Really Thin Washers

Rather than thinning an existing washer, wouldn't it be easier to cut them out the of the correct size sheet? You could still use the same method of gluing them to the block in the lathe chuck, but the cuts would be easier.

I make thin washers by this method, either from bar stock or from existing washers. Shellac is a good adhesive because it releases quickly on heating, and is easily cleaned using alcohol. An alternative is superglue which releases by soaking in acetone, though it may take a few hours to penetrate a big joint. Either way, mount your washers on metal not wood.

Cliff Coggin.

If you use the Hex head screws supplied with the kit they are incorrect. The original would have had studs with nuts and washers, nuts tend to be taller than the screw heads so look the right size as well as being the correct type of fixing. You also have the option of buying one size smaller hex nuts which can be handy in tight spaces. If you are using metric fasteners then they will look wrong watever you do.

The best place for nuts & fixings is EKP Supplies as they make for a lot of the ME outlets.

This is the cylinder for my traction engine and I think the washers look fine.

Jason

It's readily available from woodwork suppliers; it's a standard high quality finish.

Look for either shellac or french polish.

The "real thing" is sold in flake form, which last pretty much indefinitely, but needs dissolving in (very pure) alcohol for use.

The more commonly found form is pre-dissolved, which is convenient, but has a 1-2 year shelf life.

Liberon is the most widely available brand, at hardware stores and/or antique shops.

BugBear

Following on to the suggestion of using sheet, you can use the method favoured by Dave Fenner in a recent MEW article. Drill sheet to correct hole size, cut out washer approx to size, clamp between two pieces of round wood(drilled through same diameter), bolted into threaded round bar, fix in chuck, then turn down to correct diameter. Type of wood not critical but harder rather than soft wood may be better. I've used this method and it works well. Mike

The kit is provided with 7BA studs and nuts - which look OK in a scale sense, it's purely the washers I need to look scale I think.

Steve

I have made thin washers by drilling a series of holes in a sheet of the appropriate material and thickness, deburring the holes and roughly cutting out the washers oversize. The washers are then mounted on a mandrel and turned on the outside.

Washers for cylinder head nuts on auto engines tend to have a hard surface skin to reduce deformability and possibly surface friction. I suspect they are punched out of something like hard skinned cold rolled carbon steel sheet. My worry is that if you make washers out of ordinary mild steel thinned down on the lathe you'll just be introducing another compressible or deformable interface which will lead to the nuts losing tension and clamping load over time.

However maybe the forces acting on a model engine are not severe enough to worry about such things and everything is specced well within its tolerances. Try it and see I guess.

I wouldn't do it on a hardwood block anyway. I'd turn a small recess to your target thickness in a steel or aluminium bar to the o/d of the washers, glue them into that with pressure from the tailstock until the glue has set, turn them carefully and release them with heat from a camping gas torch. You might find that Loctite does the job ok. Some of the grades have pretty high adhesive properties and they tend to soften and release with heat.

I use Loctite 242 medium strength retainer for gluing 3mm shank miniature emery flap wheels into mild steel extension holders to get more reach when I'm polishing cylinder head ports. Once the Loctite has set you can't twist the flap wheel out of the mandrel by any means. The shank of the flap wheel will twist off before the bond breaks but if you play a torch over the mandrel for a few seconds the Loctite softens and the flap wheel just pops out and you can then stick a new one in. 638 is a higher strength Loctite which I use for severe duty applications and I'd say that generates a bond nearly as strong as soldering. When the inner shaft of my flexible shaft porting gear spun out of its crimped and soldered aluminium end piece I glued it back with 242 and it failed almost immediately. A mate sent me a bottle of 638 and it's been solid as a rock for a couple of years now. Some of the bigger porting cutters put some pretty severe torque on the system when I'm really hogging metal out but 638 handles it without any problem.

Loctite is fearsomely expensive but for the few drops you'll need I could post you a small bottle to be sent back once you're done.

I'll change that advice. It would be better to turn a centralising "pip" on your metal bar for the washer to fit over then you can more easily insert a thin blade to release the washer from the outside once you've softened the adhesive with heat.

Thanks Dave. Sounds like a plan to me. . I have loctite in a couple of grades, one has has been the sole fixing method for the cams in a 15cc IC engine I built and they haven't moved so I'll try that first. The engine will only be run once or twice then go on the display shelf, so not too worried about material types I just need them to look right.

Steve

Had a trial run using loctite 270 and some 6mm washers as a trial. Degreased everything and left the washers under pressure in the loctite overnight. Absolutely solid. Tried cuts 0.05m and worked upto 0.2 mm, they were not for budging. Blow lamp and they quit, just like you said!

Steve

:)