Author Topic: Going over to the dark (CNC) side!  (Read 54867 times)

Offline Jasonb

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Re: Going over to the dark (CNC) side!
« Reply #345 on: May 20, 2022, 07:02:26 AM »
Thanks for all the comments. I'll probably start a new thread for any more work on this one as the swarf starts to be produced. Though as I type this I have just thought of something on the engine that the CNC would be the ideal tool for :)

Offline Zephyrin

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Re: Going over to the dark (CNC) side!
« Reply #346 on: May 20, 2022, 09:24:40 AM »
this is a great project !
looking at the variable crank, I seems to me that the piston move faster on the downward stroke to minimize heat transfer before its expansion, a very clever design by Otto...in 1873 !
this is certainly a model to do, simply out of respect for the thoughts that gave rise to this engine !



 

Offline Roger B

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Re: Going over to the dark (CNC) side!
« Reply #347 on: May 20, 2022, 07:33:36 PM »
Another interesting project to follow along  :)  :)  :ThumbsUp:  :ThumbsUp: 
Best regards

Roger

Offline Jasonb

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Re: Going over to the dark (CNC) side!
« Reply #348 on: July 24, 2022, 06:58:47 PM »
A bit more pattern making completed today. The aim was to try and produce a flywheel pattern that had a similar look to the curved spoke flywheels used on National Gas Engines



Quite pleased with how it turned out



More details in the video

<a href="https://www.youtube.com/watch?v=AloAsKTpV4I" target="_blank">http://www.youtube.com/watch?v=AloAsKTpV4I</a>

I was the first time I used the peristatic pump fed fog buster in anger and very pleaed with how it performed giving just enough liquid to wet the tool and stop tip build up and meant I could leave the machine running unattended. I used about 40mls over the six hours of machining which did not leave me with a dripping pile of swarf.

Offline Admiral_dk

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Re: Going over to the dark (CNC) side!
« Reply #349 on: July 24, 2022, 11:16:37 PM »
Great result Jason - and I can only agree, that you got the Fog-Buster dialed in perfectly  :ThumbsUp:
But still surpriced how tiny an amount you used for that session  :o

Per

Offline Jasonb

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Re: Going over to the dark (CNC) side!
« Reply #350 on: July 25, 2022, 07:02:22 AM »
I did turn it down quite a lot from what can be seen in the video for the finish cuts as they remove such a small amount of metal and that was about half the cutting time.

Offline Jasonb

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Re: Going over to the dark (CNC) side!
« Reply #351 on: March 20, 2023, 04:15:45 PM »
Well it's been a while but a couple of castings from the patterns above arrived today. Look to be quite good with little flash and the two halves seem to line up well. hopefully they will have soft centres.

I did have to get them out of the unexpectedly heavy parcel quickly to avoid the risk of cross contamination from the other well maturted castings with that special coating that made up the other 80% of the contents :naughty:


Offline Alyn Foundry

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Re: Going over to the dark (CNC) side!
« Reply #352 on: March 20, 2023, 05:52:57 PM »
Great to read that they arrived safely Jason.   :ThumbsUp:

Have no fear, the foundry have altered their Iron recipe slightly with the addition of a little extra Copper. I found the flywheel quite easy to machine and managed the whole operation in under 20 minutes.

The casting was so symmetrical I was able use the boss initially to clean out an inner rim. Once clean I then expanded the 3 jaws into it and then do the usual, all faces and boss in one operation.

 :cheers:  Graham.

Online Twizseven

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Re: Going over to the dark (CNC) side!
« Reply #353 on: March 20, 2023, 08:06:37 PM »
That looks really nice Graham.  Between you both you have done a very good job.
Colin

Offline Jasonb

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Re: Going over to the dark (CNC) side!
« Reply #354 on: May 11, 2023, 01:06:59 PM »
I've been wanting to try thread milling for a while and the need finally came up so time for a new adventure.

The part in question is a gland nut that fits onto the end of a steam engine cylinder to seal the piston rather than it having piston rings. The lower lip just needs to clear the 19mm dia piston and the thread I chose was M22 x 0.5mm and needs to go as close as possible to the lip.


 

I made use of a bar end of 1" brass and milled the top flat enough using the jog function as a glorified power feed control and then use the CAM in F360 to produce the code to firstly rough out the two bores leaving 0.3mm of material which was then taken to finished size in to passes of 0.2 and then 0.3mm.

A change of tool to a single tooth,5 flute thread mill took care of the thread, I ha dread of possible tool deflection so took light 0.1mm steps and a spring pass.

Quite happy with how it came out so will be using it again particularly as one cutter can do several pitches and almost unlimited diameters both internal and external

<a href="https://www.youtube.com/watch?v=5Y58fe95IFw" target="_blank">http://www.youtube.com/watch?v=5Y58fe95IFw</a>


Offline Vixen

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Re: Going over to the dark (CNC) side!
« Reply #355 on: May 11, 2023, 01:53:47 PM »
Hello Jason,

Nice work.  :ThumbsUp: Thread milling will produce near perfect internal and matching external threads over a wide range of diameters and materials.

I usually go for full thread depth in one pass followed by a spring pass. I have had good success using a single tooth thread mill made by grinding all but one teeth from a standard tap. That worked well over a range of thread pitches and diameters, but eventually the single tooth cutter becomes dull requiring a new cutter to be made.





I know commercial thread milling cutters are available, the ones I have found are very expensive and way above my pay grade. I would be interested to know just where you sourced your 5 flute cutter and how much your 5 flute thread mill cost.

Cheers

Mike
« Last Edit: May 11, 2023, 02:24:38 PM by Vixen »
It is the journey that matters, not the destination

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Offline Jasonb

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Re: Going over to the dark (CNC) side!
« Reply #356 on: May 11, 2023, 02:26:50 PM »
Thanks Mike, I do wonder if some of what I read regarding tool flex applies more to the multi tooth cutters that will do the whole vertical depth of the thread in one helical revolution and obviously harder materials than brass.

I seem to get most of my carbide ( and inserts for that matter) cutters from APT, still a bit pricy and not something you would want to snap on the first attempt so may be a bit bolder next time. But compared with what it would cost for a few taps and dies if you had to do it by traditional means and it saves having to play about with change wheels when you get to the larger diameters so it's not a bad investment.

This is the one I got which does 0.5 to 1.0mm pitch

https://www.shop-apt.co.uk/single-tooth-thread-mills-for-general-use-internal-60-partial-profile/internal-partial-profile-60-thread-mill-05-10mm-pitch.html

Offline Vixen

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Re: Going over to the dark (CNC) side!
« Reply #357 on: May 11, 2023, 03:20:35 PM »
Hello Jason,

I have seen those APT thread mills before; not exactly inexpensive. The 0.5 to 1.0mm pitch [24 to 56 TPI] milling cutter you chose seems like it will cover most of our model engineering needs and offers the best value for money. It is probably the only one we would need. I can understand your cautious approach to the first attempt, however you should be safe for a full thread depth single pass. as it's only a shallow thread.

I have thread milled in aluminium alloy, brass and mild steel using mist coolant. Tool flex did not seem a problem but I cut at a slower feed rate than your video: nice and gentle. Could be a different story with some of the harder steels

I suffered from some cold welding last time I thread milled aluminium. Probably due to my single point tap cutter becoming dull (it's done a lot of work!!). I applied some Trafelux tapping paste inside the hole and that seemed to help.

When I milled the four threads in the cylinder heads, the first turn of each of the four threads started in exactly the same angular position; beautifully regimented.

Cheers

Mike

It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline Vixen

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Re: Going over to the dark (CNC) side!
« Reply #358 on: May 11, 2023, 03:38:19 PM »
Hello Jason,

Thread milling gives the finest finish from climb milling. This means internal threads should be cut from the bottom, upwards and external threads from the top, downwards. Your Fusion 360 probably does that by default.

Cheers

Mike
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline Jasonb

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Re: Going over to the dark (CNC) side!
« Reply #359 on: May 11, 2023, 04:31:13 PM »
Yes Fusion tends to default to climb milling and I stick with that for just about everything as the machine and tool sounds happier with that.

Out chip loads are probably similar as with 5-flutes my feed of 500mm would be similar to a 100mm feed with your single point cutter


 

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