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heavy bowl blank advice needed

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Forum topic by Karda posted 04-27-2018 05:10 AM 835 views 0 times favorited 25 replies Add to Favorites Watch
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Karda

1284 posts in 698 days


04-27-2018 05:10 AM

I have a bowl blank that is the biggest I can get on my lathe it a 10×18 harbor freight. The blank is a little over 10 inches and about 5 inches thick and weighs a bit over 12 pounds when I get it cut down to about 9.75 it will still be over 10 pounds. I will mount it on a face plate with longer screws and use tail stock. Is it safe to mount a blnk of this size on a lathe as small as mine Thanks Mike


25 replies so far

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Woodknack

12369 posts in 2524 days


#1 posted 04-27-2018 05:57 AM

You’ll know when it starts spinning. Depends on the balance and how securely the last is bolted down.

-- Rick M, http://thewoodknack.blogspot.com/

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Lazyman

2521 posts in 1532 days


#2 posted 04-27-2018 11:40 AM

I’ve done something similar, though probably not 10 pounds, on my Excelsior lathe which is probably the exact same machine as the HF model. If it is out of balance even a little, it will likely cause your lathe to jump across your bench if it isn’t bolted down and the bench isn’t heavy enough. If you have a big enough band saw, try to at least make it round first. Then, try mounting it without the belt engaged with the pulley and slightly spin it by hand to see if one side always ends up down. If so, trim a little more off that side. Repeat until it doesn’t seem to settle with the same side down or at least takes longer to settle. And make sure you use tailstock support and start at the slowest speed. If it still jumping around too much take a little more off.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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Dustin

557 posts in 885 days


#3 posted 04-27-2018 11:54 AM

What Rick said: you want that lathe bolted down for this one.

Also, for roughing it out/balancing it, have you considered just turning it between centers before mounting it on the face plate? This will make it a little easier to mount, spin-by-hand, and readjust/re-balance to find the rough center of mass, which will help reduce the inevitable vibration. Just make sure you’re standing out of the line of fire with this thing, and go slow with a freshly sharpened tool.

-- "Ladies, if your husband says he'll get to it, he'll get to it. No need to remind him about it every 6 months."

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Karda

1284 posts in 698 days


#4 posted 04-27-2018 03:09 PM

thanks, never thought of using centers to find balance, another thing my slowest speed is 750. i can’t bolt down no [pla ce to bolt to best I can do is blck the feet so it can’t move. I headed of to trim more I’ll let you know if I survive thanks mike

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LesB

1816 posts in 3587 days


#5 posted 04-27-2018 08:14 PM

You speed may be just a little fast and you should probably weight the lathe down with something.
One time when is still had a 12” Delta lathe I had to use a 2×4 braced against the rafters in the garage/shop to keep the lathe still until I had the large blank balanced. That was scary but it worked. Sand bags work too….
When truing up a large blank I almost always use the tail stock for added support where you can. You can even use it while you start hollowing the inside of the bowl, removing the remaining center column the tail stock supports after you have taken out a lot of the other wood around it.

If you don’t have one add a lathe chuck to your list of tools to get. Then try this method for mounting your blanks:
http://lumberjocks.com/LesB/blog/118409

-- Les B, Oregon

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Karda

1284 posts in 698 days


#6 posted 04-27-2018 09:07 PM

I have a chuck and use recesses most of the time. I like them became when they are made they are done. For a piece this large is a recess ok or is a tenon better

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LeeMills

599 posts in 1445 days


#7 posted 04-28-2018 01:46 AM

Just a couple of possibilities to help..
It appears the feet screw in from the bottom. If so get a couple of lengths of 2X4 or similar about 16” long. Angle iron would be great.
You will need bolts the same thread and install from the bottom side (recess the bolt head). You now have a base 16” deep to clamp or attach to your work surface.
As to the tenon or recess. What size are your chuck jaws? If 2” then I would go with a recess (leaving 1” of wood around) as it will give 3X the amount of wood that has to break away for an orbit. If you have 4” jaws then I would probably go with a tenon due to the max size of 10”. It also depends on if the wood is wet or dry. The dry will be much stronger to resist being sheered off if you get a catch.
The other suggestions for balancing first should be used.

-- We cannot solve our problems with the same thinking we used when we created them. Albert Einstein

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Karda

1284 posts in 698 days


#8 posted 04-28-2018 03:10 AM

Thanks for the suggestions, I’ll remember them next time. when i went down to trim the blank dowm more I saw a long and deep crack right through the middle. This is getting aggravating that the second ash blank that has cracked while I was working on it, could it be that i had to bring it inside. I end sealed it when I cut up the log but was unsealed after I rounded it on the band saw.
I wanted to bold my lathe down, my table is heavy enough but the lathe has screw inrubber feet the thread is probably metric about 1/4 inch. I would want a larger bolt wouldn’t i

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LeeMills

599 posts in 1445 days


#9 posted 04-28-2018 04:24 PM

Just guessing but…
If you had a crack down the middle maybe you didn’t remove enough of the pith. I normally just get cracking on the ends.
A lot of folks do round on the bandsaw for turning later and it works for them. I leave mine more in log form and about 2” longer on each end for potential cracks. I only round them when I get ready to turn them.
You did not say how long after rounding them on the bandsaw (and with no seal) it was before you turned them. Once rounded you have exposed grain again and I would place in plastic bags if were to be more than a few hours/days before I turned them.
It may help to bring them inside but the air in the house is normally dryer than outside or in a shop so it probably would not help. I would store in the coolest place without direct sun or wind such as the floor of your shop.

I suggested the lathe mounting method because that is what I did with my daughters Nova Comet.
A 1/4” bolt is plenty strong enough because the stress will be along the length and not side pressure. I used the “runners” because I just can’t get down to install from under a bench. On the underside against the bolt head I would suggest a couple of large fender washer to spread the stress to the wood.

-- We cannot solve our problems with the same thinking we used when we created them. Albert Einstein

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Karda

1284 posts in 698 days


#10 posted 04-28-2018 05:38 PM

I meant across the blank more or less dividing the blank equally. cracks show on both sides about in the same place. This piece was well away from the pith sow that is not an issue. I started rounding the blank then put on the porch outside for a couple days, I sealed the end with glue later decided to turn it, There was a shallow but long crack that would turn out. I started cutting it down to a size I can mount. went to lunch and forgot to bag it While trimming it to removing binding spots I noticed the crack had deepened almost all the way through the blank. The cellar is not heated but there is heat coming off the pipes when the furnace is running and it does get hot and stuff in the summer. ventilation is poor, the windows don’t open. What do people do who live where it is hot all the time

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Nubsnstubs

1404 posts in 1874 days


#11 posted 04-29-2018 01:51 AM



I meant across the blank more or less dividing the blank equally. cracks show on both sides about in the same place. This piece was well away from the pith sow that is not an issue. I started rounding the blank then put on the porch outside for a couple days, I sealed the end with glue later decided to turn it, There was a shallow but long crack that would turn out. I started cutting it down to a size I can mount. went to lunch and forgot to bag it While trimming it to removing binding spots I noticed the crack had deepened almost all the way through the blank. The cellar is not heated but there is heat coming off the pipes when the furnace is running and it does get hot and stuff in the summer. ventilation is poor, the windows don t open. What do people do who live where it is hot all the time
- Karda

You live with it. I don’t do anything to any of the wood I get. It’s usually piled outside in direct sun until I’m ready to turn it. There are ways to recover from cracks…...... Jerry (in Tucson)

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

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Karda

1284 posts in 698 days


#12 posted 04-29-2018 02:09 AM

could you give me so ideas,

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Nubsnstubs

1404 posts in 1874 days


#13 posted 04-29-2018 02:10 PM

The first thing would be to turn out the cracks. That usually causes your turning to shrink quite a bit, especially if you were planning on a larger size finished piece.

Epoxy and CA applied into the cracks seem to be the number one products to use. Some people like to mix coffee grounds, wood chips, or different colors of Inlace products to enhance the filler. I even use key filings I got from Home Depot.

My favorite thing to use is dowel rod that I make of woods from my local area. I turn my piece until I think it might become unsafe to go any further. That could be anywhere from 1/2” to 3/4” thickness. Next thing I do is to figure how you want to orient the dowel. Usually I span the crack or cracks. The dowels used are 3/8 x whatever is needed to reach each end of the hole. I am using the Kreg drill bit that is used for their pocket hole system.

My piece is mounted into the chuck, positioned to be comfortable drilling the hole, and then I drill where ever I think stabilization is needed. If the hole isn’t deep enough, I have a 10” bit that I use after the Kreg bit is used as a starter.

When all drilling is done, I fit the dowels to each hole according to length because the holes are drilled through the edge of most bowl, plate, or hollow form walls at an angle in order to try and stay within the wall. After fitting the dowels, I usually use Titebond glue, unless there are a lot of cracks that might expose the glue when you’re trying to apply finish and see a some of the butt ugly glue. In that case I use CA only after the dowel is inserted.

Just yesterday I did 12 Mesquite plates 12” od using dowels to support all the cracks so they would fly apart while I was turning them. The dowels can become a feature if they’re planned properly. On about 4 of the plates, I drilled straight down the cracks making sure I came out through the surface of the inside bottom of the plates. The holes were from 4-7” deep, or long, depending on how you look at it. The dowels were glued and driven in with a mallet. After reaching my plate dimensions, the dowels were only about 2 – 2 1/2” long, but still exposed as I put a 3/8 dowel into a piece of wood and then turned it down to 1/4” thick.

With the dowel glued and inserted into a hole, the wood has a good bond , and if you turn out some of the dowel, there is still some of it that is doing what the intent was, and that was to stabilize the piece.

A lot of people talk about butterflies for stabilizing wood. My opinion is they are the worst thing to do to a round form as it takes a lot of time and effort to make and set them.

If you got this far, good luck.

I might have a video on youtube not showing how I do this, but what it looks like after it’s done. Go to my website, click on one of the videos, then when you get to YT, look for one that might show a form with the dowels. www.woodturnerstools.com. Better yet, when you get to my YT channel, subscribe to it…........... Jerry (in Tucson)

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

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Lazyman

2521 posts in 1532 days


#14 posted 04-29-2018 02:35 PM

I recently turned a chunk of apple wood that was so cracked I almost didn’t bother to try turning it. I used thin super glue, the kind used to finish wood pens turned on the lathe, to completely fill the cracks. You can see the results in the second picture of the last project I posted. You may find that you have to add a little more as you round and approach the final shape. Note that the super glue will darken the surface around the crack where you apply it so make sure that you fill the cracks before you make your final finishing pass.

Here is a picture of the piece I cut off the apple blank showing the cracks. I found even more cracks as I started turning.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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Karda

1284 posts in 698 days


#15 posted 04-30-2018 02:15 AM

thanks for the info, I almost threw out a nice piece of cherry, had a lot of crack but after a couple months and the cracks didn’t grow I turned it that worked. here are some picture of the crack in the blank in ?



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