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machines which I have made, am making, or intend to make, and some other stuff. If you find this site interesting, please leave a comment.

Tag: engraving

Piston rods for triple, and some engraving.

A good aspect of retirement is that the there is time for learning a new skill.  (Time, but not necessarily brain power.)

A case in point for me is the trials and errors of engraving.

In previous posts I outlined the steps in setting up the engraving spindle on my CNC mill, and the mechanical issues now seem to be fixed.

But getting lettering which is crisp, clear and attractive, in brass is a bit more complicated than, say, using a computer printer.

Issues:  Selection of cutter (angle of point, flat area or not),Spindle speed, feed rate, depth of cut, coolant or not, and selection of font are all variables to consider, and try out.  Also whether the letters are raised or excavated.

Each brass plate (65 x 32mm) takes 15-30 minutes to engrave, plus set up time.  So I have spent many hours in the last week trying various combinations and permutations.

Here are some pics of early results.

Finger for scale, and for privacy of the recipient. The quality is OK, but not quite as sharp as I would like.

Finger for scale, and for privacy of the recipient.
The quality is OK, but not quite as sharp as I would like.  Lettering is 0.75mm deep.  Perhaps a little too deep.

Label for a steam engine.  It is crowded and fussy, but I will probably use it until I get around to making a better one.

Label for a steam engine. It is crowded and fussy, but I will probably use it until I get around to making a better one.

Some progress on the triple expansion steam engine, but not much to show visually.  The pistons and piston rods have been made and fitted.   The piston rods screw into the pistons, and then have a lock nut on top.  The lock nut will be loctited at the final assembly.

I had an issue with the piston rods not being exactly concentric with the pistons, probably due to inaccuracy of my lathe chuck.  So I skimmed the piston surface while holding  the piston rod in the most accurate chuck in my workshop, which is the engraving spindle.  See the photo.

The pistons, piston rods and viton rings.

The pistons, piston rods and viton rings.

Turning pistons on a vertical mill. Not the clearest photo. It shows the high pressure piston (the smallest one) held in the collet chuck of the engraving head, being skimmed with a lathe tool which is held in the milling vise. It worked very well indeed!

Turning pistons on a vertical mill.
Not the clearest photo.
It shows the high pressure piston (the smallest one) held in the collet chuck of the engraving head, being skimmed with a lathe tool which is held in the milling vise.
It worked very well indeed!

24000 RPM spindle for CNC Mill

IMG_2718

The mill quill and spindle is on the right hand side, with a 1 inch cutter insitu. The high speed spindle and its VSD controller is on the left hand side. Of course the cutter on the rhs will be removed when an engraving cutter is installed in the high speed spindle. The wiring hook ups, and coolant pump and lines are yet to be installed It does not look much but it took me a whole day.  The setup is quite rigid.

Today I spent a few more hours setting up the high speed spindle on my CNC mill.

I will post a video when i am doing some label engraving.

Make Your Own LONG SERIES TAP

My current project is a diversion from the triple expansion steam engine, which is about 33% completed.

I wanted to do some engraving on my CNC milling machine.  It is accurate enough in XYZ movements, but the spindle has a maximum RPM of approximately only 3000.  Engraving with a cutter with a tip of diameter 0.1 to 1 mm diameter really requires 10-20 thousand RPM.

I also have in mind making some wooden things using router bits, and they usually rotate at 12-26 thousand RPM.

I wondered about a manufacturers attachment for my mill but could find nothing.

So I decided to make my own.

I briefly considered attaching an electric  router to the mill, but since many projects require constant spindle work for several hours at a stretch, I decided that the spindle should have an inbuilt cooling system.

What I bought was a 2.2kW spindle, 3 phase, with a variable speed controller, giving an RPM range up to 24,000.  It is designed for liquid cooling, and can be used for long periods without overheating.

The spindle has an 80mm diameter, and I will attach it to the 110mm diameter quill on my milling machine.

So, I cut some holes in 16mm aluminium plate.

 

IMG_2713

The aluminium plate attaches to the milling machine quill, like this.

 

To clamp the plates to the quill, and to the spindle, I cut some slits into the holes in the plate, and drilled and tapped some 6mm holes. (done after the above photo was taken).

My problem was that my 6mm taps were all much too short for the job.
I went to my usual industrial tool supplier to buy some long series taps, only to be informed that long series taps are not kept in stock, and would take several days to arrive on special, and very expensive order. Long series taps apparently cost at least 3 times as much as conventional length taps.

Having had success at silver soldering band saw blades, I wondered whether I could add some length to a conventional tap by silver soldering some steel rod, end to end, to the tap.  It was also quite succesful.

Here is the setup for the soldering. (Sorry Americans, what you call soddering the rest of the English speaking world calls soldering).
IMG_2714The angle iron is held in a vice. The tap to be lengthened rests in the angle (after thorough cleaning and application of flux), and the rod likewise (in this case, a cap screw of the same diameter as the tap). The join is silver soldered in the usual manner.

This is what the lengthened taps look like.

I wondered whether the silver soldered join would be adequately strong for the tapping.  the tap was totally buried in the workpiece, and would have been irretrievable if the join had broken, and ruined the workpiece. So I was very cautious when doing the tapping.  Used a tapping oil, and backed the tap out of the workpiece every few turns for cleaning.

I wondered whether the silver soldered join would be adequately strong for the tapping. the tap was totally buried in the workpiece, and would have been irretrievable if the join had broken, and ruined the workpiece.
So I was very cautious when doing the tapping. Used a tapping oil, and backed the tap out of the workpiece every few turns for cleaning.  It worked fine.  It was a demonstration that silver solder is really very strong.

One advantage of using a cap screw for the lengthening rod was that the hex head proved ideal as an attachment for a tapping handle. The tapping handle being an Allen key.

I will post more pics of the engraving-routing spindle when it is finished.

ps. my expert friend Stuart T tells me that silver solder has a similar tensile strength to mild steel!

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