What tool to bore this (aluminum, plastic) on a lathe?

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Long Tom
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What tool to bore this (aluminum, plastic) on a lathe?

Post by Long Tom » Wed Dec 07, 2011 2:19 pm

Hi folks.

The machining I've done in the past was all on a mill, so I'm learning on the fly on my lathe- which is really fun- and my next trick to learn is boring holes. The parts I need to bore are generally "shallow" disks- 1/2" to 1.5" thickens 4"-7" in diameter, and the holes are from about 1" to 2.5" in diameter.

I have a Swiss MultiFix toolholder on my 12x36 Logan lathe. The MultiFix has a channel about 7/8" wide to accept cutters, held down by 3 set screws. Works fine for the carbide and HSS cutters I've been using. Will it work to hold a boring bar, or do I need to buy or make a stouter holder?

Any suggestions as to the appropriate boring bar to buy are appreciated. Also any boring tips.

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BadDog
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Re: What tool to bore this (aluminum, plastic) on a lathe?

Post by BadDog » Wed Dec 07, 2011 2:26 pm

Many boring bars have flats so you can hold them in a regular tool block (as you describe). The only real problem is that you may need packing depending on bar size, and how much vertical adjust you have in the tool post. I prefer the round tool block just because they work for most all round bars and don't require the flats. But that requires a selection of bushings for different sizes. And some boring bars are ground from square stock, so require the standard square tool block. Also, accurate answers require knowing what you are boring. The answers for UHMWPE plastic, aluminum (which alloy?), mild steel, annealed high carbon, pre-hard, titanium, etc can vary quite a bit. Likewise if features require large overhang, and so on.

As for suggestion, just depends on what you find, and what you envision needing. The "perfect" bar for this job may not lend itself to general duties. Frankly, given your description, and if you can't find a convenient (cheap) option, I would just drill slightly under size and then bore with a hand ground bit. That will get this job done (and maybe the next several), and allow you time to figure out what you want/need, and hopefully find a matching "deal" down the road.
Russ
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Long Tom
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Re: What tool to bore this (aluminum, plastic) on a lathe?

Post by Long Tom » Wed Dec 07, 2011 4:01 pm

Thanks. Gotcha.

Can't really drill anything close to the size of the larger holes... I do have some bits that approach 1" but boy, those things do apply some torque to the part and tailstock (I'd think)...

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refinery mike
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Re: What tool to bore this (aluminum, plastic) on a lathe?

Post by refinery mike » Wed Dec 07, 2011 5:37 pm

If it were me i would take the pieces out of the lathe and drill a hole through the center with a hole saw first. for that size they are pretty cheap and remove a big slug of metal that does not need to be turned into chips. Just using a hand held drill motor. not all that close to finished diameter, just to remove the bulk of the material first. (That is if the hole goes all the way through.) Then clamp it to a face plate with a spacer behind it, center it, and then bore it to finished size.

For a boring bar holder, i make a simple holder to clamp onto the T slot of the carriage. I use an unconventional tool post for my lathe but you can adapt this to your type easily. I clamp a blank tool holder on the T slot. Put a drill in a chuck in the head stock and drill a hole through the block and ream it to 1/4 inch over the size of my boring bar. then I machine a brass bushing to fit in that hole with the ID of the boring bit and OD of the new hole. after it is machined i slit the side of the bushing and provide set screws to clamp everything tight. You can come out the end of the holder (if you wish) but I find this more convenient for my uses. The slot on the end is made for square shank bars. I machine it so it will put the boring bar edge dead on center of the lathe.
Hopefully a picture will explain it better.
Attachments
boring bar..jpg

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BadDog
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Re: What tool to bore this (aluminum, plastic) on a lathe?

Post by BadDog » Wed Dec 07, 2011 5:43 pm

Max drill size is a function of power available, bit config, material, and machine rigidity. No idea what your specific situation would allow.

Mike has a good suggestion on using the hole saws. Saving the slug is good if the material is not cheap, and even if it is, that reduces the requirements for use considerably.
Russ
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samthedog
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Re: What tool to bore this (aluminum, plastic) on a lathe?

Post by samthedog » Thu Dec 08, 2011 9:27 am

RefineryMike: That's a neat idea. I will have to knock one of those up for my lathe as it reduces a great deal of set-up time with my standard tool post.

Paul.
Speak with the circus owner instead of arguing with the monkeys.

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tornitore45
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Re: What tool to bore this (aluminum, plastic) on a lathe?

Post by tornitore45 » Thu Dec 08, 2011 12:39 pm

Trepanning, which akin to Face-Parting.
Is a pain, but large holes require less relief.
I like to keep the groove wider than the tool.
Mauro Gaetano
in Austin TX

Long Tom
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Re: What tool to bore this (aluminum, plastic) on a lathe?

Post by Long Tom » Thu Dec 08, 2011 3:34 pm

Hi again. Just wanted to repot back. I bought a boring bar that fits my MultiFix toolholder, along with a 10-pack of some insanely expensive inserts just for AL, and used it last night. Worked great. The biggest pain is having to drill a hole big enough to get it started.

Long Tom
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Re: What tool to bore this (aluminum, plastic) on a lathe?

Post by Long Tom » Thu Dec 08, 2011 3:44 pm

Also, I like the hole saw idea. And, I have a rotary table for my mill. There's no end to the ways I could do this! :)

I've got a hole saw set. I'll do some head-scratching on that. Clamping the parts on my little mill table and using that machine for that job wouldn't suck. Getting the parts more or less centered would be a pain... hmm... I could dimple them with a center drill on the lathe first, then let the part "find" it's center under the pilot drill on the hole saw... then clamp and drill. Then use the boring bar to finish.

Hole saws exert so much torque a guy would really want to get things clamped down tight, that's for sure!

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refinery mike
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Re: What tool to bore this (aluminum, plastic) on a lathe?

Post by refinery mike » Thu Dec 08, 2011 5:13 pm

Hole sawing thick pieces of aluminum can be tricky.
First use a sharp blade
go slow. i use a hand drill because my drill press will not go slow enough.
do not put lube down in the hole. paint the lightest coating on the teeth of the blade (not dripping) regularly.An oily curf will gather chips and choke the teeth.
if the teeth get clogged you have to clean them out
IF possible drill a half inch hole right inside the circle of curf this allows the chips to drop down out of the curf, and not clog up the teeth.

Trepanning is the proper way to do what you are doing. Look up on line. but it is not for beginners. with good (expensive) tools and procedure,it can be painless, but everything can go south quickly.

Harold_V
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Re: What tool to bore this (aluminum, plastic) on a lathe?

Post by Harold_V » Fri Dec 09, 2011 1:33 am

refinery mike wrote:do not put lube down in the hole. paint the lightest coating on the teeth of the blade (not dripping) regularly.An oily curf will gather chips and choke the teeth.
if the teeth get clogged you have to clean them out
Pretty much all of those issues can be well addressed by not using oil. Use kerosene, or WD-40 if you prefer. And---keep the cut wet. That helps prevent chip welding. Also, clear the chips often, so the gullets don't get loaded. The hole drilled for chip evacuation is a great way to address that issue, assuming they can escape from the hole.

Harold
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refinery mike
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Re: What tool to bore this (aluminum, plastic) on a lathe?

Post by refinery mike » Fri Dec 09, 2011 6:41 pm

I have tried most every lube on aluminum, but once the hole saw gets down a quarter inch or more there just isn't any where for those curls to go and that clogs the works. you will be amazed how much easier it is to hole saw deep holes if you allow an out for those chips. I use hole saws to cut out large disks to be turned on the lathe as well, but i use the companies hole saws. they get kind of expensive in the larger sizes. And aluminum doesn't wear the blades out. For disks i just lay it out, so the curf extends half way over the edge.
If you have to hole saw a hole over an existing hole. hole saw a hole through a board and then clamp it over the spot you wish to drill out. no need for a pilot.
On one job i spent a full three months doing nothing but hole sawing 3 inch holes. It was painful to several parts of my anatomy. Now it is hard to find a part of my body that isn't painful.

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