Dumore flex grinder revisited

I fixed the Dumore flex shaft grinder yesterday...
the square keyed end of the flex shaft had broken off ahead of the
flex itself, leaving a small swaged feature, with the wire sticking
out of the end of it.
So I used the TIG, and melted the end of the wire into a mass, then
chucked the swaged end in a collet, and cleaned it up, then bored a
very small counterbore about .250 x .020 deep.
I then made a matching end piece, with a square key, by turning it on
the lathe, then chucking it in a spin indexer and milling the square
key, then reversing it after parting it off to length, and machining a
boss to fit the counterbore in the swaged piece (to keep concencitity)
Then clamped them together in a vise, and using a .040 electrode,
tig'd them together. Putting the welded assembly in the collet, I
cleaned everything up in the lathe, then put it back together.
It runs fine.
I think however..I made a mistake..I filled the flex shaft with
grease, and stuck in the flex wire..now it runs hot. The handpiece
runs very hot, even though the bearings appear to be free and spin
easily. I filled the handpiece with ATF over night, and will see if it
still runs hot here in a little bit.
Any hints on care and feeding of a flex shaft and hand piece?
Gunner
"Pax Americana is a philosophy. Hardly an empire.
Making sure other people play nice and dont kill each other (and us)
off in job lots is hardly empire building, particularly when you give
them self determination under "play nice" rules.
Think of it as having your older brother knock the shit out of you
for torturing the cat." Gunner
Reply to
Gunner Asch
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"Gunner Asch" wrote: (clip) Any hints on care and feeding of a flex shaft and hand piece? ^^^^^^^^^^^^^^ I once repaired a Dremel flex shaft by silver-soldering a square drive on one end (a less elegant verseion of what you did.) In order to make sure it engaged at both ends, I made it a little long--that was a mistake. You need to have some end play. If it is too long, it compresses on assembly, which results in the flex shaft trying to buckle, so it rubs on the sides of the outer case. The extra friction causes it to run hot.
Reply to
Leo Lichtman
That may be the issue, though I did take some pains in trying to make it a bit short for that reason. Ill knock off some more length.
Thanks for the response
Gunner
"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.
Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner
Reply to
Gunner Asch
I once attached my Dumore to some linear bearings....
Reply to
Tom Gardner
Blush......
Gunner
"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.
Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner
Reply to
Gunner Asch
Gunner, I have one of these dumores, love it. The first time I actually used it, my son was using it to wirewheel some paint off of a bicycle. As he used it, it heated up, like yours, and then runny, burning hot, black grease came running out of the hand piece. Kid got a bit of a burn from it. When I disassembled the shaft, someone had greased the spring and apparently the handpiece bearings as well. My son has been suspicous of it ever since...
I wiped off all that I could, cleaned it all out with some kerosene, and then lubed it with a bit of light struff, might have been Kroil, making sure to let any excess drain out. Works great now, like a giant dremel on steroids and no more "hot oil treatment"!
I would guess ATF would likely accomplish the same end.
Dumore still makes these things (or some version of same) (
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). Thier webbsite is not too informative, but a glance around only tells me that they are too pricey for my budget. I expect that repacement parts costs are a killer.
Good job on the fix, thanks for posting the details, I'll file that away.
-AL A.
Reply to
Al A.

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