Putting a 14.5" dia. hole in 1/4" Aluminum plate

[Bernd]

A bit of an update on the turning of the Morse Taper #4 adapter I talked about in this thread. I completed the turning. Unfortunately I didn’t quite get the taper right, I was a bit off, plus the finish was not that great. But it did prove that what I am planning on doing worked.

Anyway I cleaned up the second MT #4 I had and it worked OK. Here’s what I did. I turned the pilot which had a Jacobs taper on it and turned it to 1” dia. Next I took a steel block. Bored a 1” hole in it and Locited the two together. I bolted on an arm of ½” thick by 2” wide aluminum. Then I made a holder to hold the motor and spindle of my Sherline lathe head on the arm. See pics below.

I aligned the plate so the center of the spindle is in the center punched mark on the aluminum sheet. You can just make out the punch mark above the upside down 14. Next I clamped the plate down, put an 1/8” cutter in the spindle and proceeded to try and cut out a 14 ½” dia. Center. My basic setup is a rotary table in reverse. The whole setup didn’t work very well do to the setup not being stiff enough. I did eventually break the cutter bit. The cutter loaded up and the springiness or windup of the whole gear train and belt made it difficult.

I did finally put on the tread mill motor and used an 1/8” HSS lathe tool. I didn’t get pics yet of that setup but will in the next day or so, so stay tuned. I did break a couple of those bits also due to to much flex in the whole system. But I’m not giving up. I need to cut out those plates for the guy. It’s spending money for the shop, plus I’m learning how design cutter tooling on the fly, so to speak.

Regards,
bernd

 

[mklotz]

A plate that big with no center hole is a tough nut. What accuracy do you need to maintain on the 14.5" diameter?

I've made larger circular plates sans center hole by first roughing out a twelve sided polygon, then epoxying a bushing to the center. The bushing is then used as a pivot to rotate the polygon against a disk sander to make a circle. A torch breaks down the epoxy to remove the bushing.

Another possibility is to clamp a suitably sized wooden disk to the aluminum sheet and trace around the outer edge with a trim router using a piloted carbide cutter. Here again, I would first rough shape the aluminum with saw and sander to minimize the amount of material the router needs to remove.

The reasonability of any of these suggestions obviously depends on the accuracy required but my experience has been that things that large seldom require high precision.

 

[Mcgyver]

gotta give you an A+ for ingenuity.

what is the tolerance? have you tried a jigsaw? even with a good one, it'll rattle and shake and be the job from hell, but it'll get it done. put a deeply scribed circle in place and carefully file to it afterward.

 

[gilessim]

Being a wood butcher ,as Marv says, I would have hacked off most of the waste with an angle grinder with a 1mm disc on it so that the cutter is only cutting one one side (if you can fit a 1/2"-3/8" cutter you won't break so many!),I've cut quite a few 2' plus table tops in rosewood (almost as hard as ali!) by glueing the centre pivot with a piece of paper between with no problems (these were with a big router though), anyway an ingenious idea!

Giles

 

[Bernd]

A plate that big with no center hole is a tough nut. What accuracy do you need to maintain on the 14.5" diameter?

Marv,

No accuracy required as long as the center of the hole is in the proper place. Basically it’s a clearance hole for the torque converter so I’d say maybe +/- about 1/16” on the dia. If you go back to the other plate I showed in the taper attachment thread you’ll see that hole was smaller, but on the same center. They just made the plate bigger and the hole bigger.

This will actually be the second plate I’m making. The first I used chain drilling to make the hole. Then came using the router to try and smooth the perimeter. The wood router is way to fast. The material is 6061 aluminum and is quite gummy. I’ve got some ideas. Problem is I’m kind of under a time constraint. They need two plates yesterday. I’ve got several ideas on how I’m going to do this project.

gotta give you an A+ for ingenuity.

Thanks. I’ve been wracking my brain on how I can do this. If I had a nice big mill it would be no problem, but I’m working with what I have right now.

what is the tolerance? have you tried a jigsaw? even with a good one, it'll rattle and shake and be the job from hell, but it'll get it done. put a deeply scribed circle in place and carefully file to it afterward.

I did try a jigsaw. Again way to fast. 6061 aluminum just gummed up the teeth. I don’t’ have a speed control on the jigsaw. They way I did the first one left a bit of a rough surface. I filed until my arms got tired. When the guy got the plate he wasn’t satisfied with the finish.

Giles,

Remember I’m cutting out the center. I’m forming a 14.5” dia. hole in the plate. I don’t need the disk. That’s the waste.

I forgot to take pics of the operation today. I’ll do that Friday. I have some ideas of what I need to do to make this setup sturdier. I’ll keep everybody update by posting pics in this thread.

Again guys, I appreciate your input on this. Hopefully it’ll give somebody else an idea of how they might solve a problem they are having with their project.

Now here’s what I would like to do. First I’d like to make a square table for the drill press out of say ½” or ¾” thick aluminum. It’ll have a center hole in it for a bearing. The bearing will guide a pilot on the end of the arbor to keep the spindle from flexing side ways. I’m also thinking of using two cutters 180 degree opposite each other. Kind of like a fly cutter. Hopefully this will balance the load on the spindle and force it to stay on center. This design is going to happen because like I said earlier, this job provides a bit of income for the shop to buy tools and raw material.

Bernd

 

[Bernd]

Here's the rickshaw design that's worked for now. I plan on doing some major redesign of the cutter bar. The one pictured here was desinged to hold the Sherline headstock with a milling cutter. That failed do to the whole setup not being rigid enough to the point I acutally broke an 1/8" milling cutter. To much spring in the whole drive train. New desing has been thought out and I purchased the steel today. This is going to take some time to develop but will post updates. Now for the pics and some comentary on them.

First. Here's what i did to quickly mount the tread mill motor. I welded it to a piece of angle iron that I clamped to the wood supports of the jackshaft. You can also see the control board haging in mid-air that controls the speed. Works great by the way.

a closer look of how I held the motor.

I modified the plate were the headstock was mounted. I milled a 1/8" slot to hold the tool bit. It's the slot that ends in the hole.

Here I'm trimming up the OD.

A closed look at the tool holding method and tool.

And here's the finished product.

The steel I purchased today will be used to build a better tool holder. Hopefully one with less vibration when cutting. Anybody have any idea of how I should grind the tool bit to cut without chatter. I'm only going through 1/4" 6061 aluminum plate. Applying kersone seems to help.

Bernd

 

[rake60]

Very nicely done Bernd.

Making what you need from what you've got is a big part of home
machining. It's also a daily practice in just about every industrial
job shop.

Your home crafted trepan set up looks great.
Thanks for the info and photos!

Rick

 

[Bernd]

Thanks Rake60. BTW, that 1-2-3 block is clamped on there to see if it would dampen the vibration. It didn't. I've already started on the much better designed trepan tool.

I did do a video but it turned out to be over 50 megs. The camera uses Quick Time. I personally do like it. I wish there was a way to convert to MPEG. Oh well.

Bernd

 

[rake60]

Thanks Rake60. BTW, that 1-2-3 block is clamped on there to see if it would dampen the vibration. It didn't. I've already started on the much better designed trepan tool.

I did do a video but it turned out to be over 50 megs. The camera uses Quick Time. I personally do like it. I wish there was a way to convert to MPEG. Oh well.

Bernd

Bernd Check your PM's
I might be able to help you out a bit with that.

Rick

 

[roadrage17]

for the current project i need to screwcut m19 x 1.

I tried to grind up and internal and external screwcutting tool, using a gauge to get the angels at 60 degress to screwcut it put had no sucess when trying to screw the two together.

My guess is the two tools i ground up were not the same.

Any ideas on how to do it more accurately or other methods of doing it.

i have done screwcutting before but not needed to make my one tips for it before

Best regards

RR17