grinding a taper

[android]

hi guys, great site you've got here. i'm excited to try out my first pipe here soon. i'm a hobbyist woodworker and have enjoyed smoking a pipe for a few years now. i'm not in any hurry to dive in, but i am curious to know how you go about tapering a drill bit for the bowl. i read a few old posts concerning it, but still have a few questions.

do you just taper the lower inch or so? and do you try to maintain the same shape of the helix angle for wood shavings to exit?

also i see the point goes away, do you just start your holes with a pilot?

thanks, i look forward to enjoying this site.

[KurtHuhn]

A lot of folks use a pilot hole, but if you're drilling on a drill press or lathe (as opposed to drilling freehand after shaping) it's not strictly necessary. I never drill a pilot if the block is clamped down.

For reshaping bits, the process is diffferent for Silver and Deming or spade bits. Spade bits are easier and require less work - and are less expensive if you screw one up. Basically you just draw a profile on the bit for the shape you want, and grind off anything that doesn't match. Be careful to keep the steel cool. If it gets too hot, it will get soft and you'll have a tough time keeping it sharp. Grind off as much as is needed based on the shape you want.

For Silver and Deming, the process is a little more involved. You basically need the bit spinning while grinding in order to keep is symmetrical. Spinning it in reverse will also help reduce the amount of work you have to do after the fact. So, chuck in the lathe and go to town with an angle grinder. Or chuck it in a drill and go to town on the bench grinder. I've done it both ways, and prefer the lathe. You only need to shape the last half inch to inch depending on the shape of tobacco chamber you want. A lot of makers keep a pile of these in lots of different shapes, and which one they reach for depends on teh shape of pipe they're making.

After your S&D bit is rough profiled, you need to clean up the area behind the cutting edge. I use a dremel with one of those sanding sleeves on it. You don't need to remove much, just enough to keep the cutting edge in contact with the wood, and to keep the land behind the cutting edge from rubbing the wood. Again, it's not much, but you do need to be careful to stay away from the edge.

When I grind an S&D bit, I tend to stay away from the point. The first one I re-ground, I kind of messed up the point, so it wanted to wander a little. If you leave the last few millimeters alone, you won't have that problem - just work the shape of the bit around the last couple mm and you'll be okay.

[android]

thanks for the reply. i imagine i'll try it on a spade bit first. so, i assume you grind the point of the spade bit off and it still drills in OK? i mean, good enough for a beginner? and then grind your cutting edges on opposing sides of the newly shaped bit?

also, if i'm going to amass a collection of strictly starter bits and i go the spade route, i'll get a few of those to play with, a long tapered 3/32", an aircraft 1/16", one for the tenon (1/2" ?) which i'm sure i have a few of and which size of forstner is generally used for facing the tenon hole?

last thing, if i remember correctly and i know there's various ways to do this, but the drilling for the stem usually goes tenon, 5/32", 1/16", right?

thanks again.

[KurtHuhn]

thanks for the reply. i imagine i'll try it on a spade bit first. so, i assume you grind the point of the spade bit off and it still drills in OK? i mean, good enough for a beginner? and then grind your cutting edges on opposing sides of the newly shaped bit?

It should still drill fine. I never have a problem with mine at least. One thing I forgot to mention is that you need to keep a cutting geometry on the leading portion of the bit. It will look similar to the point of a regular twist drill bit. It's difficult to describe, but easy to understand once you see it. If you imagine that each side of the bit is going to be ground with a cutting edge, and you preserve that cutting edge all the way to the point, you'll end up with a diagonal vertex.

Bah! Difficult to describe, easy to understand. And I don't seem to have a photo handy....

And if it doesn't cut well? Just use a pilot hole drilled with a 5/16" or 1/4" bit.

also, if i'm going to amass a collection of strictly starter bits and i go the spade route, i'll get a few of those to play with, a long tapered 3/32", an aircraft 1/16", one for the tenon (1/2" ?) which i'm sure i have a few of and which size of forstner is generally used for facing the tenon hole?

last thing, if i remember correctly and i know there's various ways to do this, but the drilling for the stem usually goes tenon, 5/32", 1/16", right?

You tenon can be whatever you like. I prefer 5/16", but some makers use anything between 1/4" to 3/8". It sometimes depends on the shape of the pipe too. Some pipe with long extensions (like bamboo) actually use a 3/16" or 5/32" tenon size.

The procedure I normally use for drilling rod stock is:
- square the face
- drill the tenon (I use delrin, so the rod stock gets drilled)
- drill the airway using a 5/32" tapered bit to within about 3/4" of the end
- spin the rod around and mark the center with the tapered bit - no actual drilling. This is just to give me a guide for when I cut the slot later on.

If you're more comfortable drilling the finish of the airway with a 1/16" bit, then by all means go for it.

[android]

thanks again kurt. i appreciate your willingness to help out.

i'd love to see a picture of one of those ground spade bits if anyone has one. and a pic of a ground S&D too for that matter.

also, what size forstner do you use to face your tenon hole?

and i've seen that some countersink around the tenon hole, is this necessary?

[KurtHuhn]

thanks again kurt. i appreciate your willingness to help out.

i'd love to see a picture of one of those ground spade bits if anyone has one. and a pic of a ground S&D too for that matter.

I'll see if I can post a pic tonight.

also, what size forstner do you use to face your tenon hole?

and i've seen that some countersink around the tenon hole, is this necessary?

I face the end of my shank with a 1-1/4" forstner bit. The tenon hols in both the stummel and the stem are drilled entirely with a 5/16" forstner bit that I modified slightly.

[android]

thanks kurt, no hurry on the picture.

and unless it's a closely guarded secret, what is the nature and purpose of the modification on the 5/16 forstner bit?

[KurtHuhn]

and unless it's a closely guarded secret, what is the nature and purpose of the modification on the 5/16 forstner bit?

It's not secret at all, it's a well known machinists trick for getting a drill bit to behave it's makeing a slightly oversize hole. All you do is knock the shoulder down slightly. I use a diamond hone, and all it takes is a few passes on each flute. What it does is reduce the leading cutting edge of the shoulder slightly. If that's not clear, let me know and I'll take a photo of this bit too.

[android]

that sounds clear. just a picture of the spade if you get a chance. i saw some other pictures but i can't quite figure out how the cutting edge is ground. thanks.

[KurtHuhn]

I finally got a chance to snap a pic. It can be found here:
http://www.pipecrafter.com/images/spade_bit_grind.jpg

The shape of this bit is a perfect semi-circle, it's not pointed or tapered at all. If you do want a tapered bit though, the cutting edge grind angle and leading edge would be nearly identical. I grind mine on a 1x42" belt sander with a tilting table - the Delta model that everyone carries.

[android]

thanks a lot kurt. i look forward to grinding one up.