Bosch Mitre Saw help...

[ventureoverland]

Guys,
First off guys, not sure if this is the right place to post... I normally hang out in the metal section.

I have a Bosh GCM12SD Miter saw but stumbled across a problem the other day.

http://www.boschtools.com/Products/T...px?pid=GCM12SD

On the whole its a brilliant bit of kit but last weekend I had to use the depth stop for the first time. Either Im stupid or its crap!


Setting the depth was easy and in principle its hard to see how one could go wrong - lower the saw to required depth, turn the depth stop. Job done.


I was making a small box to house my orbital sander, nothing special just some 12mm marine ply that I wanted to cut a 6mm rebate around the edges to form some half decent joints. The problem I had was that I found it very difficult to get a consistent depth of cut, particularly at the start of the cut.

My base was approx 300mm x 190mm. The 190mm edge wasn't too bad but when the saw was pulled right out and then down there is too much flex in the arm system and on a 6mm deep cut I could vary the depth by about +1.5mm by simply dropping the saw down too quickly.

It didn't seem to matter how hard I tried, I found in incredibly difficult to get consistent cuts of depth along the length; made worse by the fact that I needed to run the saw 3 times in parallel to get a 6mm wide cut.

I also found out that whilst the saw will easily cut through a 300mm wide section, when you set the depth stop and want to make a rebate you loose about 2 inches of travel against the fence, so each cut took 6 passes (3 in one direction, then turn around and 3 more).

Anyone else had this problem? If so, whats the fix.


I should probably say I don't have a plunge router & tooling which would probably have been my tool of choice if I had one!


In the end I got my box made but its not as pretty as I would like and has left me thinking what is otherwise a brilliant machine has a weak element in its design.

R
Jon

[Treecycle]

I don't have the Bosch, but have a Makita and the depth stop on that is probably only suitable for carpentry type joints where the accuracy is usually not quite as critical as box making joints. I have exactly the same problem because the stop is not very rigid in its design and there is so much leverage from the stop location to the actual blade. A very small variation of where the stop does stop the arm movement is magnified in your cut depth. I don't know if any of the SCMS brands have a better system.
I don't know of any method to get rid of the lost stroke length against your fence when doing a stopped depth cut. Would be interested if someone has any smart ideas for this too.
Sorry I can't help, but I feel your pain.

[ventureoverland]

I don't have the Bosch, but have a Makita and the depth stop on that is probably only suitable for carpentry type joints where the accuracy is usually not quite as critical as box making joints. I have exactly the same problem because the stop is not very rigid in its design and there is so much leverage from the stop location to the actual blade. A very small variation of where the stop does stop the arm movement is magnified in your cut depth. I don't know if any of the SCMS brands have a better system.
I don't know of any method to get rid of the lost stroke length against your fence when doing a stopped depth cut. Would be interested if someone has any smart ideas for this too.
Sorry I can't help, but I feel your pain.

Thanks for the reply. At least it suggests that Im not a complete idiot (at least not in this regard ).

I don't have a planer or table saw, or room for them come to think of it... But I do have shelf space! Am I right in thinking that a router (with a cutter with bearing on the bottom) is probably the best tool for this application? If not, whats the best way to get a constant depth cut for a rebate?

thx
J

[Jone5y]

I've got an earlier version of the same saw, I think it's the GDL or similar. I concur with what you have found regarding the depth stop. There is some flex in the system when the stop is used and that means that varying amounts of pressure deliver slightly varied depth of cut. Really annoying and almost impossible to resolve. Another issue i have with using the depth stop is that its range of use is not always suitable for the task I need - the threaded piece that determines the depth isn't very long so trenching in thicker timber is best done elsewhere.

To get around the problem of losing saw travel at the fence, i put a straight piece of timber in front of the fence to push the workpiece further from the fence and make the cut. This avoids having to turn the workpiece around.

For months i battled with non square cuts from my machine before eventually resorting to just using the fence on the LHS and forgetting about the right altogether. I would square everything up from one side, make a cut, test - spot on - Bewdy. Put a longer piece on, cut, check - not square !?!?!? turns out the RHS fence was curved. I'm still waiting on the replacement part i ordered. In April.

[ventureoverland]

...the threaded piece that determines the depth isn't very long so trenching in thicker timber is best done elsewhere...

M'mmm I'll have a look at that, I haven't come across that problem yet (most of my work isn't very thick). Im assuming that being a European brand the thread will be metric - I should be able to simply turn up a longer threaded stud!

...To get around the problem of losing saw travel at the fence, i put a straight piece of timber in front of the fence to push the workpiece further from the fence and make the cut. This avoids having to turn the workpiece around.

In the end thats exactly what I did - It didn't strike me as obvious though until around half way through the job, then I couldn't believe it had taken me so long to figure it out

[Handyjack]

Two possible solutions without using as SCMS.

Use a plain circular saw and fence set to the correct depth. You would still probably need to make multiple pass, so not the fastest way to do the job, and possibly clean cut with chisel.

As you suggested use a router. The bit does not need bearing guide if you use a fence. In your case a 6mm straight bit with a suitable guide either attached to the router or the work would allow you to do the groove in a few passes. A rebate bit with bearing would be the fastest way to do the job (and is the one I use) if the rebate is to be on the edge.
If you look at this thread https://www.woodworkforums.com/f40/wip-nail-gun-box-196261 despite them being a bit rough, I have done the joins on the box with a router using both a straight bit and a rebate bit. While it is not shown, the 6mm base is sitting in a groove in the sides.

Like most things the setting up is what takes the time. I use an off cut to check my settings.

[springwater]

I have an older Makita SCS and have experienced the same probs as you've described. To my knowledge there isn't a SCS with an accurate and repeatable depth stop but I stand to be corrected. BUT I can get by. I can't say I could achieve perfection over 300mm, I'm not even sure my saws' travel reaches that far, especially with a block behind it but over shorter distances I can achieve a reasonable result by maintaining an even downwards pressure. I have to first use a scrap piece to get to the right depth and it usually, on a good day takes about three goes of loosening then tightening a nut to get going. Agree with others that a router is the way to go but that's another matter