Cutting Cast Acrylic on a table Scroll Saw - Overclock.net

CattleRustler · 06-24-08

Yesterday I picked up a Hitachi 16" Scroll Saw station because I want to be able to cut intricate patterns in stuff. Today I need to cut some cast acrylic to finish off my Gumdrop project. The saw can do 400-1600 Strokes Per minute, I picked up two types of blades: 11.5 tpi and 46 tpi spirals. What SPM and blade type will work best for cast acrylic with paper backers on both sides? Also my test/scrap piece doesnt have the paper but has a clear film on both sides, should I remove it and replace with masking tape to better mimic the real pieces for testing?

any help/info/advice you can give on cutting cast acrylic with a scroll saw would be great. if you have pics, even better

thanks

(hopefully after today I wont need to ask so many questions about acrylics

)

*radodrill* · 06-24-08

When cutting acrylic, a high tooth count is critical; I'd probably start with the saw at a medium speed then go from there.

CattleRustler · 06-24-08

so your saying i am better off with the 46 tpi spiral? hmm. I have seen else where people saying use low tooth count, and low to medium speeds.

wastedtime · 06-24-08

High TPI and medium speed will do the job. I have noticed a blade with low TPI will snag on the acrylic and lead to less than optimal cuts.

A good quality blade will also go a long way in ensuring a good cut.

I wouldnt bother taping the test piece to mimic the real pieces. But yes if you are trying to cut a piece with the clear film you are better off taping it with masking tape because :
1. You cant draw on the film.
2. It has a tendency to peel off easily.

Syrillian · 06-24-08

Heya CattleRustler.

I don't know it all acrylic that has the clear/plastic backing is the same (as in manufacturing technique), but from my experience that type of acrylic is extruded. You may want to to test your saw out on the same type of acrylic that you plan to use (which I take it, is cell-cast). If you are going to use the plastic-coated piece for testing, then leaving the plastic in place may be in order.

I have found that the protective backing of the plastic type to seperate too easily. In the past I have run blue painters tape along the perimeter of the piece to ensure that it does not come off. The downside to that is that occasionally the tape will hinder movement due to it snagging... not something one wants when making precision cuts.

In the past I have needed to go back and make cuts on pieces that I already thought were done (Girface's Testbench). I covered the surface in blue tape with a single layer wherein each strip did not over-lap (causes "catching").

Radodrill has already commented on tpi and rpm; Although I am not a professional, I have the inclination to agree with him based on my experience (or should I say mis-experiences -lol)... high tpi for sure.

I have never used a scroll saw on acrylic, so I am not qualified to comment directly, but I have used a jig saw (sabre saw). The specialised blades for acrylic come in 2 types: blades for < 1/8", and blades > 1/8".

The blades that are for < 1/8" have a double row of teeth.... since both of these tools' cutting actions are perpendicular to the piece being cut, perhaps the same logic applies: See if there is a plastic-specfic blade.

I look forward to your progress, as I have been in the market for a scroll saw (need to save some scratch... and throw more dishes away (read: donate) so there is some storage space in the kitchen).

Kudos to you for spending so much time on something for your child.

Good Daddy! ...World needs more of 'em.

*radodrill* · 06-24-08

Quote:

Originally Posted by CattleRustler

so your saying i am better off with the 46 tpi spiral?

I'm not sure if a spiral bit is best or not (I have never used a scroll saw so take this FWIW); but from what I can tell, the spiral blades cut from all sides allowing more intricate cuts but may be a bit harder to control than a straight blade.

The high tooth count, on the other hand, is important since it makes finer cuts, is not as aggressive, and is less likely to chip the material. The reason why people who use lower TPI blades recommend lower cutting speeds is that with the slower speeds it doesn't cut as aggressively and thus isn't as likely to chip; but it is still more likely to chip than with high TPI blades.

Even with high TPI blades you don't want to go too high on the cutting; at very high speeds it melts the plastic instead of cutting

**The Duke** · 06-24-08

As temperamental as molded acrylic (non-lexan type) is this should prove to be interesting.
Most molded case side covers are a common acrylic and tend to crack easily.

CattleRustler · 06-24-08

thank you all for the help - it is very much appreciated +reps all around

I will start with the 46 tpi and medium speed, on a piece that has the paper backing on both sides, which is the same as the real piece.

another question that you guys might be able to answer: The plate part of the machine seems to be coated in a greasy/smelly machine oil, I guess from the factory. I am guessing I need to clean it all off before using, right? Also I have seen people say that they coat their work plate with some kinda "wax paste" or "paste wax", does anyone know what this stuff is, and if its necessary

I recall them saying it was to make their work piece slide/turn more easily on the plate - thanks

*radodrill* · 06-24-08

I'd certainly clean off as much of the oil as possible as it could potentially react with the acrylic; the reason why it's there is that the oil helps protect the metals and keep them from rusting when in storage for an extended period of time (same reason why old guns should be oiled and wrapped in an oil-impregnated rag for storage)

The need for a surface lubricant (i.e. wax) is dependent on what materials you're working with and how much friction there is between the workpiece and the surface.

Quote:

Originally Posted by The Duke

As temperamental as molded acrylic (non-lexan type) is this should prove to be interesting.
Most molded case side covers are a common acrylic and tend to crack easily.

Also very dependent on the formulation of the plastic; factory side windows (in addition to being thin (1/8"-3/16"), which isn't helping) are generally a very stiff but also brittle formulation, while a lot of the acrylic sheet you'd buy isn't nearly as brittle and thus not quite as stiff. The more brittle the acrylic is the more likely it is that it'll chip.

*repo_man* · 06-24-08

Wow, some really good info in here!

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Cutting Cast Acrylic on a table Scroll Saw

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