How do you make decent looking limber/vent holes?

[roedj]

Every time I try to open up the limber holes on a sub it looks like I did it with an air hammer. I'm just not good at doing this. What is the secret of making nice holes? Do you use a metal guide, special tools, CNC mill - what?

A friend of mine and I are slowly working on a Sheerline Type 2D and we're using a mill - not CNC - to open up the holes. We've been working on it for over two years now with no immediate end in sight. Every time I read some build thread where the builder says something like, "I opened up the bazillion vent holes in a couple of nights." and the results look perfect I just shake my head and wonder - how the @#$# did he do it? - here's looking at you, Bob - I love your work on the OTW Type XXIII.

Help - please,

Dan

[RCSubGuy]

In my experience it's all down to the right tools. I have small square, rectangular and circular files with fine teeth that do a respectable job. In the end, you get real good, real fast when you have a hundred to do...

[roedj]

OK, but how do you keep the edges so straight? Do you use a metal guide, perhaps one that's case hardened, so the file doesn't wear it down too?

Dan

[He Who Shall Not Be Named]

Every time I try to open up the limber holes on a sub it looks like I did it with an air hammer. I'm just not good at doing this. What is the secret of making nice holes? Do you use a metal guide, special tools, CNC mill - what?

A friend of mine and I are slowly working on a Sheerline Type 2D and we're using a mill - not CNC - to open up the holes. We've been working on it for over two years now with no immediate end in sight. Every time I read some build thread where the builder says something like, "I opened up the bazillion vent holes in a couple of nights." and the results look perfect I just shake my head and wonder - how the @#$# did he do it? - here's looking at you, Bob - I love your work on the OTW Type XXIII.

Help - please,

Dan

Accurate punching out of limber and flood-drain holes is a series of operations shared, to some degree, by successful scribing. Both tasks require accurate plans and pictures; a means of accurately lofting the location and shape of those holes from documents to model; marking those holes onto the model with accuracy and repeatability; and finally (if you want holes) selection and use of the right tools to punch out thos bazillion holes.

Documentation is everything! Accurate orthographic presentations (plan, profile, and sections). You can't mark out the model with any precision without this.



Lay-out (marking off) the location and shape of the holes is done with a stencil. You scribe the shape of the hole onto the model (pen and pencil lines are too sloppy). It then becomes your job to cut within the boundries of the engraved shape.









Use of a milling machine speeds the task along and gives precise X and Y positioning, and the tools will render the same cut, no matter how many holes in a row. But the machine presents problems of holding the work (usually round, or half-round) securely on the cross-slide.





And the tools used to punch out those gazillion holes:







More pretty pictures here: http://s262.photobucket.com/user/dme...-drain%20holes

David

[roedj]

David,

Thanks for you reply. But, as usual, I have a question.

Are you using the drill press to merely drill a starting hole and then you follow up with hand filing or are you using the drill press as sort of a poor man's mill, using a mill tool, to produce the whole hole? My buddy and I are using milling tools with his mill and an X-Y table to slowly, and I do mean slowly, open up the vent holes on the Sheerline 2D. We've finished the hull holes and are now doing the bazillion deck holes. Our setup looks almost exactly like yours portrayed in the pictures. The work looks great but the progress in painfully slow. If I were to attempt to open up all the deck holes by hand I'm sure the end result would look like I did it by hand, i.e., ug-a-ly.

Dan

[greenman407]

David,

Thanks for you reply. But, as usual, I have a question.

Are you using the drill press to merely drill a starting hole and then you follow up with hand filing or are you using the drill press as sort of a poor man's mill, using a mill tool, to produce the whole hole? My buddy and I are using milling tools with his mill and an X-Y table to slowly, and I do mean slowly, open up the vent holes on the Sheerline 2D. We've finished the hull holes and are now doing the bazillion deck holes. Our setup looks almost exactly like yours portrayed in the pictures. The work looks great but the progress in painfully slow. If I were to attempt to open up all the deck holes by hand I'm sure the end result would look like I did it by hand, i.e., ug-a-ly.

Dan

No Problem, practice first. Take a piece of scrap plastic, scribe a small square or rectangle. Then take a hand drill and drill out a hole right in the center but of course smaller than the outside edges. Then put a small SHARP file in the hole and file the opening open all the way over real close to the edge. It wont take but a minute. Stop right before you reach your line. Then tackle one of the other sides. Once you got all four sides pretty close, go in and go all the way to the line.
Take a look at your files. Some flat modelers files have cutting teeth also on the edge. They are useful in making a sharp corner, but after that corner is made, use a file with NO teeth on the edge to file down the next side without cutting into and ruining the corner that you just finished. After you do a couple it gets MUCH easier. LOOK..................If I can do it.............so can YOU!

[He Who Shall Not Be Named]

David,

Thanks for you reply. But, as usual, I have a question.

Are you using the drill press to merely drill a starting hole and then you follow up with hand filing or are you using the drill press as sort of a poor man's mill, using a mill tool, to produce the whole hole? My buddy and I are using milling tools with his mill and an X-Y table to slowly, and I do mean slowly, open up the vent holes on the Sheerline 2D. We've finished the hull holes and are now doing the bazillion deck holes. Our setup looks almost exactly like yours portrayed in the pictures. The work looks great but the progress in painfully slow. If I were to attempt to open up all the deck holes by hand I'm sure the end result would look like I did it by hand, i.e., ug-a-ly.

Dan

How dare you, sir!!! ... the OUTRAGE!! That's a proper three-axis milling machine, not a common drill press! Indeed ...!

OK ... its a Chinese, Harbor Freight POS. BUT! ... its rock solid the gibbs keep everything tight, and the spindle shaft bearings are sound. If only the damned thing could cook, Ellie would be in trouble.

I use 'punching' end-mills, using them to penetrate the work with the Z-axis motion, lock the spindle down, then use the X and Y-axis motions to approximate the hole geometry. I use the smallest radius end-mill to leave the smallest radius corners to the hole -- requiring just a little work with square sectioned second-cut file to sharpen up a hole that features right-angle edges. But, I don't work all this out on the model. I cut a piece of scrape and attack it with the machine to work out the hole spacing and hole geometry, logging the axis indexing dial measurements to insure accuracy of repeatability. Makes a row of equally spaced, specifically shaped holes an easy and quick matter. The hard part is working out a holding fixture to secure the work to the cross-slide bed.

Here are various means of holding and positioning the work to the bed:









More pretty pictures here: http://s262.photobucket.com/user/dme...achine%20tools

David

[roedj]

David,

Thanks, again. Your setup mirrors ours. The Sheerline 2D is quite large so we built a special jig to rotate the hull so that the hole to be drilled is mostly perpendicular to the end punch mill tool. We've also added a digital readout to the X/Y table - never going back to the old read the dials again.

I'll keep practicing.

BTW, nice to see you wearing eye protection in the latest pictures. The earlier ones you weren't wearing any.. I know you're mister macho but let's be safe out there.

Dan

[He Who Shall Not Be Named]

David,

Thanks, again. Your setup mirrors ours. The Sheerline 2D is quite large so we built a special jig to rotate the hull so that the hole to be drilled is mostly perpendicular to the end punch mill tool. We've also added a digital readout to the X/Y table - never going back to the old read the dials again.

I'll keep practicing.

BTW, nice to see you wearing eye protection in the latest pictures. The earlier ones you weren't wearing any.. I know you're mister macho but let's be safe out there.

Dan

Yeah. I've taken enough chips in my time. recently I burned both with some molten white-metal that steam-flashed on me. God putting his foot up my back-side. I'm much more careful with the eye-gear since then.

David

[roedj]

I've been looking online and in stores for a special file - let's call it the "open up the limber/vent holes on a model sub" file. I can find rectangular files where the long side has the teeth and the short side is smooth but I want one that's the opposite of that - teeth on the short side and long side smooth. These files should typically be small on the short side for holes in 1/96 scale models.

Does it exist? (I assume so) - where can I purchase it?

Dan

[He Who Shall Not Be Named]

I've been looking online and in stores for a special file - let's call it the "open up the limber/vent holes on a model sub" file. I can find rectangular files where the long side has the teeth and the short side is smooth but I want one that's the opposite of that - teeth on the short side and long side smooth. These files should typically be small on the short side for holes in 1/96 scale models.

Does it exist? (I assume so) - where can I purchase it?

Dan

Just take a file that has teeth on all faces, and grind off the teeth you don't want. Duh!







You people!



David

[roedj]

I hate you so much - that's just so effing simple.

Dan

[He Who Shall Not Be Named]

I hate you so much - that's just so effing simple.

Dan

LOL. I know. I wish I had a buck for every smart idea that sprang into life, but only decades after I had been doing something ass-backwards. I teach well because I've spent most of my life recording my ****-ups and corrective actions. I'm that donkey that requires a two-by-four up side the head before being able to figure something out.

[trout]

I'm that donkey that requires a two-by-four up side the head before being able to figure something out.

Good to know I am in good company! LOL

[Subculture]

Another method I've used in the past is to use some insulating tape on the edge of the file I want blanked off.