mounting cores

[Brian LaRochelle]

Greetings, I've been a member for around a year. I intended to make a post in Introductions, but I'm a lurker and don't stick my head up often.

Anyway, I have a coring system and I usually pop out the smallest core first then work my way out. I don't like jamming the cores and putting a tenon on it just go out of round anyway, and I like to leave the decision of tenon/recess till later.

I like the method, that seems to be attributed mostly to Richard Raffan, of putting a recess on the inside of the roughed and dried bowl blank. Finishing the outside and refining the tenon/recess, then flipping for the inside.

Problem is to get the bowl blank in place to make a recess on the inside. I usually would take the core, use some sort of jam chuck, or Glen Lucas's bowl reversing plate, make a tenon and start from there. But I'd really like to skip this step. And I tend to like a recess for the cores anyway.

So I took a dried bowl blank I thought would be a good size/shape for most cores, and put on some 1/2 inch adhesive neoprene strips. I took a little inspiration from odd-not's Mono vacuum chucks. I have the number 3 and I really like it so far. I actually think the number 5 may also work well for this 'problem'. Some day soon I hope to get it and try it out.

#5 Mono — OddNot

The #5 Mono is our largest size vacuum chuck in our premium vacuum chuck lineup with a 1 1/4”-8 thread. It measures 5 inches at it’s outside diameter and has the greatest holding force in the Mono series.

www.odd-not.com

So I get my tailstock and banjo reachable and ready. Put the core in hold it with my right hand, manually turn it getting side/end grain edges matching, move the tailstock in and cut the recess. Having the right tool to cut the recess between the tailstock and side of bowl is key here. Then I can flip it and finish the outside and decide on recess or tenon, flip finish inside, flip and vacuum to finish the foot.

So far I'm really happy with the results. I was worried the 1/2 neoprene might give too much when cutting, but that hasn't seem to be an issue, yet.

Has anyone else had solutions to the same problem? Critiques/criticisms welcome.

 

[Sam Fleisher]

No criticisms here. I have the same lathe though, are the feet the factory v2? Or did you use something else on it?

I'm one of those people that if it works for you it must be right!

 

[Brian LaRochelle]

No criticisms here. I have the same lathe though, are the feet the factory v2? Or did you use something else on it?

I'm one of those people that if it works for you it must be right!

I just used the factory feet. I've been considering bolting it down to something of a hardwood base to increase stability. Haven't put much thought into it yet.

 

[Lou Jacobs]

Here’s a wacky idea: get the largest forstner bit you can and just use it to drill a recess into the bowl that’ll fit one of your jaw sets. You could use a drill press or the lathe. Here’s a 3” bit I found with a quick search. Perhaps you could find a larger one.

 

[Brian LaRochelle]

Here’s a wacky idea: get the largest forstner bit you can and just use it to drill a recess into the bowl that’ll fit one of your jaw sets. You could use a drill press or the lathe. Here’s a 3” bit I found with a quick search. Perhaps you could find a larger one. View attachment 64314

Interesting idea, I would definitely want a dovetail in the recess for better holding security. Not sure how to apply that with this method. Centering the piece might be tricky too.

 

[Lou Jacobs]

I’m not sure you want a dovetail. Having it straight sided would allow you to adjust the piece on the jaws. A dovetail would limit the positioning options.

 

[hockenbery]

You can with a little practice just friction drive the bowl core over a partially open chuck.

If you mark center on the core bottom before drying, using that center point makes it even easier.

If you centered the bowl on the grain it will warp symmetrically making the recentering easier too

What I want when recentering a bowl is to center the rim. This gives me the biggest finished bowl.

I mark the two low parts of the rim and the two high parts of the rim.

The I get the two high spots equal distant from the head stock and equal distance from the tool rest
Then I check the two low points put the one nearest the headstock straight up and rotate the bowl downward keeping the two high points rotating evenly as I reposition the bowl to align the low points.
I want the two low point equidistant from the headstock and tool rest.

Then check and fiddle. It may take you 5-10 minutes the first time you do this.
After a little practice this recentering takes about 30 seconds.

Then with the friction drive you can turn your tenon.
Or recess.
In most cores I would opt for a tenon.

 

[Brian LaRochelle]

You can with a little practice just friction drive the bowl core over a partially open chuck.

I've used this method to put a tenon on the bottom of the cored bowl, tho I tend to use a Glen Lucas reversing plate more often. But my goal is an attempt to skip this step and go directly to a recess on the inside of the bow.

If you mark center on the core bottom before drying, using that center point makes it even easier.

I keep trying to remember to do this, and keep forgetting.... one of these days.

I mark the two low parts of the rim and the two high parts of the rim.

This is a good idea, I think I'll start marking the two side grain and end grain points to balance with a sharpie before hand. Sometimes its difficult to make them out when balancing.
I use mostly the method you describe for balancing the rim.

I've mostly only use tenons, only recently started using recesses for bottoms of cores. Mostly due to inexperience with coring and leaving myself less than ideal amount of material at the bottom of the core.

 

[hockenbery]

I've used this method to put a tenon on the bottom of the cored bowl, tho I tend to use a Glen Lucas reversing plate more often. But my goal is an attempt to skip this step and go directly to a recess on the inside of the bow.

Not sure what you gain by having a recess inside. In my thinking it’s an extra step with no added value to me.
If it gets you closer to achieving your goals that works for you.

Glenn Lucas reversing plate - gets you close to balancing the rim.
It’s a good compromise of speed and balance.

 

[hockenbery]

I've mostly only use tenons, only recently started using recesses for bottoms of cores. Mostly due to inexperience with coring and leaving myself less than ideal amount of material at the bottom of the core.

When I do hemispherical cores a tenon uses less wood than a recess.
To make a recess I have to turn away the tenon wood to make the recess.
Also my calipers run up to the chuck give me the thickness of the bottom when I have a tenon.

If you are doing flat bottomed cores the recess probably save you wood.

 

[Brian LaRochelle]

Not sure what you gain by having a recess inside. In my thinking it’s an extra step with no added value to me.

So my line of thinking is this:
I want to finish the outside bowl first. Final shape, sanding, and leave a tenon/recess for reversing later.

I can do this with some sort of jam chucking, or reversing plate, and it works well. When doing this, I won't bother with a recess on the inside. Tailstock will be in the way, but that isn't a big deal.

However, cutting a recess on the inside allows me to reverse the bowl and get full access to the outside bowl without the tailstock in the way, while setting your base alignment. I really enjoy this method. So if I don't have a tenon/recess on a cored bowl blank, I can gain something in skipping that step in this scenario.

Often I have a dried roughed out bowl with a tenon. I can put that on the chuck and it is still aligned well enough for me and plenty to hold while I cut a small recess on the inside. This sets the base alignment for me to finish the outside and true up the existing tenon.

 

[Paul Paukstelis]

Seems to me that this is still an extra step. Put the the recess on the inside of the bowl before you core it. Sure, it will warp some as the blank is drying (not nearly as much as toward the rim), but it should be perfectly fine for remounting and shaping the exterior once it is dry. You'll be truing to the outside anyway and you will eventually have a recess or tenon on the exterior.

 

[robo hippy]

I once turn my bowls, all of them. I core with the McNaughton. I drill a recess, and I think I learned this from Richard Raffen, not positive though. I take the biggest core first, then work my way down. With the drilled recess, it is easy to center the bowl for turning the core. I use a recess every time. If I was to use a tenon, then I would mark the center. This would be most handy for twice turned bowls, and should give you a pretty close center. Most of the time, for my recesses, the warping goes to a fairly even oval. With the Pacific Madrone, my favorite wood, you never know what is going to do. I can wiggle my extended fingers jaws around to get a mount that is secure enough for sanding, but I would not consider it secure enough for turning.

robo hippy

 

[hockenbery]

I want to finish the outside bowl first. Final shape, sanding, and leave a tenon/recess for reversing later.

I can do this with some sort of jam chucking, or reversing plate, and it works well. When doing this, I won't bother with a recess on the inside. Tailstock will be in the way, but that isn't a big dea

Depends on the gouge grind and how you use it.

I use a friction drive with the jaws of the chuck for returning the dried bowl. Rough true the rim, turn the outside and then true the tenon. I can turn between centers when I use an Ellsworth grind that makes both push and pull cuts with the tailstock support.
When I put it in the chuck it usually run true enough to be left alone. If needed I will turn the outside true.
Then I finish turn the rim and hollow the bowl.

I sand the whole bowl except for the bottom where the tenon is.

If you use the 40/40 or similar. You can’t do a push cut because the handle hits the tailstock.
Trade - offs

 

[Brian LaRochelle]

If you use the 40/40 or similar. You can’t do a push cut because the handle hits the tailstock.

I have three grinds I use regularly. A near 40/40, 55 Irish grind, and about 64 degree bottom bowl gouge.
40 and 55 degrees are different styles and I'm trying to practice both. I've used pull cuts on the 55 to good effect, tho I don't practive pulls as much as I should.
Each has their moments to shine, trade offs as you say. I try not to favor either, but do lean more on 40/40 for outside and 55 for inside.

I've used the method you describe with success, and will again as needed. I find the jam in my first post useful, as it allows me to get several cores of varied sizes balanced, with recesses, and ready to be mounted without a tailstock, quicker than I've managed any other method. Figured someone would find this useful or is doing something similar. Seems I was mistaken.

 

[hockenbery]

find the jam in my first post useful, as it allows me to get several cores of varied sizes balanced, with recesses, and ready to be mounted without a tailstock, quicker than I've managed any other method. Figured someone would find this useful or is doing something similar.

Looks effective.
The thread sort of drifted away from your big cup chuck.

Some will find it useful.

 

[Dean Center]

KISS. Put recess on the face, make the large core first to get your 'money bowl.' The resulting core will still have the recess on the face, so mount that on your chuck, shape the outside, put a tenon on the bottom (or recess if you want), turn it back around mounting it face out on the chuck, make the next largest core, and keep going for however many cores you can do.

 

[Brian LaRochelle]

Ok. Let me put it a different way. I have around 100+ cores dried out and ready to be finished. All the retrospective ideas are great and all, but won't really help the task at hand. This post is specifically addressing that task, an alternative way of mounting a core without an existing tenon.

 

[Brian Gustin]

Ok. Let me put it a different way. I have around 100+ cores dried out and ready to be finished. All the retrospective ideas are great and all, but won't really help the task at hand. This post is specifically addressing that task, an alternative way of mounting a core without an existing tenon.

If I had a bowl without a tenon or other means of mounting, I'd chuck it up on a friction drive (AKA Jam Chuck) with bottom or wherever I was wanting to place tenon towards tailstock, and cut a new tenon (or recess if I don't want to re-co the whole bottom and outside) I have had to do that once when a bowl I'd roughed out and set aside to dry cracked through the tenon but otherwise was fine - I was able to turn a new recess (I had to grind myself a scraper tool to scrape a dovetail recess out of an old oil seal puller tool I had laying around with a "close enough" bent shape to it) and chuck it up that way to finish the bowl. It worked out well.

*edit to add* I did have a lot of fiddling around with it to get it as close to "centered" as I could, but seeing as bowl was warped anyways, "pretty close" was good enough.

 

[JeffSmith]

Often I have a dried roughed out bowl with a tenon. I can put that on the chuck and it is still aligned well enough for me and plenty to hold while I cut a small recess on the inside. This sets the base alignment for me to finish the outside and true up the existing tenon.

This is my scenario - pretty much without exception. The only dirrence is that when I core, I go from largest to smallest, with a recess in the blank face to immediately reverse the blank for turning the tenon. The blank is then reversed for coring the next blank.
May seem like extra work, but I protect the larger blanks in the process.

 

[Kent Jaffrey]

I have three grinds I use regularly. A near 40/40, 55 Irish grind, and about 64 degree bottom bowl gouge.
40 and 55 degrees are different styles and I'm trying to practice both. I've used pull cuts on the 55 to good effect, tho I don't practive pulls as much as I should.
Each has their moments to shine, trade offs as you say. I try not to favor either, but do lean more on 40/40 for outside and 55 for inside.

I've used the method you describe with success, and will again as needed. I find the jam in my first post useful, as it allows me to get several cores of varied sizes balanced, with recesses, and ready to be mounted without a tailstock, quicker than I've managed any other method. Figured someone would find this useful or is doing something similar. Seems I was mistaken.

I totally understand where you are coming from with this method. I too really like doing the outside of the bowl while mounted on a internal recess (no tailstock to work around and especially on cores there is no nub in the middle of the tenon that remains from the using the tailstock to hold the jam chucked bowl).

My only question would be whether the extra time needed to mount the “bowl” chuck would make the two methods a wash in terms of time savings.

I would like to see what you use to cut the internal tenon without tailstock interference as that is one hing that has kept me from doing it in a similar fashion.

 

[Brian LaRochelle]

I would like to see what you use to cut the internal tenon without tailstock interference as that is one hing that has kept me from doing it in a similar fashion.

A bedan for the initial recess. Then I modified an old tool to something like the following:

Dovetail Scraper - Lee Valley Tools

www.leevalley.com

 

[Vincent Vogel]

I know everyone has their favorite method, but here's what I do most of the time. I usually use a tenon slightly larger than the ideal size for the chuck being used, this allows me to true the tennon once it's dry. i always put a center mark on the tenon for future use. If you balance and center the grain of the bowl carefully I've found it usually shrinks pretty evenly from side to side and for height also. Then when I remount it I put my chuck on the lathe and use it for a jamb chuck and put the point of the live center in the tenon divot I made previously and re round the tenon to fit the chuck. Then reverse the bowl onto the chuck and turn away. This usually works when I follow the 10% of diameter rule for rough bowl thickness. Hope this makes sense.

 

[Gary Beasley]

When I core I start the blank on a faceplate and create the profile of the money bowl. I leave the faceplate in place and core the next size dowm freeing the money bowl. The core is screwed back on the lathe and a tenon made. Turn that around and core the next size down, take that core and repeat the process until the smallest core is done. The tenon is made, the faceplate removed, and the inside roughed on the smallest core and all done.

 

[Jim Woods]

A bedan for the initial recess. Then I modified an old tool to something like the following:

Dovetail Scraper - Lee Valley Tools

www.leevalley.com

Brian, that is what I use, made one from an old cheap skew

 

[Neil S]

When I core I start the blank on a faceplate and create the profile of the money bowl. I leave the faceplate in place and core the next size dowm freeing the money bowl. The core is screwed back on the lathe and a tenon made. Turn that around and core the next size down, take that core and repeat the process until the smallest core is done. The tenon is made, the faceplate removed, and the inside roughed on the smallest core and all done.

.
Ditto
.

 

[hughie]

I would be cutting a tenon/groove on the inside prior to coring the next one and on the first do the same. It works for me as I have a set of the Nova long jaws 75mm long

 

[Neil S]

I would be cutting a tenon/groove on the inside prior to coring the next one and on the first do the same. It works for me as I have a set of the Nova long jaws 75mm long

Yep, working in from the largest to smallest core, the last thing I do before removing a cored blank from the lathe is to add that internal recess so I can remounting it later.

For remounting I use PowerGrip jaws on either the 4" SN2 and 5" Titan chuck and if they those jaws are not long enough I add an extension adaptor to the headstock spindle. Occasionally I need that for deeper bowls...

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