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Ridges on platters

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Forum topic by SiRiC posted 04-30-2020 12:30 PM 437 views 0 times favorited 7 replies Add to Favorites Watch
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SiRiC

32 posts in 3263 days


04-30-2020 12:30 PM

Hi,

I am using a Jet 1442 lathe and am using EWT carbide tools to turn platters between 8” and 16”

Whether on the concave or convex side I get jumping when I am moving the tool across the surface. I understand that this could happen when the blank is not yet balanced, but it happens even after I round the edges and the surfaces.

I have tried placing the tool rest at various distances from the work – between 1/4” and 1/2”, but get the same result.

This leads to concentric like ridges on the surfaces which I then have to sand.

Have been searching but the answers that I have seen refer to bowl gouges and the length of the bevel in relation to the curvature of the platter/bowl.

Would appreciate ay insight.

Thanks
Steve

-- Measure twice...ummm.. i forget the rest!!


7 replies so far

View Nubsnstubs's profile

Nubsnstubs

1803 posts in 2972 days


#1 posted 04-30-2020 12:44 PM

Steve, my first question is, How are you turning 16” diameters with a 14” lathe? Outboard?

My next question. Are you turning green or is the wood dry? If green, more than likely it’s moving after each cut.

Another question. Are you cutting at center, below center, or just above. Just above center would be better than right at center.

I have the EWT ’s. I had to grind the bar back at a steeper angle in order to get clearance when turning smaller diameters, but on larger stuff like what you are turning, there shouldn’t be any problems with the bar rubbing on the wood. ............... Jerry(in Tucson)

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

View SiRiC's profile

SiRiC

32 posts in 3263 days


#2 posted 04-30-2020 06:26 PM

Hi Jerry,

Yes, turning outboard on dry wood. Cutting along center line of piece.

I did some further checking and there seems to be some vibration with the lathe itself. Will do some further checks tomorrow.

Steve

-- Measure twice...ummm.. i forget the rest!!

View Wildwood's profile

Wildwood

2959 posts in 3376 days


#3 posted 04-30-2020 06:47 PM

I am not sure what wood species dealing with here but assume looking at early/late wood giving you the problem. As move carbide cutter across wood surface your getting up & down movement with the tool (Jumping). Can get that with a gouge too! Some species with pronounce early/late wood more of a problem than others.

Carbide cutter excel in scraping if could turn tool so shear scraping might help clean up those ridges. JMHO, easier to go back & sharpen a gouge to slice through or turn gouge for shear scraping those ridges we’re talking about.

Hard & softwood can be either ring porous or diffused porous. Ring porous wood has clear difference between early/ late wood. Diffused porous wood little or no different seen early/ late wood. Getting down to cell & vessels in wood which too much info for most turners including myself. .

-- Bill

View MrUnix's profile

MrUnix

8772 posts in 3441 days


#4 posted 04-30-2020 07:32 PM

Like bill suggests…. have you tried doing a very light final pass with a wide flat shear scraper?

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

View HokieKen's profile

HokieKen

19358 posts in 2380 days


#5 posted 04-30-2020 08:37 PM

Is it the round tool giving you this issue? If so try following it with the square tool. Just due to the geometry of the cutting inserts, it’s harder to prevent the round one from forming scallops in my experience.

-- I collect hobbies. There is no sense in limiting yourself (Don W) - - - - - - - - Kenny in SW VA

View OSU55's profile

OSU55

2830 posts in 3231 days


#6 posted 04-30-2020 09:23 PM

Any dings or nicks in the tool rest? Is the bottom of your tool bar smooth? Try some paste wax on both. Doubt you will get a ridgeless final cut – sheer scraping can smooth it all out. Carbide isnt sharp enough for sheer scraping, need hss.

View mike02719's profile

mike02719

306 posts in 5028 days


#7 posted 04-30-2020 11:17 PM

Is it possible your lathe is out of line? Put something with a point in the chuck and run the tailstock right to it. While running, they should be dead on or vibration will occur.

-- Mike, Massachusetts

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