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[4]

Boring bar advice. (moved from another thread)

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bigloudvtwin

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I'm going to be chucking up a piece of steel round stock 4" dia x 10" long. I want to bore into it approx. 8" deep. Final bore size to be 1.675 (golf ball interference fit). I don't have any drill bits this long to make a pilot hole for bar clearance.
Can I do the entire hole with a boring bar from a flush face to final cut?
I can either buy a bar or build a tool holder for a smaller bar. Just need the right angle on the cutting face. My experience with cutting angles is a trial and no chatter/galling error process.
Thanks
 

Richard King 2

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#2
I answered this in the other place, but it did not come with.
I said..
What kind and size lathe do you own? What type of tool holder? Do you have a boring bar? What size taper in your tail stock ?

Have a steady rest? It's hard to help with out know these things..... Rich
 

bigloudvtwin

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I answered this in the other place, but it did not come with.
I said..
What kind and size lathe do you own? What type of tool holder? Do you have a boring bar? What size taper in your tail stock ?

Have a steady rest? It's hard to help with out know these things..... Rich
Rich, It is an Enco 12 x 36. Pretty tight throughout. Quickchange tool rest, no I do not have a boring bar at this time, Tailstock is MT3, yes I have a steady rest. Attached pic of cheapo cutters I could possibly make a longer tool holder for. (the ones in the wood block)
 

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bigloudvtwin

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Rich, It is an Enco 12 x 36. Pretty tight throughout. Quickchange tool rest, no I do not have a boring bar at this time, Tailstock is MT3, yes I have a steady rest. Attached pic of cheapo cutters I could possibly make a longer tool holder for. (the ones in the wood block)
Sorry Rich, the block is holding an assortment of small boring tools, the longest of which is about 4". I also have a boring bar holder for my tool rest with a 5/8" bore.
 

Richard King 2

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http://www.grizzly.com/products/12-...UjZAu2UCqxUHhALVBYkKC6klRyqqYcbxoCuEMQAvD_BwE

After looking at the machine and seeing the steady rest I would think you would be better having someone do it on a bigger machine.

If the steady rest would open so you could rest the OD of the shaft on it after turning the OD with the tailstock engaged, I would think you could do it. But if you can't use the steady rest then I think you are looking for trouble. Hanging it out 10" and only holding it on the reversed jaws it could fly out and not only damage the machine it could kill you or mame you. Better safe then sorry I would say. Rich
 

benmychree

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I agree with Rich, all you'd need to do is touch the workpiece with the boring bar without the part steady rested, and you would knock it out of the chuck, likely springing the jaws, possibly breaking something, and at the very least, causing some big dents in the ways; the advice to have someone else do the job for you is good, sound advice.
 

stupoty

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have you considered line boring with a bar in centres ?

Stu
 

benmychree

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have you considered line boring with a bar in centres ?

Stu
He has stated that the bore is to be about 8" deep in a bar that is 10" long, so line boring is not an option, and creating a initial hole to subsequently bore is still a insurmountable problem is no steady rest is available. Also, the boring bar to finish the (blind) hole would need to be nearly as big as the finished hole to have the necessary rigidity to accurately finish the hole; a reamer would possibly be the best method for finishing the bore.
 

T Bredehoft

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No one has suggested an 1 5/8 gun drill. Then bore to size.
 

benmychree

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No one has suggested an 1 5/8 gun drill. Then bore to size.
Given the size of the lathe, I do not think that is an option; still, we have the steady rest situation, not to mention power available for the cut and As far as I can see, no way to mount a boring bar of sufficient diameter to accurately size the hole and to be rigid enough to avoid chatter.
 

bigloudvtwin

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I have a steady rest to support the piece. I hadn't planned on making any big cuts at 1500 RPM. I'll figure it out.
 

stupoty

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He has stated that the bore is to be about 8" deep in a bar that is 10" long, so line boring is not an option, and creating a initial hole to subsequently bore is still a insurmountable problem is no steady rest is available. Also, the boring bar to finish the (blind) hole would need to be nearly as big as the finished hole to have the necessary rigidity to accurately finish the hole; a reamer would possibly be the best method for finishing the bore.
a 10 " part should be able to be line bored on a 36" lath bed I would have thought, the holes could be roughed on a drill press perhaps then bored for alignment, he didn't say the OD had to be concentric so that will make it a lot easier.

Just thinking as you say that trying to stick a boring bar 10 " down a pipe may lead to errr, issues :)
 

bigloudvtwin

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a 10 " part should be able to be line bored on a 36" lath bed I would have thought, the holes could be roughed on a drill press perhaps then bored for alignment, he didn't say the OD had to be concentric so that will make it a lot easier.

Just thinking as you say that trying to stick a boring bar 10 " down a pipe may lead to errr, issues :)
Stupoty, It has to be between 7"-8" deep. Yes I understand the bar flex issue. I actually was thinking about making one out of a piece of titanium that I have. I WILL make this happen. I will post pics of the carnage and progress. I appreciate everyone looking out for myself, my lathe's and my workpiece's safety. Trial and error baby! Thanks
 

Cadillac

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From what I can pick up on with his details here’s acouple things. Your gonna want a radius on the end of bore. A squared bore isn’t desired in this application. Think about doing a two piece setup. Line bore your 8” pc. Then make yourself a cap radius in the center to match bore diameter. Bore a charge recess. Make a stepped flange on the matting surfaces for pressure. I would weld the cap personally but with proper studs and meat on diameters it can be bolted. Fun project I’ve debating making many of times.
 

stupoty

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Stupoty, It has to be between 7"-8" deep. Yes I understand the bar flex issue. I actually was thinking about making one out of a piece of titanium that I have. I WILL make this happen. I will post pics of the carnage and progress. I appreciate everyone looking out for myself, my lathe's and my workpiece's safety. Trial and error baby! Thanks
sound interesting, remember photos.

I bored a hole last week, just to small for the biggest boring bar I have and just a bit too long for the one that fitted in the hole. Often the way :)
 
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