Spiral upcut router bits

[Deadhead]

Did you check Brian's bits?

http://www.holbren.com/home.php?cat=7

[vaking]

I am using 1/4" solid carbide bit because this is most frequently used bit. As for 5/16 and 3/8 bits - I use regular straight bits or HSS onsrud bits. Either bit will take you through several projects. Straight bits will require you to clean the mortise after each pass because they don't eject the wood but they will do the work. I have 1/2" solid carbide bit thanks to a deal from Brian, but it is not a frequently used mortise size for me.
So far the only broken bits was 1/4" straight and plywood smallest bit. I suggest checking onsrud bits at LeeValley - they are more reasonable in price even with shank adapters.

[drumpriest]

You certainly can cut mortises with a plunge straight bit. I cannot expound upon the differece enough though. A solid carbide spiral cuts MUCH MUCH smoother than does a standard straight bit.

[Boomer_01]

Shopsmith Mortising Option - Dont Laugh!

I don’t know if anyone will admit it or not, but just in case there are any Shopsmith owners secretly lurking in this forum (like me) here is a mortising option you might consider.

Last month I read an article about a horizontal mortising set up in one of the woodworking magazines. The set up had two platforms sliding on perpendicular axis to provide stock movement parallel and perpendicular to a spiral cut bit mounted in a horizontally oriented PC Router. The sleds allowed the stock to move back and forth across the cutter as well as toward and away from the cutter for depth control. Each sled had stops, and with each cutting axis pre-measured and the stops in place production runs were possible.

I thought the set up looked pretty slick so I decided to build one so I wouldn’t have to do the drill and chisel routine to cut my mortises. As I stared thinking through the process It struck me that the horizontally mounted router looked very similar to my old Mark IV which I long ago relegated to a horizontal boring machine and lathe. The Mark IV (that my wife bought for me as a present in 1985) never really lived up to the hype as a table saw but it does a pretty nice job on certain drilling tasks and is a great BT3000 extension table.

So there it was sitting quietly with its adjustable height miter deck, with its ability to slide on its tubes toward and away from the horizontally mounted motor. So after a little ciphering and a couple of sketches I devised a pretty nice little mortise sled with an adjustable fence and toggle clamp positioned perpendicular to the motor and resting on the IV’s miter table. The sled moves the stock across the cutter and the IV’s quill can be pre-set to the proper cut depth, then (using multiple passes) plunged into the stock to cut the mortise.

I ordered a 3/8” Freud upcut spiral bit from Router Bit World and the proper router bit collars from Shopsmith (in 21 years it was the first purchase I have ever made from them except for the Mark IV).

Well last night I finally received the router bit via parcel post, and finished tuning the sliding jig. I tested it out on several different length and depth mortise combinations, low and behold with the motor speed (I as was bit trepidations on the first few cuts and kept the speed way down) set on “Route” the darn thing worked pretty well on ¾” Poplar.

The motor does seem to have a little bit of run out so if I got very aggressive I could feel a chatter, but after increasing the speed and just taking my time I got a very nice cut, centered in the stock and the correct depth.

I strongly recommend using the spiral cut over the straight bit for plunge cuts. As I was developing my sled I did a couple test cuts using a 3/8” straight bit and the vibration was really scary, once it even caused the toggle clamp to open in mid-cut, that one made me leave the shop for a couple of hours thankful that I didn’t end up with a piece of 1 x 3 poplar lodged firmly in my forehead.

So anyway I know this is a long post but I thought maybe any of you clandestine Mark IV owners might be interested in a new use for your “All in one woodworking marvel”.


Thanks,
Boomer

[JimD]

I too would use a 1/4 solid carbide upcut spiral bit, I have one and it works nicely. I have busted several router bits, I am not real gentle, but not this bit. It will cut wider mostises. To do so, I would put a template guide on the router and make a little jig. Even for a 1/4 inch mortise, a small jig makes cutting the mortise relatively fool proof. If you are cutting several mortises it will make things much quicker. For instance, I would use a 1/2 inch OD template guide, like for a dovetail jig, and make the opening in the jig 1/2 inch plus the width of the mortise over 1/4 inch. For a 3/8 mortise, the opening would be 5/8. Length of the hole in the jig must be 1/4 longer than the desired mortise.

Jim