Dotco Right Angle Die Grinder Bypasses Air

[MrMark]

I have a small dotco die grinder that just started acting up yesterday. It runs well, but occassionally when I pull the trigger it doesn't run and the air just passes through. If I move the arbor assembly a little it runs. This is a pretty simple design. Anyone ever have similar issues with die grinders or air tools in general as I don't think this issue is particular to die grinders.

 

[ranger302]

Try oiling it.

 

[justanengineer]

Likely its time for a rebuild if parts are available for those. Im not a SO snob by any means, but I do pick up their air tools when cheap because almost all are 100% rebuildable.

 

[MrMark]

All the parts are available for these. Dotco is above Snap on even when it comes to air tools. This is designed to run all day for industrial use. I was looking at the parts diagram and I am just wondering how the air is passing through without spinning the air motor.

 

[emeraldcoupe]

there is probably crud built up in the rotor causing the vanes to stick. you can get parts for them, just be pepared for sticker shock, they are not cheap. i've rebuilt probably 15-20 of the dotco grinders.

 

[crankshaftdan II]

All the parts are available for these. Dotco is above Snap on even when it comes to air tools. This is designed to run all day for industrial use. I was looking at the parts diagram and I am just wondering how the air is passing through without spinning the air motor.

AMEN:
These are the "Lexus" of american die grinders-it might be that the tool has been setting for a long time and the vanes in the rotor have swelled up due to moisture and are binding against the end plates? If you feel confident you can take it apart and microwave the blades to dry them out or just buy new ones! Sometimes the end plates finish wears groves and you loose air that way. Throttle valve also could be gummed up due to improper oiling (Only use air tool oil or light wt. turbine oil) and blowing air around the "O" ring? Maybe just real dirty inside? Pressed in bearings in end plates could also be bound up from moisture? Just a few suggestions to get you up & running....Cranky

 

[MrMark]

there is probably crud built up in the rotor causing the vanes to stick. you can get parts for them, just be pepared for sticker shock, they are not cheap. i've rebuilt probably 15-20 of the dotco grinders.

Bingo. I am going to take it apart and check the vanes. I supposedly can lap them lightly with 280 grit or so. First thing though is I need to figure out a way to get the assembly apart. There is a main nut and a lock nut, both the same size, larger than 1" it appears. The lock nut is THIN and it looks like the only thing I can do is make my first visit to Harbor Freight and buy a wrench to grind down to about 3/16 thick to get on that nut.

 

[MrMark]

AMEN:
These are the "Lexus" of american die grinders-it might be that the tool has been setting for a long time and the vanes in the rotor have swelled up due to moisture and are binding against the end plates? If you feel confident you can take it apart and microwave the blades to dry them out or just buy new ones! Sometimes the end plates finish wears groves and you loose air that way. Throttle valve also could be gummed up due to improper oiling (Only use air tool oil or light wt. turbine oil) and blowing air around the "O" ring? Maybe just real dirty inside? Pressed in bearings in end plates could also be bound up from moisture? Just a few suggestions to get you up & running....Cranky

great advice, thanks.

 

[emeraldcoupe]

as posted, check the bearings also. if they are binding just replace them.

 

[MrMark]

This is going to be a PITA to get apart. I need TWO 1 1/4 wrenches, one of which will have to be ground down to about an 1/8" thick. I don't have any wrenches that big. Only up to 30mm.

 

[Charles (in GA)]

Just pour a bunch of MMO (Marvel Mystery Oil) thru the inlet and run it, and keep doing that, it will loosen up and clear out. The ones at work do this, as they rarely get oiled (air tools blow alot of oil out when you oil them, this makes a mess which everyone hates, so they don't oil them)

Run it till it won't run any more, then worry about repairing it.

Charles

 

[oldtools]

This is going to be a PITA to get apart. I need TWO 1 1/4 wrenches, one of which will have to be ground down to about an 1/8" thick. I don't have any wrenches that big. Only up to 30mm.

Times to modify HF wrenches. I assume you don't want to grind down SO wrenches for a one time use.

 

[MrMark]

Luckily I did get it apart without having to make my first purchase at Harbor Freight. It was reverse thread on the main nut (a really clever design) and I just needed an adjustable wrench at 1 1/4 and my Columbian vise to hold the head in some leather. I think to set it back together I may need the ground down wrench though, don't know yet.

Now I see the problem is a bad front bearing. It has a bit of a rough spot to it. I need to figure out how to get it out.

Also a slight bit of corrosion in the air motor cylinder, it looks like where it had been sitting and a line of corrosion from a vane is in the cylinder. Not bad though. I'm thinking just light scotchbrite to clean the spot?

The vanes look good and it wasn't too dirty. No grease at all in the head though.


Anyone have a source of parts for these?? And how do you get the bearing out of the carrier? It looks like it has to be carefully punched out from the backside at an angle?

 

[vssjim]

I usually just warm up the end plates and the bearings will fall out, I have done all types of air tools and light heating makes bearings and cases fall apart and together.

 

[MrMark]

I usually just warm up the end plates and the bearings will fall out, I have done all types of air tools and light heating makes bearings and cases fall apart and together.

On a hot plate? I saw a guy do that with a coffee maker.

 

[vssjim]

I use a little propane torch I only get them warm to about 150 or about that it doesn't take much. A hot plate gets fairly hot so don't over due it just alittle bit.

 

[jabberwoki]

"These are the "Lexus" of american die grinders"!!!!!


Since when does lexus stand for the best??? I`ts always been "The Rolls Royce"

 

[MrMark]

I use a little propane torch I only get them warm to about 150 or about that it doesn't take much. A hot plate gets fairly hot so don't over due it just alittle bit.

OK, I hate using a torch but I am going to give it a try.

Thanks.

 

[vssjim]

alot of the time it will hold the inside of the bearing in the bore with c clip type pliers or inside snap ring pliers and spin the housing as the torch is warming it and the housing will fall off when it grows just a touch. You could use your hot plate just don't make it too hot, the bearing may fall out after just setting on it for a short time.

 

[crankshaftdan II]

If you have to replace the bearing and cannot find the original part-you might be able to take the bearing to a local bearing industrial supply house and they can usually match them up with a comparable brand-they usually have a number stamped on the inner/outer race-they can cross-reference!.....cranky

 

[Catalyze]

I just needed an adjustable wrench at 1 1/4 and my Columbian vise

Way to go Mark! Insert a vise plug in to an air tool thread. Now lets get back to painting your other Columbian. On the other hand....I just got a 505 1/2 Columbian today. Now this is practically a Columbian thread.
Craig

 

[Elroy]

Since when does lexus stand for the best???

Excellent observation