing the chips actually makes for a tighter fit since you're not rubbing that stuff against the walls of the mortis. I'm using a forstner bit, so that may be the difference.

See, ask a dozen pipe makers how to make a pipe, you'll get a dozen different answers....

When I used a brad point, I got better accuracy drilling the mortise in one motion. With a forstner I get better accuracy backing out the bit and cleaning it off. Regular jobber bit I've never had much success with.

[Nick]

When I used a brad point, I got better accuracy drilling the mortise in one motion. With a forstner I get better accuracy backing out the bit and cleaning it off. Regular jobber bit I've never had much success with.

I wonder why that is? Is it really just the excess sawdust rubbing into the sides of the mortise?

[KurtHuhn]

Based on my experimentation, yes. It collects in the flutes, expands into the mortis walls pushing them out, heats them up and dehydrates them, burns it slightly, and glazes the interior - basically seizing the wood into a slightly larger interior diameter.

[Nick]

Fascinating!

[hazmat]

All of this stuff is fascinating. It's interesting reading all the different methods and tools everyone uses to achieve the same end.

I went from jobber bits to brad point to pilot point and have kind of stayed with the pilot points. I've yet to try a forstner but will at some point. There's other aspects I want to focus on before I make anymore changes to my processes.

[ArtGuy]

Also, another critical tip for those usuing delrin and have trouble getting a snug fit.... Do not back out the drill while drilling the mortise. Do it in one motion and you will get a more accurate diameter.

Really? I've found that backing out the bit and clearing the chips actually makes for a tighter fit since you're not rubbing that stuff against the walls of the mortis. I'm using a forstner bit, so that may be the difference.

See, ask a dozen pipe makers how to make a pipe, you'll get a dozen different answers....

I bet the forester bit does not clear the chips as well as a fluted bit does and that is why. I used to use brad point bits but have switched to jobber bits only for aesthetic reasons. I have also found that Irwin brand bits seem to be plenty accurate enough in diameter to work well with delrin.