Chop / mitre saw questions - oak framed building

[AJB Temple]

Morning all

I have the current iteration of the Bosch 12GDL saw, now housed on a Bosch trolley. I will do a review at some point, but in the meantime I have a couple of questions for others who run big saws like this.

Here is the saw, parked up for the night in my timber framing barn.
download/file.php?mode=view&id=55203

And here is one of the two frames I am currently in the middle of making in my spare time, so you can see what I am dealing with. Much of the oak has been air drying for about a year and a lot of it is pretty hard.

download/file.php?mode=view&id=55203

It is actually a very good saw - not perfect.
Question 1 - when I am cutting angled notch cuts in rafters say (4" square oak), I am obviously not cutting to full depth (the depth stop is pretty rudimentary by the way - verging on hopeless as it does not have a wide enough range of adjustment) and need to watch the saw bottom out on the marked line by guiding it visually. Usually I am cutting (say) a 34 degree angle with the saw tilted over to the left or right as appropriate (ie these are not vertical mitre cuts). When I release the trigger, unless the saw has been fully returned to its idle position, the moment the power comes off, the saw tends to plunge about 5mm as if some inertia force has grabbed it. It is a bit disconcerting. My much smaller Elu chop/ mitre saw does not do this. Is this normal do you think?

Question 2 - the saw is fitted with a laser guide. This is extremely hard to see if I am working outside in daylight. Works great in a darkened room..... Anyone know of a means to make it more visible?

I have a lot of thoughts about this saw, but don't want to bore you all to tears. So will do a separate thread at some point if anyone is interested.

AJ

 

[AJB Temple]

Sorry all - for some reason the snaps have rotated 90 degrees and a link has appeared as well. Clearly I am doing something wrong but have no idea how to do an edit fix.

 

[Fitzroy]

The saw diving when you release the trigger. My 12" Makita does similar, although sitting here in the office my memory tells me it trys to rise up. Anyhow either way i'm pretty sure it's to do with the momentum stored in the spinning blade, when the saw tries to brake the blade there will be a transfer of energy which will cause the saw body to want to move. The bigger the blade, and the faster the brake, the larger the force from the resulting energy transfer, and hence the more pronounced the effect you feel through your hand. No idea about the laser, that's electronic magic.

F.

 

[AJB Temple]

That makes sense Fitzroy. The saw is heavily braked (also has soft start). Diving is exactly what it does. It may simply be a case of me having to get used to it.

 

[Steve Maskery]

I have the same saw. I love it, it is excellent, but, as you say, imperfect.
I don't do much in the way of trenching cuts, but F's explanation above sounds good to me. Either that or a gyroscopic effect.
The laser is the one thing that I think is not good about it. It's hard enough to see in my workshop, it's invisible outside. And, although it is adjustable, the closer you get the laser line to the blade, the more the blade shadows it, so it ends up being just an indication only, rather than a reliable reference.
But in every other respect, I think it is superb, particularly the ease with which I can alter the bevel and mitre angles quickly and accurately. It's excellent.

 

[AJB Temple]

Bevel! That was the word I was looking for.

 

[Woody2Shoes]

Morning all

I have the current iteration of the Bosch 12GDL saw, now housed on a Bosch trolley. I will do a review at some point, but in the meantime I have a couple of questions for others who run big saws like this.

Here is the saw, parked up for the night in my timber framing barn.
download/file.php?mode=view&id=55203

And here is one of the two frames I am currently in the middle of making in my spare time, so you can see what I am dealing with. Much of the oak has been air drying for about a year and a lot of it is pretty hard.

download/file.php?mode=view&id=55203

It is actually a very good saw - not perfect.
Question 1 - when I am cutting angled notch cuts in rafters say (4" square oak), I am obviously not cutting to full depth (the depth stop is pretty rudimentary by the way - verging on hopeless as it does not have a wide enough range of adjustment) and need to watch the saw bottom out on the marked line by guiding it visually. Usually I am cutting (say) a 34 degree angle with the saw tilted over to the left or right as appropriate (ie these are not vertical mitre cuts). When I release the trigger, unless the saw has been fully returned to its idle position, the moment the power comes off, the saw tends to plunge about 5mm as if some inertia force has grabbed it. It is a bit disconcerting. My much smaller Elu chop/ mitre saw does not do this. Is this normal do you think?

Question 2 - the saw is fitted with a laser guide. This is extremely hard to see if I am working outside in daylight. Works great in a darkened room..... Anyone know of a means to make it more visible?

I have a lot of thoughts about this saw, but don't want to bore you all to tears. So will do a separate thread at some point if anyone is interested.

AJ

Hi, I have a DW708 - an old style SCMS of same size:

- I find the depth-stop feature pretty useless and try and avoid using it - I use other methods for notching/trenching/dado-cutting;
- My saw also "dives" when the blade slows - basic physics I fear - so I lift the blade away before switching off;

A very productive way of cutting lots of common rafters is gang-cutting, where you clamp, or temporarily nail, a whole set together and run along them with a circular (or track) saw - you can do the seat and plumb cuts as well as the birds-mouths this way. Of course, your setting out needs to be good so that identical common rafters actually fit (DAMHIKT!!) and you need to measure extremely carefully or you can scrap a lot of timber in one go. Here's a pic of someone doing a few: https://bethepro.com/wp-content/uploads ... _31611.jpg and this scary-looking job: http://www.arktikosbuilders.com/uploads ... 7_orig.jpg

Re. lasers outdoors, the only tip might be rose-tinted specs - you can get laser specs which may help somewhat by filtering out some of the competing light - e.g. https://www.amazon.co.uk/Bosch-REDGLASS ... B005K5U7W6 - I've never used them myself.

Cheers, W2S

 

[AJB Temple]

Thanks Woody, really helpful.

Now - time to fess up. This is the first time I have made an oak frame building entirely on my own. It is surprisingly difficult, when dealing with green oak, to get a building perfectly square and level. The wood moves and although beams may look straight they can run out by a couple of cm over a 6 metre length. so my building is out of square by 30mm. This means if I take the rear catslide rafters (which are in) the distance between birds mouth cut outs on number 1 (extreme left) is different by about 20mm by number 9 on the extreme right.

Most 'Kit" buildings of this type, that you see advertised, use much smaller cross section timbers and most of the rafters and infill are softwood. I am using oak which is expensive and takes ages to arrive, so I can't afford cutting cock ups. Therefore my approach is to work along the rafters one by one so that each is a template for the next - that I can adjust by a few mm. It is slower I know.

One frustration is that for the catslide rood the cutting angle for the ends and one side of the birds beak is 34 degrees. That means the other angle on teh birds beak is 56 degrees. The maximum bevel angle on the Bosch saw is 47 degrees. My Hilti saw has a ten inch blade and at a shallow angle like 56 degrees, there is not enough depth of cut. Therefore I end up doing two cuts by hand on each rafter.

Once I get on with the main rafters, the angles are within the range of the mitre saw and that will make my life easier. I have never made a roof structure before so the measuring is proving challenging!