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cuslog
05-05-2009, 04:03 PM
Hi guys;
I'm trying to make my own 15 degree dovetail router bit - a rather large (1.500 dia) that I haven't been able to find for under $500, hence my attempt to make one.
I turned the body out of 4140 and I've cut 15 degree wedges out of planer blade (I'm assuming its HSS). I made one and silver soldered the blades to the body but wasn't feeling good about the results - questioning the bond and the balance. I ran it in the router @ 22,000 rpm - seemed to work OK but I'm still a bit concerned about the bond - at that RPM I don't want a blade coming off.
I'm in the middle of making another and plan to attach the blades w/ 8-32 flat head socket head screws, countersunk so the head is flush.
What is best for drilling / countersinking HSS planer blade ? I am thinking of ordering a carbide center drill - or is there a better way ?
Other comments or suggestions ?

Lew Hartswick
05-05-2009, 04:16 PM
Center drills are 60 deg and "most" flat head screws are 82 deg.
There are 90 and 100 deg flat heads but not the "run of the mill" ones.

I "think" (note havent given it a whole lot of thunk yet) I'd use the
idea of the way the blades are held in a jointer to hold the blade in
and use a single blade and try to balance it. If there is room for two
blades it would be "balanced by design". :-)
Also I wouldn't ty to run that big a bit at any where that speed,
for a 1-1/2 " dia I'd use the low end of the speed range on my
router.
...lew...

FatWheels
05-05-2009, 04:23 PM
The first thing that comes to mind is . . . duck and cover:eek: but I admire your initiative. If you have a router that is remotely big enough to swing that bit and power it through a cut, might it not also have a speed control as well? I'd never run it much past eleven thousand rpm which might calm your nerves when it spins up. That is pretty much a shaper cutter in size and mass and they run much slower than your 22,000 rpm.

A typical shaper running hss cutters is going to be in the 6,000 - 10,000 rpm range and even then the larger cutters will burn and/or burnish edges of your work easily. Hope this is of some help.

regards,

Jim

p.s. This is at least a two and half horse router with a half inch collet mounted in a statiionary bench or table, right???

cuslog
05-05-2009, 05:14 PM
Lew / Jim - thanks. yes. it worries me a bit too, I thought a pair of screws might be more "positive" - I'm unsure of the HSS / silver solder bond.
3.25 hp Makita router, single speed, though there is a variable speed model available for about $450 - 9000 min rpm.
There are 2 blades

cuslog
05-05-2009, 05:22 PM
Here's a link to show what I'm trying to do, a couple glorified router jigs and a big router. They sell for about $6,000.
A guy with a lathe and a mill and time on his hands should be able to build something like this for a lot less than that.
http://www.timbertools.com/Products/LignaTool.html

Rustybolt
05-05-2009, 05:45 PM
Try brazing the cutters on. Failing that , make the whole thing out of O-1 or some other drill rod.

Bruce Griffing
05-05-2009, 06:51 PM
+1 on two points. For that diameter, you need to slow down. 22k is too fast. As said above, maybe 6k. If it were me, I would use carbide silver soldered (silver brazed) to a steel blank. Or if you are ready to sharpen it often, make it out of O1 and harden it. Then it would be only one piece. The screws would scare me to death in this application.

thistle
05-05-2009, 07:36 PM
http://www.carbideprocessors.com

this site has very good info on brazing carbide.
the gentleman who owns it frequents the PM forum.

FatWheels
05-05-2009, 08:16 PM
Just wondering . . .

I understand how easy it is to maintain clearance angles with brazed hss or carbide bits, but I wonder where to find clearance angles for one piece bit of O-1 or similar. By the time you've gone to the work of making one, you'll want to have optimum sharpening angles on a tool and cutter grinder. Anyone know where to find them, and how do milling cutters compare, They are quite a bit cheaper than woodworking bits of the same size. At least historically, there's been an influx of dirt cheap router bits of late. The same set I bought for one hundred twenty five bucks ten years ago is now about thirty.

regards

Jim

cuslog
05-05-2009, 09:58 PM
Fatwheels;
I'll try attaching a photo album here, hope it works.
http://s726.photobucket.com/albums/ww262/cuslog/
I cut 2 notches in the body, canted 5 degrees in both directions. If the photo album works, theres also pictures of a grinding / sharpening jig I made / adapted to rough grind the blades.
I'm also thinking I'll make a shop built tool post grinder so I can do the final grinding / sharpening on my lathe.
Thistle; thanks for the link, I've spent some time there and probably much more - I may re-visit the silver solder or brazing idea maybe with better technique.
oops, the car wasn't supposed to be in there :confused:

FatWheels
05-05-2009, 10:13 PM
You've got first rate work with nice pictures to illustrate, good job. I'm with you on the diy attitude. They claim their process took two and a half years to perfect, but must they make it all up on the first sale?:eek:

I'll admit I like their screw-on template. That self locking sliding dovetail is clever also. If you could maneuver the logs easily enough I might add to the process by hogging out that tenon with a circular saw set of templates. Big savings in time and cutter life, not to mention holding that router out in the middle of space to nibble all of that endgrain. Might get heavy after two or three hundred.

regards,

Jim

Robin R
05-05-2009, 11:50 PM
I agree that the Ligna Tool prices are way to high, I made up some MDF templates to try that idea out and they worked just fine. Making them up in aluminum certainly wouldn't be difficult and I don't think it would take two years.
What depth of cut are you aiming for, I went with 1" and I doubt you would need more than that, depending on the size of timbers you are using of course. If that would be enough, Dimar make 1" 14 carbide bits, I think they are about $40. House of tools sells them, if there is one of their stores near you, the one nearest me was in Campbell River, but it just closed.
CMT make a bit with 1 1/4" length of cut, but that's an 8 bit, which might not work for you.

fredf
05-06-2009, 12:08 AM
Hi guys;
I'm trying to make my own 15 degree dovetail router bit - a rather large (1.500
. . . Other comments or suggestions ?

how about just making a template to cut the shape out with a smaller bit?? it would take a bit longer, but less risky. I'm assuming they make one with an adequate depth

fred

J Tiers
05-06-2009, 12:13 AM
Wheeeee....... if I didn't mess up the calculation, 22k rpm and 1.5" max diameter gives about 8600 SFPM........... or about 100 MPH cutting speed.

I know wood routers go fast, but I thought the usual SFPM was more along the lines of 3300 SFPM max.

FatWheels
05-06-2009, 11:27 AM
I checked out their web catalog and Grizzly makes a 14 1" dovetail bit with a 1.125" cutter depth. Price was nice too, $18.95 per. I still admire the work and attitude though.

regards,

Jim

cuslog
05-06-2009, 12:06 PM
Thanks for the comments guys.
Yes, I think the Ligna system is really slick and I can see that they have put in a lot of development work. But there's no way those 2 templates are worth $4,000, not to me anyway. And $400 for a router bit reminds me of those "free" inkjet printers you get with some computer deals, then they want $50 for an ink cartridge that only holds a teaspoon of ink :eek:
I'm a log home builder, handcrafter, using quite large logs and timbers, the Ligna system would work for some of our joints but for lots, it would be too small. I would really want at least the 40 mm depth of cut the ligna gets if not more, that's why the 1.5" width and the 15 degree taper. I'd also be making other templates to "adapt it" to our system. Its really designed for timber framers using 8 or 10inch timbers, we're using bigger than that.
Things are pretty slow for us right now and money is tight, I want to play around with this system and get it adapted for our use. If it works like I think (hope) it will, I'll replace the old single speed (22,000 rpm) router with a new variable speed which goes as low as 9,000 rpm. Or maybe one of those nice Mafell 220v ones :cool:

Swarf&Sparks
05-06-2009, 12:18 PM
How about you just slot a nice solid piece of steel (turned to roughly the right profile) then braze in one solid piece of carbide and grind to finish profile?

T'was the way it was done when my mad mate had a tool business and had to make a custom profile.
I've used his cope and mould sets up to 1.5" in a 3 HP router.
Speed was well down though, minimum the (Hitachi?) router would run.

cuslog
05-06-2009, 03:42 PM
Yep, carbide is next on my list. I just tried the planer blade because I have some "in hand", the carbide I'll have to order in and it would take a week or more to get here (I'm in a small town, no local supplier for carbide blanks)
and yes, if this works, I will be buying a variable speed router and turning it way down.