Delrin Cylinder Wall Thickness

DelLorto

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I need a cylinder out of Delrin. I'll start with 150mm long x 93mm diameter stock and bore a 53mm hole leaving 20mm wall thickness. I'll leave one end solid to a depth of 20mm until the end.

My question: Am I going to run into trouble clamping the bored end (hollow cylinder end) in a 3-jaw chuck without distortion extending out to the face for my final face cut?

Thanks for any assistance. Trying to force some activity to learn to use the Shopmaster Patriot that's been sitting idle in my shop for close to 5 years now!

Stephan
 

matthewsx

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Hello and welcome to the forum.

I suspect you will need something to keep things from going wonky when you do the final face cut (I'm assuming on the closed end).

First question would be can you do that face cut first so you don't have to go back to it?
If not then I would suggest clamping a metal cylinder or pipe that just barely fits inside your Delrin piece into your chuck so the finished piece doesn't have to be clamped into it at all. You can use heat to your advantage here if you have a heat gun.
Alternatively you might be able to reverse your jaws and secure from the inside of your part.


Cheers,

John
 

JimDawson

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Welcome to H-M :)

A 20mm wall in Delrin should be fine. When in doubt I turn a snug fitting solid plug to fit the hollow end, that way the chuck can't collapse it. Don't forget to thread the plug so you can pull it out with something :)
 

darkzero

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Or if you have a 6-jaw. :big grin: But yeah I agree with Jim, 20mm is plenty of wall thickness to hold with a 3-jaw.

Delrin .032"/.81mm wall thickness. Funny seeing you SN, not sure if it's for the same thing I had in mind but this sleeve was actually for Dell'Orto clone carb, well I'm assuming. It's a China carb that belongs to my buddy and it looks almost identical to my Dell'Orto carbs.

20190826_200413.jpg20190826_200444.jpg20190826_200503.jpg


Rather than flip the part to face the other end. Can you just part the end off at the length you need? I don't ever like to part off under power but depending on the part, delrin is the only ti.e Inwod ever.part off usingbthe power feed to get a decent finish.
 

DelLorto

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Great input all! Thank you.

I’m embarrassed to admit I hadn’t even thought of clamping from the inside. That seems like my easiest option as it keeps me from making anything else and at my level of proficiency nothing is coming out of my shop very quickly.

Jim, If I chose the plug route, would I shoot for a slight interference fit (0.001”?) and insert using some heat?

Darkzero, your comment about 6-jaw chucks answered some questions I had about them. It’s nice to know I need one ‘cause they sure are sexy looking items. I never would have dreamed something that thin walled could be machined.

Thank you for the help and welcome,
Stephan
 

JimDawson

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Jim, If I chose the plug route, would I shoot for a slight interference fit (0.001”?) and insert using some heat?
I normally just use a tight slip fit, maybe 0.001'' clearance fit.
 

Boswell

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I would think that there is just as much chance of deforming when clamping from the inside as from the outside. Perhaps that will not be a problem for just facing the end.
 
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