Hot Knife for cutting parts from sprues?

Model Railroader General Discussion (Model Railroader)
1

Working in n-scale, some of the kit parts are extremely fine, and I’ve damaged some here and there cutting from sprue with standard X-acto with no. 11 blade. I was wondering if anyone has tried using a hot knife to cut parts from sprues, and whether the results were any better? (Sometimes my sprue cutter won’t fit.)

2

Ken,

I’ve never tried a hot knife but here’s a couple of suggestions to try:

  1. Buy yourself a quality pair of flush-cutting (vs. flesh-cutting) wire cutters with a narrow head. These do a really nice job of getting at those hard-to-reach sprue supports.

  2. If you support the part from behind BEFORE you cut it with a #11 blade, it’s far less likely to break the part. The edge of a small block of 1x2 has worked very well for me in the past.

Tom

3

It would seem to me that the hot knife would be melting its way through the plastic, rather than cutting. This being the case, how would you prevent the attached portion of the part from mooshing (is that a word?) from the heat?

4

There is a tool specifically for this, called a sprue cutter; they look like tweezers, but with sharp cutting points at an angle. Greatest thing to use, can clip teeny parts right next to them without harm. Check Micro-Mark’s online catalog.

5

Here 'tis.

http://www.ares-server.com/Ares/Ares.asp?MerchantID=RET01229&Action=Catalog&Type=Product&ID=15212

OR, you can get a de-spruing tweezer:

http://www.ares-server.com/Ares/Ares.asp?MerchantID=RET01229&Action=Catalog&Type=Product&ID=82393

Ain’t technology grand?

Andre

6

I’m with Mark and Andre–sprue-cutting tweezers should be the answer. I’ve got several pair in different widths, and they work like a charm. To my way of thinking, a hot knife would not only melt the sprue but quite possibly the part you’re trying to separate–especially in N scale. I mean, those parts are TINY! [:P]

Tom [:)]

7

I use a small fingernail clipper.

8

Hey Fellas,

I don’t know if you noticed but the OP stated in his very last sentence that he already had sprue cutters and that they were too short. I guess it depends on which pair of cutters he already has.

Tom

9

Thanks all for the quick responses.

Those $37.95 cutters are a little pricey for my budget – Jeffrey, I may try the clippers, hadn’t thought of that. I admit, I’d rather spend the money on trains than more tools. Tom, I’ll also give a small pair of flush-cutters a try; they’re in the toolbox.

Bob – The sprue cutters I have are pretty good on most parts, but sometimes tough to get to a tight fit. Hoped I wouldn’t have to spring for another pair.

I do back up my cuts, but still have broken some pieces; not all that bad, they glue back together easily enough and can’t tell the break.

Again, thanks for all the help.

10

I Found these at My local Pharmacy, I can’t remember the exact name of them but they work really nice for cutting most parts off of sprues. The angle of them makes it easier to get into small areas…And they are under $5

11

Hi!

I would NOT get a hot knife anywhere near those parts sprues! Pick up a pair of “sprue cutting tweezers” from Micromart and that should take care of the problem.

Mobilman44

12

Sometimes you can cut the sprue apart - a section of it away from the whole sprue. This makes it easier to position those small parts so you can cut them off easier. My [2c]

13

Some sprue cutters will break the parts. I had this problem when using mine (Made by Testors, got it for 12 bucks) on P2K frieght car kit’s grabs and stirrups. I use a #11 blade for those.