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Mcgyver
03-06-2010, 10:06 AM
As some of you may know I've been rebuilding a chevalier tool and cutter grinder. There's a jack shaft in the motorized workhead that was problematic...disassembly reveals the two diameters that mate with the roller bearings are small - one end is .003" and the other .007" :eek: :mad: . (after doing a ground up restoration, my opinion of this company's products is that the should have chosen harbor freight as their distributor :p, well at least the bearings are mid range quality)

Ok, question is, how to repair. I'd make a new shaft, but threads are metric and custom and my lathe isn't set up for them...I may still go that route but am interesting in trying a welding repair. any precautions to avoid warping the shaft? i've a mig welder; just lay down a around the shaft (figuring out how to rotate it while welding)? the bead is typically easy to machine?

I haven't done this before so am looking for the tips and hints on how to make it a success

thanks

TGTool
03-06-2010, 10:22 AM
John Stevenson is the go-to guy for experience with shaft build up and restoration.

I also seem to remember thin sleeves available for needle bearing inner races that might have some application.

Are you positive there isn't a way to persuade your lathe to produce a metric thread? I do metric with some regularity on an old Atlas. And (since you have an affinity for special tooling) there's that slide mechanism to produce ANY thread you want. It's essentially a secondary longitudinal slide under the compound linked by a bell crank to a track fixed to the bed. This track can be angled so the thread actually cut will lag or lead the thread set by the leadscrew. I'm not sure I've saved any pictures but can probably track something down if it's not clear and you're curious.

motorworks
03-06-2010, 10:24 AM
Hi
I usually try to avoid welding.
Had an old guy/instructor once tell me
'welding is aways your last choice'

Anyway:
First turn the shaft down to appro 0.050 to 0.100" under the bearing fit size
Use mig , around ,and let cool slightly between welds to TRY and prevent wrapping.
When finished,let it cool slowly on its own.
Chuck up, clock in and turn to a bearing fit.

vpt
03-06-2010, 10:45 AM
I would also try to sleeve the shaft if possible. if you can turn the shaft down a bit so you can build a thicker more workable sleeve to press on the shaft.

I turned and pressed a sleeve on my new acme screw for my BP grinder.

New shaft on top:

http://img18.imageshack.us/img18/1541/newscrew032.jpg

digr
03-06-2010, 10:49 AM
Is it possible to use American thread or are there special nuts involved?

Dr Stan
03-06-2010, 10:54 AM
Welding will only result in a very warped shaft. As I see it you have two choices:

1) Make a new shaft (maybe someone on the forum could do the threading)

2) Have the old shaft plated. Tank plating is not your only option, nor is hard chrome. Check around to see if there is someone in the area that has brush plating. When I was stationed on a repair ship in the US Navy I was sent to the Dalic Brush Electro Plating school in California. Even in the less than optimal ship board conditions we could hold size on a bearing housing or journal to plus or minus .0001" on the diameter. Our "rule of thumb" was if it was less than .025"/side we plated, over that we spray welded.

VPT also has a good idea. Just use a shrink fit and finish turn the OD after assembly.

Glenn Wegman
03-06-2010, 11:07 AM
A pic of the shaft and it's use would be helpful.

If you desire to maintain any form of concentricity with other features on the shaft, I would grind, plate, and finish grind to size the damaged areas. Sulfamate Nickel, Electroless Nickel, or Hard Chrome. I use mainly hard Chrome as that's what the prints usually call for, but Electroless Nickel is excellent for such repairs.

I cant imagine a guy that scrapes everything for accuracy wanting to weld on a shaft....:)

Mcgyver
03-06-2010, 11:12 AM
TGT, story of my life, stopping making one tool cuz i need to make tooling to make the tooling to make the tooling :) I would be interested in the lathe device you mentioned, maybe worth starting a thread on it? on this one though I think I will make a new shaft, thread the ends imperial and make the nuts it needs

thanks guys....I'd turn down and sleeve but on one end but it would meaning turning down threads as well....by the time i sleeve both ends and do the threads, easier to make a new shaft and nuts....this is good ....i've been scraping for months, time to make some chips...I hope i remember how to turn the lathe on

vpt
03-06-2010, 11:18 AM
I'd like to see progress pics.

lazlo
03-06-2010, 12:05 PM
Ok, question is, how to repair. I'd make a new shaft, but threads are metric and custom and my lathe isn't set up for them..

Michael, you still have that Standard Modern, don't you? That's easy to put a conversion gear on the banjo. Bruce Griffing has one on his.

I'd make a new shaft, rather than plate and re-grind. I've got a commercial electroless nickel kit, but they recommend a maximum thickness of 2 thou.

hardtail
03-06-2010, 12:28 PM
Weld buildup is done all the time.........one of migs shining applications........weld and cool is better to keep things straighter, but the returning will get things back true.......John should have recommendations on wire type and inserts.......good luck!

wierdscience
03-06-2010, 01:35 PM
Easy fix,turn the shaft back true just in the worn area.Turn up a sleeve to fit the shaft,but leave the OD .03-.05" oversized.

Split the sleeve,clamp the two halves on the shaft and weld the splits closed.

Automatic shrink fit and if a little weld bleeds through so much the better.

Finish the OD to taste and your done.

John Stevenson
03-07-2010, 06:18 AM
Sorry I'm late for the post - literally, went to the post office in the next town and they have converted part of it to a pub.

http://www.jdwetherspoon.co.uk/home/pubs/the-last-post

So a pie and a pint later I got sidetracked :D
Anyway hard to say what method to use given no picture, true the shaft will distort with welding no matter how careful but if you can hold on a non welded part and single point a new centre in the other end you can turn true again.

Darren's method of a split sleeve is also a good one and I use this at times with a slight mod. I always make a wide cut as I want it to weld to the partent shaft and on large sleeves I drill a couple of holes at 90 degrees to the cut line so I can plug weld to stop any lifting off the parent shaft.

There is no real hard and fast method to repair shafts, each has to be taken on their own merits depending on size and circumstance.

.

davidfe
03-07-2010, 08:23 AM
http://www.jdwetherspoon.co.uk/static/gallery/742-pub-page.jpg
















FEATURED PHOTO!!

John, sorry. It is SO interesting to see what the chain's
priorities are.

No bar maids, no pints, no pub grub. The above and other mundane
pictures.

Lots of locations though.

Lot of fun to see the other side of the pond's values.

Thanks for the real machining content.



Sorry I'm late for the post - literally, went to the post office in the next town and they have converted part of it to a pub.

http://www.jdwetherspoon.co.uk/home/pubs/the-last-post

So a pie and a pint later I got sidetracked :D
Anyway hard to say what method to use given no picture, true the shaft will distort with welding no matter how careful but if you can hold on a non welded part and single point a new centre in the other end you can turn true again.

Darren's method of a split sleeve is also a good one and I use this at times with a slight mod. I always make a wide cut as I want it to weld to the partent shaft and on large sleeves I drill a couple of holes at 90 degrees to the cut line so I can plug weld to stop any lifting off the parent shaft.

There is no real hard and fast method to repair shafts, each has to be taken on their own merits depending on size and circumstance.

.