Making curved parts

[Steve HuckinsParticipant @stevehuckins53362]

I’m struggling with my latest casting kit which is the Rachel Wall engine from EKP. The drawings have some missing dimensions but I can work with that. Not quite ready to move to the part I need help with yet but thought I might start to ask for advice sooner than later.

I haven’t yet made a part that’s cup shaped and I have two to make as seen in the photos.

Im not aware of the sort of tools I would need and how to machine them.

Any help please .

Steve

[Steve HuckinsParticipant @stevehuckins53362]

Also the two larger ones on the cylinder one of which is part of the end cap.

[JasonBModerator @jasonb]

Form tools are ideal for this. You can use a piece of gauge plate and machine the profile into that so for the outsid eof the cup I would drill an 8mm hole and then use a 1.5mm endmill to form the bead. Harden and then feed that into your work.

Or you could make two separate tools, one a 1/4 circle and the other a half circle and do it a bit at a time.

[noel shelleyParticipant @noelshelley55608]

As per Jason, form tools made of gauge plate or tool steel.  Noel

[JasonBModerator @jasonb]

Did not have time last night to post this link, but it is a nice pictorial build of the engine, although it does not use much in the way of castings. Also shows that for one offs like the cylinder cups hand work is another option

http://www.eckartkercher.de/elianebau04.htm

[Steve HuckinsParticipant @stevehuckins53362]

Thanks for the recommends.

Is gauge plate ok to drill and mill with HSS tools ? And what thickness would you suggest the gauge plate ? What sort of reliefs should I aim for and how ? if I needed to use the bench grinder for instance. Finally, how do I harden the tool once shaped ?

I imagine there is some publication explaining about this subject but could you recommend some please.

As ever, I am really grateful for everyone’s advice and taking time to help a relatively new hobby machinist. Every days a school day of course.

Steve

 

[JasonBModerator @jasonb]

You can machine it with HSS no problem, not quite as free machining as EN1A but basically the same as silver steel.

The easy way to get some relief is to hold the piece of bar at an angle of say 5-7 degrees in the mill vice.

Provided you don’t have too much sticking out the tool post, something like 10mm x 3mm or 3/8 x 1/8 would do the job.

I just heat the working end with a blowtorch to cherry red and quench in water. I don’t bother about tempering.

 

Hold at an angle, mill across the end then using an 8mm cutter form a half circle, depending on your mill you may be able to feed in sideways or if less rigid make a series of plunge cuts moving the work over in say 0.5mm steps.

Take a 1.5mm cutter and form the half round bead detail, I would definately plunge with this, 0.1mm stepovers

Probably not needed on this simple form but you may find the sides needs a small amount of relief which can be done with a half round needle file before hardening.

[Mike HurleyParticipant @mikehurley60381]

The workshop practice series of manuals will cover all these topics and much more at a reasonable price.

Its pretty much how I learned from zero start point.

[BazParticipant @baz89810]

Not criticising Jason’s methods they are correct and work well, another way of machining the required hole in gauge plate is to hold it flat in the vice and use a conecut drill, this will give you a relief all round. Only problem being you are cutting with the bottom of the tool upwards so not so easy to measure the required diameter. Plus side is that you can make any diameter hole within the cutter range. I was fortunate to get a lovely little one with a capacity of 2-10mm diameter in a local hardware shop for very little cost.

[Chris GunnParticipant @chrisgunn36534]

I do it exactly as Jason suggests, so quick and easy that way, after all the job is more or less a one off or two off. I have tool holder that holds a short piece of gauge plate, so easy to hold a wider piece, this did not take long to make either, size will depend on what lathe you have. Just watch out for chatter if it is a wide cutting edge, i sometimes make a final light cut turnng the chuck by hand to eliminate the chatter.

Chris Gunn

[PeteParticipant @pete41194]

I’d second Mike’s thoughts about the Workshop Practice series of books as well.

https://www.teepublishing.co.uk/books/workshop-practice-series/hardening-tempering-heat-treatment-1/

About the only item that might be worth adding, there’s 3 basic types available. Water, Oil or Air hardened tool steels.

 

[roy entwistleParticipant @royentwistle24699]

I’d cut them by hand using a graver such as a watchmaker would use

Roy

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