Turning detail on long acetal rod

[Androo]

Hi All,

This is my first post so please bear with me!

In recent years have frequently needed to accurately machine detail features on both ends of acetal (Delrin) shafts. The rod diameter is too large for the spindle bore, so the fixed steady was used. Obviously the three steady jaws cannot run on the workpiece, so a suitable bearing was used with a turned rigid PVC collar bush which was a push fit on the workpiece and on the inner race of the bearing - though not too tight a fit as the parts have to be separated afterwards without causing damage! The fixed steady jaws contact the outer race of the bearing. A dti can be used to centre the workpiece accurately as per usual method, when required. It would be better if the collar bush had a flange to prevent swarf getting into the bearing, and the o.d. of the flange needs to be slightly smaller than the o.d. of the bearing. I have set this up to show the principle only, using bits lying around. When I made the precision prototypes, the full length of the workpiece o.d. was machined to close tolerances and had various detail features of different diameters, so a number of collar bushes were required to complete the part.
The photo might help to make the set-up clearer. I hope this is of help to someone sometime!

[charles scozzari]

Nice work and great solution that can be used on other material as well.Thanks for posting your idea.

[natie123]

Great idea Androo. A sealed bearing could be used if swarf is a problem. I will be stocking up on a few to have handy when I use your idea.

[DIYer]

Thanks Androo! We've added your Delrin Turning Setup to our Lathes category,
as well as to your builder page: Androo's Homemade Tools. Your receipt:

Delrin Turning Setup by Androo

tags: lathe, Delrin, turning

[Rorschach]

Good idea. I have considered drilling tapping the fingers of my steady to take some bearings.

[Thunderbelch]

I have turned acrylic with great success using a toolpost grinder (Dremel toolpost mount for us home gamers). The same goes for polycarbonate, composites and even hard rubbers given enough patience. As far as the OP's post is concerned the common solution is to keep several gasket sheets around of various ID's to keep chips put of your steadies. Can't find the specific reference now but here is an example of Adam Booth applying the technique (more in his other videos):

[kickinback]

Great idea. We have similar problems with square shafts and this is a great solution.

[marksbug]

long long ago I did a bunch of derlin stuff, it stinks.... I was making air seals for office chairs( prototypes) and some bushings for some other stuff( pully bushings* guides for watter tower painting curtin's and some other stuff too. it was a bitch doing the seals where it has to taper way down and be flexiable enough to seal with only air pressure from your butt....no not that air ...from sitting on the seat. it was also the bushing that held it all in place. all that seems like another life ago.

[Toolmaker51]

In lieu of sealed bearings, a flanged washer in front of the bearing would suffice 'pressed' onto the bar being turned. An O-ring or felt seal against the bearing on backside of flanged washer, makes it complete.
Running on bearings is technically a pillow block, with less center height adjustment problems.
This was a common occurrence repairing feed roller shafts; bearings ran in steadies to circumvent turning a clean band on the roller itself. None of those would fit any spindle bore, unless a big turret lathe; inadequate bed lengths for that work.