Any machinists?... I need advice.

superjet104

superjet104

Location
lake geneva
I recently licoriceed up my 2012 KTM swingarm while doing a bearing replacement.

Stupid me was using my ironworker to press out the old bearings, the punch went off of center and scraped the wall of the bearing surface.

I have an idea to fix it, I want to bore the surface out, polish it and then I will machine a hardened 416 stainless bushing which will be pressed into the oversize hole, the ID of the bushing will be bored to accept the new bearings.

Question #1
I'm trying to level and clamp this swingarm on my table, the closest I can get is .005". Is that close enough or should I mess with it to get closer which will take a while? I've already spent about and hour tightening and shimming to get it perfect.

Question #2
Where can I get a cheap <$100 boring head to bore about a 1.1875" hole?

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I'm not a seasoned machinist, I'm 20 years old and i have been teaching myself.
 
cookn

cookn

Kamikaze
Location
where you live
I think you are over thinking it. You have the right idea about making a sleeve if the hole was really out of round but if you just nicked it then just buff the nick down with a small flapper wheel on a die grinder. It won't distort the bore enough to effect the bearing. If it is really bad then you need to block up the swing arm right under the end you are boring and try and clamp it down there. That should keep the bore perpendicular. Lastly I am not aware of a 100 doller mill boring bar that would do a decent job in a bore that long ,you would have to make something custom out of a lathe boring bar. I'm not turning you away from trying this but i have screwed up many a bores trying to do what you are about to do with less then capable equipment, and when you get into metal removal it's pretty much game over if you make a mistake. So I would start with the buffing then try the boring if that doesn't work and then just buy a new swingarm for the cost and effort you will put in
 
superjet104

superjet104

Location
lake geneva
I'll send a pic of the damage tomorrow, the problem is the bearings have tight tolerances and the pin wouldn't go thru. I'll try grinding and polishing tomorrow then.

I tend to go way overboard with things.:(
 
alberta guy

alberta guy

Location
edmonton
Yah I'm not a machinist by trade I'm a welder. But I work in a massive machine shop for an international company. Like it was said earlier that swingarm needs to be blocked and clamped way better. You'd be amazing how much a 4" thick plate will flex from the pressure of a cutter. How much of the hole did did you actually mess up? Where on the hole did you hit? A hole will still hold a bearing fine with 25% off it gone. As long as it is not on the top side that takes the pressure. And lastly why where you using an iron worker punch to press out a bearing?????
 
alberta guy

alberta guy

Location
edmonton
Also to press in a sleeve to fit the bearing isn't as simple as you think. Once you press the sleeve in you will still have to remachine it. The hole will squish out of your tolerance for the bearing to fit correctly. If you make the sleeve lose enough not to squish. It will be to loose in the hole. Not to mention every good machinist will say never sleeve a hole. You gotta scrap it and start over.
 
superjet104

superjet104

Location
lake geneva
Im a tig welder also, I own a fabrication shop and picked up a prototrak mill and a lathe a while ago and have nobody to teach me.

I usually get way over my head with stuff, and I was already questioning the rigidity of clamping it like that.

Like I said, I'll send a pic of the inside of the bore and post it tomorrow morning.

Side note: I was using an iron worker because the KTM dealer couldn't get the bearings out with their tool, and I don't own a bearing press. I figured I could do it with my punch press, got one side in perfect, the other not so well. I'm an idiot sometimes
 
cookn

cookn

Kamikaze
Location
where you live
Yea you did a pretty good job on that. You will have to do the repair sleeve. Get a lathe boring Bar that is good for slightly larger then your bore and mount it in a collet holder or make something to hold it in your mill. That should bore the hole out decent enough for a sleeve and use some loktite retaining compound on the sleeve. That choke tube looks pretty nice, so you seem to have a pretty good handle on the machining. Just take your time. Machining stuff like this is always a learn as you go process, because you never know what will throw a wrench into the gears lol. Good luck
 
superjet104

superjet104

Location
lake geneva
Another question... On my South bend 13" lathe, there's about a quarter turn of play on the cross slide, sometimes when I cut the pressure forces the cross slide to move, especially when cutting a small taper with the compound slide. Also I get chatter when taking deep cuts. Is that normal or what needs to be replaced?

I have a long indexable insert mill that was included with the mill when I bought it that might be the right size for boring out that hole if I can find it haha
 
cookn

cookn

Kamikaze
Location
where you live
the gibs on the lathe need to be tightened, it is a wedge inside there and there should be a screw in the end of the cross slide somewhere to take that out. on manual machines it will never be perfect, it is what you call backlash, and when machining on a manual, you can avoid this effecting your work by only turning your slide into your work, if you have to back it off, give it a few turns back, before going forward so you can take this "slop" in the machines threads out.
 
TheBuzzard

TheBuzzard

Location
the jetski grave yard
that one little booger on post #10 is nothing. if its a sealed bearing that presses in, its just the outside race that contacts that whole hole. its just a swing arm, its not a crank or rod bearing that actually turns thousands of RPMs, it barely moves! knock the high spot off so the bearing will press in and be done with it. i've been a professional mechanic for well over 30 years and working on primitive stuff like that , for even longer. you are doing way too much! too late for the simple fix, carry on.
 
SuperJETT

SuperJETT

So long and thanks for all the fish
Location
none
I love stuff like this, fix the problem instead of just replacing parts by throwing money at it. Nicely done.
 
amitchell

amitchell

Location
Victoria BC
looks good. How did you keep the bores concentric and parallel on either end of the arm? tough setup.
 
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