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Tricks of the trade

MAKING GRATINGS
This is one way to make gratings so they sit properly inside the coamings and head ledges.
This is based pretty much on how Bernard Frolich describes making them in his book The Art of Ship Modeling. There are various thickness slitting blades so an appropriate thickness slitting blade can be chosen to have ledges, battens, and the openings wind up around two inches to three inches rather than the gigantic openings we often see in kit gratings. Total time needed to make enough gratings for a model is about 2 hours plus time for the assembled gratings to dry when sprayed with lacquer following step 6 below.

Start with a slat of close grained hardwood like pear, castello, Alaskan cedar, Europeon boxwood or similar species.

1. Make a board with a plywood board and glue a guide and cut a slot for the blade so the distance between the edge of the guide and blade is the size of the opening that you want.
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2. Make shallow cuts
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4 Make deep cross cuts that do not quite cut through the board.
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5. Make batten material
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6. Inserting battens. Once they are all in place spray with lacquer to glue them in place.
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7. Sand away excess wood on the bottom and clean up any remaining unwanted wood. The piece on the right is nearly sanded through.
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8 Assembled grating stock from which individual gratings can be cut. As can be seen in the photo, some light sanding is needed to clean up this stock piece.
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It is best to cut the pieces of grating as close as possible to the size in the drawings so there is a solid edge all around. Openings with hanging ends of battens and ledges was never done like in the second photo below. The battens always ran fore and aft. Once the gratings are made, then make and install the coamings so there is a tight fit.
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Delusional kit gratings below. The gratings never should have open holes along the outboard edge. The holes were normally between 2" and 3" square so a sailor's heel could not go into it.
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I realize not everyone has the tools, but for those that do, I hope this will be helpful.

Allan
 
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Hi Allan, very similar to how I am doing them now. I think the problem arises is when you cut the grooves off at 90 degrees off the original and with the slight movement of the saw blade, even sharp blade teeth, does cause the small square section to be destroy with the flexing of the saw blade, regardless how hard you try to go slow. I do here the blade making this sound like chatter.
I was wondering if after cutting the initial grooves, a wash is added to the wood of very thin PVA glue (like a thin wash) and left to dry completely, before the other cut is made.
What I have found is the second cut on my setup I must cut the side of grooves first and then turn it upside down to do the finishing cut to slice off the battens and then I interlock. You will notice my depth of cut is only just on halfway thru the wood. I believe doing this method I am doing is ok, but I think I may try the PVA Glue wash to see if that stops the thin square bits from breaking off. I will go back to my log with the results.
I do feel I may have to run over the first lot of grooves again to clear out the PVA residual.
BTW I am making this grating up at 1:48 scale and the opening is at around 1.31 mm. My saw blade is having a width of 1.2mm. I bought this saw blade in mind for making grating and is a Proxxon Blade product which I was able to purchase at a place that sells a few Proxxon parts, luckily. The slit after sawing is around 1.25 and I reckon that is close enough for me. Also, it meets the requirements of the grating opening size.
 
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saw blade, even sharp blade teeth,
Hi Gary, Thank you very much for your input. ThumbsupThumbsup

Are you using a cutting blade or a slitting blade? I tried with a cutting blade the first time I did this years ago and I had the same issues as you described. The slitting blade does not have these problems in my experience. The end rows sometimes get knocked about, but I usually make the initial blank well oversized then cut off pieces at the sizes I want as I need them. A key item is what wood is being used. I would love to use true boxwood, but the cost is prohibitive, so I usually use castello and it works very well.
What I have found is the second cut on my setup I must cut the side of grooves first and then turn it upside down to do the finishing cut to slice off the battens and then I interlock. You will notice my depth of cut is only just on halfway thru the wood.
Sorry Gary, I am not sure what you mean, there are no photos in this post.

Your idea of a thin wash of PVA is interesting. If you do try it please add a note with the results.

Allan
 
Hi Gary, Thank you very much for your input. ThumbsupThumbsup

Are you using a cutting blade or a slitting blade? I tried with a cutting blade the first time I did this years ago and I had the same issues as you described. The slitting blade does not have these problems in my experience. The end rows sometimes get knocked about, but I usually make the initial blank well oversized then cut off pieces at the sizes I want as I need them. A key item is what wood is being used. I would love to use true boxwood, but the cost is prohibitive, so I usually use castello and it works very well.

Sorry Gary, I am not sure what you mean, there are no photos in this post.

Your idea of a thin wash of PVA is interesting. If you do try it please add a note with the results.

Allan
Will do, Allan. I will take some photos when I do it. I do show how I cut the battens in the video on YT, but you may have missed it.
 
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In this example, it has turned out to be a failure because I did not follow my normal protocol, as I wanted to try an alternative approach. I am still trying to get it down pat that it will work every time. You can see I went amok with the saw blade. I must point out at this time, before doing another slit, always check you have got the correct depth, as I had not done so, and then on running the piece through the saw again I made a mess of the grooves.

Ok, so what I do is put about that amount of PVA glue ( as shown in the Photo with the glue added into the bottle cap) into the lid and add enough water to dilute it, enough to cover both sides of the piece of wood. Now this is the tricky part, as we know, when water is added to a fragile piece of wood, it does crazy things. It will warp the wood and even to the extent of actually splitting it, so first up, apply the wash to the non-grooved side and then to the grooved side. It will still warp, but by placing the piece between 2 pieces of glass, as I have done here, and adding weight to it, the piece will straighten. Allow at least 3 hrs before removing.
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The wood here is warped, as shown in this pic, before placing it between the glass pieces. You will see I had not cut the grooves on one side yet, as I was trying another method, which did not work.

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Here is the piece now with the grooves added, and I have a pointer showing a bad mistake......
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I will carry on with this again soon.
 
MAKING GRATINGS
Allan,

I checked your book. There are Establishment and contract dimensions for grating ledges and battens. The hatch opening must fit a specific formula for its length and width for the gratings to work out to have a ledge at the fore and aft end and a batten P&S.

I did not see it in Goodwin but does the grating match the arc of the deck?
On a model if the grating can be bent to the arc it would have match the geometry. I think it would need support under the middle of the ledge.
Goodwin shows a shelf for the ends of the ledges. I did not see shelf running athwartship.

I see the possibility of splits and cracks if the grid is bent. I see the battens and the ledge spacers appearing to be wider than dictated if the arc is sanded.
Is this a real but too small a difference to matter sort of thing? Arm chair experiments cannot determine that.

Slitting saw blades have no set. They are perfect for shallow grooves as that is their purpose. With no set more than one of them could be used together - except that the Jim saw arbor is not wide enough if it is 3/8".

I dusted off my Jim saw and cut some 1/8" Maple. A very narrow slitting blade was already mounted. (From an unsuccessful keel rabbet experiment I think.) I did not change it . It seemed to do OK as an edger: rough edged stock. But when I used it to turn the 2" stock into 1" stock the blade cut a right handsome serpentine path. Some lessons need to be relearned.
Anyway, a blade with zero set is pretty much necessary for cutting grating channels.

I wonder if there are small diamond coated bits that can route the channels?
 
I wonder if there are small diamond coated bits that can route the channels?
I would guess this is possible but as using slitting blades works, I have never given that a try.

I have no idea how much round up is needed on the gratings in some cases, it has only been a guess based on contemporary models of the same era as the model on which I am working. Some show the top of the head ledges with a lot more rounding than the deck but the gratings do not always match the head ledges in those cases. Lot of guess work. If it's a severe amount I have made the grating extra thick and sanded the round up on top and leave the bottom flat. If it is slight I have heated it with a hot air gun and make it the meat of a sandwich and using the two pieces of wooden "bread", one with a concave shape, the other with a matching convex shape. Never had them break apart or otherwise be a problem.

here are Establishment and contract dimensions for grating ledges and battens.

If, and that is a BIG if these days, I remember correctly, the only scantlings for grating ledges and battens I have come across are in Steel which were used in the scantlings book, but I have no idea if those dimensions are valid for earlier or later time periods. Contracts and the Establishments give the overall dimensions but not the battens and ledges. Lacking better information, I doubt anyone would fault them. Depending on the size of the ship the ledges are from 2.5" to 3"thick and 3"to 4" thick. Battens were 2¾" broad and ¾" thick with openings no more than 2¾" square. As I mentioned before I take the dimensions of the inside of the coamings from the drawings or contract then make the gratings to match as closely as possible with a solid out edge. Then I make the head ledges and coamings fit tight around the finished grating.

I hope this is making some kind of sense.
 
Flat bottom spiral milling cutters are available into tiny diameters. Unfortunately, the smallest that I have found in HSS is 3/64” (about 0.045”). Smaller than that you’re dealing with carbide. Not gratings, but I have been cutting grooves in pear to make homemade miter boxes for cutting 1/32”- 1/8” brass tubing. They produce beautiful clean cuts.

Roger
 
Roger Pallet says "Flat bottom spiral milling cutters are available into tiny diameters. Unfortunately, the smallest that I have found in HSS is 3/64” (about 0.045”). Smaller than that you’re dealing with carbide."
I do not know if this would work to make gratings and I would say be very slow. Although when making the grooves and cutting a strip off, must go really slow with the cutting feed. Cheers.
As Allan has said, he does make the grating bigger to compensate for the first few missing pieces that break. I am trying to find a way to not have any breakage.
I must add I am following a method by another hobbyist and also very similar to how Allan makes them, but he has the same problem as all the other hobbyist that make grating. I think this is a huge topic as you just don't go out there to your Proxxon and Byrnes saws and smash out gratings like they are falling off the back of a truck. There is a lot of wastage and also fixing up of the grating that has to be done. Even Allan says it here, in a reply to me, and the video by the Mr Kenny, on the You tube, says "he gets better at it as he goes along" That is how I have learnt understand about what people say over the years.
So, when I have more info and pics, I am having a little success with PVA wash but knowing how to apply the wash is very important.
I must also add I am using a Carbide saw blade with no rake. So, the groove is flat at the bottom. The width of teeth is 1.25mm. However, I would have like the blade to have many more cutting teeth, as 20 teeth saw blade on a 50mm diameter saw is a little bit less than what is needed. Anyway, I will have more to add as I have already said.
Anyway, I don't think many people are watching to what I am typing, so may just sit back. I am a beginner only, but a Machinist for well over 55 years, not just a backyarder with a hefty pocket to buy books and tiny milling machines. Just doing the best I can and thought I could put something forward, but I see it falls on deaf ears and blind eyes. Comments are welcomed
 
Flat bottom spiral milling cutters are available into tiny diameters. Unfortunately, the smallest that I have found in HSS is 3/64” (about 0.045”). Smaller than that you’re dealing with carbide. Not gratings, but I have been cutting grooves in pear to make homemade miter boxes for cutting 1/32”- 1/8” brass tubing. They produce beautiful clean cuts.

Roger
Hi Roger, so what RPM would you run the cutter in your machine to accomplish a groove? How long would your cutter last, do you think? Would the cutter be Carbide? What depth of cut would you be able to machine a groove in wood?
If the thickness of the piece of wood being machined is around 2.5mm, what method would you use to hold the wood level and firm?
 
cutting a strip off,
Hi Gary,
Are you speaking about removing a damaged row or a row or two to get it to the final size? In that case a fraction of a second on the sander works perfectly. I cannot think of any other reason to cut strips but I am probably missing something here. :( :(
Allan
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