Shellac Mandrels and Chucks.

[Lauri]

Hi.

Also superglue (cyanoacrylate) often works well. Most of them can be dissolved in an acetone bath, or in nitromethane.
Also, I sometimes use epoxy to mount parts for machining, or just to support brittle or thin parts. Epoxy is then removed with dimethylformamide.

Lauri

 

[petertha]

This is an interesting post. FWIW - I recently used medium-thick CA glue to sandwich some aluminum sticks together as a pair, since they had to be machined to same dimensions. The mating glue surfaces were sanded nice & flat on 600 paper under a glass plate & then cleaned really well with brake cleaner. When I first glued it together I was more concerned about how to eventiually get them apart, the joint seemed permanent.

Well it 'almost' lasted to the end of machining, then the 2 pieces fell apart. I havent done much of this in machining but have used CA glue & all its varieties a lot in typical RC hobby applications.

Now I'm wondering if petroleum based cutting fluids (I was using AlumTap) was slowly getting at the glue & weakening it? Also the glued surface was flat, but the outer surfaces were regular stock. Maybe that was causing unequal stress on the joint as it was in & out of the mill vice for sequential operations? Or just machining vibrations?

I'm intrigued by the shellac/wax. I hope to see more results & recipies. I'm curious about the specs of it vs. glues. Also after heating to remove, how to you get any remnants off? With alcohol or acetone type solvent?

 

[goldstar31]

Regarding the shellac/wax comment, I was pointing to none other than what was used by Tubal Cain and probably described in one of his general books on machining rather than one on a specialist model engine.
I'm sorry, I'm too old( 83) and have seemingly everlasting real family problems to dig out the exact stuff. You will have to do this and I can assure you that your time will not be wasted. Tom Walshaw was actually a lecturer in engineering and passed his extensive knowledge on- not exactly freely because you will have to buy the books!

As for removal of the stuff, all that you have is what the constituents of a good old fashioned varnish or paint mixed with paraffin wax. So you have a sort of old fashioned paint/varnish remover 'body' and you simply add the solvent/soluent to choice. In other words any old thing that went into old fashioned paints. Mebbe, petrol or diesel or barbecue fluid would do.

I got fed up with sourcing and settled for the Black and Decker sticky stuff that was used to stick glass/sand/emery paper or cloth to a face plate. As you see, this would have made problem getting surfaces flat- before machining. Of course, soft soldering is another useful skill.

Does this help?

Norman

 

[Tony Bird]

Hi,

I'm intrigued by the shellac/wax. I hope to see more results & recipies. I'm curious about the specs of it vs. glues. Also after heating to remove, how to you get any remnants off? With alcohol or acetone type solvent

I was apprenticed in the Watch, Clock and Jewellery trade many years ago where the use of shellac was fairly common. In watches and clocks it was used in machining and holding jewels into pallets, in jewellery work in was used to mount stones. Shellac is dissolved in wood alcohol to make French polish, with dye added it is used to make engraving wax which is melted into engraving then smoothed flat.

What do I know about shellac? It is a natural resin secreted by the female Lac beetle which after collecting is then refined. It is available in various states of refinement the clearest is used to make lacquer. In its solid state it available in stick or flake form, the flake is used by cabinet makers as a filler and polish. It melts around 84C.

In machining it is melted on to some form of chuck the work piece is placed on it while it is still molten and the work piece heated until liquid shellac comes out of the joint between work piece and chuck. It is allowed to cool before machining. There are three ways of removing the work piece from the chuck, too deeper cut while machining, not desirable! The other two require heat, first by heating with a gas torch the reverse of gluing the work piece to the chuck or if the work piece is fragile boiling in water. To remove the shellac left on the work piece in is placed in some wood alcohol, here in the UK methylated spirits is mostly used.

Does shellac have any advantages over modern adhesives? Well both can separate due to vibration. There are possibly three advantages that shellac has, it doesn't stick fingers together, the work piece can be moved after fitting to the chuck, the work piece can be glued to and removed from mandrels. I cannot think of any real disadvantages other than fairly mild heat has to be used also the heating and cooling of the shellac takes time.



For multiple machining's where centring is required a removable spigot can be fitted to the chuck. The spigot can be offset for eccentric turning.

I hope this helps, any question please ask, there will be a late reply as I am away to the land of skirted men and strong water for a few weeks.

Regards Tony.

 

[MachineTom]

A previous post mentioned a supplier in Rochester, they offered a sample package of their products. A quick email yielded a package of six sticks of different waxes.

First I warmed up a 3/8 shaft and a snug fitting collar. AL collar steel shaft, melted some low temp 135, and smeared it on the shift and slid the collar on. Took some light cuts and all was well, went to.015 doc, and I spun on the shaft.

Just then a project arrived .needed to make a thrust washer, bronze 2.75od,2.0 I'd and. 008 thick, and is at 45 degree angle.
Began with 3" bronze, cut one side at 45degree then parted off about. 250" piece, turned a AL to a 45degree mandrel.
Using the strongest wax 170 degrees I glued the work to the mandrel.
Then turned the bronze to. 008 thick, allowing. 002 for the wax.

At 170deg a propane torch worked better than a heat gun, the AL really sucks the heat, the gun did not have enough btu: '

Don' t know when I' ll use it again, but it worked great on this job.

 

[Humph7ey]

The place I worked at used sulphur powder to fix grinding stone rings to a backing plate. Just apply the heat and hold your breath. Never heard of one coming off.
I often use soft solder paste to make false centres to a hardened shaft.

 

[Wagon173]

Perfect rookie, "Oh Sh*t" Moment! I never thought about finding a way to glue things to the lathe. You fellas have probably saved me a fair amount in end mills Thanks for posting this!

 

[dman]

Hi,

I'm intrigued by the shellac/wax. I hope to see more results & recipies. I'm curious about the specs of it vs. glues. Also after heating to remove, how to you get any remnants off? With alcohol or acetone type solvent

I was apprenticed in the Watch, Clock and Jewellery trade many years ago where the use of shellac was fairly common. In watches and clocks it was used in machining and holding jewels into pallets, in jewellery work in was used to mount stones. Shellac is dissolved in wood alcohol to make French polish, with dye added it is used to make engraving wax which is melted into engraving then smoothed flat.

What do I know about shellac? It is a natural resin secreted by the female Lac beetle which after collecting is then refined. It is available in various states of refinement the clearest is used to make lacquer. In its solid state it available in stick or flake form, the flake is used by cabinet makers as a filler and polish. It melts around 84C.

In machining it is melted on to some form of chuck the work piece is placed on it while it is still molten and the work piece heated until liquid shellac comes out of the joint between work piece and chuck. It is allowed to cool before machining. There are three ways of removing the work piece from the chuck, too deeper cut while machining, not desirable! The other two require heat, first by heating with a gas torch the reverse of gluing the work piece to the chuck or if the work piece is fragile boiling in water. To remove the shellac left on the work piece in is placed in some wood alcohol, here in the UK methylated spirits is mostly used.

Does shellac have any advantages over modern adhesives? Well both can separate due to vibration. There are possibly three advantages that shellac has, it doesn't stick fingers together, the work piece can be moved after fitting to the chuck, the work piece can be glued to and removed from mandrels. I cannot think of any real disadvantages other than fairly mild heat has to be used also the heating and cooling of the shellac takes time.



For multiple machining's where centring is required a removable spigot can be fitted to the chuck. The spigot can be offset for eccentric turning.

I hope this helps, any question please ask, there will be a late reply as I am away to the land of skirted men and strong water for a few weeks.

Regards Tony.

shellac has a weird ability to bond to almost anything including polished metal. it seems it is used by jewelers to hold delicate pieces. it's not as strong as a modern adhesive and many modern adhesives bond to metal but the thing about using it as a chuck is it has to be removable, cleanable and in the case of shellac it is even reusable. the shellac is removable with heat and any leftover can be cleaned with alcohol.

 

[Tony Bird]

Hi,

Used some shellac today to hold the steam chest cover to the steam chest while they were being machined.






Regards Tony.

 

[golddustpeak]

Any thoughts about the DIY construction of a shellac chuck, say 3 inches in diameter?

Grove diameters and depths etc.

TNX

 

[Tony Bird]

Hi,

Any thoughts about the DIY construction of a shellac chuck, say 3 inches in diameter?

I don't think it matters a great deal. The attached photograph shows one I made and use which is about 4" diameter and the rings are about 1/4" apart. On smaller chucks I usually put them closer together. Depth doesn't matter but make them at least a 1/32" wide. For smaller work pieces it is probably better if they are closer together.



Regards Tony.

 

[golddustpeak]

Tony,

THANKS!!!