Vent line designs

[HDS]

I suppose most of us here has seen the intricate patterns on certain custom molds that tend to be seen a lot around here ;)

http://i.imgur.com/gdYQs.jpg

I showed a picture of a Mihec mold to a guy, this picture above infact, and he said that the maker was running the something or other too fast in his mill. He seemed to think the vent-line patterns where a flaw. I told him they where vent line patterns and he said thats a strange way to make a vent line.

So I'm sorta wondering why the mold lines in some designs follow these patterns rather than the old fashioned straight lines, any advantages to it for the user or producer?

As for the picture in the photo I did not take it, can't even remember where I found it originally.

[MikeS]

I don't know for sure, as I don't know exactly how MiHec moulds are made, but by looking at it, it looks like he did a pass over the mould blocks (before the cavities were machined) with a tool called a 'fly cutter' with a fairly fast feed rate to make those vent lines. The advantage of making the vent lines this way is that it's a fairly easy way to make vent lines that function every bit as good as more traditional straight vent lines. Traditional straight vent lines are probably made with a gang of slotting saws, tools that are much more delicate than a fly cutter, and if just one of the slotting saws breaks while cutting the vent lines, it ruins the block(s) that it was cutting.

I would also think that using a fly cutter is a much more CNC friendly way to make the vent lines, and I know that MiHec moulds are made on CNC machines. I'm not 100% sure on this last part, I've never run a CNC machine, so don't know all the ins & outs of running one.

I do know that these style vent lines work every bit as good as any other style of vent line. One thing I've always wondered is why mould makers don't put vent lines on the tops of the blocks? I have one old SAECO dual cavity mould, and it has vent lines across the tops of the blocks, and I never have base fillout problems with that mould.

[Cap'n Morgan]

Mihec is obviously using a fly cutter for cutting venting lines. The smart thing is you can use the same cutter for taking a finish cut one the mold flats - and then lower the cutter slightly and run it across the surface one more time with slower RPMs & higher feed to cut the vent lines - a mere five seconds extra cutting time to add venting to a mold!

And, yes, vent lines on top of the mold is important for base fill out. I'll even say they are more important than vent lines on the cavity sides, as long as the air can escape between the sprue hole and the spout.

[blackthorn]

Some of the old Ideal, Lachmiller and other moulds had no vent lines at all on the face of the block(s) and they worked fine!

[John Boy]

Some of the old Ideal, Lachmiller and other moulds had no vent lines at all on the face of the block(s)Normally the Ideal tong tools had no vent lines

http://cartridgecollectors.org/antiquereloadtools/fig10.jpg

[GLL]

An old unvented IDEAL 454190.

Jerry

http://www.fototime.com/720B35FD551CEF8/orig.jpg

[John Boy]

GLL, what weight bullets does your Ideal 454190 drop at?

[MtGun44]

Save money and make vent lines really easily by running the flycutter with a power
crossfeed. Smart, makes great vents without any difficult setup.

Bill

[JIMinPHX]

I make curved vent lines like that when I make mold blocks & sprue plates. The tool that I use is basically a modified fly cutter. I use an "E" profile bit that is held straight up & down as opposed to using an "AL" or "AR" profile bit held at a steep angle like you normally would in a fly cutter. It works well as long as you don't go too deep with the cut. A few thousandths is all you want. The Lee 6-cav molds have vent cuts like that too.

[MiHec]

Yes, it is fly cutter. :mrgreen:

It is the easiest way to cut the vent lines and I think they do what they suppose to do :mrgreen::mrgreen:

[DukeInFlorida]

So, once you cut them up, how long do you have to cook em before you serve em??

http://t1.gstatic.com/images?q=tbn:ANd9GcRjAd2CkQiAJYRiWqIINIuezMUPHFJHg ce-t9tX2Wfx6RS94aWnyQ

Thanks for the schooling on vent lines.

[Doc Highwall]

I think that one of the benefits of vent lines like MiHec uses over straight vent lines is if one gets clogged it can still vent by the fact that it crosses multiple vent lines.

[cajun shooter]

I have a Lachmiller 358 mould that is a two cavity and no vent lines. I first bought it and came home and was very worried about how it would handle the pouring of the alloy. To my surprise, it works fine. I also have an original Ideal mould for the 44-40 that is only part of what was called a loading tool. It primes and seats the bullet. It also has no vent lines. It seems to me that a mould that has no lines would drop bullets with air pockets as it can't burp, so to speak. I don't know if that is correct or not, just me thinking on how things work

[SwedeNelson]

We did some very extensive research in to our vent lines.
Cut with a fly cutter in a radial pattern.

http://i69.photobucket.com/albums/i80/swedenelson/Bodyandventlines.jpg
Did some micro inspection of the parting line and was very pleased with the out come.

http://i69.photobucket.com/albums/i80/swedenelson/Noseventopenings.jpg

Swede Nelson

[44man]

I use a fly cutter with a special ground end. I cut only one block face, that is enough. I turn it by hand, .002" deep and advance by .025".
The top is never vented but the very best surface is what is left by the end mill when I surface the tops before using the cherry. The end mill on the sprue plate is also the best.
No surface is dead smooth or polished. The tops with a thin film of Bullplate or Mold Prep is super because the marks left from an end mill will hold the lube.
The vents on that Mihec mold are perfect.

[Echo]

Yes, it is fly cutter. :mrgreen:

It is the easiest way to cut the vent lines and I think they do what they suppose to do :mrgreen::mrgreen:

And they are PURTY, too!

[JIMinPHX]

Swede, those are great pictures. They really show what is going on in there.

If you don't mind me asking, how deep & how wide do you cut your vent lines?