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Toolmarks inside bowl

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Forum topic by JoshNZ posted 02-24-2019 08:25 AM 849 views 0 times favorited 16 replies Add to Favorites Watch
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JoshNZ

133 posts in 1952 days


02-24-2019 08:25 AM

Topic tags/keywords: woodturning bevel lathe marks

Hi Guys,

Just wondering if anyone knows why I might be getting tool marks inside my bowls only. The outside finishing cut is fine enough that I can start with 240 and only needs a quick pass. The inside however takes a lot of sanding. They’re not edges but more inconsistent ridges. Even after a constant bevel ridden pass from the rim all the way to the centre, at varying depths with successive attempts. I seem to create more ridges than I remove sometimes.

I feel like a possibility is shavings riding around the edge of the bowl then getting forced down behind the bevel and hence raising the edge slightly but I’m not sure. Is this a common problem? Any advice for a clean final pass?

Thanks in advance
Josh


16 replies so far

View jmos's profile

jmos

917 posts in 3252 days


#1 posted 02-24-2019 12:59 PM

I’m a VERY new turner, so, take it for what it’s worth:

I assume your using a bowl gouge, and you say you have good bevel contact the whole way in. That was my first thought. How deep are you going? The further you go out over the tool rest the harder it is to control; maybe you’re getting a little bounce at the end of the gouge? If so, you may be able to get the rest closer to the work. Of course, sharp helps too.

Have you tried a bowl scraper for the final passes? Not as fine a finish, but maybe more consistent and fewer tool marks.

Good luck.

-- John

View Mainboom's profile

Mainboom

92 posts in 640 days


#2 posted 02-24-2019 01:47 PM

im a new turner as well but I agree with jmos. id try a round sided scraper. I have used ones my club has that are rounded completely at 60 degress then have a neg 15 degree bevel on the top and they work great. take it for what its worth.

-- CRANE OPERATORS START EARLY because iron workers need their heros ready when they wake up

View Kirk650's profile

Kirk650

680 posts in 1631 days


#3 posted 02-24-2019 02:59 PM

Big scrapers are what I use to smooth out the bowl bottoms and sides. Big thick scrapers. And a tool rest that will let you get as close to the face of the wood as you can. And a real light touch…

View gwilki's profile

gwilki

359 posts in 2356 days


#4 posted 02-24-2019 05:00 PM

Josh: You could be seeing tool marks made by the sharp heel of the bevel. If you haven’t done so already, try grinding the heel of the bevel off and see if that helps.

-- Grant Wilkinson, Ottawa ON

View Gittyup's profile

Gittyup

207 posts in 2839 days


#5 posted 02-24-2019 05:11 PM

Ideally, you rough cut with a winged bowl gouge, v-groove seems to work best for me. Then switch to a bottom grubber bowl gouge (Steeper angled with very short wings). Then clean up with a scraper. I prefer negative rake because I find it easiest to use. You can skip the grubber and just use a bowl scraper. The grubber is good where you transition from side to bottom. Not matter, I can’t get the lines out without using a scraper (or sanding forever).

-- tel

View bigJohninvegas's profile

bigJohninvegas

808 posts in 2344 days


#6 posted 02-24-2019 08:07 PM

Some photos of your bowl would help. Could be a few different issues.
I never use a scraper, and to go straight to 240 on the outside it sounds like your tools are sharp enough.
I do sometimes use the wing of my bowl gouge to shear scrape a little rough spot.
And what both Gittiup, and gwilki touched on. If the marks are deeper into the bowl, a gouge with a micro bevel.
And while it sounds like you have sharp tools, If I have a wood that is giving me trouble. I will go to the grinder and touch up the edge and then do my finish cut,
Here is a photo of the 3 grinds I use on my bowl gouges.
The gouge in the middle has a micro bevel, and the gouge on the left will get into really
deep areas, like the bottom of a vase.

here is a better shot of the micro bevel. good for a tight curve.

-- John

View JoshNZ's profile

JoshNZ

133 posts in 1952 days


#7 posted 02-24-2019 09:18 PM

Thanks for all the replies.

I would prefer to stay away from the round nosed scraper, I have tried it and I guess it does scrape away the marks but then I have a scraped finish which isn’t ideal either, particularly with some of the woods I have here which do suffer from tear out if I’m not slicing.

I have tried removing the sharp heel of the tool too, to no avail. If I have lets say a 12” diameter bowl, 4” deep, the marks are all in the top 1.5” of the bowls side (below the rim). Once I get around the guts of the curve and into the easing out floor of the bowl I don’t have any marks at all, so I don’t think it is a problem with my grind angle.

I do always touch up for final passes as well. I will try and get a photo of what I’m talking about today, maybe someone will recognise it.

View Nubsnstubs's profile

Nubsnstubs

1732 posts in 2613 days


#8 posted 02-25-2019 02:04 AM

Are you hogging equally down the inside from the top to bottom in each pass? Or, do you hog out in steps, like the first 1 1/2 inches to final thickness, and do another 1 1/2” and then the last bit to clean up the bottom?

I get chatter if I take it down one pass at a time as it gets thinner, but doing it in steps is a little cleaner. .......... Jerry (in Tucson)

-- Jerry (in Tucson) www.woodturnerstools.com

View JoshNZ's profile

JoshNZ

133 posts in 1952 days


#9 posted 02-25-2019 07:30 AM

Are you saying your finishing passes are done in steps too then Jerry? I hog off in steps I suppose, but my finishing cut is always done last, from the rim all the way to the centre in one uninterrupted pass.

View JoshNZ's profile

JoshNZ

133 posts in 1952 days


#10 posted 02-25-2019 09:29 AM

This is a particularly bad example of what I’m talking about but this was one constant controlled (or so I thought?) pass from the rim to the centre, with a gentle swing of the handle the whole way. Maybe 1mm depth of cut, constant all the way. I’m betting you wouldn’t believe I was riding the bevel looking at that! I better take a video hah.

View gwilki's profile

gwilki

359 posts in 2356 days


#11 posted 02-25-2019 10:36 AM

What angle do you grind your gouge to? That really looks like you are coming off bevel support and you are cutting on the nose of the gouge.

-- Grant Wilkinson, Ottawa ON

View Underdog's profile

Underdog

1551 posts in 2918 days


#12 posted 02-25-2019 11:53 AM


This is a particularly bad example of what I m talking about but this was one constant controlled (or so I thought?) pass from the rim to the centre, with a gentle swing of the handle the whole way. Maybe 1mm depth of cut, constant all the way. I m betting you wouldn t believe I was riding the bevel looking at that! I better take a video hah.
- JoshNZ

From here it looks like bruising from the heel of the tool. Mark Sillay takes the heel completely off with the grinding wheel and makes it rounded so that it cannot bruise the wood. He even goes so far as to polish it a bit…

But you say these are actual ridges in the wood after the cut, no sanding?

-- Jim, Georgia, USA

View Nubsnstubs's profile

Nubsnstubs

1732 posts in 2613 days


#13 posted 02-25-2019 02:34 PM



Are you saying your finishing passes are done in steps too then Jerry? I hog off in steps I suppose, but my finishing cut is always done last, from the rim all the way to the centre in one uninterrupted pass.

- JoshNZ


When I do the step thing, I try to get wall thickness as close as I can. When I’m done hogging, I make a final pass with a Sorby Bowl scraper.

The one above gives me a 220 finish on landscape pine that abounds in Tucson. I call it that as there are no wild pine trees in the desert floor where Tucson is located. It’s all brought in, planted into peoples yards and parks.

After the pass with the scraper on other woods, I break out with my 80 grit 3000 rpm gouge. hehehehe …......... Jerry (in Tucson)

-- Jerry (in Tucson) www.woodturnerstools.com

View HokieKen's profile

HokieKen

15157 posts in 2021 days


#14 posted 02-25-2019 02:40 PM

Another thing I like to do when a bowl is giving me a hard time is to reverse the spindle and try a couple of light finishing cuts on the opposite side. Sometimes, it’s just a matter of the grain direction giving me a hard time.

-- Kenny, SW VA, Go Hokies!!!

View OSU55's profile

OSU55

2658 posts in 2872 days


#15 posted 02-25-2019 03:33 PM

I think its simply tool control. All it takes is an imperceptible wrong movement of the tool – you know it happened due to the marks left behind. Great turners have extremely good tool control, the rest of us use scrapers and sandpaper.

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