Help rank amateur figure out bit type for small groove on mill
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    Default Help rank amateur figure out bit type for small groove on mill

    I wanted to machine a part out of aluminum that I attached.part.jpg

    Basically it is a 15mm hole, surrounded on two sides of a flange with cylinders that are close to the same size (20mm and 21mm). The 20mm cylinder needs an o-ring to fit in a groove.

    That groove is 1mm tall x 0.85mm deep (cut into the cylinder wall from outside).

    I know I should have a lathe for this specific part, but I do not have access to one. I have access to a Tormach 770m (thanks to all the people here that helped me try to pick a mill).

    It seems I could machine this part by doing half, flipping it and doing the other half except that groove for an o-ring to sit in. I have been trying to figure out what sort of bit I would need to cut that. There is no rotary so I cannot put the part sideways and rotate (like a lathe too bad I don't have one). Anyway if someone can give me a heads up on the type of bit that might work I would appreciate it. I found some stuff at seco that might work, but am not sure if I am looking in the right place. Maybe an abrasive wheel could even work, but those change size so quickly I doubt it would be useful.

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    Before you cut metal, I'm suspicious of your o-ring groove size. What size o-ring do you intend to use? How did you define the width and depth?

    As for cutting it, why couldn't you just interpolate the circle with a groove cutter?

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    If you have a lathe grooving tool you could clamp it in a vise and put the part in a collet and put it in the spindle and use the mill like a lathe. A 1/2"Øx 1/32" keyway cutter would be close, but if it's not you could grind the shank back enough for clearance.

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    woodruff key or keyseat cutter. If they are to wide for your groove then grind it to whatever you need. -Which can be done by putting the cutter in a drill and spinning the face against a bench grinder. It doesn't cut on the face so it does not need precision.

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    I've used a vertical mill to machine the outside of the pin in a forged radial-pin spanner that was too large to do on my lathe. The trick was to use a boring head rotating backwards, with boring bit reversed, so we could in effect perform reverse boring, to yield a precise outer diameter. I don't see why this approach wouldn't work to make an external O-ring groove. It would be a bit slow unless one had a boring head capable of facing et al, but it would work.

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    Quote Originally Posted by AARONT View Post
    If you have a lathe grooving tool you could clamp it in a vise and put the part in a collet and put it in the spindle and use the mill like a lathe. A 1/2"Øx 1/32" keyway cutter would be close, but if it's not you could grind the shank back enough for clearance.
    yes! you can treat your tormach like an upside down vertical lathe. put a lathe tool in your vise and put the part in the spindle. you can have multiple cutters in multiple vise locations like a gang tooled lathe.

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    Quote Originally Posted by BoxcarPete View Post
    Before you cut metal, I'm suspicious of your o-ring groove size. What size o-ring do you intend to use? How did you define the width and depth?

    As for cutting it, why couldn't you just interpolate the circle with a groove cutter?
    To respond just to this, the o-ring is a 1mm ring and the inner diameter is 18mm. The groove is square so that the o-ring can be smooshed flush with the outside metal as it seals. That is the plan anyway.


    To everyone, thank you so much. That is a really great idea about putting the part into the mill and the tool into the vise. I had not even considered that. Thanks,
    Scott

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    Quote Originally Posted by sxotty View Post
    To respond just to this, the o-ring is a 1mm ring and the inner diameter is 18mm. The groove is square so that the o-ring can be smooshed flush with the outside metal as it seals. That is the plan anyway.
    That's what I suspected. For a 1mm o-ring, you'll want a slightly wider groove, like 1.35 to 1.4 or so. That way, when the assembly is fit together, the o-ring has a chance to oblong itself within the groove. It'll make your life easier for many reasons, including installation force and performance. Overfill is a common mistake in seal design. Let the rubber and the fluid do the work, it doesn't all have to be done by the metal. 0.85 is an OK value for depth using a 1mm o-ring.

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    For the proper dimensions for an O-ring groove, it's best to consult the Parker O-Ring Handbook. This is the Bible.

    https://www.parker.com/Literature/O-...ORD%205700.pdf

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    Put a jewelers saw on a arbor in the mill spindle. Part vertical in vise. Interpolate a circle, with x and Y table motion.


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