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Bowl Transituation (Read 683 times)
 
Jerry Lear
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Bowl Transituation
Aug 22nd, 2017 at 12:47pm
 
I have been turning for awhile but still have trouble on the inside of the bowl on turning onto the transition and across the bottom.  I use a side ground bowl gouge with a 60 degree bevel and the heel is relieved.
I know this is end grain but I was hoping someone could give me some pointers to help control the tool when making the transition.
Thanks
Jerry
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Glenn Jacobs
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Re: Bowl Transituation
Reply #1 - Aug 22nd, 2017 at 2:40pm
 
In this area, I use a scraper.

Glenn J.
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Bert Delisle
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Re: Bowl Transituation
Reply #2 - Aug 22nd, 2017 at 3:27pm
 
Glenn Jacobs wrote on Aug 22nd, 2017 at 2:40pm:
In this area, I use a scraper.

Glenn J.


+1  Thumbs Up scrapers do it, gently.
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Tom Coghill
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Re: Bowl Transituation
Reply #3 - Aug 22nd, 2017 at 6:39pm
 
I have a GREAT little 3/8 inch bowl gouge that I call  my "Bottom Feeder".  It is ground just like a roughing gouge - no sharpening jig, just laid flat on the grinder rest and rotated.  It is SO SWEET.  It does not scrape.  I use it to get a shear cut, leaving the wood cut smooth.  I use a water based sealer, which then raises the grain.  Let it dry then sand lightly with 180, 220 and the 320. Repeat starting at 320.  SWEEEEEET!  Thumbs Up Thumbs Up Thumbs Up

It is like the photo attached but a much smaller gouge, but the grind is about the same, maybe a bit steeper.  You need to be able to ride the bevel around the corner and onto the bottom of the bowl.
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Ed Weber
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Re: Bowl Transituation
Reply #4 - Aug 22nd, 2017 at 7:15pm
 
As always, I would like more information.
How big is this bowl?
How sharp of a transition are you talking about?
What size bowl gouge are you currently using?
What type of 'trouble" are you having?
You mentioned end-grain.
Turning a standard bowl with the grain running perpendicular to the ways, a cut down the inside transitioning to the bottom is not an end-grain cut. it a downhill cut whic is the proffered way.
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Steve Doerr
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Re: Bowl Transituation
Reply #5 - Aug 22nd, 2017 at 8:28pm
 
I have just started using the bottom feeder that Tom describes.  It does a GREAT job.  It does take some practice to get use to it.  The only thing I would suggest is that you soften the corners on the gouge, otherwise you might get a catch.
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robert baccus
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Re: Bowl Transituation
Reply #6 - Aug 22nd, 2017 at 10:06pm
 
I started grinding and posting about these 25 years ago and still many people have not discovered this grind.  Buy a cheap BB 1/2" deep bowl gouge and regrind to this photo.  75 deg +-  and it will cut the transition and flat bottoms and finish cuts also.  A 1" roughing gouge turned exactly the same cuts great on the OUTSIDE of vases and bowls only as well.  Does a great finishing cut---do rub the bevel and do not use as a roughing gouge.
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Ed Weber
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Re: Bowl Transituation
Reply #7 - Aug 23rd, 2017 at 8:11am
 
robert baccus wrote on Aug 22nd, 2017 at 10:06pm:
Buy a cheap BB 1/2" deep bowl gouge and regrind to this photo.


No photo Robert
If you add a photo, do not use preview
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Rick Caron
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Re: Bowl Transituation
Reply #8 - Aug 23rd, 2017 at 6:01pm
 
I just turned a  locust  bowl  dulled my gouge   so i  changed to a scraper     did good      then   went to  a  negative rack scraper    to take  all tool marks      then  sand  paper      worked  really    good .....
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Glenn Matthies
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Re: Bowl Transituation
Reply #9 - Aug 24th, 2017 at 6:41am
 
robert baccus wrote on Aug 22nd, 2017 at 10:06pm:
I started grinding and posting about these 25 years ago and still many people have not discovered this grind. Buy a cheap BB 1/2" deep bowl gouge and regrind to this photo. 75 deg +- and it will cut the transition and flat bottoms and finish cuts also. A 1" roughing gouge turned exactly the same cuts great on the OUTSIDE of vases and bowls only as well. Does a great finishing cut---do rub the bevel and do not use as a roughing gouge.

I did the same thing with a BB gouge.  It works well.  I did replace the handle with one I turned myself.  The standard BB handles are too short IMO to be used on any decent sized bowl.
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Ed Weber
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Re: Bowl Transituation
Reply #10 - Aug 24th, 2017 at 8:41am
 
There are countless ways to achieve the same task, so whatever works best for you.
IMO
Most bottom-feeders and/or transition gouges are ground straight across (not fingernail)
With a high grind angle two things happen. One is that you can navigate (sweep) the corner or transition area without loosing bevel contact and therefore control. Two is that the grind angle is so high the ability to dig in or get a catch ("gouge" the wood) is diminished.
I will say that grinding a bowl gouge to 75+ degrees you are effectively making a curved scraper.
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robo_hippy
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Re: Bowl Transituation
Reply #11 - Aug 24th, 2017 at 9:51am
 
My preferred BOB tools are 70 degree bevels. I use several different ones. One is the fluteless gouge from Doug Thompson which is half round bar stock. I have a ) shaped nose on it, so with just a little sweep to it. Another is a very shallow fluted detail/spindle detail gouge, same grind. I have one more standard half round flute shape with the same nose profile. Part of the reason for the sweep is to get the corners out of the way. They can be more prone to catching if you have the flutes straight up. I never have flutes straight up because the top side wing can catch. I keep them rolled over to about a 70 degree angle for a high angle shear cut because the higher the shear angle, most of the time, the cleaner the cut. They are not used like a scraper at all, which most of  the time is used with no bevel rubbing, and the cutting edge at 90 degrees to the spin of the wood/flat on the tool rest.

robo hippy
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Don Stephan
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Re: Bowl Transituation
Reply #12 - Aug 24th, 2017 at 6:42pm
 
There are so many different possible shapes for the side, transition, and bottom of a bowl.  Is the side near perfectly vertical, gently curving in, or even curving out?  Is the transition radius tight like a ping pong ball, moderate like a tennis ball, or generous like a volleyball?  Does the bottom have a very gentle downward curve to the very middle or is it perfectly horizonal immediately out of the transition?  It took a number of bowls over a couple years, but I can shape pretty well a more flowing transition with a 50 deg bowl gouge, using a left relieved heavy wide scraper to remove minor tool marks.

With the bowl mounted on the lathe but the lathe off and the tool rest in position, can you move the tip of the gouge down the side, around the transition, and onto the bottom without losing the bevel and without a tool overhang more than 2" at any point?
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robert baccus
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Re: Bowl Transituation
Reply #13 - Aug 24th, 2017 at 9:35pm
 
Yes and they work on flat faces like a platter very well.  They do cut--not a scraper and do great finish cuts.  The corners are not a problem with a narrow--1/2" gouge.  I do hone this grind lightly.
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Ed Weber
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Re: Bowl Transituation
Reply #14 - Aug 25th, 2017 at 9:56am
 
robert baccus wrote on Aug 24th, 2017 at 9:35pm:
They do cut--not a scraper and do great finish cuts.


The point I was making is that like a scraper (that cuts) a 75+ degree angle is more blunt than the standard bowl gouge angles of 60-65. With less of a pointed tip it won't dig in and get a catch.
Every bowl has a different transition shape curvature, diameter, etc. Without knowing exactly the circumstance (I did ask the OP) we are all guessing.
What works for one person doesn't always work for another.
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Tom Coghill
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Re: Bowl Transituation
Reply #15 - Aug 25th, 2017 at 10:09am
 
Ed is spot on  Cool - What works great for one person and they will never do it any other way, will not work at all for another.  I think all methods are acceptable (if they are safe) it just depends on how much practice you put in to each as to what you find favorable to you.

When the bowl is done and on the shelf, what method one used to get there is of no concern. Thumbs Up
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Rick Caron
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Re: Bowl Transituation
Reply #16 - Aug 26th, 2017 at 6:49pm
 
Just turned a  scrub  pine bowl.   Would normally go  from a gouge  to   negative rack   to sandpaper.    This bowl    had to be sanded  out     because  negative rack would  not take out the   gouge  marks.    And  added   some tear out.   Some wood is too soft.    But after sanding   it's going to be a good looking bowl....
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robo_hippy
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Re: Bowl Transituation
Reply #17 - Aug 27th, 2017 at 1:17pm
 
Rick, this is a situation where I would use a shear scrape. It will cut cleaner than the NRS in side grain. Scraper, 70 degree or so bevel, and hand burnished burr.

robo hippy
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Rick Caron
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Re: Bowl Transituation
Reply #18 - Aug 27th, 2017 at 6:50pm
 
Robo that is a skill i haven't mastered yet. Guess you need a pretty high speed to make that work?
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« Last Edit: Aug 27th, 2017 at 8:48pm by Rick Caron »  
 
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Rick Caron
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Re: Bowl Transituation
Reply #19 - Aug 27th, 2017 at 8:53pm
 
Meant to say    NRS added some tear out at end grain  so i had to use  80 grit sandpaper.   Haven't mastered the  shear scrape,  guess you need a pretty high lathe speed for that?
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Tom Coghill
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Re: Bowl Transituation
Reply #20 - Aug 28th, 2017 at 9:22am
 
Rick - you can minimize the tear out by making the wood stronger.  Try applying some sanding sealer or a water based cell sealer, allow it to dry, then make your final cut. On your final cuts, take fine light cuts. Thumbs Up
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robo_hippy
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Re: Bowl Transituation
Reply #21 - Aug 28th, 2017 at 10:14am
 
I do my shear scraping at the same speed I turn. I do turn a bit faster than most though. Mostly it is a light touch, and a good burr. Most of the time the burr from a 180 grit CBN wheel is fine. Some times a honed burr or 600-1000 grit CBN wheel works better. Now, I hand burnish a burr on my scrapers for this. Some prefer the gouge, but you can't manage to fit one on the inside of the bowl because the bowl, tool rest, and lathe bed get in the way.

robo hippy
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Rick Caron
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Re: Bowl Transituation
Reply #22 - Aug 31st, 2017 at 5:14pm
 
Multimedia File Viewing and Clickable Links are available for Registered Members only!!  You need to Login or Register
And i ordered    25 more discs    of each grit          the green    vinyl backed dics    Will last  me   years............
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Don Stephan
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Re: Bowl Transituation
Reply #23 - Aug 31st, 2017 at 6:12pm
 
Don't know how much sanding you do each month, but these small discs do not last long.  Remember reading one person said he replaces disks after 3 minutes of use, and I have been replacing almost that frequently.  I try to remember how much sawdust a new disc makes at each grit, and replace when the quantity of sawdust produced drops off noticeably, not when the disc no longer makes sawdust.

Compared to random orbit sanders, the surface area is extremely small so each square inch has to do so much more work than on 5" and 6" ROS discs.

Second, if the same amount of pressure is applied through the disc onto the wood (as with ROS) the small surface area builds up heat almost immediately, and heat can cause checks in the wood and dramatically shortens the life of the interface pad - the glue softens and the velcro comes off the foam.  Sanding at high rotational speeds also builds up hat almost immediately, shortening the life of the interface pad and even the mandrel.  For several months I refused to sand "daintily" but finally realized that approach was costing me money for more sanding supplies and not giving the results I wanted as efficiently as possible.

I've also noticed that removing a disc from an interface pad puts a lot of pressure on that glue, so that interface pads were not lasting  for me as long as they should.  For a year now I have been using a separate interface pad for each grit - for example a yellow radius pad just for 80 grit, a yellow tapered pad just for 80 grit, and so on, and with a Sharpie I write the grit on the back side velcro of the pad,  So when I change grits, or between tapered and radius pads, I simply remove the pad and disc together from the mandrel.

I've also found much better results using discs whose diameters match those of the pads, so I have  2 3/8" 80 grit discs for the yellow tapered pad and 2" 80 grit discs for the yellow radius pad, and so on.

I HATE having so much sanding supplies inventory, but I think this approach gives me better results more quickly.

Explore the contents of the assortment with an eye to seeing what is most efficient for you.  But you may find that the assortment is not all you need.
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