Thread: Bosch GCM 12 GDL - Adjustment Issues

Are you measuring things at the cut or on the machine? A lot of blades have the disk slightly hollow ground on both sides for clearance in the cut, then have the carbide chips weld on overhanging alternate sides of the disk. i.e. the disc is slightly thinner toward the centre than it is at the outer edge, even if you place a straight edge across the blade from gullet to gullet.

If you then set the bevel so that the blade is square to the deck on one side, it might be tilted slightly to the the side you are squaring to. Then check for square on the other side and there is an error visible, equal to twice the degree of hollow grind in the blade disk, because you offset the bevel on the first side when setting the head. Ideally, you need to be checking for square on the cuts and adjusting accordingly, but for an initial adjustment, tweak so that the obvious error when squaring from the table is the same for either side of the blade

It is not uncommon for sliding compounds to have free play and poor rigidity in the arm mechanism. They are a real compromise between versatility and spot on accuracy, and generally the cheaper they are, the more float they have. I doubt that there has ever been one made that can compete with a reasonable table saw and aftermarket mitre guage or even a well fettled radial arm saw for accuracy when doing cuts for detail work.

It's an expensive saw. If you have an issue past 12 months warranty, you should be covered under Australian consumer law.

One could argue that if registering results in 6 year warranty, that they think that is a reasonable period for the saw to last in good function.

Originally Posted by malb

Are you measuring things at the cut or on the machine?

This

Measuring the blade will give you a guide, but you have to cut something and check the cut to know what's actually happening.

That being said, the table not being flat means it's physically impossible to get a perfectly square bevel on both sides; you can either balance them equally, or choose one side to be square and the other side will be whatever it will be.

6 thou over 4.5" (approximate distance from the edge of the table to your feeler gauge position) works out to about 0.076 degrees. I doubt you will have any claim on that

The seven thou between the straight edge across the tables should not be an issue provided that the red insert that the blade passes through during the cut is at the same level as the straight edge. It should be what is supporting the material at the cut, and provided you have a good sharp blade, there should not be enough load on the material to cause it to flex into the table depression. If the red support strip is below the the straight edge, I would suggest measuring the error and shimming the strip up to counter it. If it is above the straight edge, the only options I see would be to reduce it's thickness somewhat, then shim it back to straight edge height, which may not be easy, or to make up your own insert set up as a zero clearance and adjusted to the required level.

However, if the table is ramping down from the outer ends to where the support strip is located, then the ramp in the surface will also influence the the square that you are trying to reference the blade position to.

The second photo suggests the RHS of the red throat plate is maybe sightly lower than the right hand side of the table alongside it?

I have this saw and there is no play in the arms and only a slight amount of flex at full extension. I have done thousands of cuts and it is still feels tight and smooth.

I have never adjusted it for square as I found it pretty good out of the box. I have mainly used it for carpentry type jobs where squareness isn’t super important. Although I have checked cuts with an engineering square and they appear to be square.

Maybe elaborate more on the play you are experiencing?

Perhaps this could help.

Interestingly enough, I have had the same problem with a GCM 12 GDL saw. It needed the 0/90 degree setting adjusting from new and there is a high spot on the rotating table (left hand side) which causes a straight edge to rock when placed on the table. It's probably not going to affect my woodworking but when you spend over $1K on a tool one expects better. I also noted deflection in the glide system and some play in the saw shaft arbour. Strangely enough, my little cordless Dewalt CMS seems not to suffer from this malady even though both saws come out of China so it's not a "made in Europe is better" thing. I wonder what the factory tolerances are for this sort of thing?
A quick check with some feeler gauges indicates a .013" gap between a straight edge resting on the rotating table and the fixed left hand side of the saw. There seems to be no gap on the right hand side. There is a definite "thump"as you slide a piece of wood onto the saw table from the left hand side. Definitely not what I expected from a reputable manufacturer.

Rather than going with the option of getting the saw either repaired under warranty or replacing it I just took it back to the dealer and got a refund. A Festool Kapex could be a replacement if there are any in the country. There are just too many places on the Bosch Glide saws where if things wear accuracy will go out the door faster than the expiry of a politician's promise.

Perhaps get your local service centre to align it?

I spent hours trying to realign my Kapex and while I made improvements it was never perfect.

15mins with the Festool service centre it was back to new [emoji4]

I will never attempt to align it myself again

I had thought about going through the process of having the saw repaired but it seemed that, based on taking measurements as the base was swivelled from left mitre to right mitre, the pivot bearing or axle was bored out of vertical alignment. The rotating part was tilted so that the left hand side was high but the right was level. Added to this there was side-to-side movement of the saw head amounting to .7mm when the head was extended from back to front. I thought it was the way I was holding the saw when I was extending the head but it would happen if I pulled the saw with just one finger in the handle. I had done the you-tube research thing before I bought the saw and there seemed to be some mention of this problem but the one video I watched where the American gentleman was using a dial indicator to measure runout of the mechanism resulted in a minimal error. In my case the saw head moved if you put your hand on the handle to squeeze the switch.
I also compared the Bosch with my Ryobi "one+" and Dewalt saws, both costing a fair bit less than the Bosch, and they both had dead flat tables.
There is a Kapex sitting in Port Macquarie with my name on it. I'm going to wait until after the traffic congestion settles down and the mothers take their kids to school and then go and check it out.

Have a look on the Festool Owners Forum for problems that have been encountered by owners of the Kapex. I don't think the motor issues apply here but there are numerous other problems just as there have been numerous problems with just about any brand. With the numbers sold it is just about inevitable that problems in mitre saws get reported by unhappy owners and neither the Kapex or the Bosch Glide are immune from that. I certainly think the after sales service is better with Festool or that has been my experience but I know others have had problems.

I agree, there have been and will be problems with any brand of tool. I could have chosen to swap the crook Bosch for another saw of the same type but there were other issues with that type of saw that I didn't like but could have lives with. In the end I went with the Kapex (which is still in the back of the ute). One of the things that the Kapex does well and the Bosch does not do as well is the swinging of the head for bevel cutting. The Bosch was a real struggle for me to swing for bevel cutting whereas the Kapex is so easy and the Kapex scale is easy for me to see whereas the Bosch was awkward.
Was the Kapex worth the extra money? I don't know. I have to set the thing up on a stand and cut some timber but it felt much better in the shop. I have some 300x45 Paulownia to cut so I'll find out soon enough.

I know that to like or dislike something is somewhat subjective but I had a bit of a play with the Kapex today and I am certain it has found it's new home. I fitted it onto the Bosch "Gravity Rise" saw stand that I bought for the Bosch saw that I returned and it's a good combination, easy to fold and unfold, easy to move when folded and quite stable when unfolded into the working position.