Archived from the Tools In Action forum (Ryobi). This thread is read-only.
Problem: the shaft deflects enough to touch the side of the opening in the case.
I am using the tool to remove grout between the tiles on my deck. The attachment is a half moon diamond / carbide blade. When using this attachment the force on the blade and the shaft is rotational to body of the case. This is different than pushing down on the case for sanding or pushing forward on the case to scrape or to plunge cut.
The motor and transmission are mounted to the case on rubber bumpers. Most of the bumpers are rectangular and sit in slots in the case. The ones that locate the head of the transmission in the case to limit rotation are rubber washers about 1/2″ across and about 3/16″ tall with a hole halfway though the center. The washers fit in a cup molded into the transmission with the holes facing out. The case has plastic pins molded onto each half that fit in the holes in the washers.
The rubber washers fail by the plastic pin in the case wearing though them, then the pin is ground away. After this the shaft can rotate enough in the case to touch the sides of the opening in the case and start to grind it away.
The rubber washers are not even shown in the parts diagram.
My fix: I went to my ACE hardware store and bought the following from their Hillman fastener selection:
Hillman # 405937G rubber grommet ( 1/2″ OD, 9/32″ ID )
Hillman # 4608A fillister head phillips screw ( 1/2″ long, 10-24 thread, fillister head is important )
Hillman # 44210C 10-24 thin pattern USS Nylon Insert nut (you don’t need the thin nut, any 10-24 nut with the nylon insert will do)
Take the case apart and make note of where each of the rectangular rubber bumpers go and how they were positioned. The screw heads are T10.
Cut out what is left of the plastic molded-in pins ( they are hollow ).
Use a small diam. drill bit to drill a pilot hole through the center of the old pin from the inside of the case out ( I used a 5/64″ bit because it was handy ).
I used a 5/32″ bit to drill the hole from the outside of the case in.
Screw the fillister head screw through the body from the inside out and attach the nut. The head is replacing the plastic pin.
Put the rubber grommets in the cups on the transmission or on the screw heads in the case.
Make sure all rubber bumpers are in place and the new rubber grommets end up in the cups and on the screw heads.
Reassemble and see that the side to side motion of the output shaft is now under much better control.
I have 12″ tiles on a 16′ x 24′ deck, plus some walkway. It will be over 1000 linear feet of grout to grind out. I am replacing it with silicone caulk. I did a test section 2 years ago and it held up quite well.
I found that putting too much pressure on the cutting head actually reduced its effectiveness and may have led to an earlier demise of the rubber grommets. Now I use the weight of the tool and hand that is holding it to apply pressure most of the time.
I did buy a second multi tool when the first one failed. I had work to do. I used the second one in a gentler manner described above. The rubber grommets still failed, but I watched for it and replaced the original grommets with the hillman ones before any damage was done to the case. I think that the repaired one will hold up better than the original one. I will update on that later. I still use both because the over temp cut out activates before I am ready to quit.
Have you noticed if the rubber bumpers on other parts of the tool are showing any similar wear or if the plastic parts around the case are also getting affected by the force?
GregMN wrote:
On 11/20/2025 at 11:54 AM, GregMN said:Problem: the shaft deflects enough to touch the side of the opening in the case.
I am using the tool to remove grout between the tiles on my deck. The attachment is a half moon diamond / carbide blade. When using this attachment the force on the blade and the shaft is rotational to body of the case. This is different than pushing down on the case for sanding or pushing forward on the case to scrape or to plunge cut.
The motor and transmission are mounted to the case on rubber bumpers. Most of the bumpers are rectangular and sit in slots in the case. The ones that locate the head of the transmission in the case to limit rotation are rubber washers about 1/2″ across and about 3/16″ tall with a hole halfway though the center. The washers fit in a cup molded into the transmission with the holes facing out. The case has plastic pins molded onto each half that fit in the holes in the washers.
The rubber washers fail by the plastic pin in the case wearing though them, then the pin is ground away. After this the shaft can rotate enough in the case to touch the sides of the opening in the case and start to grind it away.
The rubber washers are not even shown in the parts diagram.
My fix: I went to my ACE hardware store and bought the following from their Hillman fastener selection:
Hillman # 405937G rubber grommet ( 1/2″ OD, 9/32″ ID )
Hillman # 4608A fillister head phillips screw ( 1/2″ long, 10-24 thread, fillister head is important )
Hillman # 44210C 10-24 thin pattern USS Nylon Insert nut (you don’t need the thin nut, any 10-24 nut with the nylon insert will do)
Take the case apart and make note of where each of the rectangular rubber bumpers go and how they were positioned. The screw heads are T10.
Cut out what is left of the plastic molded-in pins ( they are hollow ).
Use a small diam. drill bit to drill a pilot hole through the center of the old pin from the inside of the case out ( I used a 5/64″ bit because it was handy ).
I used a 5/32″ bit to drill the hole from the outside of the case in.
Screw the fillister head screw through the body from the inside out and attach the nut. The head is replacing the plastic pin.
Put the rubber grommets in the cups on the transmission or on the screw heads in the case.
Make sure all rubber bumpers are in place and the new rubber grommets end up in the cups and on the screw heads.
Reassemble and see that the side to side motion of the output shaft is now under much better control.
I have 12″ tiles on a 16′ x 24′ deck, plus some walkway. It will be over 1000 linear feet of grout to grind out. I am replacing it with silicone caulk. I did a test section 2 years ago and it held up quite well.
I found that putting too much pressure on the cutting head actually reduced its effectiveness and may have led to an earlier demise of the rubber grommets. Now I use the weight of the tool and hand that is holding it to apply pressure most of the time.
Now, I’m no expert in tools, but it got me thinking about the similar challenges of making repairs and fixes in all areas of life—whether it’s fixing a power tool or restoring a space. One of my friends, who was an expert at Cairenn Foy Interiors faced a very similar situation when working on a home renovation project. While reworking a vintage piece of furniture for a client, he came across a problem where the old structure of the piece wasn’t holding up properly. At the moment i am unable to contact him. I did buy a second multi tool when the first one failed. I had work to do. I used the second one in a gentler manner described above. The rubber grommets still failed, but I watched for it and replaced the original grommets with the hillman ones before any damage was done to the case. I think that the repaired one will hold up better than the original one. I will update on that later. I still use both because the over temp cut out activates before I am ready to quit.
Your repair using Hillman rubber and screws is a solid solution to reinforce the mountings and improve stability of shaft. but to ensure a longer fix, I recommend regularly inspecting the rubber grommets, especially after heavy use, as they can still wear down over time. also, consider reducing the pressure applied during heavy tasks like grout removal, as too much force can contribute to premature failure of the grommets and other components.
The fix allowed the tool to be used longer. Long enough for the bearing on the tail end of the motor to fail, and then with the play of the shaft the plastic cooling fins could touch the side of the body and be quickly ground off. Then it would overheat almost immediately. This is apparently designed as a light duty tool. I returned for exchange 2 times to complete the job. As stated in my original post, after the first failure, I used the tool gently with just the weight of the tool and I installed fresh blades often. I found a pack of 10 for $7.99 that worked as well and as long as the ones that cost $15 each at harbor freight.