Making traditional bowl gouges from Tungsten Carbide

[Neil S]

Fellow forum member @hughie and myself are using traditional style bowl gouges made from Tungsten Carbide (TC) to turn the hard woods that we are working with. The TC gives us better edge durability when working with those woods. This thread shares how we went about making them for anyone who would also like to make one/some traditional style bowl gouges from TC for themselves.

I have previously posted how Hughie and I have made bowl gouges from HSS…

www.aawforum.org/community/threads/grinding-short-flutes-to-make-new-bowl-gouges.20906

I have also posted the results of my testing of the performance of the TC bowl gouges that we made and compared their cutting edge durability against 15V, 10V and M42…

https://www.aawforum.org/community/threads/testing-tungsten-carbide-bowl-gouges.21532/

The technique we have used for making the TC bowl gouge tips is similar to how we made the flutes in HSS described in the thread above, but there are some additional aspects for TC and this thread is about those additional requirements.

Sourcing round TC bar

Living in the part of the world where we do, we sourced the TC bar stock from China. No doubt you will find similar sources in the US. We have used both solid round bar and some with a centre hole pre-formed in it. The thinking with the second type is that it would help locate and keep the centreline of the blank (it didn’t always) while grinding.

TC grade designations can be a bit of a mystery. The advice on the most suitable grade of TC for woodworking is below 1μm carbide size in 6%, or less, of cobalt matrix. I settled on the submicron grade YG6X (6% Cobalt with a HR(A) of 93).

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BTW, at Rockwell 93 HR(A) you have an extremely hard, but brittle material… push it into fast spinning hardwoods for all you are worth, but don’t drop it on your concrete floor or whack it against another very hard material.

Given the durability of TC, only short flute tips of it are required to provide a gouge that will last a very long time. Unfortunately TC round bars are manufactured in standard 12” lengths, however, some suppliers will pre-cut it into 6 and 4” lengths. With 4” lengths I grind a single flute of about 1-1/2” length and a double flute (one on each end on opposite sides) on 6” lengths.

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If you have the skills to silver-solder (I don’t) you can go with shorter lengths of TC brazed to SS or silver/bright steel bars of the same diameter, but you won’t get 2” pre-cut lengths, so if you decide to go that way cutting it to length will be your first task.

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[Neil S]

Cutting/Grinding the flute

I begin by marking out the flute profile I want to achieve with a felt pen…

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I then scribe that line with a fine diamond point in a Dremel. This is necessary because the felt pen line will burn off and disappear with the heat generated during cutting and grinding…

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The abrasive wheels that are used with HSS won’t get you anywhere with TC. And, although CBN could be used, it is only 66% as effective as diamond and gets knocked about very badly by the TC, So, diamond is the only real option.

I use a combination of thin diamond cut-off wheels to cut to depth, diamond points in a Dremel to shape the flute profile, and slightly wider wheels to smooth out the flute profile. As I am only making short flutes, I have found that smaller diameter wheels (4” or less) work best. I use continuous rim diamond wheels. The interrupted segmented rim type will chip the brittle TC.

Thin diamond cut-off wheels have a sintered construction and the grinding wheels are resin bonded diamond wheels. I mostly use about #150 grit wheels. Coarser grit diamond wheels may cut quicker, but they are more prone to chip off edges where you don’t want that to happen.

Sintered diamond
cut-off wheels​

Frequent ‘sharpening’ of the diamond (i.e. exposing fresh diamond) with fine carborundum blocks is required, particularly with the cut-off wheels. This may seem counter intuitive, but is necessary to keep the diamonds on the edge of the wheel exposed and cutting.

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[Neil S]

I mount the diamond wheels on various power tools, including angle grinders, chainsaw sharpeners and circular saw blade sharpeners.

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Those tools are mounted at a workable height and I handhold and manoeuvre the carbide rod against the wheels on top of an improvised ‘tool rest’. The arbor sizes of the diamond wheels that are available don’t always match those machines, but bushings can sometimes help to crossmatch.

I used additional lighting (not shown in above photo) to better see what I was doing.

If you have a means of wet cutting by all means use that as the diamond will cut more efficiently and minimise the dust issue.

 

[Neil S]

To begin with I do cuts adjacent to each other with the thin cut-off wheels and then snap off the brittle remaining sections between the cuts before grinding down to the final profile. Warning: the shards can be very sharp and adequate eye protection is essential.

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[Neil S]

Then I use the Dremel with the TC fixed at a suitable height and I sit low so that I can sight down the flute line and grind with the diamond points using a handheld flexible shaft. As the flutes are only short, the length of the diamond points work for that. I use those in various diameters so that I can create the flute profile that I am after. I get the sintered style diamond points in whatever grit sizes they happen to come in.

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Note: You can get small (about 2” diam) diamond discs for rotary tools, but I found that they were of very limited value for cutting the thin deep cuts.

This is what I get after using the diamond points…

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[Neil S]

The remaining serrations that are left from the diamond points are then ground smooth with a fine grit diamond resin matrix grinding wheel.

Diamond resin matrix wheels

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If working with a short length of TC that is not brazed to a shaft, I hold it while cutting and grinding in the same handles that I will use while turning with it.

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Note: The TC gets very hot during cutting and grinding, so be careful not to burn yourself!

 

[Neil S]

Polishing

Loose diamond grit and paste in various micron sizes is now readily available and relatively inexpensive. The loose diamond grit can be mixed into a paste with oil/wax and applied to hard buffing wheels. Make (turn) your hard buffing disks to match your flute profile from a soft fine grained wood. Clean off thoroughly between grits or use separate ones for each grit grade if you get to do more than just a few TC gouge tips. I make templates of the flute profile that I’m after to mark out the flute profile for cutting/grinding and also to shape the hard buffs…

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The positive side of the template can also be used to check the flute profile while cutting/grinding…

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Depending on how fine the grind was off the last wheel before polishing, start with an appropriate grade of diamond paste grit. I have started with 40 or 20μm and worked down to 1μm. That may be excessive, but at least go down to 5μm to match the bevel grind, which I recommend be done on #1,000 diamond.

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[Neil S]

Time to make

After getting everything required together, the first run through to complete a TC gouge tip to this stage was about a day. For example, the following photo shows the progress on making the initial thin cuts to depth at the one hour and 15 minute mark…

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So, you have been warned that cutting and grinding TC is a slow process, but the payoff comes later when it keeps cutting after all the other gouge metal types have quit and gone home… :~}

 

[Neil S]

Sharpening

As diamond is the only real alternative for sharpening TC gouges, a means of doing that is a necessary consideration.

I have posted a separate thread on various ways you might sharpen TC…

https://www.aawforum.org/community/threads/sharpening-tungsten-carbide-gouges-with-diamond.21540/

Not shown in that thread on sharpening TC gouges is the initial formation of the bevel that I do with any new gouge that I get or am making.

Present the flute towards the grinder and shape the required wing profile first.…

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With TC I cut away close to where the bevel will be with a thin diamond wheel before fine grinding because that is faster…

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Then fine grind to #1,000. If you have interim size diamond discs go through those to get to #1k…

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[Neil S]

Safety: Lung and eye protection

Your life… your decision!

The cobalt, as distinct from the tungsten, in tungsten carbide is a known source of toxicity…

https://www.nj.gov/health/eoh/rtkweb/documents/fs/1960.pdf
https://pmc.ncbi.nlm.nih.gov/articles/PMC2679595/

I avoid breathing in the fine dust that comes from cutting and grinding by using a filtered face mask and capturing as much of it as I can at source. The above link to sharpening TC has some of what I have done to try to capture the fine grinding dust at source.

Adequate eye protection is also recommended as sharp shards can fly off the TC while cutting and grinding it.

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All the best if you decide to have a go at making your own TC gouges
and if you do come back and share with us how they performed for you.​

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[Alan Weinberg]

This is fascinating, beautiful work, especially so to one such as I who can’t make anything tool-wise. I often wondered why carbide gouges weren’t used.

I think I figured out an easier way for me than making one myself—can I buy one from you? Hahaha, but is this process commercially viable?

Second question, when it invariably does dull, does it
require owning a diamond wheel to sharpen? So a second grinder becomes a requirement?

Great thread and thanks.

 

[Neil S]

I think I figured out an easier way for me than making one myself—can I buy one from you? Hahaha, but is this process commercially viable?

Second question, when it invariably does dull, does it
require owning a diamond wheel to sharpen? So a second grinder becomes a requirement?

Alan

On sharpening TC, there are a number of other options to a diamond wheel, which are now a bit hard to come by anyway. I've covered some those other options in a separate thread... https://www.aawforum.org/community/threads/sharpening-tungsten-carbide-gouges-with-diamond.21540/

I'll leave the question about commercial availability to my colleague, Hughie, who is more over that side of things than me.