Is my grinder repairable?

[alancaddy]

Hi all, I have a Bosch 4.5" (PWS 720 115) which isn't working and wondered if it can be repaired or should I get a new one.. It's about 5 years old but doesn't see an awful lot of use, although I am using it more and more..

The motor runs at full speed when I turn it on but the disc turns slowly and stops completely under load. Taking it apart there is a small bevel gear on the output shaft of the motor, which turns the larger one. The small gear is completely free to spin on the shaft and has a few mm up and down play also. Should it be fixed solid to the output of the motor? It seems to me like the motor is turning but the gear isn't, although I'm no expert.

I'm restoring a mk1 caddy which is my 1st welding project. I'm getting fairly stuck into it and have next week off so could get a lot more done, I'll need my grinder though so is it a repair or replace?

 

[brightspark]

there normaly a press fit on,the shaft some have small keys in some havent. if it hasnt u can remove it and locktite it in position i had one do the same

 

[BrokenBiker]

I have the same grinder but am in work, if you have no joy by the time I get a chance to strip it I will look in mine for you.

for what its worth you can pick up decent grinders quite cheap now. My Bosch was 30 quid, I treat them as consumables

 

[alancaddy]

Thanks, not sure about gluing it in position as it would probably break free again under heavy load, I've looked at exploded diagrams of some of the other bosch models which look to have a nut holding the gear on, mine doesn't have that though.

Screwfix are doing a deal on Hitachi's, a 4.5" and a 9" for £100, are they any good?

 

[BrokenBiker]

cant speak for the grinders but I ha e a hitatchi 18v combo drill that impresses me everytime I use it

 

[slim_boy_fat]

Hitachi are good.

A 9" grinder in the wrong hands is capable of MUCH damage.......

 

[BrokenBiker]

Hitachi are good.

A 9" grinder in the wrong hands is capable of MUCH damage.......

as you read this i am watching a contractor cutting single lengths of m6 threaded bar with a 9". Holding them down to a pallet with his foot. Talk about overkill...mind you, he is a contractor lol

 

[AndyStobbs]

Everyone bangs on about 9" grinders as if they are out to kill you, just use it properly and within your limitatons ie. strength, position and you'll be fine. Using any kind of grinder to cut 6mm is sheer lazyness.

 

[DanielW]

http://www.mtmc.co.uk/product.aspx?...e=googlebase&gclid=CPnaqvP1ocACFazItAodvTwAdw

 

[DanielW]

Thanks, not sure about gluing it in position as it would probably break free again under heavy load, I've looked at exploded diagrams of some of the other bosch models which look to have a nut holding the gear on, mine doesn't have that though.

Screwfix are doing a deal on Hitachi's, a 4.5" and a 9" for £100, are they any good?

Check the brushes first before buying,normally when tool motors start slowing down under load the brushes are worn down or broken?

 

[alancaddy]

Thanks for the replies. Daniel, the link you posted above is the diagram i mentioned which shows a nut over the small bevel gear. If you look at the other diagram for that model (different serial number) it shows without the nut.

I don't really know how to check the brushes. It's not slowing down under load, it isn't spinning at all. Judging by the sound, the motor is spinning at full speed. The disc spins at maybe 60rpm and can be stopped with a finger - there is nothing turning it really, probably just tiny bit of friction from the motor onto the small bevel gear causing it and the disc to spin a little.

As I am gonna need a grinder start of next week, guess ill just buy another. I don't really need a 9" it's just it seemed like a good deal to buy both together.

 

[Robotstar5]

Try loctiting the small gear on, you've got nothing to lose.

 

[BrokenBiker]

mine has a nut on it...no help to you though. I have found that even cheap superglue will work for things like this as long as its left to harden off properly before being used

 

[Wallace]

Can you post a photo?

 

[the snooper]

mine has a nut on it...no help to you though. I have found that even cheap superglue will work for things like this as long as its left to harden off properly before being used

I have also replaced this gear in the past mine mine had a nut aswell

 

[BrokenBiker]

I have also replaced this gear in the past mine mine had a nut aswell

maybe we are finding a common issue here

 

[the snooper]

maybe we are finding a common issue here

damn thing had the nerve to burn out a while later

 

[Wallace]

damn thing had the nerve to burn out a while later

User error?

 

[mike 109444]

Sometimes there are 4 screws that attache the head unit to the main body .This is what I think you have taken apart so far. There are sometimes another 4 screws that hold the head unit together. If looking end on at the disc mounting thread there maybe 4 screws around perimeter that may have worked loose. Hope that makes sense!

 

[the snooper]

User error?

nooooooo how dare you it just started to get hot quickly when using it, it had seen a lot of work and just retired its self it was of pensionable age