# Shellac Mandrels and Chucks.



## Tony Bird (Jul 28, 2013)

Hi,

I have just started making a Stuart S50 mill engine.  When making an engine from castings I often start with the cylinder and members might be interested in my approach. Having filed off any casting joints which on Stuart castings are very small I just flatten off the port face.








The cylinder is then bored and its one end cleaned up but not to size.





A piece of mild steel is centred both ends and set up between centres in the lathe.  It is then turned to a good slide fit in the bore of the cylinder.  Then shoulders of the same diameter are turned one at each end of the rod leave a raised portion which is less than the length of the bore of the cylinder.  This raised section has several grooves cut in it.





This rod is then heated and shellac melted on to its.  the cylinder is also heated and fitted over the rod.  The shellac when cool will hold the cylinder in place.





The result can then be set up between centres and the cylinder machined to size.





 The cylinder and its rod can then be removed from the lathe and mounted in the mill to do its flat surfaces.








When finished the combination can be heated and the rod can be removed from the cylinder.  This has not been done as the steam chest and cover will be attached for machining.





A lot larger cylinders can also be done in this fashion.  One I did as a demonstration for my model club.  The ones on my 5" gauge locomotives were done the same way





The more usual way of using shellac on a disc chuck.





Hope this is found interesting.

Regards Tony.


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## starnovice (Jul 28, 2013)

Where can you get that type of shellac?


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## tornitore45 (Jul 28, 2013)

I assume the grooved mandrel slip fits the bore to define center.
What is the purpose of the grooves?
Is shellac loaded into them?
From the picture I can only see the shellac on the outside.


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## phrodo (Jul 28, 2013)

I have also used stuff called blocking wax. It's used by lens grinders to hold a piece of glass on to a plate or mandrel so it can be polished. Same idea, heat everything with a heat gun and let it flow together. When it cools it's not going to come apart easily. Great for holding thin sections or bigger parts that have to have at thin section milled in them. Just like the shellac method the beauty is that the part is perfectly held with no distorting forces.


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## enfieldbullet (Jul 28, 2013)

shellac can be bought from art supply stores.

nice example of application, great pictures! thank you!


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## Tin Falcon (Jul 28, 2013)

I do not expect it is any sort of special shellac. I buy bulls eye brand at the local hardware store and home center.   
Tin


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## Mechanicboy (Jul 28, 2013)

I used locktite as clue when i turned the cover for steam chest for Stuart compound.


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## Sshire (Jul 28, 2013)

Regular per-mixed shellac, like Bullseye, is shellac flakes dissolved in alcohol.  Think I'd want to mix a much more concentrated shellac that would be very viscous. 
The optical blanking wax mentioned earlier, comes in various holding strengths. 
In my experience, the Stronghold blanking waxes, hold exceptionally well. The same company makes a "Blanchard Grinding Wax" which is actually for the initial rough shaping of lenses. Holds like epoxy. Heat gun and it's released.


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## Beachside_Hank (Jul 28, 2013)

That's a great tip, but furniture and cabinet grade shellac is priced at a premium nowadays as the last few seasons harvest are reported to be very sparse. I'm just about out of mine, it is my goto problem solver for a lot of applications and even in flake form it only has a shelf life of about a year or so. I wonder if hot melt glue would work the same.


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## phrodo (Jul 28, 2013)

Just realized Stronghold is 15 minutes down the road. Check their website, they have a sample kit they they'll send out for free. Might be just the thing if you only need a little bit on occasion.


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## Tony Bird (Jul 29, 2013)

Hi,



*Where can you get that type of shellac?* 

Here In the UK I get it from a Horological & Jewellery supplier Cousinsuk.com.  It comes in sticks either refined or not, either work, I recently bought some 200grms (6oz ish) of  unrefined for £4.50.  

*I assume the grooved mandrel slip fits the bore to define centre.*
* What is the purpose of the grooves?*
* Is shellac loaded into them?*
* From the picture I can only see the shellac on the outside.* 

Sorry I didn't make this clear.  Yes the grooves in the mandrel are charged with molten shellac before sliding the cylinder on.  What can be seen in the photograph is the overflow of shellac.

I have used the furniture trades shellac flakes by meting the flakes in a small pot/tin and spread it on the chuck with a hot pallet knife.  Solid shellac does not seem to have a shelf life.

I forgot to mention that after the work piece from the chuck any residual shellac can be removed by placing the work piece in alcohol.

Stub mandrels can also be used in blind holes but they have to have a hole drilled through them to allow the air out.  This works really well for things like pump bodies and thin wall displacer pistons used in Stirling engines.

Regards Tony.


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## Mosey (Jul 29, 2013)

I have used the 3M double sided adhesive tape designed for this purpose for small thin parts on the mill with limited success. It will not hold under heavy cuts. It is pricey, and hasn't worked well. I'm sure I could improve my method, and may try it again. One problem is removal after machining, difficult.
Mosey:fan:


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## dondoerner (Jul 30, 2013)

Have you tried Resin from the Archery shop used to hold the nock onto the end of an arrow shaft. It works very well for me. Also requires heat to hold and release. Donald C Doerner CET


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## goldstar31 (Jul 30, 2013)

Shellac is part on what used to be used to make wax chucks.
It was added to the wax to give a slightly higher melting point and to give a bit of body. I recall that Tom Walshaw as Tubal Cain wrote up a recipe.

Again I used to get tubes of the stuff from Black and Decker to stick sanding disks onto faceplates. Probably, I still have some lying about.

Today, I would suggest that the most useful stuff is the translucent glue sticks and their heat guns. Far cheaper and far more available!

As for the removal of sticky stuff from tape, I'd suggest either 'sticky stuff remover' which is probably orange oil or WD-40.  Frankly, I have never had any faith in the double sided tape for surface grinding. I find( or don't find) bits which have 'come loose' like missiles.

I bought a trio of magnetic tables and chucks. One I like, I got it given as a present with my Clarkson tool and cutter grinder. It is round and energises with an electric switch and is ideal for scraping slides etc.

Recalling Tubal Cain, he designed something called a 'thin piece vice' which was mechanical and this appeared in one of his books with wax chucks and a massive Gibraltar tool post for the Myford.

A hint to some- about shellac. Age and heat change its properties.


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## Tony Bird (Jul 31, 2013)

Hi,

*A hint to some- about shellac. Age and heat change its properties.* 

Just curious what happens to the shellac?

Regards Tony.


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## goldstar31 (Jul 31, 2013)

I'm somewhat surprised at the question  but shellac is one of the constituents of paints and varnishes.

Just another hint- it goes into some abrasive wheels as the binder. 

Basically- all the oils and whatever change their state.

Which reminds me- the impellor pump on the dishwasher has cracked into a thousand bits - plasticiser has gone. I'm 83 and I'm shrinking- plasticiser going. Tedious, Tony- but true.

Regards

Norman


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## Mosey (Aug 3, 2013)

Which Loctite?


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## Mechanicboy (Aug 3, 2013)

Mosey said:


> Which Loctite?



Blue treadlocker. Apply on the part and mount to the disc, let it stay 5-10 minutes under press from tail dock before work. Take light cut each time. After use, heat up the part to dismantle from the disc. Not tried on bore/shaft due i am not sure i can dismantle the parts each other.


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## Tony Bird (Aug 8, 2013)

Hi,

There is at least one area that shellac might have an advantage over other forms of sticking parts to be machined on face plates.





It allows the work piece to be centred about a hole.  This requires that a extended wax chuck is made that allows a blow to be played on the back of it.  The work piece is held to the chuck in the usual way and is allowed to cool until it is held, while still hot it is put in a 3 jaw chuck and its back heated until the shellac becomes mastic again.  Using the set up shown above the work piece is centred while it is rotating, it is rather like a potter throwing a pot.








A sort of reverse of the mandrel type wax chuck can also be made and used to put '0' ring grooves in pistons while on their rods.




















Regards Tony.


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## MachineTom (Aug 8, 2013)

After reading the thread, I dropped an email to Stronghold, and received a nice sample kit, of different blocking waxes. I'll be making a test shortly on holding some SS washers in the SG. 

Its why these forums are so good.


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## Lauri (Aug 12, 2013)

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


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## petertha (Aug 27, 2013)

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?


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## goldstar31 (Aug 28, 2013)

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


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## Tony Bird (Aug 29, 2013)

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.


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## MachineTom (Sep 2, 2013)

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.


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## Humph7ey (Oct 2, 2013)

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.


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## Wagon173 (Oct 12, 2013)

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!


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## dman (Oct 12, 2013)

Tony Bird said:


> 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*
> 
> ...



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.


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## Tony Bird (Oct 28, 2013)

Hi,

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










Regards Tony.


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## golddustpeak (Nov 20, 2013)

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

Grove diameters and depths etc.

TNX


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## Tony Bird (Nov 20, 2013)

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.


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## golddustpeak (Nov 22, 2013)

Tony,

THANKS!!!


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