Worn straight plain bearing spindle, hard-surfacing build up?

RevetsP · Jul 5, 2011

I have an old Becker-Brainard milling machine, similar to the #7 in the 1888 cataluge from shopswarf, but the spindle if worn pretty well, about ~0.007 at the big end, and asymetricly as well.

I was considering building the surface up back to the original size and then up 0.010" or so, and boring the straight bronze bearings while seated in their housing in the casting.

Does using a hard-surfacing rod (arc welding) or wire (mig or tig) seem like a horrible idea, and would totally stress the original spindle? I'm assuming it's a crucible steel given the age of the machine.

I have a friend with a bunch of hard-surfaceing rods he doesnt want, so those should not bee too expensive to obtain. To true up the surface of the spindle grinding seems like an optimal option for this.

thanks,
Steve

moonlight machine · Jul 5, 2011

No way I would build it up with a stick welder, I don't see any way it will be any thing like straight when you are done. If you want to build it up, spray welding is the only way to go. Abom on this forum does it. Yes, I would build it oversize and bore the original bushings in place

Forrest Addy · Jul 5, 2011

0.007 under? Can you machine the worn journal undersize to clean up? This presumes the journal has successively smaller diameters needed for axial assembly. Then you have to make a non standard undersized bushing to fit.

There may be a slight reduction in spindle rigidity but I think in balancing negatives the probability of un-successful conclusion to a weld repair far out weighs the rigidity loss.

Similar methods are common throughout industry. Engine rebuilders have used standard undersizes for crank and rod bearing and over sizes for pistons.

Re-cutting the journal and bushing the bore eliminates the very large "surgical risk" associated with a weld build-up on a heat treated and highly accurate part like a machine tool spindle.

Heavey Metal · Jul 5, 2011

Check the bearing bore for taper quite often the bearing is adjustable. You must not think much of your machine if you are going to weld on the spindle. What is your oil clearance? What are you going to use the machine for? I personally would rather have oil clearance than weld.

johnoder · Jul 5, 2011

Most of the older spindles were higher carbon - like 70 points. The worst stuff around to weld on - never mind warping something that is supposed to be straight.

Undersize is the way to go. Then make the new bronze boxes to fit. Here are some for a similar deal, though they had to be very thin wall.

http://img.photobucket.com/albums/v...Older One/Boring Apron/Machining/DCP_1238.jpg

J.O.

cash · Jul 5, 2011

How about building the spindle up with ceramic?

Then resize your bronze bearing to match.

This is what we do with the surface grinder spindles.

You will want to make a master to scrape the bronze bearing round.

You need to have some space for oil.

mark thomas · Jul 5, 2011

There's spray welding, and also spray metalizing. The latter seems more common these days. There's a number of PM folks who do it. Neither causes distortion like arc welding will. But if you have to replace bronze bearings anyway, and other geometries don't dictate keeping current shaft diameter, it's simpler to turn/grind down than to build up and turn/grind down.

locoguy · Jul 5, 2011

Machine true, chrome it up, grind finish? New bushings.

Mike C. · Jul 5, 2011

Spray metallizing is the ticket to get back up to original diam. It wil not affect the heat treat or warp the spindle. Finished material will be slightly porous as well, for improved oil retention. If the bearings are shot, makes no difference whether you build it up or cut it down, though. You still have to make new bushings, either way.

If there's plenty of meat, turn it .010 under. DO NOT weld it.

DaveE907 · Jul 5, 2011

All of the above suggestions are viable, your circumstances and resources will help you choose the best of them for your situation.

To reinterate: no arc sparker welding, it's the road to ruin for your spindle.

Rollerman · Jul 5, 2011

Hydraulic piston rods are hard chromed, would this work on a spindle?
Do not weld, by any process unless you need a boat anchor.

magneticanomaly · Jul 5, 2011

Does anyone here have experience with brush plating?

I have welded and remachined a lot of things: I would NOT do a machine spindle.

If for some reason it is impractical to make new bearings for undersized spindle, you could machine the spindle true, and undersized by 1/8" or so, and make a sleeve to shrink on, then machine back to original size, or to an oversize to allow refinishng the original bearings.

Still, when only a few thou have been lost, I've always wanted to plate.

RevetsP · Jul 5, 2011

Gotcha, ditch the arc welding.

The OD of the bronze bearings are tapered, an important detail that was left out for you guys...

I never thought of using a ceramic coating, I'm not sure what advantages/disadvantages that would provide. I could probably turn/grind the whole spindle down to fit the bearings.

I can take off the whole overarm/spindle housing and tighten the bearings in there, and bore them out. For best accuracy the housing could be indicated on the boring mill be the overarm support, on the side opposite of the bolts to tighten the overarm. I do have access to a horizontal K&T #3 or #4, as well a #2. Neither of them would be too much trouble to use. Otherwise I might be able to use a horizontal HAAS, though I'm not a fan of that route.

I would like to make chips with this and be able to safely reach some higher RPM's and more horsepower than the original setup, I plan on using a flow-through oil system of sorts, pretty much pump a motor oil though the bearings at 30-60psi and put in new lockrings and seals at the ends, and put in an inlet and outlet line for each bearing and filter it, alot of engines really do well with this system :crazy:

.

tdmidget · Jul 5, 2011

Motor oil is for internal combustion engines. If you have to improve(?) on a circulating or R&O oil, then perhaps an antiwear hydraulic oil. But it won't have any effect on the bushings and if you chrome/metal spray it won't do any good there either as it is only effective on ferrous metals.

Winterfalke · Jul 5, 2011

Sounds like a good candidate for HVOF buildup; but as that's still relatively new, I thinks its still really expensive.

Tyrone Shoelaces · Jul 5, 2011

Grind or turn the spindle below size to clean up, build up with hard chrome, grind to the new size to suit your bearing. I seem to recall you could chrome to a maximum of 0.020". Regards Tyrone

Search

Largest Manufacturing Technology Community on the Web

Search

Worn straight plain bearing spindle, hard-surfacing build up?

RevetsP

Cast Iron

moonlight machine

Diamond

Forrest Addy

Diamond

Heavey Metal

Banned

johnoder

Diamond

cash

Titanium

mark thomas

Titanium

locoguy

Hot Rolled

Mike C.

Diamond

DaveE907

Titanium

Rollerman

Cast Iron

magneticanomaly

Titanium

RevetsP

Cast Iron

tdmidget

Diamond

Winterfalke

Stainless

Tyrone Shoelaces

Diamond

Similar threads