drill bit size for screw chucks

[Jay Coulson]

Hi All,
I am having a bit of a problem with larger blanks holding on my screw chuck. I have several screws..a one way that came with the only one way chuck that I own (a stronghold), the Vicmarcs...go with all of my Vicmarc 100 and 120 chucks and, a 3 piece screw chuck with a glaser screw...my favorite. I almost always use the 3 piece with the widest face. That glaser screw is 3/8 and, I generally drill a 5/16 or 19/64 hole to hold blanks up to about 14 inches with no problems--with or without the tail stock. It is very sharp and holds the smaller 14" or less blanks like super glue. However, on blanks that are 18" or larger, even though the EVS coasts to a pretty quick stop, the blanks want to unscrew (yes, I'm using the tail stock on these slightly larger blanks). Of course, it's worse on blanks of this size when I am roughing them wet...they are much heavier and the inertia unscrews them faster.
I've thought about going to the fatter "one way" screw and drilling about a 9mm hole but, I'd rather use my favorite 3 piece chuck. I personally don't care for the one way screw...just my preference.
So my question to the forum is, what do you folks use for a pilot hole on the various screw chucks? I'd like know what the forum is using for all 3 of the scews that I've mentioned.
I know, this sounds like a silly question but, a good friend in Australia and I are having a debate about this issue...and he usually knows all of the answers. He also doesn't care for the one-way screw and, has the same 3 piece unit and claims to not have ever had this problem in a very long time.
Thanks,
Jay

 

[Steve Worcester]

measure the size of the screw without the threads with digital calipers, and drill a hole that size.

For softer woods, I would usually drill one size smaller. But for holding anything but faceplate type stuff, I wouldn't use a screw chuck. I would use a spur drive and make a tenon to hold it in a chuck.

 

[Richard Baker]

If the EVS stops too quickly, tending to unscrew the workpiece, you might just reduce the speed more slowly, manually. Not the answer to your question, but possibly one answer to your "issue".

 

[Gretch Flo]

screw chucks

Along this same line, what do you do to unscrew the stuck ones from the blank?????
I have a talon chuck.-predrilled with the rec size (don't have that size at the tip of my computer fingers) Especially on some small bowls 3-5 inches diameter- I don't have a grip with my arthritic thumbs. For removing the stuck screw I use a vice grip. The outside is already finished. On rare occasions (osage orange lately), I have had to use my wood carving tools to dig around the screw as I couldn't hold it tighly enuf with my left hand. Larger bowls don't seem to be a problem as I can use mu arms and chest. Then I asked my visiting son to unscrew that wood he gave me-he had no problems-but I may not have had problems at that point!!!. I have used paste wax on the thread-"no soap"!!!, So I now use a larger drill bit on green hard wood, and am doing ok so far. Gretch

 

[Joe Greiner]

If the EVS stops too quickly, tending to unscrew the workpiece, you might just reduce the speed more slowly, manually. Not the answer to your question, but possibly one answer to your "issue".

This issue isn't unique to screw chucks; can also occur with faceplates and scroll chucks, unless heroically fixed to the spindle. The problem is coasting to a "pretty quick stop." If you can program the EVS to a slower stop, try that. Otherwise, apply frictional resistance to the workpiece, e.g. sandpaper or a sacrificial glove on top to restore tightening. Move the toolrest out of harm's way first. BTDT.

 

[john lucas]

I never use a screw chuck except for platters however I do like steve suggested. I measure the thickness at the bottom of the threads. If it's a really hard wood I go one drill size larger.
I prefer to mount bowls between centers so I can readjust them if I prefer to alter the shape or orientation of the bowl.

 

[MichaelMouse]

Hi All,
I am having a bit of a problem with larger blanks holding on my screw chuck.

So don't use a screw chuck. I never thought much of them even when they were standard equipment with smaller faceplates.
http://i35.photobucket.com/albums/d160/GoodOnesGone/Method-One.jpg

My choice, and an excellent holder for work in progress, wet, dry, soft or hardwood. Price is up to 70 bucks, but it's a standalone, so you can keep favorite jaws on your other bodies. www.bestwoodtools.com

 

[Joe Greiner]

So don't use a screw chuck. I never thought much of them even when they were standard equipment with smaller faceplates.
http://i35.photobucket.com/albums/d160/GoodOnesGone/Method-One.jpg

My choice, and an excellent holder for work in progress, wet, dry, soft or hardwood. Price is up to 70 bucks, but it's a standalone, so you can keep favorite jaws on your other bodies. www.bestwoodtools.com

Which tool or accessory are you suggesting? The second link seems to have an internal road map only, with no unique addresses.

 

[MichaelMouse]

Pin chuck, as shown in the jpg. The bit size is 1", BTW. You have to look fo it on the website.

The pictures you see shows it being used to re-turn. Simple matter of boring the hole back to 1" and mounting after drying. Centers within 1/8 inch, normally, so the mortise is not enlarged much over optimum when re-turning.

 

[Jay Coulson]

screw chuck clarification

Guess I didn't explain very well.
For fast production and the least and most uncomplicated fixings, here's the 2 step sequence...especially for roughing wet blanks.
1) mount the new blank onto the screw chuck. Turn the rough profile (oversize by at least 10%..including the tenon for chucking).
2) Reverse and chuck up to hollow with over-thick(10%) walls.
End.

So, the problem is not in the chuck un-screwing from the spindle with the larger blanks. The heavy green blanks want to unscrew from the screw chuck when I hit stop. This can of course cause a 50 pound blank to fall on your foot if the tail stock is not in place.
All that I was hoping to glean from my post was a variety of specific sizes of drill bit sizes that folks have found successful for various different screw sizes. I have tried measuring the shaft of the screw with digital calipers and, that proved to still be too large to keep a big blank from unscrewing at stop.

As for hollowing...I don't care for the "cone" hollowing method...just personal preference.
Screw chuck or 4 jaw unscrewing? I Can always secure the chuck to the spindle with a locking collar.Texian, I have done exactly as you recommend in slowing down the variable speed before hitting stop. It works but, shouldn't be necessary.
Hope this makes my dumb question clearer.
Tks,
J

 

[lark leazar]

Gretch,

Re - small bowls and arthritic fingers. Have you tried something like this? http://www.ridgid.com/Tools/Strap-Wrench

 

[odie]

Guess I didn't explain very well.
For fast production and the least and most uncomplicated fixings, here's the 2 step sequence...especially for roughing wet blanks.
1) mount the new blank onto the screw chuck. Turn the rough profile (oversize by at least 10%..including the tenon for chucking).
2) Reverse and chuck up to hollow with over-thick(10%) walls.
End.

So, the problem is not in the chuck un-screwing from the spindle with the larger blanks. The heavy green blanks want to unscrew from the screw chuck when I hit stop. This can of course cause a 50 pound blank to fall on your foot if the tail stock is not in place.
All that I was hoping to glean from my post was a variety of specific sizes of drill bit sizes that folks have found successful for various different screw sizes. I have tried measuring the shaft of the screw with digital calipers and, that proved to still be too large to keep a big blank from unscrewing at stop.

As for hollowing...I don't care for the "cone" hollowing method...just personal preference.
Screw chuck or 4 jaw unscrewing? I Can always secure the chuck to the spindle with a locking collar.Texian, I have done exactly as you recommend in slowing down the variable speed before hitting stop. It works but, shouldn't be necessary.
Hope this makes my dumb question clearer.
Tks,
J

Hi Jay.......

I can't give you specific drill bit sizes, because I use a method that is similar to Steve's....but, I generally "eyeball" the drill bit held to the screw, making sure the bit matches the shaft but threads are larger in diameter.

I know that doesn't address your specific question, but I do have a suggestion for you.......

I use screw center faceplates extensively, and have not experienced the problem you have. My larger screw center faceplates are 4 1/2" in diameter. These have three screw holes near the outer rim. I seldom use these screw holes, but with my heavier blocks of wood, I do. I mainly do this for added grip strength, but it would serve to be the perfect solution to your particular needs.

My screw center faceplates have these screw holes when purchased, but it would be an easy thing to add, if yours do not.......just drill a few holes in your screw center faceplates, add a few smaller screws to the mount, and you will NOT have this problem anymore.........!

ooc

 

[Gretch Flo]

strap wrench

Gretch,

Re - small bowls and arthritic fingers. Have you tried something like this? http://www.ridgid.com/Tools/Strap-Wrench

Thanks Lark. Yes I have tried a long time ago. It was a cheap one and I was going to break the plastic handle. I must be using them wrong as I have not been successful in getting a oil filter off my ?? log splitter or some beast a few years ago. But the place I bought it had to do it and said it was tough. Maybe I'll try again. The vice grip works well. Just on some very smooth small (3-4" diameter) green pieces is where I have had the problem. Will remember to try next time rather than chiseling out . Gretch

 

[odie]

Thanks Lark. Yes I have tried a long time ago. It was a cheap one and I was going to break the plastic handle. I must be using them wrong as I have not been successful in getting a oil filter off my ?? log splitter or some beast a few years ago. But the place I bought it had to do it and said it was tough. Maybe I'll try again. The vice grip works well. Just on some very smooth small (3-4" diameter) green pieces is where I have had the problem. Will remember to try next time rather than chiseling out . Gretch

Gretch Flo........good morning!

The suggestion of using a strap wrench is a good one. I've been using one for many years for the exact same thing you are asking about in your previous post on page one.....removing wood from a screw center faceplate.

When you apply pressure to the handle of the strap wrench, the strap becomes tighter as you remove your wood......that's the secret to it's use.

Get one with a metal handle.......a good one will last a lifetime.

Later, lady.......

ooc

 

[Jorge Castaneda]

Face Plate

Jay,
I use a face plate and did away with the screw chuck, it was more trouble than is worth, and yes, with big blanks I keep the tail-stock as long as possible, even after shaping the tenon and the whole outside, once is chucked and start to hollow I still keep it until it gets on the way.
Give it a try
Jorge

 

[Joe Greiner]

Odie's "eyeball" method can work for any screw, absent tables of thread dimensions. Hold a candidate bit next to the screw, forward and back, until you find the best match with the minor diameter. It's more exact for pre-drilling in metal; since wood is more compressible and more variable, you can start smaller, and enlarge if necessary. For faceplate screws, I keep a dedicated bit, along with screws, in their own container (retired pill bottle).

 

[Mike Peace]

Teknatool chuck documentation calls for a 5/16" hole for their 3/8" wormwood screw that comes with each chuck. Works for me. Never had one come unscrewed when stopping. I keep the tail stock supporting it whenever I can and always do when I turn the lathe off.

 

[hockenbery]

I use a 10mm bit for the oneway screw.

I use the Oneway screw in my vicmarc. The oneway screw can't turn in the chuck

I often use the screw mount in some bowl demos and in beginning bowl classes. It greatly simplifies the mounting for beginners and speeds the process up for demos. Don't leave wet wood on a screw too long it gets harder to get it off. Also a wax on the screw can help with the on off.
It is a great mount when technique wen technique and from are dominant goals.

with careful blank preparation you can get a decent grain pattern in the bowl with a screw chuck.

For most bowls I rough between centers because I like to control the grain pattern.

-Al

 

[Fog Tanner]

Jay,
In the past I have used the Oneway screw, for that I use a 9mm drill bit. When I use the screw in my Vicmarc, I use a bit that is the size of the screw body or the next one down. It is best to be a bit smaller than larger when dealing with green wood. But, several years ago I changed to a dedicated faceplate similar to the Glaser. Mine is a Craft Supply with the same basic screw. For that I use a 1/4" drill bit. I have never had a problem with any blank want to unscrew, at times just the opposite. I have a Vicmarc with the electronic braking dialed out. I stop it using the hand wheel, so I can change the "rate" depending on the blanks I am turning. I use the screw chuck on everything from 3" to 23". The little 6"-7" bowls will stop in a couple of seconds, while the 23" blanks take some longer time. I have never found any electronic braking that was right for all situations, so I have it all dialed out on all my lathes now.

I start out the roughing with the tailstock in place, regardless if it is a 6" or 23" blank. This is habit from the offcenter work I do, were the tailstock is in place for the majority of the work on the outside and some of the inside. For bowls up to 14", I use plywood spacers to reduce the depth of the screw to 1/2". Larger blanks I remove the spacer.

Fog

 

[Jay Coulson]

screw chuck...

Hello Fog...I have a pic of one of your multi axis bowls that Christian sent to me. Great stuff...I'd like to correspond more with you about that. The Kelton off-center face plate etc. He's sending me another ball to do squirly looking bottle stoppers.

As for the "screw chuck"...my apologies to everyone. I should know better by describing my Vicmarc 3 piece as a screw "chuck"...it's of course a 3 part screw faceplate with a 3/8" glaser screw. I had been drilling a 5/16 pilot hole for mounting just about everything.But, when an 18" wet blank came spinning off after I moved the tailstock on to the swing-away, it fell on my foot and scared the be-geez out of me. I've since gone to a 19/64 or 9/32 and all seems to be well. It also helps to change belts on th VL300 to the low pulley which provides a much more gradual stop when I hit the knee brake on big and heavy stuff. It's very seldom(if ever) that I use the screw mounted in a vic 100 or 120. Like wise, I know that alot of people love the one way screws...Al, thanks for you sizing for a drill for those. I found them a little bit tough to extricate a green blank from (on occassion) but, I know that's better than it un-screwing. Believe that my Australian friend who says he's never had one unscrew will find all of this interesting. Of couse, he says he used to turn 18" platters on a #14 screw so...I can't argue with him...just wasn't sure I believed it or at least, would ever consider trying it.
.
I am not aware of how to make adjustments to the braking speed in the inverter...I thought that Vicmarc had that pretty well locked in at the factory for safety reasons.
Thanks to everyone,
J