DW788 Rebuild

Rick_B

Rick
Corporate Member
I am in the process of disassembling a DW788 scroll saw and examining pieces and parts. The motivation was what I thought was/is excessive noise/knocking. I am using a 4 part youtube series forthe disassembly. Why initial thought was to just replace all the bearings and sleeves - the saw is 20 years old. Thar sounded good until Instarted lookingat replacement costs - pretty steep if you do them all. My question - has anyone done this and found a reasonably priced source for the needle roller bearings and sleeves? As a point of reference I have found sources at $7.00 a bearing - there are roughly 16 bearings in the machine. Sleeves are not much cheaper.

Thanks for any thoughts
Rick
 

sawman101

Bruce Swanson
Corporate Member
My experience with the DW788 is that tightening the rod with the 90 degree bend in the top arm one or two clockwise turns will reduce the knocking sound prevalent in that saw. Bearings will last almost forever in that saw. After tightening the rod, you will also notice you will achieve proper tension at a much lower number on the tension lever. Good luck on the rebuild. Incidentally, Dewalt repair center had a deal on their website where they claimed they would rebuild the entire machine, replacing even the motor and giving you a 1 year warranty; I don't remember the price, but I took mine in for the rebuild and they replaced my old saw and charged me around $150. This was a few years back.
 

Rick_B

Rick
Corporate Member
My experience with the DW788 is that tightening the rod with the 90 degree bend in the top arm one or two clockwise turns will reduce the knocking sound prevalent in that saw. Bearings will last almost forever in that saw. After tightening the rod, you will also notice you will achieve proper tension at a much lower number on the tension lever. Good luck on the rebuild. Incidentally, Dewalt repair center had a deal on their website where they claimed they would rebuild the entire machine, replacing even the motor and giving you a 1 year warranty; I don't remember the price, but I took mine in for the rebuild and they replaced my old saw and charged me around $150. This was a few years back.
Thanks Bruce - after seeing the bearing and sleeve pricing I have decided to evaluate each set individually and only replace what is obviously bad - hopefull I can tell that. Also thanks for the suggestion to check and adjust tension - it sounded to me like the knocking was comoing from the upper arm so you may be on to something

Rick
 

ScottM

Scott
Staff member
Corporate Member
NCWW member Charles Lent (that is his screen name) has had a lot of experience with that saw and rebuilding. I think he once put together a cross ref list of aftermarket bearing and sleeves. He is not very active on the site but if you send him a message I am sure he will reply. He is from the Charlotte area.
 

Rick_B

Rick
Corporate Member
NCWW member Charles Lent (that is his screen name) has had a lot of experience with that saw and rebuilding. I think he once put together a cross ref list of aftermarket bearing and sleeves. He is not very active on the site but if you send him a message I am sure he will reply. He is from the Charlotte area.
Thanks Scott - I will send Charles a message. I suspect I am not going to find a bearing/sleeve source that has acceptable (to me) pricing. My current approach is to evaluate each of the bearings and sleeves individually and replace as necessary. Hopefully Charles can give some guidance on what a bad condition is. The video series I watched (and Bruce recommended) has some guidance but hands on is always better. I suspect Bruce is right that the bearings are unlikely to be bad. The sleeves may be a different story.

Rick
 

Hmerkle

Hank
Corporate Member
Thanks Scott - I will send Charles a message. I suspect I am not going to find a bearing/sleeve source that has acceptable (to me) pricing. My current approach is to evaluate each of the bearings and sleeves individually and replace as necessary. Hopefully Charles can give some guidance on what a bad condition is. The video series I watched (and Bruce recommended) has some guidance but hands on is always better. I suspect Bruce is right that the bearings are unlikely to be bad. The sleeves may be a different story.

Rick
Rick,
It would be nice to have @Charles Lent 's list in our reference material especially if the pricing is more palatable!
BTW what video series did Bruce @sawman101 recommend?
 

Rick_B

Rick
Corporate Member
Hank - the videos I watched were made by Bob Brokaw and sponsored by the Gwinnett Woodworkers Association. I don't see where Bruce recommedned a video?

I will check with Charles about bearing/sleeve list and sources. IO have seen some posts by him on other scrolling sites - if I don't hear back from him I'll check those sites again.

Rick
 

Hmerkle

Hank
Corporate Member
Hank - the videos I watched were made by Bob Brokaw and sponsored by the Gwinnett Woodworkers Association. I don't see where Bruce recommedned a video?

I will check with Charles about bearing/sleeve list and sources. IO have seen some posts by him on other scrolling sites - if I don't hear back from him I'll check those sites again.

Rick
Oh, I misunderstood when you said "The video series I watched (and Bruce recommended) has some guidance"

The Bob Brokaw and sponsored by the Gwinnett Woodworkers Association were the ones I was thinking of!
 

Rick_B

Rick
Corporate Member
Oh, I misunderstood when you said "The video series I watched (and Bruce recommended) has some guidance"

The Bob Brokaw and sponsored by the Gwinnett Woodworkers Association were the ones I was thinking of!
Got it - I did mean to include a link to the video
- this is the first part - the others will appear as you watch this one
Rick
 

ScottM

Scott
Staff member
Corporate Member
Rick more on DW788 PM. One of the failure points is the on/off switch. I highly recommend leaving the switch in the on position and using a foot switch. It needs "dead man" or a "click on /click off" switch and not a variable speed foot switch. For the bearing and sleeves you don't change make sure to apply a quality synthetic grease.
 

Hmerkle

Hank
Corporate Member
Rick more on DW788 PM. One of the failure points is the on/off switch. I highly recommend leaving the switch in the on position and using a foot switch. It needs "dead man" or a "click on /click off" switch and not a variable speed foot switch. For the bearing and sleeves you don't change make sure to apply a quality synthetic grease.
Thank you Scott - I was actually going to post / ask that question about grease...
Bearings tend to last a LONG time when well greased and not getting "foreign material" in them!
 

Rick_B

Rick
Corporate Member
Charley lent got back to me and provided a lot of good advice. He didn't have his bearing list handy but I was able to find the information on other forums - mainly scroll saw workshop.

I am using the Bob Brokaw videos (1st one linked above) - there are at least 6 available. You can easily find them by searching "bob bnrokaw" on youtube.

As noted above I have the left side of the machine disassembled. Todays plan is to disassemble each bearing/sleeve, clean, manually evaluate, lube the bearing with a valvoline semi synthetic grease and reassemble. I will also be cleaning all of the other parts as I go along.

Here is the list of bearings and sleeves I have found so far
From vxb.com - Bearings

HK0810 - 3 each

HK1412 - 2 each

HK0609 - 12 each

From servicenet.dewalt.com - Sleeves

286294-00 - Short Sleeve - Qty 8

286295-00 - Long Sleve - Qty 2

286430-00 - Drive Link Sleeve - Qty 4

286282-00 - Pivot Rod - Qty 1

While I am disassembling Iam also cross referencing the exploded parts drawing and list I got from servicenet. I try not to trust that what is there is correct :) - I may have found an error on the explosion but more on that later.

Rick
 

Hmerkle

Hank
Corporate Member
I a curious, @Rick_B did you try Bruce's (@sawman101) suggestion "tightening the rod with the 90 degree bend"
If yes, did that change the "excessive noise/knocking"?
If not, are you going to try that first before removing and replacing all the bearings?

Also, since you have the left side of the machine open, do you notice any sloppiness in any of the bearings or linkages?
 

ScottM

Scott
Staff member
Corporate Member
I a curious, @Rick_B did you try Bruce's (@sawman101) suggestion "tightening the rod with the 90 degree bend"
If yes, did that change the "excessive noise/knocking"?
If not, are you going to try that first before removing and replacing all the bearings?

Also, since you have the left side of the machine open, do you notice any sloppiness in any of the bearings or linkages?
Hank you have to disassemble and then reassemble to test if the tightening the rod helped. Having worked on several of those machines, if I went to the trouble of disassembling it, I would inspect every bearing and sleeve. I would regrease all and replace any with any signs of wear.
 

Hmerkle

Hank
Corporate Member
Hank you have to disassemble and then reassemble to test if the tightening the rod helped. Having worked on several of those machines, if I went to the trouble of disassembling it, I would inspect every bearing and sleeve. I would regrease all and replace any with any signs of wear.
I thought Bob Brokaw showed a way to leave the left side of the saw open and evaluate the bearings an linkages.
Now I have to go back and see if my mind is playing tricks on me!
 

Charlie

Charlie
Corporate Member
I spent about 2 hours yesterday disassembling my DW788. It isn't at all difficult. I cleaned and greased all bearings. The bearing between the connecting rod and pivot arm was bone dry and rusted. I think the factory failed to apply grease during assembly. All other bearings had some grease, but needed replenishing. It is a totally different machine now. I may use it more now, but hated to use it before because it was so noisy.
 

Rick_B

Rick
Corporate Member
Well my plan was to disassemble per the Bob Brokaw videos. I ended up doing that and pulling all of the linkages apart to inspect each bearing and sleeve. Based on the criteria in the video I didn't see any signs of wear. I also didn't see a lot of lubrication. I cleaned, greased and reassembled each linkage connection. I also took the time to clean the inside of the machine of dirt and sawdust.

Once assembled the machine seemed quieter but was still knocking. I tried Bruce's approach with the tension rod (also found that solution on the internet) - didn't help but I am not sure where the tension rod should be. As Scott said - once is likely not enough so I need to keep trying. I also saw a solution that involved sanding the cap that goes over the rod and bellows. That was a solution Dewalt gave a fellow. So tomorrow I'm going to try a few more iterations with the tension rod.

Some variances I found:
1. The videos indicated the connecting rod to vertical rocker arm hardware should be a long screw that was double nutted. All the schematics I found showed a shorter screw with a lock nut (nylon insert). My machine had a short screw with a standard hex nut? I changed that nut out to nylon insert lock nut.
2. Some of the schematics show the front rocker assy to drive link having a short #38 bushing and some show that bushing as a #122 drive link sleeve. There are several variations of that depending on which schematic source you choose. One source showed a type 1 as a #38 and a type 2 as #122.My machine is a type 1 and had a #122 (bigger OD and Length than a short sleeve). All schematics I looked at that had the #122 showed a usage of 4 but my machine only had 2 - front of the drive link for top and bottom. Not sure what is going but I reassembled as the machine came to me. As a note this is the sleeve that has a thrust washer on each side.
3.The videos indicated nuts should face out(face the user if looking at the open left side) on the linkage connections. This is not how the schematics shows them - I followed the schematics.
4. The schematics I used were from toolpartsdirect.com - they showed the variable speed controller as #61 - parts list showed #61 as the PC board.
5. I didn't find any loctite on the tension adjustment knob screw.
 

Rick_B

Rick
Corporate Member
No I haven't thrown the saw into the trash :)

I correction to the discrpncies noted above - #4 - upon closer examination item #61 is described as the circjuit board and potentiometer.

So I'v adjusted the tension rod quite a few times - mainly becaue I had it out of whack pretty far. I believe the knock is gone but it is still noisy - seems to get worse as speed increases and there is a lot of vibration at high speed. The noise seems to be coming from the back of the upper arm but I'm not really sure.

I also noticed there is a lot of side to side play at one or two of the chuck linkage connection points.

I wish there was a "local" expert that could guide me.

Finally I discovered that the torx head can in fact round over.

Rick
 

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