What size drill bit gives "interference fit" for wood doweling? - Page 2 - Woodworking Talk - Woodworkers Forum
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post #21 of 49 Old 05-13-2016, 11:52 AM Thread Starter
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It might be possible I bought and used dowel pins like these from Home DEpot:

http://www.homedepot.com/p/General-T...0014/202252099

The flutes, although INTENDED to accommodate glue, would enable the dowel to "compress" a bit for a tight friction fit, wouldn't they?

Jim G
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post #22 of 49 Old 05-13-2016, 01:37 PM
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Good luck in reinventing the wheel, there is a reason why wood parts are glued together, if this is a commercial product you intend to produce hope you have a good refund policy for your customers sake.

Wise men speak because they have something to say; fools because they have to say something -Plato

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post #23 of 49 Old 05-13-2016, 01:37 PM
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I think I know what you're shooting at.
A project that can be assembled and stays that way without using glue or fasteners.
Gravity is usually your friend, for instance dowels that are vertical can be used to lock pieces together.
Other joints, like dovetails, blind dovetails and sliding dovetails can be used to "lock" pieces in place.
They are held there by the next piece of the puzzle.
I've seen some very intricate pieces made this way, unfortunately no pictures.
I did find this one link to simpler projects with no fasteners or glue.....http://www.instructables.com/id/Wood...hout-using-na/
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post #24 of 49 Old 05-13-2016, 01:42 PM Thread Starter
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Ok, turns out that Lowes also handles fluted dowels, but a different brand, with different cost perm piece and different lengths. But, here's the product description from the "Madison" brand handled by Lowes:

Poplar Dowel Pin (Actual: 0.375-in)

USA manufactured from kiln dried Poplar
Machined to close tolerance
Environmentally friendly -annual growth exceeds harvest
Multi groove - chamfered on each end
22 pieces per package
Easily joins two pieces of wood together without nails or screws
3/8-in x 2-in

Note:

- The dowel diameter for the 3/8 size is exactly 3/8" (.375")

- The wood used is Poplar, which is both low density and soft, and therefore compressible more easily

- Chamfered at each end for easier start into an interference fit hole

- Note the statement "Easily joins two pieces of wood together without nails or screws"

There is hope . . .

Jim G
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post #25 of 49 Old 05-13-2016, 02:00 PM Thread Starter
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Quote:
Originally Posted by bzguy View Post
I think I know what you're shooting at.
A project that can be assembled and stays that way without using glue or fasteners.
. . .

I did find this one link to simpler projects with no fasteners or glue.....http://www.instructables.com/id/Wood...hout-using-na/
Yes!! That is the target.

Jim G
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post #26 of 49 Old 05-13-2016, 04:20 PM
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The tolerances you work to depend on what you're trying to achieve, and what you're working with. There's no sense in cutting something to a thousandth of an inch if the material is going to grow fifteen or twenty thousandths in that dimension over night, but if you're working the other direction in the grain, or you've seasoned the wood to the cut, it can make perfect sense.

I usually start with rough cut wood, dry it out to around 12%, plane one side flat on the jointer, square one edge on the jointer, mill parallel in the face, rip parallel on the table saw and cut square ends. I do all that a quarter to a half inch over size, then I either leave it alone for a week or put it in the kiln if I'm in a hurry. (And willing to risk losing the piece.)

As the fresh cuts (and the new surfaces) dry, the board changes shape. Maybe it bows, maybe it cups, maybe it warps. Maybe it grows, maybe it shrinks. You don't want any of that to happen after you've cut fine dovetails.

After a week, ten days, or two or three days in the kiln, I go back to the wood (usually all the wood for a small project) and speak harshly to it, demanding to know if it's finished screwing around. Sometimes it gets uppity, and has twisted too much to use, or shows signs that it's not done moving. For that very reason, in my old age, I've taken to rough cutting extra pieces, particularly with Home Depot pine, "white wood" or other known ne'er-do-wells. I've cut "hem-fir" (no such tree in nature) that sprayed water in my face at the table saw.

If it's down below 10% (I used to try for 8%, but I ruined a lot of wood trying to get there) and isn't moving, I go back to the jointer and start again, taking it right down to finish size. Plane, parallel, parallel, rip, crosscut, right at finish dimension. If it's at 8 or 9%, it's probably okay to go ahead and cut joinery without further ado.

If you buy pretty dry wood in the first place (close to 10%) it usually only takes four or five days air drying between rough cuts and finish cuts.

I've never tried to interference fit a dowel, because the grain in the dowel will run end-to-end, because a dowel that swells slightly is usually a good thing.

This book changed the way I look at wood: https://www.amazon.com/Understanding...indle-redirect

"When I have your wounded." -- Major Charles L. Kelley, callsign "Dustoff", refusing to recognize that an LZ was too hot, moments before before being killed by a single shot, July 1, 1964.
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post #27 of 49 Old 05-13-2016, 05:29 PM Thread Starter
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Quote:
Originally Posted by Jammersix View Post

. . .

This book changed the way I look at wood: https://www.amazon.com/Understanding...indle-redirect
Yes, I have that book. :)

Today, in between work tasks, I am researching dowels - wood species available, types (plain, fluted, spiral), etc.

The fluted type is apparently the "best" for situaitons where you want an interference fit, as the flutes compress while the dowel is being pushed into the hole, creating a tight bond.

I plan to use well seasoned hardwoods, and to finish the completed subassemblies and assemblies with a generous coating of pharmaceutical mineral oil, so post-construction wood movement will at least be minimized.

What I want is dowel & hole size combination that results in a reliable interference fit that won't become loose enough over time and conditions to "come apart".

Jim G
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post #28 of 49 Old 05-13-2016, 06:25 PM
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...Yes!! That is the target.

lemme' just say this about my 40+ years of doing things with dowels....

not a single commercial source I've ever encountered has a reliable tolerance for the actual diameter of their product.

which kinda' sorta' really smacks the issue of "how big the hole" in the face.

last week: local sources having nothing but $0.0002 bamboo (? - dunno. gets wet, bends in half...) dowels, ordered a 3/8 dowel - ash - for a project. because dowels don't do things right....I purchased a cheapo drill index at Harbor Freight - all letters, all numbers, up to 1/2 inch by 64ths. how can you miss, right?

it's easy. drilled some scrap (hard maple) for test fit.... been here before, know better....
3/8 was too big. 3/8 dowel fell into the hole. 23/64th - too small. go figger. I could have beveled an end and pounded it in, but the hole is less than 1/2 inch from the end grain edge. pounding invites splitting - not suitable for this project... wound up cutting off a chunk of dowel and spinning it down via 240 grit sand paper to fit the 23/64th hole.

somebody pointed out the DIY Lee Valley dowel making kit. I need to look into that. wouldn't it be nice to have a dowel of a size it said it is . . . .
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post #29 of 49 Old 05-13-2016, 06:29 PM
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Hi, have you considered running a saw halfway down the dowel lengthwise, then tapping a tapered shim into it? I used to do that all the time when I was still using dowels, whenever I felt like the dowel was a little loose. Makes a huge difference, plus looks interesting.

Runout in drilling, once spent too much time delving into this. The runnout in a drill bit not under load is very different than a drill bit drilling a hole. In metal and hard wood there is very little runnout as the drill press and chuck don't have the rigidity to hold the bit off center, the bit tends to center up. Anyway, if you want to determine the end result you really want to measure the resulting hole, perhaps with a pin gauge. To the best of my ability to measure, a 1/2" diameter hole in Ipe drilled with a Norseman bit results in a hole that is exactly .500". For whatever reason the hole is almost .002 out of round (larger) over 1/4 of it's arc, acording to a Blake CO-AX.
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post #30 of 49 Old 05-13-2016, 06:46 PM Thread Starter
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Quote:
Originally Posted by TomCT2 View Post

. . . drilled some scrap (hard maple) for test fit.... been here before, know better....
3/8 was too big. 3/8 dowel fell into the hole. 23/64th - too small. go figger. I could have beveled an end and pounded it in, but the hole is less than 1/2 inch from the end grain edge. pounding invites splitting - not suitable for this project... wound up cutting off a chunk of dowel and spinning it down via 240 grit sand paper to fit the 23/64th hole.

somebody pointed out the DIY Lee Valley dowel making kit. I need to look into that. wouldn't it be nice to have a dowel of a size it said it is . . . .
I almost always will be able to keep the dowel joint far from any edge, which prompts this question which I hope someone can answer:

If you make the hole size smaller than the dowel diameter, and use a chamfered dowel (plain or fluted), how MUCH smaller can you make it and still be able to press fit the dowel in there using an arbor press, without splitting the dowel?

The very small parts being joined are typically thin enough that dowel penetration of 1/2" to 5/8" into each piece is all I need or want (i.e. total dowel length is 2 x 1/2" = 1" or 2 x 5/8" = 1.25". So, the force required from the arbor press should not be anywhere near large enough to split the dowel, if the degree of interference is sensible.

Jim G
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post #31 of 49 Old 05-13-2016, 06:57 PM
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I think most of us would just give it a try a few different ways. There are so many variations in each of the parameters I'm not sure any information you get is going to be accurate in you situation.
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post #32 of 49 Old 05-13-2016, 07:27 PM
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the right size will depend on the wood species.

and I'm not all too sure it's the dowel that will fail first. you should be pressing it in with full surface contact - it's more likely the base piece will split first. then again, I have never worked with multi-ton arbor presses in wood.

drilling a pilot hole for (any size screw...) varies quite wildly between something soft (eg poplar) and something really hard (eg hard maple)

this I learned after shearing off way too many brass screws going into maple. . . .
did you know, a #10 brass wood screw will twist in half just as easy as a #6?

I keep a list of hole sizes per screw size and per wood specie.....

one ignores the wood specie at one's risk. I have twisted off 5/16 inch lag bolts going into maple thinking "it'll fit"
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post #33 of 49 Old 05-13-2016, 07:30 PM
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Quote:
Originally Posted by JimGnitecki View Post
le

- Note the statement "Easily joins two pieces of wood together without nails or screws"

There is hope . . .

Jim G
Note the fact that nowhere in that statement does it also say "without glue". Wood is a very much dynamic material, even if you did find the right sized drill and managed to use an arbor press to force the dowels in place without cracking your workpiece, once the relative humidity changes, the wood will either shrink and fall out of those holes, or expand and destroy itself.

Long story short, even if you nailed a perfect interference fit it won't stay that way for long. Use glue, or bolts if you want to disassemble it

I need cheaper hobby
etsy.com/shop/projectepicfail
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post #34 of 49 Old 05-14-2016, 01:37 AM
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Wooden things that stay together with no glue.......http://www.designboom.com/design/pra...zle-furniture/

Many pictures of wooden things that stay together no glue..........................https://www.google.com.bz/search?q=w...pr=1.2#imgrc=_

A picture of a "Friction-fit"? dowel-like joint......
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post #35 of 49 Old 05-14-2016, 07:59 AM Thread Starter
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Quote:
Originally Posted by bzguy View Post
Wooden things that stay together with no glue.......http://www.designboom.com/design/pra...zle-furniture/

Many pictures of wooden things that stay together no glue..........................https://www.google.com.bz/search?q=w...pr=1.2#imgrc=_

A picture of a "Friction-fit"? dowel-like joint......
Inspirational! Thank-you!

Jim G
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post #36 of 49 Old 05-14-2016, 08:01 AM
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Brad point bits come in more sizes than Forstner bits, so one of them might be an option.
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post #37 of 49 Old 05-14-2016, 08:11 AM Thread Starter
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Brad point bits come in more sizes than Forstner bits, so one of them might be an option.
Yes, you are right. I like the flat bottomed hole that the Forstner makes, as it allows me to drill a deeper hole in relatively small pieces of wood, but the quality of friction fit is clearly more important here, so yes, a brad point drill size that is closer to ideal than the "nearest" Forstner bit size would be better.

Jim G
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post #38 of 49 Old 05-26-2016, 06:28 PM Thread Starter
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Did some measuring and testing

I did some measuring and testing.

First, I checked the "runout' on my new Jet JWDP-12 benchtop drill press. This is the brand new model,pn 716000,not the earlier 12" model.

My technique is open to challenge, as I have no idea how to do this "right", but here's what I did:

- I don't have any "drill rod", but I do have a costly 11/32" carbide tipped drill bit (cost $24), which appears to be high quality.

- I mounted it in the chuck, being careful to center it within the 3 chuck prongs while I slowly hand tightened the chuck.

- Then, I tightened the 3 jaws individually, progressively, with the chuck key.

- Then, I set up my digital dial indicator which claims accuracy within .0005" on a magnetic base and arms setup, so that it could indicate the runout of the drill bit shaft. Because once the bit is in the chuck only the top 1" of the exposed bit is "non-twist", I took the measurement about 3/4" below the chuck, so I was well away from the twisted section, on the absolutely round section of the drill shaft. Then I turned the chuck through a complete revolution, multiple times.The maximum runout indicated by the indicator was .00030, which is less than the claimed accuracy, so I think I can conclude the runout is well under a thousandth, which seems astonishingly good for a relatively inexpensive ($375 new) benchtop drill press.

Next, I drilled a few 11/32" holes with this bit. 11/32" of course is .03115" less than 3/8". I drilled these holes into 3 separate pieces of scrap planed 2 x 6 pine.

Then I used the arbor press to pressfit 2 standard 3/8" commercial dowels (manufacturer = Excel) into the largest of the pieces of pine. These dowels are grooved along their full length, to provide for escape of air and excess glue. I did not use any glue. The dowels required a decent pull on the arbor press handle, but not extreme.

Then, I used the arbor press to individually fasten the 2 smaller pieces of pine to the larger piece.

The net result was a strong fit that did not allow rotation of the doweled pieces.

I left the large piece with the 2 smaller peices doweld to it on my porch, where it will undergo some impressive temperature and humidty changes within just a very few days, as our Spring temperatures here in Austin are varying from about 60 degrees to 85 degrees each day, and the humidity is swigning between 20% and 100% multiple times per week. I want to see what effect these temperature and humidity swings have on the tightness of the doweled joints.

I'll report back on the results.

IF the joints do not loosen up with time spent in these varying conditions, I will next try an exotic hardwood - i have some 1 x 6 unplaned Zebrawood in the house that I can cut some sample from after I cut and plane about an 18" piece.

IF the joints do loosen up, I will next repeat the experiment but this time i will coat the component parts with mineral oil (NOT the dowel or dowel holes :) ), to see if the mineral oil finish makes enough of a difference in protecting the wood from temperature and humidity changes.

I really would like to be able to say "nothing but wood with mineral oil finish" in the items I want to make. :)

Jim G
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post #39 of 49 Old 05-26-2016, 08:03 PM
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If you're getting somewhat the force you want to drive your dowels now, it may be that you only end up tweaking your bit size. I think you said you used an 11/32 bit, which is .3438 (omitting whatever spindle runout you may have). Maybe an R (.3390) or Q (.3320) or an in between metric 8.5mm (.3346) would give you an even tighter resistance fit. Drill bits are cheap and easy to get, even the "exotic" sizes.

I think your project is probably going to be worthy of the effort. Almost anyone can build with fasteners and chemicals, but not just anyone has the patience or skill to craft with just, well... wood.

Cheers

Another $000,000,000.02 worth of advice,
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post #40 of 49 Old 05-26-2016, 08:18 PM Thread Starter
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If you're getting somewhat the force you want to drive your dowels now, it may be that you only end up tweaking your bit size. I think you said you used an 11/32 bit, which is .3438 (omitting whatever spindle runout you may have). Maybe an R (.3390) or Q (.3320) or an in between metric 8.5mm (.3346) would give you an even tighter resistance fit. Drill bits are cheap and easy to get, even the "exotic" sizes.

I think your project is probably going to be worthy of the effort. Almost anyone can build with fasteners and chemicals, but not just anyone has the patience or skill to craft with just, well... wood.

Cheers
Yes, I plan to fine tune the drill bit size as needed. I just needed to do some initial testing of basic feasibility as a starting point!

Jim G
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