The problem with screw chucks

[jefferson]

has got me using screw chucks to mount my little bowls and platters. All works well until I get a major catch - 3 over the last couple of days. The catch effectively strips the thread on the bowl - and I have to then use a face plate and begin all over again.

Is there a sure method of centering a face plate after using 's circle cutting jig (which leaves a 1/4 inch or so drilled hole in the centre?)

At least that way I could use the screw chuck, make a mistake and keep going with the face plate.

regards Jeff

[Skew ChiDAMN!!]

I've done this myself. :B

One method I use when I've lost the centre-point for reference, is to centre the faceplate by eye and then use a small steel ruler to measure the cardinal points (N, S, E & W) tweaking the faceplate until they're all the same measurement.

It's slow, fiddly and as often as not the faceplate shifts a bit when adding the screws, :~ but with care it's as good as any other method.

You probably won't align the blank so it's perfectly centred, but you should be able to position it so it only needs a whisker turned off to bring it back to true.


Another method I've heard of but haven't tried for myself, is a short length of threaded rod of the same dia & thread as the headstock, which has been machined into a cone at one end. The faceplate is screwed onto this, until the tip of the cone starts to protrude past the face. The faceplate is positioned on the blank with the tip of the cone in the hole, then the rod slowly screwed in until it starts to lift the faceplate off the blank. Back it off a bit, et voila!

I'd imagine that because the cone centres it in the hole, the faceplate would be less prone to moving when you fasten the screws. But somehow I doubt that it'd be any more accurate and that you'd still need to true up the blank afterward.

[TTIT]

Been there, done that!:B Best way I've found for centreing the faceplate is using my MT2 drive spur which just happens to slide comfortably inside the 30mm centre hole of my face plate. I just hold the faceplate up off the blank, poke the drive spur through the centre of the faceplate until the point is on the centre of the blank and drop the faceplate down - :2tsup: - never more than a mm or so out :shrug:

[Skew ChiDAMN!!]

I like it! Just went out and checked mine... too sloppy a fit. :C

Another way to do it - if you haven't already tapered the sides - is to make yourself one of these centre-finding thingies.

101899

Just scribe a line all the way across the face, then move it around 90° (if you have a 4-hole faceplate) or 60° (if you have a 6-hole faceplate) and scribe another line. Then you can simply line the faceplate up so that the lines are visible through the holes.

[JDarvall]

One tip I used once, and it seemed to work for what I was doing at the time,,,,,is to glue 2 pieces of sandpaper back to back.....push that over the screw first then screw on your work piece. sand paper helps stop spinning at the workpiece and at the screw body. It might help just enough to stop the problem.

I assume this is what everyones talking about (?) anyway...

[Calm]

Skip Robbos screw chuck idea to start with and just use the faceplate and square headed screws.

Works for me and i dont have to remount later. just guess the 1/4 hole in the middle at the start and you are set.

Then when you stop getting catchs try the screw chuck again

Cheers.

[Sawdust Maker]

Skip Robbos screw chuck idea to start with and just use the faceplate and square headed screws.

Works for me and i dont have to remount later. just guess the 1/4 hole in the middle at the start and you are set.

Then when you stop getting catchs try the screw chuck again

Cheers.

:2tsup::2tsup:

[Ed Reiss]

Make a shallow mortise the exact size (diameter) of the faceplate...makes re-centering very easy.

[Calm]

following from some of the threads above

make a "dowell" that fits the centre of the faceplate - good tight fit - with a point on the end (or a 1/4 inch bit) then you can fit it through the faceplate into the hole from the screw chuck and bolt on the faceplate - same as TTIT said but out of wood not steel.

Cheers

[TTIT]

:whs: Too easy!

[Black Ned]

Why don't you fit a thin wooden disc to the face plate and fit to lathe.
Adjust the tool rest across the face of wooden disc/face plate.
Turn on the lathe and using a carpenters pencil make ever increasing concentric circles from the centre to the outer rim.
Hold the piece you wish to turn against the disc and centering on one of the circles that comes close to the size required.
You could use hot melt glue or screws to secure the piece.

[NeilS]

Similar issue for placing a faceplate ring on a blank. I use a turned disk that fits neatly in each sized ring and locate it in place with a 1/4" pin through the 1/4" centre holes.

Neil

[rsser]

For those I use a cone with a pointed pin in the base centre which locates in the small centre hole I've made in the blank with an gimlet. Drop the ring over the cone and it's centred.

[hughie]

Hmm face plates, screw chucks. I use the "wood worm screw" supplied with all Teknatool chucks. It works so well I have used my faceplates for other things, namely to hold my Longworth chucks on permanently. On large pieces I use the tailstock for additional support while roughing out.

To date, one one pull out, mainly due to my aggressive attack with the roughing gouge..:C
Have considered making a bigger one for such occaisions but have yet to get around to it.

[Calm]

Hmm face plates, screw chucks. I use the "wood worm screw" supplied with all Teknatool chucks. It works so well I have used my faceplates for other things, namely to hold my Longworth chucks on permanently. On large pieces I use the tailstock for additional support while roughing out.

To date, one one pull out, mainly due to my aggressive attack with the roughing gouge..:C
Have considered making a bigger one for such occaisions but have yet to get around to it.

Hughie

That is what they are referring to as the "screw chuck"

Well that is what i understood it to be.

Cheers

[hughie]

That is what they are referring to as the "screw chuck"
Well that is what i understood it to be.

As far as I can determine they are one and the same thing. Except the worm screw has a different thread form. I suspect this difference is what makes it perform so well. All the other pics I could find just showed a wood screw being used.

[Calm]

As far as I can determine they are one and the same thing. Except the worm screw has a different thread form. I suspect this difference is what makes it perform so well. All the other pics I could find just showed a wood screw being used.

My experience with these has been totally hopeless. They keep stripping out so i think i either start with too big a hole or i go too hard with the gouge and it comes off. I just use a faceplate or ring now.

Saves remounting after the failure.

Cheers

[rsser]

Mine's from Garry Pye and the screw is much closer to a wood 'worm' than a std wood screw.

[Skew ChiDAMN!!]

My experience with these has been totally hopeless. They keep stripping out so i think i either start with too big a hole or i go too hard with the gouge and it comes off. I just use a faceplate or ring now.

Yeah, they do take a bit of finesse with the tools... but has anyone stopped to consider that this may be why has Jefferson using 'em? :D

A good learning experience.

Besides, I've had a couple of jobs in the past where faceplates/rings weren't suitable (eg. knobs for auto gear shifters) and a screw chuck is "the" way to go. Sure, there are always alternative mounting methods, but usually the simplest is best.

Stick with it, Jefferson. It certainly doesn't hurt to widen your repertoire. :wink:

[hughie]

My experience with these has been totally hopeless. They keep stripping out so i think i either start with too big a hole or i go too hard with the gouge and it comes off.
If the hole is too big it will strip out for sure. The drill diameter should be no greater than the core diameter of the wood worm, in this case 8mm or 5/16" is all I use.

[Calm]

Another point i failed to mention was that a screw chuck will work better on small diameter than large as the leverage s a lot less.

That is why Skew's gearstick knobs etc wood work perfectly whereas with a 250 or 300 mm bowl the leverage on the outside is really pushing the freindship.

Cheers

[jefferson]

In answer to a few thoughts / views out there:

1. indeed has me using the screw chuck for good reason. For one, it's fast. A lot faster than attaching a face plate for sure. And for two, it keeps me on my toes against nasty catches. So yes, Skew, I will persist with it for a while yet. My main concern was centering with a face plate in the event of a stripped thread and I think some good solutions have been provided. My thanks.

2. Calm, uses the screw chuck on big stuff too, the last one I saw a 350mm redgum platter. No worries either there! Obviously good tool technique goes a long way.

Of course may have some thoughts on the matter!

Jeff

[tea lady]

How about doing what my wood work club has, and drill screw holes around the edge? Then if screw thread strips screw screws through holes. Main screw is still in the middle, so no centering probs.:cool: Most probs with stripped threads for me happen with softer woods. Crapiata, Karri, Blackwood sometimes. Harder wood seems to stand up a bit better.

(Is it stripping while using a scraper? Larger surface contact so will exert more force on the thread. :shrug: )

(Also another thought, is the blank screwed on tight enough to the chuck? For the same reason as chucks need to be done up tight so they don't end up binding on the thread when they get spun on tighter by the lathe, if its not on tight enough, they have room to move and do the stripping thing..)

[hughie]

Calm, uses the screw chuck on big stuff too, the last one I saw a 350mm redgum platter. No worries either there! Obviously good tool technique goes a long way.


Same here use it for all, never mind the size.

What I do some times to prevent any deflection on the screw as it butts up to the chuck. Is to slip a 3mm x 150mm plate over the screw before screwing the blank. This then act likes a backing plate to the screw sorta de facto face plate

[mick61]

G`day I use the woodfast worm screw(Glaser screw) tha attaches to the face plate havent lost any size bowl or burl upto 300mm.
Mick:D