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Need to make a big hole in Aluminum plate

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pontiac428

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#32
I used a hardware store saw and arbor that wasn't very round or concentric, but the main issue was side wall friction and chip clearance. It took over an hour. Simply the wrong tool for the job. I might have a photo in the archive somewhere. It was a pretty ugly result. That was ten years worth of learning ago, and I haven't dared consider it since.

Sent from my HTC U11 using Tapatalk

Edit:. I found a pic of the plate, but I must have skipped the pic after the hole saw debacle.
 
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Eddyde

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#33
A hole saw will work fine if, as mentioned above, peck and use WD-40 or Kerosene. Also for that thickness I would cut it from both sides.
Edit: A quality hole saw and arbor.
 

DAT510

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#34
After cutting with a hole saw, if you are not happy with the surface finish, you could then use your Rotary table idea to take a finish cut to clean it up.
 
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Downunder Bob

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#35
Is it for the 12"logan?
 

projectnut

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#37
Personally I would enter the piece on the rotary table with a couple of 1" parallels under it. then center where the hole is to be bored under the quill . Next drill a center hole through the plate with the same size bit as the hole saw pilot. Be sure to note the coordinates if you have a DRO, or zero the dials if you don't have a DRO.

Using a hole saw slightly smaller than the finished hole make a slight to serve as an outline. Move the mill table to align the caw cut with the quill. Rotate the table drilling several 3/16"holes around the perimeter using the saw cut as a centering point. Reinstall the hole saw, move the mill table back to the zero point and cut through the plate using the pecking method and plenty of WD 40 as a lubricant and flush. Once the core is removed insert a mill in the quill and move the mill table to the proper position to cut the desired diameter. Rotate the table to finish the cut. Depending on the size of the original hole and the size of the end mill used for finishing you might want to make more than a single finish cut.
 

ezduzit

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#38
The steady I have for my 12" Logan can handle up to nearly 4" diameter. I would not want to limit myself to much less than that.

Also I would use the rotary table for producing the hole. The attached photo shows a part I made on my rotary table. The rounded portion fits inside a 4" diameter sailboat boom (so its would be ~3-5/8") and was hollowed out using a 5/8" carbide end mill.

 

dennys502

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#39
The steady rest I made could handle 5" pipe. I made it that big so I could face the ends of pipe if I needed to.
It all depends on usage.
 

derf

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#40
Here's one I made for my 10" SB, and then an adapter for my 13". It's been a long time ago, but I think I just drilled some 3/4" holes and freehanded the rest on the mill.
DSC02558.JPG
 

pineyfolks

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#41
The hole in the steady rest is only for clearance. You could mill a square or hexagon hole in it and it'll still work fine. You're using the fingers to center the workpiece.
 

whitmore

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#42
I have a small rotary table. What about mounting it so that I could turn it under the mill head, and cut with an end mill?
Yes, that'd work; you'd want to start by making the lathe bed-base part, affix the plate to it, and use the lathe to
drill an accurate center hole, to use in centering the work on the rotary table.

I've considered making a rest that takes a press-in ball bearing race, so I could make adapter inner sleeves
to slip-fit a future project. If there's a junkbox of big bearings, removed for preventive maintenance,
this can be justification for doing a really accurate circular aperture for your project.
 

stupoty

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#43
I was under the impression that a hole saw cutting that deep in aluminum was a problem. But that does look like the easiest solution. I have several hole saws already but hadn't really considered using one because as I said I thought it was somehow an issue.
I guess going slow and lots of cleaning out of chips would work and might be the easiest set up.
I some times drill from both sides on thick parts , depends if the chips are nice and leaving the hole. :)

theirs an rpm chart from starreett to give a guide to speed ,
http://www.starrett.com/docs/other-downloadable-resources/hole-saw-speed-chart---bulletin-194.pdf
 

Dabbler

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#44
This is old school, but it will give you your large hole. A steady rest will have to be cut in half anyway, so:
1) use layout blue to the preferred diameter - sounds like 3" is your best target....
2) make your halving layout and cut with a band saw.
3) continue to take cuts on the band saw until most of the hole is taken out
4) file finish - after all this is just clearance.....
 

P. Waller

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#45
What was the issue that turned you off of that method?
I suspect that chip control was an issue as there is no way to evacuate the chips from the top, this will involve a good deal of pecks.

If indeed one wants to use a hole saw for this purpose make it act like a bandsaw where the chips pass through, drill several through holes where the cut will be and the chips will exit through them clearing the blade, you will find that this approach makes using such a tool almost easy.

Like so.
 

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P. Waller

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#46
As to the size that will pass though a steady you are only limited by the diameter that will allow you to build it and fit on the machine ways.
Often you will have to turn the ends of a part that will not fit through the spindle yet is short enough to hold in a chuck on one end and the steady on the other, make it as big as possible.

This part would not fit through the spindle but was less then the 100" long would that would fit in the machine, also make it as big as possible in the event that the OD is a finished surface that requires the use of a cats head.
 

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homebrewed

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#47
It seems one apparent limitation of the rotary table approach is the disk you're making in the cut, which could jam once it's free. But you don't need to do it that way. Your follower will have some holes in it for mounting the finger adjusting mechanisms, right? Place them first then use them to mount the plate to a sacrificial piece of plywood. Mount that on your RT. Drill the center hole as big as you can, then enlarge the hole by stepping the RT over and milling with your end mill. It will be -- sorta -- like a boring head setup. Keep on stepping over and rotating/milling the piece until the hole is the size you want. You probably want to do conventional milling, not climb milling, with this setup.
 

Silverbullet

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#48
I to wouldn't just cut the three inch hole, I'd go as big as the piece will handle and leave enough room for the adjusters . And yes I'd start from the bed up , base , ring , adjusters, . Cutting the hole shouldn't be a problem , I'd drill holes close together and near the diameter size . I'd either jig saw by hand or trepan it in the lathe. But your rotary table for you sounds best and yes go from both sides . You can mount it with a sacrificial piece between the part and table to support the size.
 

Charles Spencer

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#49
This is old school, but it will give you your large hole. A steady rest will have to be cut in half anyway, so:
1) use layout blue to the preferred diameter - sounds like 3" is your best target....
2) make your halving layout and cut with a band saw.
3) continue to take cuts on the band saw until most of the hole is taken out
4) file finish - after all this is just clearance.....
I like it! I think that's the approach I would take.
 

kd4gij

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#50
The one I made for my 12" crafts lathe will hold 4 1/2: stock.
 

strantor

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#51
Last year I cut two holes through 1" aluminum with a 6" hole saw with a DeWalt wrist-snapper hand drill. It was a hell of a job. It was on a piece of large equipment that would have had to be completely disassembled and sent off for machining, very costly. So we decided to try the hole saw first. I didn't think it would work, but it did. Went at it with plenty of WD40 and stop when the drill gets too hot to hold (or starts smoking from the motor, whichever comes first) then take a 10min break. Repeat.

The surface finish was crap, but would have been better if done in a rigid machine and not by hand.

If it can be done with a 6" hole saw by hand, then surely a 2.5" hole should be no problem for any machine you have access to.
 

markba633csi

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#52
Yes I would use the lathe itself to cut it, so I would rough cut the hole first then build a temporary mount and fasten it to the carriage. Then I would build a large flycutter with an adjustable tool bit, mount it in the spindle and start taking light cuts through the hole, running the carriage back and forth, adjusting the flycutter each time.
Painstaking, but will give a beautiful machined surface if you use the power feed. I've used this technique to cut largish holes in 1/8" and 1/4" aluminum.
Also, for a project like this, I would make a fairly detailed drawing since there are many little details to work out and many different design ideas.
Mark
 
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NortonDommi

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#53
If you have the mandrel a hole saw will cost you under $10, use lube, peck drill and have a vacuum cleaner pointed at cut. Swarf is what kills holesaws.
Run at very slow speed as to fast is killer No. 2.
2 - 2.5" is not a big hole and 1.5" thick can be handled by a standard saw if you buy a long series blade. If you need to extend one just part in lathe and weld in an extension of ERW tube. Make sure the outside is cleaned smooth when done.
Clean up with a sanding drum and file the edge if you want a really flash finish.
 

coherent

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#54
I'm assuming you don't know anyone with a cnc mill or this question wouldn't be asked. If you do or can track someone down who does it would be a fairly simple operation.
 

Investigator

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#55
I'm assuming you don't know anyone with a cnc mill or this question wouldn't be asked. If you do or can track someone down who does it would be a fairly simple operation.
You're right, I don't know anyone with any equipment whatsoever.

Here's one I made for my 10" SB, and then an adapter for my 13". It's been a long time ago, but I think I just drilled some 3/4" holes and freehanded the rest on the mill.
View attachment 269526
This is pretty close to exactly what I plan to do. I don't plan to make it hinge, just a solid rest. My plan is to take the plate and put it on the mill table flat/horizontally on risers and true the bottom with an endmill. Then to remove that set up, and measure/mark the "V" way and put it back in the mill, this time vertically at a 45* angle. Then to plunge down with the spindle and make the "V" way cut through the length of the bottom. Then it goes onto the lathe.

On the lathe, I plan to make a center point held in a 5C collet in the lathe. The plate will be placed on the bed and softly mark the center of the hole. Off the lathe and use the marked hole placement as well as the true bottom on the rest to lay out 3 slots for the brass fingers 120* apart. Back onto the mill, again on risers and line up the slot and cut with flat end mill, check for fit of finger, and while still set up drill and tap the hole to hold the fingers so it is in the center line of the slot. Repeat for each finger.

Off the lathe, mark the hole better, then use hole saw to make the hole.

I think that will work nicely for what I need, but I don't know what I don't know so if anyone has suggestions I'm open.
 

Mitch Alsup

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#56
I would suggest that the hole in the SR should be at least as big as the size of a part that can swing over carriage.
 

savarin

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#57
I use a hole saw for aluminium often.
I clamp the aluminium to a plywood backing and clamp the whole (pun intended) lot onto the drill press table.
Directed wd40 spray and pecking at the drills slowest speed works for me.
Heres some I did earlier.
https://www.hobby-machinist.com/threads/the-giant-binocular.55688/page-3
last post.
I have another sheet to do soon so I will show the actual drilling.
 

kd4gij

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#58
50 BMG will blow a pretty big hole in that plate. :gangster: :laughing:
 

Dabbler

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#59
I once had to cut 6 holes in 1/4 " hot rolled steel plate, from 3" to 4". I used a fly cutter in my mill to do the job...
 

Eddyde

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#60
50 BMG will blow a pretty big hole in that plate.
Well a .500" hole. It reminds me when I was a teenager and got my first highpower rifle a .303 Enfield. I shot it at some aluminum plate and was astonished to see the lands and grooves of the rifling perfectly reproduced around the inside of the hole.
 
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