Thread: Problem cutting lid from box

Two suggestions:

1. Set the saw blade height to just NOT clear the thickness of material. Just enougth material is left so that you can easily cut thru it with a very sharp knife. This will keep the box intact and save you the effort of the packing pieces. The tiny amount of kerf left will sand away very easily. Experiment on some scrap to determine how much to leave before it becomes too fragile and breaks away.

2. Don't use a sliding jig because if there is any variation in the jig material thickness or constuction it will translate to your job. With the box remaining intact it should slide on the fence easily with you maintaining total control. Use a sacrificial piece at the back of the cut to prevent chipout.

Perhaps check that the blade is square with your fence/jig.

I know you have checked that your fence and jig are square with the mitre slot but the error may be with the blade instead, in any case it will eliminate this area.

Steven.

Many thanks for this Bodhan. I find this jig makes it easier to control the box, pushing the jig and not the box which is pressed against the jig and fence. Will try reducing the height on the next box.

Did some further testing. Found the jig had a bit of play in it. It was not a very tight fit on the fence, so I put a few layers of masking tape on the right hand upright, which brought the left hand upright tight against the fence for the full travel. And it was parallel to the mitre slot, could not feel any difference when the jig and slot were aligned

Put a piece of 200mm long MDF flat on the table against the jig and ran it through the blade. The resulting difference in width of the resulting MDF after the cut was 0.1mm, narrower at the front edge than the rear edge.

Strange, and at odds with the final width of cut above, I also noticed that as the MDF was pushed through, the last piece of the board after it is cut by the front (nearest) part of the blade is kissed by the rear part of the blade as it finished the cut. Does this mean the blade is not parallel to the mitre slot and the jig?

PS Just saw Spokeshave's post - arrived while I was typing this. Same question about blade alignment! Will check, when the shed gets a bit cooler later on today

I wouldn't bother with the tablesaw - I see a big bandsaw in the background and that will always get you a great cut if its set up properly.

A Resaw King or the Lenox Woodmaster CT blades will give you a smooth clean cut.

I just used the LW this arvo to top off 8 new boxes

I'm with Bohdan. Rather than use a jig, I use a magnetic fingerboard to make sure that the box stays against the fence. Also, make sure that the fence is perpendicular to the saw table - you can adjust it using the nylon screws at each end of the fence mount.
The fingerboard should hold the box upright against the fence. When you feed the box through, guide it by sitting your hands on the fence, rather than on the high side of the box.
I use a 1/8" blade, as I've found the 2mm one wobbles and doesn't give quite as good a cut.

Hope this helps.

Originally Posted by Dengue

Many thanks for this Bodhan. I find this jig makes it easier to control the box, pushing the jig and not the box which is pressed against the jig and fence. Will try reducing the height on the next box.

Did some further testing. Found the jig had a bit of play in it. It was not a very tight fit on the fence, so I put a few layers of masking tape on the right hand upright, which brought the left hand upright tight against the fence for the full travel. And it was parallel to the mitre slot, could not feel any difference when the jig and slot were aligned

Had a similar problem when doing a production run of boxes... and found that one way to eliminate any problems with play/sloppy construction is to build the jig in such a way that instead of sitting between the box and fence it pulls the box against the fence.

I'm lucky in that I use an old Wadkin panel saw that has a nice deep fence I can actually have the jig wrap over and use sprung wheels against the back of the fence to provide this pulling pressure. It doesn't look like you have the same luxury, but perhaps it's something for you to consider in Jig Mk II?

I agree with woodpixel. I have made numerous boxes and now always cut the top off using the Bandsaw. If the saw is set up properly and the fence is straight it is then only a matter of making sure that you cut slowly and that the box stays hard against the fence from top to bottom. I always get a good alignment and a good cut. To smooth out the edges i then put the two pieces through the drum sander and do a skimming sand and this works a treat. I put the boxes through diagonally and as i said it is only an absolute skimming sand. If you do a hard sand and try to get it right the first time you will wind up with a dish out of the sides. Well worth a try.

Good luck

Router

I'm in the bandsaw camp as well. I've only made one box where I cut the top off as the lid, and using the bandsaw and Resaw-King blade I got a really nice clean parallel cut. The thinner kerf blade meant less waste as well and because I was cutting through dovetails this still left me with a good match / look. Just make sure the blade is nice and perpendicular to the table and shim the box with tape if you have to (if the box sides aren't perfectly perpendicular etc).

Hi Dengy

I'm not an expert at this, so others may have a better method.

What I do is first tape the box - blue tape will do - and mark the cut line along this. The tape is to prevent any spelching.

I do not use a jig - it can only add extra errors - and use my bandsaw. If I were sawing a box this moment, I'd use the 1" re-saw blade that is in it for its ability to track straight. Narrow blades are more vulnerable to wander

Once the box lid is separated, I lap each side on 240 grit sandpaper to remove saw marks and ensure all is coplanar.

Regards from Perth

Derek

I agree with those above in the bandsaw camp. I also use the big 25 mm tungsten carbide tipped blades (in my case a Lenox blade) and always get a nice smooth, straight cut (as long as the blade is tensioned enough). Thinner kerf too, also as said above. When I tried the table saw method (because my tct blade was blunt from cutting a lot of Bluegum) I had the same problem that you are having - even when I did not cut all the way through. Lots of sanding and less-well-matching figure later the box was OK but not spectacular so it was back to the bandsaw (with a sharpened blade) for the next box.

Thanks Xanthorrhoeas. Do you sit the rear of the box on a piece of wood so it angles into the front and rear box sides?

Many thanks to all the contributors to this thread, it contains some very valuable information, and I really appreciate the way you share your knowledge and experience. Great Forum !!

I measured my sawblade, on the same tooth front and back of the table, and found it was within 0.002" parallel with the mitre slot. I now suspect something wrong with the fence, but that will take time to explore, and I only have exactly two weeks to Christmas Day, and three boxes to finish. The one being made at the moment is for my youngest daughter, a photographer in Melbourne, who selected the lid style. It is made of 10mm thick purple heart box sides, and 16mm thick birdseye huon pine lid, with V grooves for the rays. Very arty, not my style, but very definitely hers. The box is 300 L x 200 W x 100 H.

Not game to use the jig any more, based on the expert advice in posts above, and suspecting some curvature in the fence, I decided to go along with the bandsaw camp above and try it out on a 3/4" steel tooth blade. The box lying on its side was 200mm high. The base had been flattened, and each of the sides was at a right angle to the plane of the base.

Bit of a disaster!! As you can see from the first few photos, there is a small 0.5mm gouge into the lid, just past the entry point. I did raise the box so it cut the front edge at an angle, quite neatly actually. This gouge happened with the box sitting on the table, probably as I was changing from an angle approach to the flat approach, having passed the leading edge on the box.

It all came undone when I tried to raise the front of the box on exit. Had not thought about it in advance, and gouged the rear edge of the box with the teeth. The lid was flapping around a bit at that time. Bugger! The cut was not dead smooth as I had expected from the above pro-bandsaw camp . So, I spent a lot of time flattening the lid and the box mating surfaces on 240 grit paper glued to a sheet of plate glass. Took a fair while to get it flat.

The good news is, I only lost 2mm total in cutting the lid, and you can hardly see the joint line of the box and lid. And that would have been much less loss if I had done the cut neatly, especially the entry and exit cuts. Can anyone please tell me how this is best done?



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Apologies for my absencee... Under the pump to get orders out!

This technique by Andrew Crawford is the same as I use: Sawing a box in two with Andrew Crawford - YouTube

The entire box lid is against the fence. The bottom only touches the table top so the blade doesn't pull it down. This is so the lid is cut the same thickness from front to back. One only has to eyeball that the fence is parallel to the blade.

For clarity: the BS table top isn't a reference, the fence is the reference.

The technique is scary as hell, but it works nicely.

The last thing I do is sand the fresh cuts on a huge sheet of 180 grit from The Sandpaper Man. It is 600 wide and a metre long simply adhered to a thick bit of MDF with Super44 spray (love the stuff. Buy it from Eckersleys).

Thanks woodPixel. Who am I to question Andrew Crawford, but that technique does not look right to me, where he is jamming the lid and the box together against the blade, after the most of the box has passed the blade, to make the final exit cut. Shouldn't he put a 1mm spacer in the right hand side of the box to match the kerf?

Also, is it necessary to put the lid against the fence? I normally use the base of the box as a reference plane.