Tufnol, reaming thereof

[Bluechip]

Hi Troops

Dunno whether this belongs here or 'How To?'
Move if reqd.

Anyone know how to ream this stuff, Whale Brand, 1/2" sheet?

Case Notes:

Got three rough squares of this, epoxied together to make a 3" Sq. x 1 1/2" block.
Want a 1/2" hole thro' centre, objective is a 70mm dia. x 30mm solid cylinder to bore out into a cup shape with a 5/8" hole in end.
Want the 1/2" hole thro' to mount on mandrel to turn OD.
Drill 1/4", 15/32", ream 1/2".
OK? ....NO! ...1/2" round bar will not enter hole!
Reamed again. Reamer removes nothing. Still can't get 1/2" bar in.
Reamer IS 1/2", try another reamer.
Nothing in flutes. Not taking anything out.
1/2" bar still won't enter.
Bar is miked at .0015 undersize, not that then. No burr on it. Try 1/2" drill shank. That won't go in either.
At this point I decided any *****in' hole about 1/2" will do, as the item is not all that critical, so ..
Poked a 1/2" drill thro'.
That damned 1/2" bar will still NOT go in.
Revelation! It's got hot. Expanded and now gripping! Left it for 2 hours in a freezing cold garage.
Returned, Just the same.
So, snarling with rage and indignation, slammed a boring tool thro' it, and did the job.
Tried the same stunt on a bit of round steel, nothing seems amiss with drills, reamers, 1/2" bar etc. Did what I expected.
So ....
As I know they use the same stuff for bearings, gears etc, someone knows how to deal with Tufnol.
I don't think the epoxy was significant, it had been done for a week and cured in the house at room temp.
In any case, the bar would have to go in by 1/2" to reach the epoxy join, didn't get anywhere near that far in.

Any suggestions ? (Yes! I have thought of stopping using Tufnol).

Dave BC

[Bernd]

I'd try using a boring bar. Bore it out and keep trying the 1/2" bar. So called bore to fit.

Another idea would be to us a tapered bar, for example .495" dia on small end and .505 at large end. Believe they call these "tapered arbors".

Bernd

[Bluechip]

Bernd

True. As said, landed up boring it. Would have been nice to know if it can be reamed or not.

Ah well. Another item on the list of can't do!   

Dave BC

[Bernd]

I don't think any of that type of plastic can be reamed and held to size. Boring works the best. Probably since your only taking a small amount off at one time.

Bernd

[Krown Kustoms]

Tufnol acts like rubber just like PTFE, delrin, UHMW, and nylon. Im sure there are more I didnt mention.
When you send the reamer through the hole stretches to the dia of tool and then relaxes when you take it out.
I work alot with plastics and steer clear of the soft stuff.
UHMW in my honest opinion is the best to work with then comes acetal and delrin.

Im sure you gathered what the tooling was doing to it but I just wanted to add my 02¢ in hopes of helping a bit

-B-

[Bluechip]

Bernd, KK

Played with the stuff today, I think you're right. My reamers are maybe not 'as new' sharp, although they perform OK on metal. But it bores fine, so, as far as I'm concerned, that's it. Job over. 

I've got some other S.R.B.F. which is dark brown, I think it is 'Kite', the electrical grade. 1" round. This reams fine. So, maybe the grief only occurs on the 'Whale' Grade.

Dave BC

[bramley51]

Did I read somewhere to use water as a lubricant?

[Krown Kustoms]

Water will work on some plastics but your lathe will hate you for it.
I use WD-40 as an all around lube on plastic except the real hard stuff and then you dont need any.
Remember....slow speed and light cuts.
-B-

[Bluechip]

Water is a lubricant for some things.

IIRC I saw somewhere that ship's tailshaft bearings are/were Lignum Vitae luricated by the sea water. Presumably on the grounds that, while it was possible to forget the oil, it was unlikely to boil away the entire ocean. Dunno?

With my garage made from concrete panels, and a cold, wet British winter, I'm not to sure about any more water/condensation being needed. 

Last night had a chat with Bogs on Skype, and we came to the conclusion that the most likely cause is that the reamers are blunt-ish.

So, I think that's probably where to leave it.

Thanks for the interest ...

Now off to the shop to continue my eternal quest for other things I'm not very good at ....   

Dave BC