Need machining help
 

I bought this Smithy 3-in-1 off of Craig's list the other day. I have some projects that I'm working on and need help with a technique for cutting a round plate. I want to cut a 1/4" or 3/8" thick carbon steel plate into a disk for an adaptor on a go Kart I'm building.

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It came with a rotary table, but I'm not sure how to center the table so I can cut the plate. Also, how do you clamp the plate to the rotary tablie in order to make one continuous cut. Do I drill a hole in the plate and then bolt it to the rotary table?

Thanks for any help guys!


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It also came with about 200 cutters, reamers, end mills, parallels, edge finders, dial indicators, a 3 and 4 jaw chuck, end mill adaptors, 123 blocks, fly cutters and lathe tooling. It's mostly chinese tooling, but good enough for what I'm trying to do right now.


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I already made a fork brace for the Honda V65 which was a lot of fun and not too challenging. I free-handed the curved parts. Doesn't look too good, but it fits.

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Can't you drill a hole in the centre of the plate then mount the plate on a mandrel that you hold in the chuck of the lathe and turn the OD?
Alternatively do as you say and drill the hole in the centre and mount the plate on the rotary table with a spacer underneath.
I'd think it would be much easier to control the OD on the lathe though.

My 2 cents.

Whats the OD" If its rather small you can use solid round stock chucked up and turn down the OD to size then use a parting tool to cut off a disk.

You sure got a lot of tooling with it, nice!

Actually, I didn't even think about mounting the plate on the lathe. That would be a lot easier than what I was trying to do! And it I would just have to get close on the center hole as the lathe will true up the plate as it's cutting.

I will still need to drill bolt holes in the plate to mount it to the hub and then mount a sprocket, but once I have the center hole, I can easily center it up on the rotary table.

Now I just have to get an arbor to mount the plate on.

Thanks!

The diameter that I need to cut is 6.5". It's going to have a 3.5" hole in the middle for the axle.

Make the hole in the plate then make an arbor to fit.

Here's what I'd suggest.

1. Bore the hole in the plate well undersize to start with.
2. Make an arbor to fit the hole.
3. Turn OD on lathe with arbor mounted in the chuck (If you have soft jaws true them up first)
4. If you can hold the OD of the plate in your chuck then do so to finish bore the ID. If not then you'll have to clamp the plate on its outer edges to the rotary table, clock the OD, then machine the ID with your mill.
5. The bolt holes will be best done on the rotary table using the above set up.

Of course there are plenty of ways to do it and it really depends on the equipment you have, but that would be my approach with the information you've given us.


Great buy by the way. It looks like you did well with that. SmileWavy

On making the arbor - can I use all-thread or a large bolt and nut?

I could also turn a shoulder into a piece of round bar, then tap a hole in the end. That would be more accurate and stonger and also give me some practice on the lathe!!!

I think you're on to a winner here!

You would probably want to make the diameter on the arbor shorter than the thickness of the plate and use a big flat washer. Alternatively make a slightly longer arbor and a thick washer with recess in the centre that fits over the arbour so the outer step of the washer clamps the plate. (sort of a very broad squared off U shaped washer - yes?)

Have fun.

If you need that big a hole, holesaw the hole undersize, chuck in the hole, turn the OD, chuck on the OD and bore the ID.

Being as how the chucks may not be large enough to hold the OD, I can think of one more way to do this. Drill a hole to make a center, set up on the rotary table and drill the hub mounting holes. Then mount to your hub using longer bolts and some spacers cut evenly on your lathe. Use the hub chucked up as your arbor to cut the ID, fit it up to the hub tight and chuck it up again to turn the OD.

Shifter, I don't have a hole saw, but I could certainly find one here in Houston.

Milt, this method would work, I believe. I could chuck the hub from the inside with the plate mounted/bolted to the hub.

But I think I could grab the OD though using the correct jaws.

These are all great ideas.

One more question, when I'm cutting the center hole, what happens to the piece of metal when I finally punch through? Does that piece fall harmlessly aside, or does it get launched. I'll be turning it slowly - 100 or 200 RPM.

Wow care to share how much you paid for all of that? Looks like a hell of a deal with all that tooling included. Cheap chinese tooling nevertheless, if you have to buy it it's expensive.

The piece should fall out harmlessly at 200rpm, but always be ready if it doesn't. The biggest danger when turning are (1) getting you or your clothes caught in the chuck or piece, (2) the whole piece coming out of the chuck, and (3) the most likely, a shaving going someone it shouldn't like your eye or more likely - down your shirt when it's super hot :D

Even when the lathe is stopped, expect that every edge and every shaving is razor sharp.

Schum, I gave $850 for the whole lot. It also came with the table with drawers. I think I got a good set-up. The real machinists on this board and elsewhere don't like the 3-in-1's, but I figured I had to start somewhere.

I also got a box full of aluminum and a box of Delron plastic to practice with. And the guy threw in one of those granite measuring stones (don't know what I'll use that for) and a set of Heli-coil threading tools.

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I've been told that you can buy your mill or lathe and then spend an equal amount on tooling! So this gets me up and running without breaking the bank.

I laundered the money through eBay (sold some stuff) to keep my wife from finding out how much I spent.

Gee, you stole that.

Good deal!

When I wright the check to Pelican Parts, I then just wright in some local grocery store in the check register.:eek:

No doubt. I bought an old metal lathe a couple years ago that cost me 350 with some tools. I looked around and saw that was pretty much a bargain.

Here is a good forum to hang out at for a lot of your questions too:

http://bbs.homeshopmachinist.net/forumdisplay.php?f=3