Grinding Bowl Gouges

[NeilS]

I made some assertions about the grind that I think should come on a new bowl gouge in a another thread that I was writing in about flute profiles, see here (http://www.woodworkforums.com/f8/flute-profile-gouge-217127/2#post2081055).

The emphasis there was that new bowl gouges should come with a grind suitable for novices. Experienced woodturners can look after themselves!

In this thread I want to argue for my assertions with support from luminaries like Jerry Glaser.

Bowl gouges as we know them now are a relatively recent development.

Peter Child's 1971 book shows (pg 25 & 27) an early forged deep fluted (parabolic) bowl gouge. Peter had been using these since 1966. It was at the forefront of tool development back then but has a straight across grind, but very acute included angle that few of us would consider using nowadays.

Some years later Roy Child, Peter's son, developed a bowl gouge that had the same flute profile but milled out of round stock. It was still being made from high carbon tool steel then and it was not until Henry Taylor took over their manufacture that they were then made from HSS and called the Superflute. Roy used it with a straight across grind and Henry Taylor supplied them that way. See here (http://www.peterchild.co.uk/info1/sflute.htm).

Roy eventually adopted the swept back wings as one of his bowl gouge grinds, but he was a late comer to this with Liam O'Neill and Michael O'Donnell (thus the Irish or Celtic grind description) being credited with its development and David Ellsworth with its promotion. David credits Liam, Michael and Richard Raffan with its development.



Here are Roy's two styles of grind, swept back on left and straight across on right.


433701<strike></strike>

<strike></strike>
While all of this was going on in the UK, there was an even earlier and parallel development going on in the US.

Jerry Glaser developed the first bowl gouge milled out of HSS round stock in 1966, which he sold ready sharpened. In 1982 he released the sharpening jig that he used for sale. This was the forerunner of all later generations of commercially produced gouge jigs.

In 2001 Jerry wrote (see attached) about how he sharpened his bowl gouges. It contained the following diagram. You may need to click on it to see the details.



433702<strike></strike>

<strike></strike>
This diagram clearly shows how a swept back grind 'should be' formed. The gouge is first ground as shown on the left and then the bevel formed as shown on the right, following the flute edge established as shown on the left.

Continued in next post....

[NeilS]

My guideline in establishing the edge profile in the first step on the left (in post above) is to create an inner edge formed by the flute so that it can be seen as a mirror image of itself when viewed from the end of the gouge and looking down on the flute from above. eg


433704<strike></strike> 433705


<strike></strike>Following the inner edge profile you get the following. In this case with approx. 60deg nose angle, but the nose angle is not relevant to this.


433706

<strike></strike>
I find that this gives the base profile that works best for the particular flute profile that comes on the gouge. It can be modified from there when experience tells you what the trade-offs are, but I recommend this as your initial grind until you are confident you know what works better for you.

In the next post I will provide a link to Doug Thompson's video on grinding bowl gouges.

[NeilS]

Doug Thompson is both a woodturner and woodturning tool maker. He has ground and sold thousands of bowl gouges. In his video on the topic he shares his 'secret' on how to grind a bowl gouge. If you have been following this thread it won't be news to you. Some of his terminology is different at times, but what he shows is the key. Do as he shows, not necessarily what he says.

The video covers a range of things. The first 3 mins is about himself. The relevant section is the 5 minutes from 12 to 18 minutes in which he covers what he calls his 'secret' on how to grind a bowl gouge "properly".


If interested, he also has a section on tips for fixing up mis-ground bowl gouges starting at the 27 minute mark. There may be other sections of the video of interest to you, but those are the sections relevant to bowl gouges.

Here is the link to his video, Sharpening Woodturning Tools (https://youtu.be/ttYyulsM7wg). <strike>
</strike>

[NeilS]

Last input on this.

Dave Schweitzer is another woodturner/tool maker. He makes one of my favourite bowl gouges. The grind he provides on his tools ranges from straight across for what he calls his 'bottom feeder' gouges to swept back, like on his 3/4" bowl gouge here.



433711
<strike></strike>

No surprise to see a convex wing on that gouge.


If manufacturers won't/can't provide an appropriate grind like this on their bowl gouges they should drop back to providing a default straight across grind the way Henry Taylor continues to do.

Here is a page which includes a few different bowl gouge grinds (http://www.woodcentral.com/newforum/grinds.shtml) used by a variety of turners. Some have a straight across grind in their racks, but note the convex grinds on all of the swept back grinds. There could be a good reason for this, other than fashion.