Gallery, Projects and General > Neat Stuff

oversized holes not a problem

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John Swift:

Hi Blade,

Not working in any mechanical engineering industry , I did not know about metal spraying !

but having read your reply I quickly found this  :--


http://www.metalspraysupplies.com/videos/metallisation-flame-spray.htm


with the metal spray equipment and the borewelder  It should be more often economic to repair / refurbish equipment than just buy new all the time

then there is the maintenance of historic machines


    John

PekkaNF:
IMHO, quite a few wearing pars can be metalsprayed or welded very sucesfully. Sometimes they will outlast original. But there are quite a few places that are outright dangerous to weld/bush/fill/spray to make bearings fit. Specially modern machines are designed to get the last margin out with FEM and such. There may have been very careful consideration over materials and methods. The funny outcome is that then you have to buy spare from the original supplier....there is somewhere in the manual note that certain bearing surfaces should not be tried to be fixed.

To my knowledge most fo the brake disks (I'm talkking industrial here) should not be fixed...even skimmed, they might be pretty close to minimum thermal mass and shape to keep brake pads happy just that odd situation once a ash wednesday they might be needed....

PekkaNF

dickda1:
I worked in a steel rolling mill in Detroit long ago.  Steel was rolled from a 160 ton ingot into a continuous slab about 5cm thick and 3 meters wide.  The rolls were cylinders of alloy steel about about a 0.8 meter in diameter and 4 meters long.  Needless to say the rolls experienced extreme abrasion at high temperatures.  The rolls were removed about every 3 weeks and resurfaced with an automatic welding machine that put on an extra 2 cm of metal on the outer diameter - later trued up on lathe.  As I recall the surfacing took the welder almost 8 hours to complete the task.


-Dick

Bogstandard:
John S,

I regularly do a bit of outside expanding using a straight knurl, I never even thought of using one on the inside.

A couple of thou expansion can be obtained with basically just touching on. What you have shown there must have done a real lot more, I suspect somewhere between 0.005" and 0.010". Usually more than enough to get part to fit again.

Nice one


John

John Stevenson:
I love metal spraying  :clap: it earns me pounds because they use it where it's not suitable.

True story:-

One day the rewind company roll up just as I was leaving to go on site with a large armature, one bearing journal was very badly damaged and it was wanted immediately.
I told them that I could do it first job the following day but not that day. This wasn't good enough so it went somewhere else. They metal sprayed it and turned it back to size and returned it. Motor was rebuilt and sent out and fitted to the job which was a large travelling crane.

Motor fitted and at switch on massive bang that removed about 10 foot of very heavy bussbar from the roof and sparks galore from the motor.

Turns out they had not screened the armature when metal spraying and some of the dust had gone up the vent slots and shorted the comm out from the inside.

Bottom line was one team had to go in, remove the motor and rewind the armature working all thru the night and the following day, not an easy task as most big DC motors do not use wire but copper strip which takes a lot of bending without destroying the enamel.
Another team had to work all night to replace all the burnt out bussbars.

To add further insult about three weeks later I got the same armature back and the bearing was rattling about on the shaft but it couldn't be removed as it had hammered the metal spraying out both sides to resemble a dog bone.

I had to turn the dog bone off, remove the bearing, remove all the metal spraying as you can't build up on this stuff, then rebuild with solid weld and turn back to size.

I have had plenty of other shafts that have done exactly the same, hammered the metal out from under the bearings.

John S.

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