I know there are some experts here and hopefully someone can help. My Clark modified Hitachi planer started acting up yesterday. It will not turn at a consistent speed. At first I thought I had an issue with the power cord. This morning I replaced the power cord with the original cord. It’s still doing it. I also have an un-modified Hitachi that I plugged into the same electrical source and it runs fine. I think I have ruled out the possibility of an electrical source issue.
To further explain the issue. It will get up to full rpm’s for 4-5 seconds, then reduced rpm’s for 1-2 seconds, then slowly speed back to full, ect., ect…
Don’t run it any more until you do some investigating. Remove the brushes and check their condition. The surface that contacts the motor armature should be smooth and shiny. There should be no sign of excessive sparking or arcing. The carbon portion of the brush should be about 3/8" long. Also make sure that the brushes are moving freely in the brush holder. If there is something causing the brush to stick in the brush holder it may not seat against the armature and cause problems. Use air to blow out the brush holder before reassembly. If there is sign of arcing at the brushes and they are not worn too short you will have to take a look at the motor armature. Make sure to remove both brushes before removing the motor armature. Next remove the belt cover and the belt and turn the motor and blade drum for a quick check of the condition of the bearings. You could do this first. Hopefully if you have a bad bearing it has not spun in its housing. Hope this helps and let us know what you find.
Sounds like brushes to me also, but I’ve never had that exact ‘‘symptom’’ as the brushes expire. Definitely the first thing to check, though. Bearings usually will make noise before they start to drag enough to slow RPMs. If the bearings are that bad it would also endanger the housing. DON’T do that one. (insert prerequisite ‘‘don’t ask me how I know this’’ here) I’ve had some trigger switches do some strange things, too. Try swapping triggers with the other tool if the brushes check out OK.
Ditto on the switch as well as the connections there. Oops now I have to blow eps dust out of the laptop keyboard. Mike I just put new SKF bearings in my Hitachi with the drum and it sounds like a different machine. The planer police gave me a warning ticket last week.
New bearings feel so good! I’m using Milwaukee bearings in mine cuz my repair guy swears they’re the best. He fixes tools for half the industry here, so he sees what lasts and what doesn’t…
Did the planer police talk to you about the extra heat that grit drum puts on your bearings?
Thanks for the tips! I opened it up and went through all your suggestions including switching out the trigger switch. The only thing I can figure is it must be the bearings on the blade drum. It feels tighter and does not spin as easily when compared with my other planer. If nothing else the thing is clean as a whistle now.
Do you guys replace your own bearings or take it to a repair person ?
Might be time to spring for the abrasive drum while I’m at it.
If you have ANY suspicions re the bearing, replace it! It’s worth repeating here that overheating bearing seats can ruin the planer ‘‘body’’, leaving you with a bunch of parts begging for a new home.
I don’t do bearings (brushes and triggers about as far as I go). I think Dave does all his own repairs. I’m shaping for a living, so I just plug in a spare and keep working. I’ve got a 25 year relationship with a great guy who fixes tools all day, everyday. I figure he’s faster and better than me at the repairs.
My hitachi started smoking a few days ago. The belt had somehow jumped off the wheels and was rubbing against the plastic body. Try taking off the belt housing and make sure the belt is sitting on the wheels properly.
Might be best to take it to a shop. You need a small puller sometimes to get the bearings off and there’s a few tricks to getting them back on without damaging the bearings or the shafts. Let me know if you have any questions.
Finding a repair person has proven more difficult than I
would have imagined. Anyhow, after reading a post by Jim Phillips
explaining in pretty good detail how to take it apart and some
encouragement from my local supply shop, I decided to do this myself. I removed the cutterhead and armature attached to the backing plate in one peice as instructed.
Then tried to remove the drive wheel for the cuttter head. I was warned
not to nick the aluminum drive wheel while removing it and tried my
best. Unfortunately I buggered it up a bit. This was the hardest
part of the job so far. How this is accomplished without screwing up
the drive wheel is beyond me. Jim’s post indicated the wheel should be snug tight. These were far from snugged.
Maybe I can smooth it up, more likely
just replace it too. I then removed the bearings in a crude but
effective method. The large cutter head bearing has definitely frozen up.
Okay now I need some advice for installing the new bearings and getting this thing back together.