Looking for some boring tips

guy74

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I have been machining a shaft all day, using a very old, very large lathe. I need to bore a 5/16" hole 12 3/4 inches deep into one end now, never had to bore one this small/long. Any tips while I let it cool? I have to bore this hole then heat treat where a roller bearing runs, then I can call it a night, and finish the final threading on both ends of this 8' long mainshaft tomorrow.
 

rbh

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Mar 21, 2009
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Re: Looking for some boring tips

WOW!!! thats a long way to drill, not a machinist but even I have a hard time doing a 1 inch hole and the tap it GRRRRRRRRR:rolleyes: :D


get out the good cutting oil bud.
 

Cofe

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Re: Looking for some boring tips

Best thing I can think of is to take it to a gun smith. They have specialty boring tools for such things.
 

Bob_VT

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Re: Looking for some boring tips

Depending on what you are using to bore the hole........ Slow and lot's of cutting lubricant........ I would start small if possible and work my way up to 5/16" (which is small too. You you rush anything you will get way too much flex and end up out of round. ...... I almost would look for pre made stock manufactured that way and weld up one end.

What are you making???? :)
 

guy74

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Re: Looking for some boring tips

I'm 10 inches into this now!! Letting things cool off a bit, at this depth I only cut 1/8 at a time, and back out to remove the chips. Using a special boring drill, 16 inches long with coolant grooves. Shooting coolant down the top groove. I'm making a clutch mainshaft for a 1982 Gleaner M2 combine, the end I am boring has 3 steps, down to a 1 inch left handed thread, a keyway, a hardened place for a roller bearing (the hole I'm boring is the grease channel for this bearing, have to drill into this bore hole from the side next before heat treating), the outer end of the hole I'm boring has to be threaded to 1/2". On the other end of this 8 foot($3200) 2 3/4" shaft is 2 steps, a keyway and an internal 1/2 thread 1 1/2 inches deep. The total length of machined surface is 34" for both ends. All of the outer diminsions are already finished on this end, will heat treat it tonight after drilling, then make the finish cut on the other end, and thread the internal threads, and cut the 2 keyways tomorrow. I'm making a $3200 part for about $350, and the last 10 hours of my time, and probably 4-5 hours tomorrow.
I appreciate the ideas, Bob you are right on, I guess the only good idea is go slow! I have been on here all day during the long outer cuts, while the machine feeds itself :D
 

guy74

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Re: Looking for some boring tips

Progress report: SUCCESS!! I got it bored, and drilled from the side. Gonna call it a night, do the heat treating in the morning, then finish the shaft tomorrow afternoon. I really didn't expect any replies, but I have been out here to long, and hoped to stir up something :facepalm:
 

dwco5051

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Re: Looking for some boring tips

What size lathe are you using that can pass 2 3/4 through the headstock?
 

guy74

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Re: Looking for some boring tips

What size lathe are you using that can pass 2 3/4 through the headstock?
I'm not sure how to size it, it has about a 18" swing radius over the bed, 12" over the carriage. 7ft long between the centers if the tailstock is moved all the way back. Can pass 3" stock though the head, has a centering chuck on the back of the headstock shaft to stabilize long work. It is pre WW2 vintage, has been modified to run off an electric motor, originally was run from an overhead shaft via a flat belt. It is a good old machine, has been in the family for 40+ years. I wish I had a smaller one too, but I haven't found one that I like yet. I haven't seen another lathe like it, I had to figure out how to cut left handed threads on it today, all these years and I have never had to do that before. It isn't a quick-change anything, has about 70 different gears in the storage box that can be installed to set diferent feed speeds, or thread pitches, and a brass chart on it with all that info. But I can't for the life of me remember what brand it is.
 

funk6294

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Re: Looking for some boring tips

Ok now I want to see a pic of this monster.
 

guy74

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Re: Looking for some boring tips

I'll try to remember to take a pic of it when my camera get back to me, my daughter has it on her trip. The one in my phone doesn't work since I washed it in my pocket :facepalm:
 

Fishing Dude too

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Re: Looking for some boring tips

I'll try to remember to take a pic of it when my camera get back to me, my daughter has it on her trip. The one in my phone doesn't work since I washed it in my pocket :facepalm:

Did it have diry pictures on it since you needed to wash it? lol
 

Fishing Dude too

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Re: Looking for some boring tips

I'll try to remember to take a pic of it when my camera get back to me, my daughter has it on her trip. The one in my phone doesn't work since I washed it in my pocket :facepalm:

Did it have dirty pictures on it since you needed to wash it? lol
 

Bob_VT

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Re: Looking for some boring tips

Years ago I used to dabble for HOURS (days ;)) with a lathe and a horizontal mill............ I screwed up a few pieces by that urge to rush.

My friend has the equipment now and the latest project has been a small mortar that was bored to 1-3/4" but done with a boring bar.

Yes, I miss having a machine shop............ they save a ton of money.
 

Fireman431

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Re: Looking for some boring tips

My distant family owns a milling/grinding service and has been doing the work since Pre-WWII. They even made ordinance for the last 3 wars. Almost all of their machines were 50+ years old until the latest family members running the business dumped the big $$$ for CNC machines.

You can't beat quality workmanship, even if it is a half century old. I want to see the maching AND the part you milled. Good job!
 

Tim Frank

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Re: Looking for some boring tips

I'd have said use a single flute gun drill; but if it's bored already, it's too late. :)
 

guy74

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Jul 12, 2007
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Re: Looking for some boring tips

Did it have dirty pictures on it since you needed to wash it? lol
I will have to use that one next time I do it, lol!!

To those that want pics, my piece of art will be buried in the machine before I get my camera back. I think I have some pics from earlier that may have the lathe in them, I'll have to look.
 

guy74

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Jul 12, 2007
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794
Re: Looking for some boring tips

I got the shaft done, and mostly installed in the combine! Found a pic that was taken in my shop, and cropped it down to the lathe that was in the corner of the pic.View attachment 107083
 
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