View Full Version : How to test an R8 taper?

The Artful Bodger
06-28-2014, 10:14 PM
I got all ambitious and attempted the most critical machining I have ever tried, making an R8 arbor for my boring head, of course I could have bought one for the price of the electricity used! :lol:

It is all finished now, the thread for the boring head fits well, the keyway seems right and the small end is a snug slide in but how do I test the taper?

With a pin engaging the keyway I cannot blue and wring the taper to test for lock. I certainly do not have any measuring instruments that could test the taper angle (unless there is a method I dont know about).

The best test I can do is whack it into place (with my hand) and it stays there.

Any ideas please?

06-28-2014, 10:26 PM
Blue up the spindle, press in the arbor, pop it back out, and check what transfers. Due to the keyway, that's the only way it can be installed, so that's the only
position you care about the blue transferring.

06-29-2014, 01:32 AM
Can you take out the key for a test fit,then reinstall?

The Artful Bodger
06-29-2014, 01:37 AM
Hi, thanks for the advice.

I have blued the spindle as suggested and made a slight change and it looks good now.

Forrest Addy
06-29-2014, 05:01 AM
Take the effin' collet index key out and throw it away. It will shear at 80 ft lb. That key has damaged more spindles and spindle tooling than all the other turrret mill sized wreck modalities combined.

Anyway, remove the index set screw and blue the taper lightly. Rotate the tool a part rev while holding it in firm contact with the taper.

The Artful Bodger
06-29-2014, 05:49 AM
I am sure that is good advice, I will take a peep up the hole and see how hard it would be to remove it.

loose nut
06-29-2014, 12:29 PM
Mill something with 81 FT/LBs of force and it will remove it self.:D:D:D

06-29-2014, 12:40 PM
You could also turn a female gage if you have tooling with a known good taper to use for comparison. You then just blue your new arbor against that. OTOH, pulling the key is likely quite a bit easier.

Old Hat
06-29-2014, 12:44 PM
Take the effin' collet index key out and throw it away. It will shear at 80 ft lb. That key has damaged more spindles and spindle tooling than all the other turrret mill sized wreck modalities combined.


Pretty Much !
What a half-baked idea a whimp drive key was!

06-29-2014, 12:54 PM
What is the result of spinning the arbor in the spindle after removing the drive key?

Old Hat
06-29-2014, 01:23 PM
Use a BridgePort for a Bridgeport size / scope job.
Use tooling appropriate for a Bridgeport.
Use a force on the drawbar well matched to the cutting force.

The collet won't spin when doing the above.
As for face-mill arbors and solid endmill holders, well . . .
intellegence needs to play a roll here.

As In; knowing when to move up to a heavy-er machine
if yer do'n allotta that.

Jaakko Fagerlund
06-29-2014, 02:31 PM
If you tighten the collet properly and don't over-power your machine, that key isn't going to shear. Or if it is, then after that the collet will always spin. Why? Because if it could spin with the key, then it can definately spin without it.

John Stevenson
06-29-2014, 02:51 PM
The key isn't a drive key. It's there to stop the collet spinning if the thread on either the drawbar or collet is tight when installing a collet.

If you check the threads from time to time to make sure you don't get any tight ones there is no further use for the key.
As Forrest has said it has wrecked more tooling.

Old hat makes a good point but assumes that everyone has a shop full of machines just designed for that one job. Real life often means you have to do the best with what you have.

Old Hat
06-29-2014, 03:40 PM
Nah, I just mean think before do.
I've spent thousands of hours on Bridgeports and copy's.

Improvise instead of overdrive. That's all I mean.

John Stevenson
06-29-2014, 04:26 PM
I've spent thousands of hours on Bridgeports and copy's.


You have my heartfelt sympathies. :) I only spent 7 years nursing one before I sent the pile of junk over to India to make even more junk.

Old Hat
06-29-2014, 04:35 PM
Here Tree and BridgePort dominated every tool-room, and most Tool & Die shops.

I used to think, I'd like to build a realy good tool-room mill, and use the good features each had
and avoid the bad features. I maintain DeVlieg's law should rule though.
A table two to three times longer than the surface it slides on is never a great idea.

I like the Trak mill by Southwest Ind. But the asses made no provission for a low gear.
I guess they assume everyone can afford a cherry tool crib full of thread mills
and a drawer full of insertable helical drills.

The Artful Bodger
06-29-2014, 08:13 PM
The 'key' is the tip of a grub screw and there is very little of it 'above ground'. Whoever said these are more trouble than they are worth is obviously correct as this one is just waiting to gouge a track into an abor and lock things up real good.

I would poke a die grinder up and take the tip off if it were not for the resulting debris in the quill. Maybe I can stuff a rag in tightly to grab any debris. I am not sure I am up to taking the quill apart to get at the head of the screw.

06-29-2014, 10:35 PM
It's very easy, really. You just lower the quill an inch or 2 and remove the setscrew in the back of the ring on the bottom. Unscrew the bottom ring (usually left hand thread) and you have access to the part in question. There is usually a setscrew on top of the one sticking into the bore. Unscrew both with a regular allen wrench and you're done. Should be a 10 minute operation the first time, about half that afterwards.

At this point you can also pull the entire spindle cartridge if you want to re lube or change the bearings. You just pull the drawbar and tap the spindle down from the top. When finished, screw the bottom ring back on and re install the setscrew in the back. Don't make it too tight or it will deform the quill and make it bind going back up into the housing.

After my first experience with a spun collet with a setscrew in it about 30 years ago, I have not run a Bridgeport with one in it if I used it on a regular basis. Taking it out is the way to go.

Old Hat
06-29-2014, 10:39 PM
The reciever is a hollow closed off space.
If you want to whack the key go ahead.
Blow-down the drawbar whole to get any
debriss left from wiping with a rag.

06-30-2014, 07:00 PM
I did what Toolguy said and it was very easy and less than ten minutes. I would add that one should match mark the bottom ring to help maintain the same preload.

The Artful Bodger
06-30-2014, 08:40 PM
Thanks Toolguy, I took your advice and the job was done in 5 minutes or so. The bottom ring was only finger tight and as you said left hand thread. I made it just a little tighter when I put it back in.

Chinese machine by Yangzhou Euro Brother Machine & Tool Co., Ltd.

The new R8 arbor blued up nicely!

06-30-2014, 08:43 PM
YAY! Glad I could help. Congrats on your R8 piece!:D

The Artful Bodger
06-30-2014, 08:48 PM
Yes, I might get all enthusiastic and make some more R8 tooling. Maybe an arbor for hole saws and a fly cutter which would avoid the extra stick out I have using my ER32 chuck for those tools.

Rich Carlstedt
06-30-2014, 10:40 PM
I don't understand removing the key to check the taper ?
Why mess with a perfectly good spindle ?

Just set the new R8 on a block ( 1-2-3 ie) horizontal to a good surface.
Then do the same with another R8 but in the opposite direction and touch the tapers together and mike
over the two at both ends of the taper ( small and large) . The dimension will be the same "IF" the tapers match.


The Artful Bodger
06-30-2014, 11:11 PM
Yeabut, you can only do that if the taper is the largest diameter of the arbor.