Sander for segmented turning buying advice please.

[Alpha-Dave]

Hi,

I'm wanting to do some segmented turning, in Malcolm Tibbet's book on the subject, he says that to get a perfect join you need to finish on a sander rather than just the cut edge from a mitre or table saw. He uses a 20" disc sander, but as far as I can see those are almost impossible to find in the UK for a reasonable cost, and I'm not sure I have the space anyway.

It apears that there are 2 aspects: 1) a good, solid table so that once you set up an angle and a stop block, all pieces will be the same and 2) a wide/flat common surface so that once 1/2 circles are glued, then the 2 semicircles can have their ends sanded to create a perfect circle join, therefore the size of the sander limits the size of the final turning.

My 2 current options are:
1) a 1966 Wadkin 400 mm disc sander that a guy near me is selling, this has a 3 phase motor, so I would have to either change the motor or buy an inverter. All in cost ~£600 once I hired a van/courier to move it.
Like this, but without the linisher: http://www.conwaysaw.co.uk/images/usedmachines/503.jpg

2) a new axminster trade series BDS-612, which has a 300 mm disc and a belt sander that will have a ~500 mm plattern. The cost for this £550.
http://www.axminster.co.uk/axminster-tr ... der-505091

Obviously old cast iron is nice, but the axminster has a 3 year warrenty.

Any thoughts please? What do people here use for this sort of job?

 

[buzzby]

How big a lathe do you have? I have "built" a 12" sander by mounting a piece of plywood on a faceplate i don't use. Turing it round and then sticking a 12" sanding disk to it.
I still need to build a table that fits on the bed ways to get a true 90 degree angle but i have found this very usful and it is super easy to store. Rather than having to find space in the workshop for more tools.

I might be wrong but 20" is pretty big and you only need to sand the edges of each segment. You could possible use a super cheap 1" belt sander combo. Axmintsre do one for about £80 i think and then you could look at a drum sander to flatten the glued pieces.

Just some thoughts

 

[Alpha-Dave]

Hi Buzzby, thank you for your thoughts.

I have a Jet 3520b, so at some point I would like to try a 20" turning on there. I have a 300 mm sanding disc on a face plate, and a plattern support like this from Axminster: http://www.axminster.co.uk/axminster-su ... hes-502665 I find that this is good for flattening the bottom of bowls, but for accuracy of creating a mitre with a couple of degrees of accuracy it is too crude.

 

[CHJ]

Hi,

I'm wanting to do some segmented turning, in Malcolm Tibbet's book on the subject, he says that to get a perfect join you need to finish on a sander rather than just the cut edge from a mitre or table saw.

I would dispute this, If you have a sharp blade and set your saw up accurately in all planes for the angle then the sawn surface is more than good enough, in fact if you sand to too fine a finish you reduce the adhesion properties of the surface.
It's also not as easy as you might think to maintain an accurate angle and size on a sander, especially with small pieces.

My segmented pieces are only very basic with no intricate embedded patterns but 99 % of my stuff is cut on a budget model chop saw, my experience has been that 7 out of 10 times I've used a sanding disc to try and recover a poor mitre* I've made things worse.
If I've sanded an angle because it's outside the cutting range of my chopsaw and been done on a bandsaw it has involved the use of a jig or at least a substantial guide setup to get the accuracy and been quite time consuming with the care needed. This should not be a problem with a decent tablesaw setup which should cut with the same accuracy as the chopsaw.

Don't think anyone who has picked my pieces up has ever seen a join that shouts 'gap'.

* usually because original stock material was not perfectly square and threw the cut awry.


Some folks that can't clamp the complete segment circle in one go or assemble with no clamping or with minor angle inaccuracies assemble two 180 deg. halves then sand the ends to match the two 180 halves. This can be done on a flat abrasive sheet on a flat surface it does not need a sander as such.

Sample simple Chopsaw segment WIP

 

[Alpha-Dave]

Hi CHJ, thank you for the pdf link, that is really useful.

Your point of needing just a flat surface with some sandpaper on is very relevant: I was thinking I needed the biggest sander possible to achieve the flattening of the 2 semi-circles prior to final glue up, but I now see that as not a large amount of material would need to be removed it does not need to be powered.

As for the need to sand or not, I can only quote from MT's book; he notes that light/dark wood joins are the most forgiving, while light/light is the least. MT uses a jig where he sands the end of the stop block to make a wedge, then feeds the piece in to create a perfect angle, shimming with masking tape if not perfect. I think this is for extreme fineness though, such as when he is creating a contrasting spiral and doesn't want the joins between the same woods to be seen so that the contrasting woods are emphasised.

 

[CHJ]

If you are sanding a surface to get best fit, scribble on the surface with a soft pencil so that you can see where and if you are removing material from correct place and that you are holding it square.

 

[Honest John]

Hi Alpha Dave. I use a record Power 12 inch sander. I have read Malcom Tibbets book and have made his sub table and jigs for sanding segments. These work very well, but there is a trade off. It requires a deal of setting and checking and resetting frequently to maintain accuracy, and as CHJ said it can very easily make matters worse. I find that time spent setting up your saw, and preparing stock to be uniform and square is time well spent. I use a 2 fence sled on a table saw for all my segments now and 24 segment rings go together perfectly (usually) without having to make half rings. If I was to sand my segments off my table saw I am sure it would not improve anything, but as CHJ said would very likely reduce the glue bond. Where I find my sander excels in when I make multi piece segments for feature rings. This often involves glueing many small pieces and then shaping on the sander before more gluing and shaping. I would find this process difficult without a well set up sander, but as with all things I'm sure there are other ways of doing this. All in all I would not be without my disk sander, but a well set up saw well able to cut segments to a very fine accuracy. I have used a mitre saw with equally good results, but I found that it took more tweaking to get accurate results, and it was often necessary to glue on half rings or waste a lot of material.

 

[beganasatree]

Chas thank you for the WIP,it was really interesting and informative.

Peter.

 

[Alpha-Dave]

Thanks for the info Honest John, I admit I'm now thinking that a 12" sander would do most of what I need.

 

[CHJ]

Chas thank you for the WIP,it was really interesting and informative.

Peter.

Glad it is of some interest Peter, like all turning tasks there are dozens of different variations on 'How to' but if a WIP gives room for thought and results in finding a method that works with the gear you have to hand I'm happy.