Come back to my place I have some etchings I need help with ?

[DAPPH]

I'm looking for advice about acid etching fine turned steel , brass & aluminium to a depth of about 20 thou deep .
As the actress said to the bishop, " I've not done this before ".

We have an acid proof glass or plastic receptacle to carry out the etching in .

I'm considering etching some bigger home made reference dials with larger graduations and numbers etc. than those that are currently for my lathe , as my eyesight & fingers need all the help they can get these days .

On youtube , I've seen guys being bent over their lathes for hours & hours using the carriage & / or compound slide & a stop block to gouge out the scale devisions .
Having two knackerd shoulders , two spinal disabilities and awaiting a new left knee precludes me even considering such an exercise not to mention an old mans eyesight levels .

On ebay I won a second hand but unused precision cut six & a half inch diameter circular saw blade that has exactly 100 teeth cut into it .. I'll be making up a simple tool that uses this as the reference marking point device , for the lathe scale is one division equals one thou of thread advancement per graduation , which gives 100 thou travel per 360 degree of rotation .

My thoughts are :
Use meths to clean the turned part after giving it a boiling hot water scalding to remove as much crud as possible .

See if I can buy a small tin of etch resist lacquer/paint ( Is this available these days? ) .

Draw my designs with a triangular ground up bit of stellite rod & /or tap a fine ground chisel form blade made specifically for the purpose from bit of key-way steel into the metal .
I also hope to use a set of small number & letter punches in a special homemade sprung holder to tap them as vertically up right/ square as possible in to the metal ( as needed ) .

Acids to use ..help !
I have an old lead acid battery that I can steal some 1.25 sg sulphuric acid out of and a few big plastic syringes to do it in safety .
I don't know if it will be strong enough for long enough to etch as deep as I want to go .

My thoughts for etching are that.. there will be no raised burs , all lines should be shown in full rather than a dotted line style if i use a small electric vibrating type engraving tool . I should be able to draw perfectly straight lines with the stellite rod and a ruler .

All advice and merriment gratefully accepted .

 

[clift_d]

Draw a monochrome image of your dial out on the computer and get it printed on clear film. Then get some Positive Photo Resist spray from Maplins and coat up some copper sheet. Contact print the positive film on the dried coated copper with a UV light source (the sun?), develop in caustic soda (drain cleaner), and then etch in warm Ferric Chloride solution (also available from Maplin). Don't forget to tape up the back of the copper sheet. Simples.

 

[Maker]

I would use "Nital" for etching the steel, it's a mix of nitric acid and an alcohol (Isopropyl is probably easiest), if sure Google can tell you the required ratio.

Ferric chloride would probably work on brass, but I'm not too sure about that.

 

[clift_d]

A quick google seems to confirm that ferric chloride also works on brass.

 

[MattF]

With that thread title, I'm surprised you're not asking if anyone wants to see a puppy. Ferric should work on owt copper based. On steel and such though, it'll just rust it, as far as I recall. For aluminium, caustic will likely work best.

 

[DAPPH]

Thanks lads,
Cliff , trying to wrap a sticky sheet of plastic graduated etch resist scale with 100 graduations round a 2.4 inch dia round edge and be super accurate would be some what difficult methinks. Plus I see lots of problems if the scale stretches slightly so the scale does not precisely fit the turned diameter.

Anyway this thread has moved on a pace since I posted . It got me thinking and a looking into timing wheels , happened to win a 7 & 1/4 " dia circular saw blade off eBay for 99p the P&P cost £ 2.80
The blade has 100 teeth .. I'm going to try and use this blade as the timing wheel to set the dial graduations .... as it is 100 teeth I can use it on any diameter blank that needs 100 or any useful devision of that number .of teeth .
I happened to be lucky enough get hold of a fully working vari speed vibrating foot plate exercise machine that has a 90 v 1 hp stepper motor that has heavy duty precision bearings & heavy duty stepper motor control pack .

Out of a fire sale for £ 2.00 I also have a commercial workshops fire damaged table top drill press. The fire damage killed the external electrics , knackered the externally mounted capacitor and the fire brigades extinguishing water ruined the motor bearings.
Having stripped everything down to see if any of it was of any use I found that after putting on a new capacitor , taking out the burnt out switch and associated wiring , cleaning & working the bearings on the lathe then repacking them by immersing them in in hot melted grease I have a useful main stand & a repaired motor less the switch gear ( I'll be renewing the bearing sin the near future as they are ever so slightly noisy).

Out of all this I hope to make a precision cross slide mounted grinder /milling device and use a top of the range cutter to mill the graduations on the blanks . For the numbers I'll make a simple guide that will allow me to slide a turned down small number punch onto the dial at the right place , then give it a light tap to impart the numbers on to the dial .

 

[octo0072000]

what about a pair of office glassers chunko has some something about parallax
keeps thing in focus zero to about 10 feet

 

[clift_d]

Okay. You weren't clear that you wanted the scale on the edge of a disc / side of a cylinder. I still think photoetching would be a better method than a circular saw blade for setting out. If you photoetched a graduated circle on the end of your cylinder then you could easily carry the engraved lines onto the cylinder side.

 

[DAPPH]

That's an interesting thought Cliff , I wonder how accurate it will be over a 3 inch diameter dial ? Meaning will th printer accurately replicate th design or will ther be a slight diffference in the distances .

I know for sure that positively locking the blade down onto a fixed triangular edge will see me hit the root of the tooth accurately every time , so moving the carriage with the powered precision engraving tool held fast & locked up in the saddle so it will just pass across the blank & engrave it a depth of 20 or so thous will also give great accuracy every time .
Without me having to use a magnifying glass to see If I've got the cutter in sync with the photo etch markings & trying to lock the spindle up in the same position ..

I'll let you know how it works out , if it's a failure I'll give it a go your way .