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Machine Shop and Tool Talk

Van Norman 777S Advice Needed


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  #1  
Old 03-20-2012, 10:08:54 PM
sabre85rdj sabre85rdj is offline
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Default Van Norman 777S Advice Needed

I'm boring out my neighbor's John Deere two cylinder block and I'm using a new to me Van Norman 777S boring bar. I've used Kwik Way boring bars before and I'm comfortable with the adjustments and controls but something doesn't seem quite right. The paws don't center the bar in the cylinder. The best I was able to do was about .010 off center after cleaning the bore and multiple attemps. It's pretty repeatable but it won't center the bar. I had to tap the base with a hammer to get it any better. Is that normal for this type of machine? Second, I see no good way to check the bore durning the boring process. I'm boring a 4.50 hole to 4.75 for and big bore kit and I'd really like to check my gage for accuracy. I'm trying to use a telescoping snap gage in the bore and there's no good way to do it. If I raised up the cylinder off the floor, I could check it from the bottom but there's no way to check the top of the cylinder. The bottom of the cylinder is getting some chatter where the cylinder protrudes below the block casting and is more flexible. I think if I take lighter cuts and use a higher speed, I can get rid of the chatter but I don't trust the cylinder measurement at the bottom of the block. So I could use some advice on how to get the bar to center in the bore and what folks use to check the cylinder diameter.
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Old 03-21-2012, 01:21:48 AM
D Reachard D Reachard is offline
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Default Re: Van Norman 777S Advice Needed

Did someone spin the cutting head before he loosened the centering fingers & wore the ends down? Pull the fingers & measure them. Grind to length if that is the problem.
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Old 03-21-2012, 03:17:05 AM
GundyGuy GundyGuy is offline
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Default Re: Van Norman 777S Advice Needed

Sounds like someone might have played with the boring bar and put it back together a little off
Also if the main Rod isnt a neat sliding fit in the housing you will get chatter when it is extended
Also a badly sharpened tool will cause this as well
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Old 03-21-2012, 05:39:53 AM
Matt Montague Matt Montague is offline
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Default Re: Van Norman 777S Advice Needed

I have two 944 VN bars which are very similar to the 777, the cats paws should center you up in the bore. If they are not then the paw inserts are worn or there is a chip or burr on one. The max cut on my 944 before it starts to chatter is 0.040. Are you touching up your tool with the lapping fixture on the top of the machine? I have found that if I have a lot to bore out I need to sharpen the tool several times. I do not use a grinder only the diamond lap and the fixture. As for measuring, I remove the bar measure the bore reset the bar and run out the cats paws to recenter and start cutting, it's about that fast.
Matt
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Old 03-21-2012, 06:38:51 PM
Mike Cummins Mike Cummins is offline
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Default Re: Van Norman 777S Advice Needed

You are will need to swap catspaws around to get centering as close as possible, then file or lap the catspaws down till it centers within .001" or better. When you start to bore, you should expand the catspaws out against the freshly bored cylinder. Set catspaw tension [totally a feel thing], and let the catspaws ride the cylinder all the way down. If you still have chatter, tool is most likely the culprit. The center of the three angles is most critical, it should be as narrow as possible so as it just tapers off to nothing at the trailing edge. You should be able to cut .025" per pass easily. Make sure block is up off of floor so chips can get away. Take your time. Mike
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Old 03-21-2012, 10:30:43 PM
J.B. Castagnos J.B. Castagnos is offline
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Default Re: Van Norman 777S Advice Needed

If the cats paws are not centered, check them without the extension blocks. You should be able to clamp an indicator on the cutter head and rotate it to compare all 4. I got an 888 ,replaced the scroll plate and paws, before reassembling I put the post in the lathe and used a tool post grinder to get them all the same. The 888 is a heavy machine and some one must have slid it against the block, broke the teeth off of one of the paws. It's made like a self centering 3 jaw chuck.
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Old 03-22-2012, 07:07:51 PM
sabre85rdj sabre85rdj is offline
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Default Re: Van Norman 777S Advice Needed

Well, I've got an update. I had installed the paws upside down. The portion that is overhung goes down. When I reversed them, it centered up nicely. I was able to take the bar off the block, replace it and not remove any material if I didn't adjust the bit holder.

Now my only issue is getting the bar to clamp tight enough to keep it from moving on the cylinder block. I mistakenly had the bolt too far back on the hold down clamp and the bar would walk a little bit during the cut or as I cranked the spindle back up. It didn't move much but it just seemed a little inconsistent from one pass to the next. Moving the bolt closer to the foot of the hold down clamp increased the hold down force on the boring bar and it seems to be doing better.

I also sharpened the bit. When I looked at it with a magnifying glass what looked to be a stain was a small chip. So the boring bar, seems to be cutting straight and round when I checked it with my bore gage.
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Old 04-26-2012, 02:43:57 AM
suga bear suga bear is offline
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Default Re: Van Norman 777S Advice Needed

Quote:
Originally Posted by sabre85rdj View Post
I'm boring out my neighbor's John Deere two cylinder block and I'm using a new to me Van Norman 777S boring bar. I've used Kwik Way boring bars before and I'm comfortable with the adjustments and controls but something doesn't seem quite right. The paws don't center the bar in the cylinder. The best I was able to do was about .010 off center after cleaning the bore and multiple attemps. It's pretty repeatable but it won't center the bar. I had to tap the base with a hammer to get it any better. Is that normal for this type of machine? Second, I see no good way to check the bore durning the boring process. I'm boring a 4.50 hole to 4.75 for and big bore kit and I'd really like to check my gage for accuracy. I'm trying to use a telescoping snap gage in the bore and there's no good way to do it. If I raised up the cylinder off the floor, I could check it from the bottom but there's no way to check the top of the cylinder. The bottom of the cylinder is getting some chatter where the cylinder protrudes below the block casting and is more flexible. I think if I take lighter cuts and use a higher speed, I can get rid of the chatter but I don't trust the cylinder measurement at the bottom of the block. So I could use some advice on how to get the bar to center in the bore and what folks use to check the cylinder diameter.
Hey freind pull out catspaw clean screw holes properly, rescrew catspaw be sure its securely tighten and if its still not centering you will have to regrind all on a surface grinder because there probably worn.
For the chattering i recomend extending catspaws to already bored section of cylinder plus you might want to tighten the bar a bit
By the way i have a 944 vn but i need a complete tool kit any ideas where i could locate one, thanks in advance
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