Forward/Backward blade travel on DW788

[OCtoolguy]

I hope I'm not  going to ask a question here that has been discussed ad nauseum but after reading something on Rick's Scrollsaw site, I got to wondering about my saw so I checked it out. I measured the amount of blade movement throughout the entire up/down range and it seems to be in excess of 1/16". I was wondering if those of you using a DW788 have experienced this and if so what did you do to cure it? The explanation of how to fix it is a bit murky on Rick's site so I thought I'd ask here. My saw is an old type 1 that I bought used. I have no idea how much it had been used prior to me getting it but I don't think it had many miles on it. If this has been discussed before, maybe you can steer me in the direction of that duscussion. Thanks,

 

Ray

 

[JTTHECLOCKMAN]

I remember answering this question not that long ago but do not remember the forum or the topic of discussion. With the type #1 there was a table problem front to back and a shim was needed to lift the back of the table to take out the travel. Getting old and the memory is not what it use to be. I had shown a photo of my fix also. If I have time I will have another look but it is an easy fix. 

[OCtoolguy]

15 minutes ago, JTTHECLOCKMAN said:

I remember answering this question not that long ago but do not remember the forum or the topic of discussion. With the type #1 there was a table problem front to back and a shim was needed to lift the back of the table to take out the travel. Getting old and the memory is not what it use to be. I had shown a photo of my fix also. If I have time I will have another look but it is an easy fix. 

Thanks John but maybe I'm not explaining myself clearly. The movement I'm trying to describe is a blade movement that moves from the rear to the front in almost a "chewing" motion that makes the wood jump up and down a bit. Not bad but enough to be bothersome. With the saw turned off and the blade all the way either up or down, moving it through the entire cycle you can see that the blade is moving front to rear and back again. I did read on Rick's site about how to fix it but before jumping in and cutting and grinding out screw holes I wanted to throw it out to "the experts" here. I'm going to try to video the movement with my phone and attach the video here. That may prove to be another can of worms though.

 

 

Ray

 

Edited September 14, 2017 by octoolguy

[Iguanadon]

Just now, octoolguy said:

Thanks John but maybe I'm not explaining myself clearly. The movement I'm trying to describe is a blade movement that moves from the rear to the front in almost a "chewing" motion that makes the wood jump up and down a bit. Not bad but enough to be bothersome. With the saw turned off and the blade all the way either up or down, moving it through the entire cycle you can see that the blade is moving front to rear and back again. I did read on Rick's site about how to fix it but before jumping in and cutting and grinding out screw holes I wanted to throw it out to "the experts" here.

 

Ray

 

I think he knows what you're referring to.  He said there was a known issue with the Type1 in that the table needs to be shimmed in the back, which makes sense to correct the front to back travel of the blade... Can't adjust the blade, so adjust the "pitch" of the table to align 90 degrees with the blade.  Hopefully he finds the "easy" solution to share with ya.

[JOE_M]

Yes, I watched that video a while back and did it, it's a nice improvement. After I did it though it was still a bit more aggressive than I, as a newbie, was comfortable with. So I took off the two bolts that hold the table down, and put a washer on each one as a spacer - in effect lifting the front to make the table more square to the blade - and that made it even better. 

 

[Lucky2]

Ray, you can adjust that forward to backward motion by adjusting the motor. I'm not real familiar with what you have to do to make this adjustment, but I do know that it can be adjusted. It has something tto do with twisting the motor, I don't know what direction to twist it but you might find out how on the net. It can be done on the EX also, you do it in the same way. Keep searching, and you should find what you're looking for.

Len

[OCtoolguy]

4 hours ago, JOE_M said:

Yes, I watched that video a while back and did it, it's a nice improvement. After I did it though it was still a bit more aggressive than I, as a newbie, was comfortable with. So I took off the two bolts that hold the table down, and put a washer on each one as a spacer - in effect lifting the front to make the table more square to the blade - and that made it even better. 

 

You mentioned a video. Where did you find a video? I'd be interested in seeing it. I read the article on Rick's site but I saw no video. Maybe I missed something. I 'll go back and check it out. Thanks for the shimming idea.

 

Ray

 

[JTTHECLOCKMAN]

Edited September 14, 2017 by JTTHECLOCKMAN

[JTTHECLOCKMAN]

Not sure if this photo will stay or not but the fix as I said was to put a spacer in back of the table to raise it. Some did it in the front. Take a 90 degree straight edge and put behind the blade and by hand raise and lower the arm with a blade set the way you always do. You will see where the greatest gap is when you do this if it is at the top then the back needs raising and if at the bottom then the front needs raising. This problem is as old as those saws are. The greater the gap the more aggressive the cutting is. 

 

www.scrollsaws.com/SawReviews/DewltTuneUp.htm

 

Edited September 14, 2017 by JTTHECLOCKMAN

[OCtoolguy]

I just did a quick search on youtube and found this video. It gives a very good explanation of what to do to fix the problem I described. Tomorrow, I will give it a try and I'll give feedback as soon as I have some.

 

Ray

 

[JOE_M]

Ray, I think that's the video. You found it before I woke up this morning.

[JTTHECLOCKMAN]

I guess that method will work as well. Someone must have discovered that after the method I mentioned because it was Rick and others that did the table tilt when the Dewalt first came out. It basically is the same thing. I see my photo is gone because of PhotoBucket I do have to get my photos transfered to another source. You will always have the rocking motion because of the action of the arms. 

[Lucky2]

15 hours ago, Iguanadon said:

I think he knows what you're referring to.  He said there was a known issue with the Type1 in that the table needs to be shimmed in the back, which makes sense to correct the front to back travel of the blade... Can't adjust the blade, so adjust the "pitch" of the table to align 90 degrees with the blade.  Hopefully he finds the "easy" solution to share with ya.

Iggy, you can adjust the blade by twisting the motor, you should be able to adjust it to run straight up and down. I've watched a couple of videos on how to make the adjustment, I just don't remember where I saw them. It had to be on You-tube or Steve Goods site I think, I know there is a video or information on this on Rick Hutcheson's site.

Len

[Sparetime Scroller]

I did that cutting and grinding fix on my Dewalt a couple of years ago and it really does the trick. It does need some resetting every now and then. Not recutting the hole,  but just loosening the bolts and pulling the blade holder forward again, and tightening it back down. I do this when I notice some of the back to front movement coming back, maybe every 6 months or so. It might look hard to do, but it's really very easy.

 

Ray F

[OCtoolguy]

Thanks everybody for your patience and suggestions. I have not had a chance yet to try either of the fixes yet but as soon as I know something one way or another, I'll let you all know.

 

Ray

 

[CharleyL]

I made the modification in the video to correct the front to back angle of the blade in my 788, and not to change the aggressiveness of the cut, although it may also help slightly with this. I do mostly compound cutting, so any side to side or front to back blade angle causes problems for me. Ideally, I would like the blade to be exactly 90 degrees to the table in all directions. 

Because the upper and lower blade arms of a DeWalt 788 and similar designed saws actually move in a slight arc, you can adjust the motor position to move the blade movement range slightly up or down, which may reduce the front to back shifting of the blade slightly , but you can't completely eliminate it in any saw that uses pivoting arms to move the blade. I would own an Eclipse saw, if it was still available, because the blade in it moved perfectly straight up and down. No saw with a swinging arm blade movement can move the blade perfectly straight up and down. There will always be a slight forward - back movement. of the blade as it moves, which is larger in saws with  longer blade arms.

The Delta Q3 has a "rocking C" blade arm where the blade is attached between the two ends of the C frame and the pivot point of the C is at the back end of the saw. As the C frame pivots up and down, the blade tips forward on the down stroke and backward on the up stroke, making for a very aggressive cut, but this rocking motion also makes it very difficult to do compound cutting in thick materials. However,  it is great and much faster cutting than most saws when cutting materials up to about 3/8". Above this thickness, the forward - backward movement at both ends of the blade motion begin to interfere when doing compound cutting  So there are saws that do one type of cutting better than others, and it will depend on the type of cutting as to which is best for you and what you make. It will also depend on how well the saw is adjusted. When following the video, all he is doing is adjusting the front-to-back angle of the blade very slightly. If it solves your need...great! Turning the motor slightly will make the blade up and down movement range a little higher or lower. In it's center, the blade movement forward and back will be the least. Move it significantly up or down and you will get more front-to-back blade movement. Again,  it depends on what you are cutting as to which setting will be best for you.

Charley

Edited September 15, 2017 by CharleyL

[OCtoolguy]

2 hours ago, CharleyL said:

I made the modification in the video to correct the front to back angle of the blade in my 788, and not to change the aggressiveness of the cut, although it may also help slightly with this. I do mostly compound cutting, so any side to side or front to back blade angle causes problems for me. Ideally, I would like the blade to be exactly 90 degrees to the table in all directions. 

Because the upper and lower blade arms of a DeWalt 788 and similar designed saws actually move in a slight arc, you can adjust the motor position to move the blade movement range slightly up or down, which may reduce the front to back shifting of the blade slightly , but you can't completely eliminate it in any saw that uses pivoting arms to move the blade. I would own an Eclipse saw, if it was still available, because the blade in it moved perfectly straight up and down. No saw with a swinging arm blade movement can move the blade perfectly straight up and down. There will always be a slight forward - back movement. of the blade as it moves, which is larger in saws with  longer blade arms.

The Delta Q3 has a "rocking C" blade arm where the blade is attached between the two ends of the C frame and the pivot point of the C is at the back end of the saw. As the C frame pivots up and down, the blade tips forward on the down stroke and backward on the up stroke, making for a very aggressive cut, but this rocking motion also makes it very difficult to do compound cutting in thick materials. However,  it is great and much faster cutting than most saws when cutting materials up to about 3/8". Above this thickness, the forward - backward movement at both ends of the blade motion begin to interfere when doing compound cutting  So there are saws that do one type of cutting better than others, and it will depend on the type of cutting as to which is best for you and what you make. It will also depend on how well the saw is adjusted. When following the video, all he is doing is adjusting the front-to-back angle of the blade very slightly. If it solves your need...great! Turning the motor slightly will make the blade up and down movement range a little higher or lower. In it's center, the blade movement forward and back will be the least. Move it significantly up or down and you will get more front-to-back blade movement. Again,  it depends on what you are cutting as to which setting will be best for you.

Charley

Thanks Charley, you took some time to write all that. I appreciate it.

Ray

 

[OCtoolguy]

On 9/14/2017 at 2:56 PM, Sparetime Scroller said:

I did that cutting and grinding fix on my Dewalt a couple of years ago and it really does the trick. It does need some resetting every now and then. Not recutting the hole,  but just loosening the bolts and pulling the blade holder forward again, and tightening it back down. I do this when I notice some of the back to front movement coming back, maybe every 6 months or so. It might look hard to do, but it's really very easy.

 

Ray F

I just finished doing the grinding of the holes and I move the whole think forward about a 1/16" but if anything it got worse. I also tried doing the washers under the front of the table too. I tried one washer, then two and then three. No improvement. Can you tell me how much you moved the lower assembly forward? I ground the holes out a good amount and can still go a bit more but it seems that it's getting worse. I'm going to try moving it back a bit but it seems like nothing is really making much difference. The blade is moving about 1/16" in the center of the stroke and then on both ends it moves rearword that same 1/16". I don't know if I will ever get the arc out of it.

Ray

 

[OCtoolguy]

On 9/13/2017 at 11:09 PM, JTTHECLOCKMAN said:

Not sure if this photo will stay or not but the fix as I said was to put a spacer in back of the table to raise it. Some did it in the front. Take a 90 degree straight edge and put behind the blade and by hand raise and lower the arm with a blade set the way you always do. You will see where the greatest gap is when you do this if it is at the top then the back needs raising and if at the bottom then the front needs raising. This problem is as old as those saws are. The greater the gap the more aggressive the cutting is. 

 

www.scrollsaws.com/SawReviews/DewltTuneUp.htm

 

J.T. what does it mean when at the top of the arc and at the bottom of the arc, the blade is against the square but in the middle of the arc it is approx. 1/16" of an inch forward of the square when the square is behind the blade? It truly is swinging in an arc.

 

Ray

 

[JOE_M]

I used a small machinist square behind the blade and adjusted until front/back motion relative to the table was almost un-noticeable.

[OCtoolguy]

1 hour ago, JOE_M said:

I used a small machinist square behind the blade and adjusted until front/back motion relative to the table was almost un-noticeable.

I just tried the table leveling thing. I'm not sure how you would raise rear of the table as it is in a fixed position but I did take it loose from the bracket and started shimming it with washers to get the table 90 degrees to the blade. It take a 1/2" of washers to accomplish that. So, that's not gonna happen. I'm going to keep messing with it until something fixes the problem but so far, all I've done is make it worse. Bummer.

 

Ray

 

[JOE_M]

3 minutes ago, octoolguy said:

so far, all I've done is make it worse.

If it's worse, then just remove the washers and push the bottom of the blade bracket back to wherever it was when you started. You haven't made any changes that can't be undone.I didn't have to raise the back of the table to square it, I had to raise the front and it only took 1 thick regular washer on each side.

[OCtoolguy]

1 hour ago, JOE_M said:

If it's worse, then just remove the washers and push the bottom of the blade bracket back to wherever it was when you started. You haven't made any changes that can't be undone.I didn't have to raise the back of the table to square it, I had to raise the front and it only took 1 thick regular washer on each side.

Thanks Joe, that's what I have done so far. I put it all back to where it was and it is working "OK" but I'm not satisfied with just "ok". What I have managed to do is build in a vibration above number 4-5 on the speed dial. I have opened the saw up before and made sure everything inside is tight so the only thing I could do from here is the bearing replacement. The saw is usable but just not right. I'll mess with it some more but at this point, I'm going to start shopping. I would like to get to scrolling instead of fixing. Maybe I'm chasing a problem is this just inherent in these saws. I do want to thank you for your help though. Much appreciated.

 

Ray

 

[JTTHECLOCKMAN]

This is the photo of my fix. I raised the table in the rear. Had to enlarge the bolt holes but that was easy to do. 

[JTTHECLOCKMAN]

5 hours ago, octoolguy said:

J.T. what does it mean when at the top of the arc and at the bottom of the arc, the blade is against the square but in the middle of the arc it is approx. 1/16" of an inch forward of the square when the square is behind the blade? It truly is swinging in an arc.

 

Ray

 

Make sure the blade is seating against the stops in the clamps before testing and make sure the blade is straight before installing.