PDA

View Full Version : Making a Spade Bit



Walter Mooney
04-20-2017, 3:04 PM
I want to make a spade bit (aka a paddle bit), for a special project, and I'm wondering what kind of steel I should start with. Carbon steel, like 1045? Or 4140/4142? Or what? I have access to a heat-treating company, so I can have that process done after I've 'machined it' to the needed size/shape. I figure I'd start with a 1/4" or 5/16" thick flat bar about 6 - 8" long, cut part of it away to form the shaft and then grind three flat spots on it to register in my drill press. Then maybe grind the shape of the paddle end, making the pointed part and the two wings. Then grind the cutting edge on the two wings and the point, then have the whole thing heat treated. Am I on the right track with this process? Has anyone out there ever made a specialized spade bit? And what degree of heat treated do I need to go to?

Thanks in advance for any help...........

Walter

John K Jordan
04-20-2017, 7:40 PM
... Am I on the right track with this process? Has anyone out there ever made a specialized spade bit?

I don't know if it will work in your case, but when I want a special size or shaped spade bit I start with an existing spade bit and grind it as needed. This gives me the shaft and hex connection. I don't know about the hardness - most of the spade bits are pretty cheap and don't seem well hardened or made from the best still. For a better bit maybe you could braze a piece of good steel to an existing shaft, shape, then harden the working end.

JKJ

Walter Mooney
04-21-2017, 2:12 PM
John, thanks. The largest spade bit I can find is 1-1/2", and I need some tapered holes (15* taper) that top-out at 1-3/4", so I can't grind down a store-bought paddle bit. The brazing idea is certainly worth looking into!

John K Jordan
04-21-2017, 4:37 PM
John, thanks. The largest spade bit I can find is 1-1/2", and I need some tapered holes (15* taper) that top-out at 1-3/4", so I can't grind down a store-bought paddle bit. The brazing idea is certainly worth looking into!

Another idea then is to start with a 1.5" spade bit then add metal to the edge by either welding a piece on either side or just by building up a 1/8" weld bead on either side, then grinding it sharp, depending on the material being drilled and how many holes you need to make, of course.

JKJ

Chris Padilla
04-21-2017, 8:58 PM
How about a large countersink? The angle isn't what you want, however. They are also expensive.
https://www.mcmaster.com/#countersinks/=17asrfe

Maybe this one? The angle isn't listed so you'd have to inquire. Still spendy. Scroll to the "Variable Diameter Drill Bit"
https://www.mcmaster.com/#standard-drill-bits/=17asxo8

None of the above, however, are meant for wood but could work reasonably well...perhaps....

Maybe start with some drill rod and machine what you want? This one lists 4 different drill rod metals...might help guide you.
https://www.mcmaster.com/#drill-rods/=17asuej

Here is an adjustable spade bit...but it'll cut straight sides. Might be worth it for a start?
https://www.mcmaster.com/#spade-drill-bits/=17asvmb

Adam Herman
04-21-2017, 9:12 PM
i think you may be barking up the wrong tree... the sides of a spade bit do not cut the wood, only the spurs and the bottom edge do. I do not believe you will get your desired results with a spade bit with tapered sides. The sides will scrape and create a mass amount of friction and terrible hole quality if you have enough to power them scraping through the hole. how deep are the holes you need to drill?

what you really want is a tapered reamer.

Chris Padilla
04-21-2017, 9:16 PM
http://www.leevalley.com/us/wood/page.aspx?p=67385&cat=1,180,42240,53317
Lee Valley has a cheapER adjustable spade bit.

Chris Padilla
04-21-2017, 9:17 PM
i think you may be barking up the wrong tree... the sides of a spade bit do not cut the wood, only the spurs and the bottom edge do. I do not believe you will get your desired results with a spade bit with tapered sides. The sides will scrape and create a mass amount of friction and terrible hole quality if you have enough to power them scraping through the hole. how deep are the holes you need to drill? Well, ASSUMING a spade bit in the 1 3/4" existed, one would have to grind a cutting angle into the sides, of course.

Alan Schwabacher
04-22-2017, 11:14 AM
While it's not what you asked, a way to make a tapered hole is to drill a straight hole the size of the small end, and then ream it out to a taper with a separate tool. You could use the 1 1/2" spade bit, followed by a reamer you could make as described here: http://www.greenwoodworking.com/SawSteelTaperedReamerPlans

This reamer gets around the problems with cutting on the edges of a spade bit --the hole tends out of round.

Marvin Hasenak
04-22-2017, 1:52 PM
Drill your hole at the smallest diameter of the taper then with your homemade "Windsor chair reamer" taper it to size.

How to make a Windsor Chair Reamer. http://chairnotes.blogspot.com/2009/02/making-tapered-reamer-to-suit-your.html

Brice Rogers
04-26-2017, 8:39 PM
If you have access to a lathe and mill, you can make a variety of specialty bits. I've made some out of plain old cold-roll steel for cutting wood and PVC. The metal is hard enough that they don't dull too quickly and are easily sharpened. Yes, I could have bought some HSS, Drill rod or something and then heat treated it, but for a half-dozen to a dozen uses, I didn't even need to sharpen the unhardened steel.

One problem that I have with a spade bit is they can catch and make a person's wrist sore in a hurry. A 1-3/4 paddle is bit enough that you are likely to get some catches.

If I were doing this, I might consider making something more like a large tapered reamer or large "step bit". I would profile a chunk of steel rod on a metal lathe (it is also possible on a wood lathe) and then use the mill to cut 3 or 4 cutting slots and then provide some relief. I suppose that this could even be done with an angle grinder. It might not look pretty but it would work.

BTW, if you look on Amazon and ebay there are people selling bigger spade bits.

Larry Copas
04-26-2017, 11:02 PM
About five years ago, on another forum a member asked nearly the same question. He got a lot of speculation about why it couldn't be done and wouldn't work. I like doing the stuff that can't be done so I made the guy a cutter that worked just fine.

359156

359157

I made the cutter from a piece of 0-1 high carbon steel. Welded this to a 1/2 shaft than hardened, and tempered the cutter. Re-sharpened and put it to the test in some dry white oak. It took a little tweaking to get it cutting just perfect.

Brice also brought up the point about a spade bit catching and he is absolutely right. When I was drilling tests holes I found it near impossible to hold the wood by hand plus it is dangerous. Clamp the wood down and definitely use a drill press.

A couple of thoughts. Welding high carbon steel is hard especially for a hobbyist like me. Heat treating 0-1 is pretty easy with just a way to heat the metal to red hot and canola oil to quench. Temper in a toaster oven. Using HSS would eliminate that step or if it was just for a few holes about any steel would work.

John C Cox
04-27-2017, 12:00 AM
Big ship auger bits are available in sizes bigger than those you are asking for.

If all you need is a tapered hole and dont care about wobbly and egg shaped - then have a tool bit sharpening shop reprofile hour drill bit and off you go. If you need a good precision fit - then get ahold of a reamer such as shown in the post above and use that to ensure a good tight fit on your tenon.

Walter Mooney
04-28-2017, 1:51 PM
My many thanks to one and all for the responses! They've for the most part been great. Larry, your bit is pretty much exactly what I envisioned.

What I have to make are some boards ~ 3/4" thick, 6" or so wide x 12" or so long, with a series of tapered holes through them, so a spring manufacturing company can grind a flat on the top and bottom of special conical springs they make for a customer. Apparently, the person who made these 'templates' for them in the past stopped for some reason, and now they need more, because apparently they wear them out somehow. This first template is for a spring that's about 1-3/4" OD at its widest, and has a 15* taper. At some point in the future they will need templates for other spring sizes as well.

I went to HF yesterday and picked up the type of saw mentioned in the reamer links. I'm going to give the reamer a try, but I REALLY like Larry's bit!

Thanks again for all the responses. I'll let you know how it works out (hopefully in the near future)............

John K Jordan
04-29-2017, 1:25 PM
359157

I made the cutter from a piece of 0-1 high carbon steel. ...

Look great. It didn't make sense to me when some speculated a taper on a spade bit wouldn't work since I've ground several profiles on spade bits and they worked fine. A drill press is a must, of course!

BTW, does your bit work the same drilling into the side of a board as well as directly into the end grain as in your picture? I find that hollowing end grain on the lathe is easier than cross grain.

Also, it looks like the bottom is sharpened to cut. Did you drill the entire hole with that bit or first drill a hole by other means almost (forstner bit, etc) as wide as the bottom of the final hole? That might work well - a lot of people start their hollowing on the lathe like that to save a lot of time and effort.

JKJ

Marvin Hasenak
04-29-2017, 4:02 PM
I went to HF yesterday and picked up the type of saw mentioned in the reamer links. I'm going to give the reamer a try, but I REALLY like Larry's bit!


When you turn your blank for the reamer, add on about an inch on the end with the diameter of the hole that you will start with. It will act as a guide to keep your reamer running true in the hole you are reaming.

Larry Copas
04-29-2017, 8:54 PM
BTW, does your bit work the same drilling into the side of a board as well as directly into the end grain as in your picture? I find that hollowing end grain on the lathe is easier than cross grain.

Also, it looks like the bottom is sharpened to cut. Did you drill the entire hole with that bit or first drill a hole by other means almost (forstner bit, etc) as wide as the bottom of the final hole? That might work well - a lot of people start their hollowing on the lathe like that to save a lot of time and effort.

JKJ

John, it drilled about the same in side grain as end grain. I drilled the hole with only the bit shown. No pre-drilling required.

I was scared that it might chatter some so I made the cutting part out of 1/4 or 5/16" tool steel. With it being that heavy, sharp, and a slow speed it didn't have any tendency at all to chatter. I only made a couple of test holes before sending it off to the user so it may have behaved differently with other woods.

Bill Dufour
05-03-2017, 9:37 PM
Easy enough to make a spoon bit or a D bit. But they will be slow cutting compared to a proper spade bit. You could get a metal working counter bore taper ground to the needed angle. Any chance your taper angle might be a standard machine taper. Like a morse taper, R8. 5C etc. If it is they make drills and reamers to make or clean up those bores.
Bill D.

On edit:
R8 16.85 degrees
NMTB 16.5943 degrees

HSK 30 degrees

Maybe have one of these reground/sharpened to 15 degrees.

Malcolm McLeod
05-03-2017, 10:02 PM
Seems like you're off and running in another direction, but thought I'd toss this in the ring - just 'cuz no one else has.

With stock that's 6 x 12 x 3/4, it seems like it would fit in a 4-jaw chuck of a engine lathe. Pre-drill your hole to just under the final minor diameter with the tail stock; then cut the required taper with a standard tool post in the compound rest. Simple...?

Jerrimy Snook
05-04-2017, 3:23 PM
I haven't read all the responses but Carbide Processors sells router bit blanks that came to mind when I saw Larry's bit earlier in this thread.

http://www.carbideprocessors.com/southeast-tool/carving-bits/router-bit-blanks/

george wilson
05-16-2017, 10:48 AM
Don't use an ADJUSTABLE bit!!! They ALWAYS get OUT OF ADJUSTMENT and ruin the hole. They might work with a brace and bit,but an electric drill or drill press is too much for them,it seems.

Kevin Beitz
04-29-2018, 5:19 PM
My choice of metals would be drill rod. Air or oil hardened. Easy to harden after you shape it.

Lee Schierer
04-29-2018, 6:54 PM
i think you may be barking up the wrong tree... the sides of a spade bit do not cut the wood, only the spurs and the bottom edge do. I do not believe you will get your desired results with a spade bit with tapered sides. The sides will scrape and create a mass amount of friction and terrible hole quality if you have enough to power them scraping through the hole. how deep are the holes you need to drill?

what you really want is a tapered reamer.

A few years ago I made a special bit for drilling tapered socket holes to hold candles from a spade bit. I marked the bit to the angle I wanted and ground the edges of the spade so the leading edge of the tapered part as it rotated was an acute angle, making it a cutting edge. It worked just fine with no burning whatsoever.

Ted Phillips
04-30-2018, 11:39 AM
Personally, I would drill the hole with the smaller diameter straight bit - then ream the hole using one of the tapered reamers from Lee Valley. That's what I do for staked legs on benches, chairs and whatnot. Relatively easy to do and creates perfectly-tapered holes. All three of these reamers are tapered at 12.8 degrees.

http://www.leevalley.com/us/wood/page.aspx?p=54864&cat=1,180,42240,53317,54864
http://www.leevalley.com/us/wood/page.aspx?p=54865&cat=1,180,42240,53317

Clint Bach
05-01-2018, 9:04 AM
This sounds like a perfect project to use a cnc... Just saying...

C