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torker
06-03-2004, 10:07 PM
I just found and finished reading the other thread about machine bushes/pins. Quite a few years ago I was part of a contract to build up some pin holes with weld. If
I remember right they where 2 1/2" or 3" dia. and about 8" deep. We built these up on the inside with 7018 (what the company called for) and they where to machine them out. These pieces where too big to fit in a mill so I assume they used a portable boring bar. Now what in the heck do these things use for a cutter to bore out all that weld? I shudder when I have to machine rough welds like that on my home shop equipment. Thanks.
Russ

Evan
06-03-2004, 10:19 PM
http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif

http://vts.bc.ca/img/boring.jpg

[This message has been edited by Evan (edited 06-03-2004).]

wierdscience
06-03-2004, 10:35 PM
Well I use both HSS and brazed carbide,particularly c-3/c-4 becuase of the impact from the interuppted cuts.

I build my own bar right on the machine and power it with a 500 rpm 3/4" drill motor,its really not that bad since the bar is supported on both sides of the bushing,so long as the bearing mounts and bar substantial its not a problem.

I typically take a clean up pass to make sure there are no high spots and then advance the cutter out .050" at a stroke.

I just rough it out with the carbide and finish it off(last .02") with the HSS.

wierdscience
06-03-2004, 10:36 PM
I think next set I do I'm gonna post a bunch of pictures.

torker
06-03-2004, 11:13 PM
Thanks weird...I figured you'd be all over this one!!!! It sounds simple but I'll bet it isn't or....my wife'd be doing it!!! I wouldn't mind seeing pics of your setup.
Evan...Good one! That's a Williams Lake boring bar no doubt!
Russ

G.A. Ewen
06-03-2004, 11:21 PM
" I shudder when I have to machine rough welds like that on my home shop equipment."

I have found that before building up a shaft it is best to put it in the lathe and take a good cut off the area that is to be built up. This removes any impuritys that have become imbedded in the damaged area and it ensures that you will have to make at least two passes of weld (three is better) to bring the shaft up to a diameter that is large enough to turn to the desired size.

This is more important with 7018 than say, 7024. A single pass of 7018 will be full of hard spots. Two or three passes will turn to a beautiful finish.

My procedure is to set the shaft up between centers on my welding jig, preheat untill the surface that has been turned down turns blue, run a bead down the lenght of the shaft from the end to the turned down shoulder at 12 o'clock, 6 o'clock, 3 o'clock, 9 o'clock untill the whole area has been built up. The next layer is done the same way starting between say, 12 and three on the first layer. With care and attention to making uniform beads there is not to much interuption on the first cut when turning it on the lathe and none on the second cut.

torker
06-04-2004, 12:53 AM
GA... I was mostly refering to building up holes. It's pretty tricky to weld the middle part of an 8"deepX3"dia hole. I see your point though. The same as tack welds are usually harder to machine than a thick heavy weld. Must have something to do with the quench effect on a smaller weld.

John Stevenson
06-04-2004, 01:25 AM
You can get some good ideas from this site

http://www.mirage-machines.co.uk/

In particular, this page

http://www.mirage-machines.co.uk/boring.htm

John S.

Jerry D
06-04-2004, 07:52 AM
One of the shops I do business with frequently rebuilds kettles for steel mills. Part of the rebuild process entails rebuilding the holes that the kettle pivots on. They use a carbon rod the same diameter as the required hole, then build up weld around and right up to the carbon rod, when the area is sufficiently built up they remove the carbon rod and have a perfect hole.
Jerry...

wierdscience
06-04-2004, 09:07 PM
Carbon rod trick,I've done that but on a smaller scale.chevy 350 blocks that have the outside starter bolt snapped through the casting ear.I take a 7/16 arc gouging rod peel the copper off and thread it 3/8"-16,lay the "bolt" in the old threads and weld over with a layer of ni-rod,finish the build up with 7018 and chip out the carbon.Then I take and old carbon steel tap and work it in with lapping compound,the weld fills the threads in the rod so close they look tapped when the rod is chipped out.

motorworks
06-04-2004, 09:19 PM
Here is a site with a movie and good pics of a line boring set up:
http://www.yorkmachine.bc.ca/