Introduction: Make Your Own Carbide Lathe Tools
Carbide turning chisels are interesting whether you’re new to turning or a veteran. They’re fantastic for harder, more abrasive timbers and mixed materials that would normally require a lot of sharpening, and because they’re scrapers you don’t need particularly fancy techniques to get them to work well.
The downside, however, is the enormous cost. In Australia, for a ‘full size’ carbide chisel, you’re looking at over a whopping $200. I was able to make my own for under $50 each.
If you're more a visual person than a ready-all-the-wordsy person, this tutorial is also on youtube.
Step 1: Tools and Parts
- Metal - I used 4140 (12.7mm round) and stainless steel (12mm, square). There are some merits to either square or round bar stock, but from a safety point of view square is "best". Some people have luck with cold rolled steel, but I chose stainless as its a bit stronger.
- Copper plumbing connectors - I went with 25mm (1"), but 19mm (3/4") would have worked fine. One connector cut down the middle should do you just fine.
- Carbide cutters - I got mine from AZCarbide (no affiliation), but the replacement cutters from any of the 'name brand' carbide chisels will work, or even the cutters used on helical head jointer/planers
- Epoxy for attaching stuff
- Wood for handles - use a nice hardwood, I went with a native wood (Jarrah)
- Flat file
- Hack saw
- #8-32 Tap - I used the screws from AZCarbide which are the same as EasyWoodTools. That meant a #8-32 tap
- #29 drill bit - the corresponding drill bit for a #8-32 tap is a #29. If you choose to use different screws, just match screw to tap to drill bit.
- Drill press
- Cutting fluid
Step 2: Making the Handles
I made my handle blanks roughly 42mm x 42mm (1.65"), which gives plenty of room to grab it in a standard 50mm (2") 4 jaw chuck, as well as lots of room for shaping the most comfortable handle. Length is fairly flexible as it really depends on what is comfortable for you - species of wood will effect this as well as a heavier wood may need to be shorter to balance the weight properly. 400mm/16" is a a good ball park size for handles, however.
If you're using square bar you'll want to cut the handle blank one-blades-kerf wider, and then in half. That is, instead of 42x42mm, cut it 46mm x 42mm, then cut it in half to 21mm x 42mm. As its difficult to drill a square hole, cutting it in half lets you route a square channel in both halves.
Using a router table, route a channel about 120mm long, by half the height of your bar - for me that was 6mm.
Use wood glue to glue the two halves back together, inserting the square bar in to help with alignment. Wood glue won't adhere to stainless steel, but once you've got the clamps on you can always pull out the bar to be on the safe side.
For both round and square bars, mount the blank on the lathe between centres, and turn round. Turn a tenon on one end, then mount it in a 4 jaw chuck with a live center in the tailstock for support.
If you're using the round bar, use a jacobs chuck in your tailstock and drill a 12.7mm (1/2") hole as far as you can into the handle - my drill bit managed to go ~110mm. Then switch back to the live center
Turn a tenon sized for your ferule, take the blank off the lathe and glue on the ferule with CA or epoxy.
When dry, remount on the lathe and turn the handle until its suited to your hands.
Step 3: Preparing the Metal Bar
If you're using a "standard" size cutter it should measure about 15mm square, and be about 3mm thick. File a 'pocket' for the cutter to sit in, this should be 12mm back, and 3mm down.
You might find it easier to establish the back line with a hacksaw first.
Once you've ground your pocket, its time to drill for the machine screw. Place your cutter on the pocket, and find the location of the screw. Mark it, then use a center punch to create an indent.
If you're using round bar, make sure you to use a v-block to make drilling easier and safer
At the drill press with the help of some cutting fluid, drill a hole all the way through. You want as many of the threads of the screw to engage, and unless you've got a bottoming tap (as well as a taper tap), you're unlikely to be able to go too far if the hole doesn't go all the way through.
Once drilled through, head back to your vise and tap the hole. Remember to use ample cutting fluid, taking it slowly and regularly backing out the tap to break the chips. This is especially important in stainless steel which can be difficult to tap.
You may need to countersink the hole as the countersunk head on the screw that came with my cutters extended about 0.5-1mm through the cutter meaning it wouldn't hold the cutter down tightly. With some care, just use a larger (10mm/ 3/8"s) standard twist drill bit to put a slight countersink on.
Step 4: Putting It All Together
Time to epoxy the metal into the handle. Remove the cutter and screw, and tape up that end. Do a dry fit of your bar, then tape around the bar where it meets the chisel so it is easier to remove any squeeze out. Do the same for the ferule. While this isn't critical, it will make it look nicer than having globs of glue everywhere.
Any adhesive (rather than casting/etc) epoxy should do the job just fine. Read the instructions for whatever you use to find the cure time to full strength - 5 minute epoxies are never at their full strength after 5 minutes (usually an hour or more) so the chisel won't be safe to use until then.