[BradET37]

Hello All,

Please excuse me as I have very little experience with any type of bench top mini lathes etc.

I have three different questions;

Is it possible to reduce the OD of the following picture from .615'' to .607''?
If so, what is the recommended piece of equipment to purchase to do this with that will be accurate to .0005 or less?
How challenging would it be for someone with almost no experience to do this?

The "hub" in the middle has an OD of .615, the two pictures on either side of it are with rubber mounted on it for use on a "slot car". I hope that this picture shows enough detail for someone to be able to help me.

Attachment 185704

Thanks in advance!
Brad

[hanermo]

You need a lathe, some tooling and some skill.
It is very variable on how "hard" and how "productive" you can be.
The skills required are not difficult, but the total tooling is not cheap.

For very moderate needs, figure on an 8x size lathe, and about the cost of the lathe in tooling (for basic machining in general).
About 1500€ all in. Manual tooling. Double the cost for cnc.
A skilled mentor can show you how to make this one operation in lass than one day.

[Dylwad]

That would be fairly simple and easy with a run of the mill mini lathe, without too much tooling.

The trick to holding tolerances on a part like that (assuming the inside bore is concentric to the outside and axle hole) would be to machine an arbor from aluminum that the wheel slides on to, and leave the arbor chucked into the lathe between parts, if you remove the arbor you have to machine a new one for the next parts to hold tolerance. Drill and tap a hole in the end to clamp the wheel to the arbor (or use super glue if only doing a few parts, heat will soften the glue and let you remove the wheel) I could set up and machine 2 wheels to your tolerance in an hour or less, what you have is a dream operation on a lathe, most parts require much more advanced setup and tooling.

A Sherline, taig or HF 7x10 will all work perfectly, but I would lean towards a lathe with an automatic feed on the carriage for the best finish.

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[BradET37]

Thank you both for your guidance.

Dylwad, I may take you up on that offer to machine an "arbor" for my application.

I am looking to do a large quantity of these parts. Probably over 100+ if I can achieve the tolerances that I am looking for.

What is the exact "tooling" that I would need to perform the cutting that I am doing?

For best cut and highest level of accuracy, which lathe would you recommend?

Thanks

[Dylwad]

Thank you both for your guidance.

Dylwad, I may take you up on that offer to machine an "arbor" for my application.

I am looking to do a large quantity of these parts. Probably over 100+ if I can achieve the tolerances that I am looking for.

What is the exact "tooling" that I would need to perform the cutting that I am doing?

For best cut and highest level of accuracy, which lathe would you recommend?

Thanks

A manual lathe is just another tool, accuracy depends more on the operator and methods used.

The way I would do it is:

HF 7x10 lathe, AR carbide tipped bit. Carriage feed set to the slowest speed possible.

Chuck a piece of aluminum rod larger than the inside diameter, .3" + longer than the depth of the wheel sticking out of the chuck. face it and turn it down so the wheels are a tight slip fit. drill and tap a hole in the end, probably 3mm since the bore in the hub of the wheels is most likely 1/8"

Attach a wheel to the arbor you just made, touch the tool off to the wheel OD and zero the cross slide dial. Make a few light cuts until you get your final OD (dial should read .004") and lock the gibs on the compound and cross slides.

Now you should be able to make the cuts on the wheels on a single pass, using the carriage feed lever to start and stop the operation~bring the carriage away from the chuck, bolt a wheel to the arbor, bring the carriage close to the wheel, start the machine, feed the carriage until it has cut the entire wheel, stop the machine, take the wheel off, move the carriage away from the chuck, attach another wheel, and repeat.

After the initial set up you should be able to bang 100 of them out in an evening, and they should all be within your tolerances.

Your only taking .004" of material off, the lathe will barely know that it's cutting metal.

Most important is that the bit is nice and sharp, the cross slide gibs are adjusted perfectly, ways smooth and oiled, and the other gibs are locked to prevent error, due to the operator brushing against the handles.

you want a lathe with a power carriage feed, the taig will work but the finish will depend on how evenly you crank the handle to feed the bit, the HF lathe will just require you to turn a lever to start the feed, and pull it up after you have made the cut, before the bit hits the chuck.







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[Dylwad]

One more thing,

If you need to hold .0005" or better, you will need an accurate way of measuring it, which could be an entire thread on its own.

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[alfiius289]

Dylwad is absolutely correct about accuracy. Could you tell us why 0005" accuracy is so necessary? The only way I could achieve this level of accuracy on 100+/- production pieces would be by taking the time to make a near perfect "go/no-go" gauge piece.
Regards, Al