Replacement of Helical Gear Spindle Milwaukee Angle Grinder (Super Magnum) 6154-20

Replacement of Spiral Bevel Gear on Spindle Milwaukee Angle 6154-20

I recently wore out the pinion and spiral bevel gears on my 20? year-old Milwaukee Super Magnum angle grinder. It has served me well and I was able to find replacement gears without difficulty on several sites for about 20 bucks. What I did not find, despite quite a bit of searching, was information on how to remove/replace the old helical gear. The pinion gear is very easy as it is simply retained with a nut and slides off its shaft using only your fingers.

It turns out that rather than being on a keyed shaft like my larger Makita 7" grinder, the spiral bevel gear on the Milwaukee is a very tight press fit. I removed mine by carefully cutting the old gear off with another angle grinder and did avoid damage to the spindle. But, I will say cutting into the spindle would have been easy, so I would recommend pressing it off. So, you don't have a good-sized hydraulic press? No problem. I found that my Kurt milling vice was just equal to the task. All you need for disassembly and reassembly is a roughly 2" diameter (a little smaller or larger would work) 1.5" length of pipe. Press out the old gear, apply some lube (Moly grease is said to be best and is what I used) and press it back together. There is a shoulder to limit the sliding of the gear and get it to the correct position.

I will not go into any detail about the rest of the procedure as it is pretty basic stuff other than to say NLGI type 1 semi-liquid grease is recommended lube for the gears and it would be good to get some on hand before doing the repair. But, for me, the key was finding that the job could be done with the milling vise (my Wilton bench vise has too coarse a screw and so does not produce enough pressure without using a cheater bar. Hate to break the vise by pushing it beyond its design limits.)

A few pics:


Denis

Added: I had originally incorrectly termed the large gear a "helical" gear but I got a very kind private message gently advising me of my sloppy terminology from EmanuelGoldstein:
"dg - those are not helical gears. They are spiral bevels. Helicals are on parallel axes, like spur gears with twisted teeth.

If the pinion is off-center, then they are hypoids, but I'm betting they are not."

I'll defer to him on the correct terminology and I corrected my title to reflect that. thank you, Emanuel.

Denis​

Interesting that I tried to correct the title by going to the "Go Advanced" page and was able to edit the title there to show "spiral bevel gear" but that correction does not carry over to the thread listing. Oh well, I tried...

Denis

i see how to pressed gear on but see nothing how you remove the gear. could you send pic how gear was removed? thanks.

goodguy said:

i see how to pressed gear on but see nothing how you remove the gear. could you send pic how gear was removed? thanks.

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From first post

"I removed mine by carefully cutting the old gear off with another angle grinder and did avoid damage to the spindle."

Denis

dgfoster said:

"dg - those are not helical gears. They are spiral bevels. Helicals are on parallel axes, like spur gears with twisted teeth. If the pinion is off-center, then they are hypoids, but I'm betting they are not."​

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Hi, Denis. That bit of wisdom above is worth the price of admission. Thanks for posting it. I learned something today.

metalmagpie

dgfoster said:

From first post

"I removed mine by carefully cutting the old gear off with another angle grinder and did avoid damage to the spindle."

Denis

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Well, he also wrote:

"But, I will say cutting into the spindle would have been easy, so I would recommend pressing it off. So, you don't have a good-sized hydraulic press? No problem. I found that my Kurt milling vice was just equal to the task. All you need for disassembly and reassembly is a roughly 2" diameter (a little smaller or larger would work) 1.5" length of pipe. Press out the old gear, apply some lube (Moly grease is said to be best and is what I used) and press it back together."

I'd also like to know how the gear can be pressed off using the milling vise...

awander said:

I'd also like to know how the gear can be pressed off using the milling vise...

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Look at the 1st and 2nd photos in the original post in this thread, and read the 2nd paragraph of the original post, please. Denis not only described the process, he illustrated it for you.

awander said:

I'd also like to know how the gear can be pressed off using the milling vise...

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It has been long enough that I cannot recall the exact arrangement of the gear on the spindle. I have a vague recollection that I would have had to make a fixture of some sort to support the gear while pressing on the spindle. Clearly, the vise generates adequate pressure to do the job. Making the fixture would be some work. I think I had in mind milling a piece of plate with a stepped hole of such a size that when the plate was sawn through the center of the hole the resulting halves could be rearranged so that the smaller diameter if the step would slide under the gear and the larger diameter would encircle the gear. I guess I was thinking of something like this which, depending on one's milling and welding skills vs grinder skills might be more work than it is worth.
The shown location of the step in the larger hole might be better positioned in the middle of the larger hole to provide more resistance to deformation. The step dimensions might require some adjustment to provide adequate strength.

Denis

sfriedberg said:

Look at the 1st and 2nd photos in the original post in this thread, and read the 2nd paragraph of the original post, please. Denis not only described the process, he illustrated it for you.

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Stu,

I think what I showed works pretty well for getting the gear back onto the spindle. But pressing it off would require a fixture of some sort to support the gear while pushing the spindle out. I think there are some folks out there handy enough with a torch that they could cut off the gear leaving the spindle unscathed. I'm not one of them!

Denis

sfriedberg said:

Look at the 1st and 2nd photos in the original post in this thread, and read the 2nd paragraph of the original post, please. Denis not only described the process, he illustrated it for you.

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Hi S, I think that you are misunderstanding the photos and the procedure written up. They show the gear being pressed ON, as far as I can tell.

awander said:

I think that you are misunderstanding the photos and the procedure written up

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Yup, you are correct!

Another way to remove the gear might be to simply drill and tap two or three holes in it and use a bar and jack screws to put it off. The gear may be hard all over or just the teeth. An oxy torch could soften spots to allow drilling and tapping if necessary.

Denis