Cutting slots on a detail?

[Jens Andrée]

Although my issue is with a tank part, this should be applicable to all kinds of modelling, hence why I post in the general area.

I'm building an E-100 from Amusing Hobby right now and have come to a halt with the muzzle break. It's just not good enough since it's solid moulded with fake slots instead of them being actual slots.
I fully understand that it'd be more or less impossible to do with the plastic injection method used, but still...



Even if I had a 0.4 mm endmill and a rotating chuck in a vise, I doubt I'd be able to mill the slots out, so the question is - what to do?

I was thinking about jury rigging a scalpel blade to my accurate soldering station, dial in the right temperature that the plastic just melts but doesn't ooze over or burn, and just carefully hot cut/plunge the slots and hope that the spillover ends up on the inside and not the outside as I pull it out?
(the best solution would be to heat the scalpel blade, plunge it and then cool the blade so the plastic hardens, but that seems like too big of a risk to be honest.)

Apart from that I'm out of ideas...

The smallest drill I've got is a 0.6 mm and that's too big. 0.3 mm would be perfect but you can't drill the slots out either so that's pointless regardless.

I would really like to cut those slots out somehow - and I will make some tests with the jury rigged soldering station, but some of you must've come across similar issues before and I'm sure there are other working solutions out there?!

Many thanks in advance!

 

[Gern]

Does anyone make a replacement metal barrel for this gun?

If not.....

How many bars are there running across the slots from front to back along the length of the barrel? I'm looking at the picture and it looks like there are four. If you sand off two of these bars opposite each other, you might be able to cut the slots with a razor saw and then replace the bars with some strip plastic.

If you did it one side at a time, the side you're not cutting would provide extra strength.

 

[Jens Andrée]

I'm sure there's a replacement part out there. At least for the muzzle break, but I wanted to push myself to improve my modelling skills rather than just buying extra parts, so I will try to fix this somehow before buying some aftermarket parts.

There's four rows of slots so your idea would work, but fixing that with two strips later will possibly be even more work than trying to just cut the ones needed, but it's a great idea that would work!
Sadly the rigidity of the part is going to suffer regardless of what method I choose and melting will probably be the least straining, but that's just what I'm thinking.

I've had one more idea and that is to make a tiny, and very thin, cutting disk for my dremel. The diameter can't be much wider than the width of the slots, and it mustn't be wider than 0.4 mm.
If I can make this then I really wouldn't need any real teeth on it since I might be able to friction cut the plastic?
I've got some brass sheets for making PE parts and I can easily etch such a cutting disk!
This is the most promising idea I've got so far...

I've got access to a 40W laser cutter since a few days ago so I can make really accurate parts from now on, but the access is via mail and my friend who owns it is busy, but if etching the brass isn't good enough I can laser cut those cutting disks for sure, and adding teeth is simple in AutoCAD.

I'm going to test the most promising methods on a plastic pipe to start with so I know if it's feasible or not. I don't want to ruin the part completely.
Last option could be to make a PE part of just the middle part of the muzzle break, cut it off and add the PE and hope it looks alright, but making a perfect tube out of brass isn't going to be easy since it's going to be tricky to solder without filling a whole bunch of the slots... sigh.

 

[Tom Rigg]

Could you cut the very front of the muzzle break off where the cutouts start then use a razor saw to cut the long sides (you can do opposites at the same time), than a hot pin or similar and a small file to shape the back (turret end) and then re-attach the front doughnut. If your worried about rigidity, maybe you can plug the end with a wooden cocktail stick or something and saw through that at the same time.
Tom

 

[Jens Andrée]

Could you cut the very front of the muzzle break off where the cutouts start then use a razor saw to cut the long sides (you can do opposites at the same time), than a hot pin or similar and a small file to shape the back (turret end) and then re-attach the front doughnut. If your worried about rigidity, maybe you can plug the end with a wooden cocktail stick or something and saw through that at the same time.
Tom

I'd prefer not to cut in that direction, but using a plug for stability is a great idea that I didn't think of so many thanks for that!
Perhaps an aluminium, or brass, rod to act as a heat sink if I go for the hot cut method? That would ensure that the plastic hardens and not just melt too much... Worth prototyping at least!

 

[Ian M]

Tamiya photo-etched micro saw blades. Very sharp. very thin and cut like a dream. Thin enough to cut a panel line through on a 1/48 scale and still have room to spare.
Failing that you could also try a bow saw made out of a stiff rod and a length of strong thread.... Dont laugh, it works.

 

[Tony]

Looking at it could you not use plastic card circles in 2 sizes - 1 small with the next one being muzz brake size then a small one and so on.

You can usually pick up hole punches fairly cheap on ebay and i am sure you could get plastic card in the thickness of one of those ribs.

 

[Jens Andrée]

Thanks Ian and Tony - both sounds like good methods!
Sadly prototyping is postponed due to me burning the finger tip on my right hand index finger on a too hot glue gun and modelling is more or less impossible until that heals...
But hopefully it's healed enough tomorrow evening to get working again.

The plan is to first try to hot cut the slots, with a heat sink to solidify the plastic as soon as it breaks through, and then ream the hole when done to clean it up.
If this fails I'm going to construct a new muzzle break, or at least the middle portion, by either using brass or thin plastic card. Punching out the rings is actually a very good idea and a kit of hole punches is something I should have - and I don't, not just for this build, so I'm going to have a look at eBay and see what's available?
I have seen a circular cutter, not a punch, before that's adjustable. Not very fast, but perhaps more versatile? We'll see.

Back when I had metal lathes and milling machines things like this would've been much easier to attack, but that's a long time ago and not something I think I will build up again in the garage, but it would've been handy to just turn barrels and such when needed!

I've looked at these etched micro saw blades and it's something I think I shall procure. I might just make my own and test although I haven't got any stainless at home, just brass.
Also "etched" in these saw blades must be "laser cut", or even "stamped" because etching stainless is much more complicated than brass! Very handy tool, and probably a must if you are building air planes with regards to panel lines, rudders and such.

The whole point with the exercise is to improve as a modeller - and make a nicer detail. There are a lot of really nice aftermarket parts out there but if I can do some of it myself I think I will be more pleased with the finished model in the end rather than just slapping on a lot of expensive parts...? At least knowing my limits. If you count hours you spend on a certain detail it's probably a better deal to just buy the part though...

...but that's the hobby I guess

 

[Airfix Modeller Freak]

JLC razor saw or CMK razor saw. I use the CMK version, which is the same, but more available.

 

[Snowman]

Have you had a look at the PE razor saw blades?

Saw Blade set in Photo Etched Stainless Steel, from Airwaves.

* 1 fret of 4 Saw Blades

* Very Fine at 0.12mm thick

** For use with No.5a Acrylic & No.3, No.7 & No.9 scalpel handles only **

https://www.air-craft.net/acatalog/Photo-Etched-Saw-Blades-Set-1.html#SID=77

 

[Jens Andrée]

JLC razor saw or CMK razor saw. I use the CMK version, which is the same, but more available.

Have you had a look at the PE razor saw blades?

Saw Blade set in Photo Etched Stainless Steel, from Airwaves.

* 1 fret of 4 Saw Blades

* Very Fine at 0.12mm thick

** For use with No.5a Acrylic & No.3, No.7 & No.9 scalpel handles only **

https://www.air-craft.net/acatalog/Photo-Etched-Saw-Blades-Set-1.html#SID=77

I knew about razor saw blades but haven't got one in my inventory - which I've realised due to this thread that I should...
Looking at videos on how people use them, mainly in aircraft modelling, made me realise what a useful little tool it is.

The small rounded one Gavin is referring to might just do the trick on my slots too!

Cheers guys!