Thread: Taster, Arbors and Repeatability

Good.
So how about two grub screws?
Any slip could lead to tears.
Could you just use a brass screw onto the flat due to limited space?(*even with a full size head thats cut and filed off, you'd have to drill it out fit you ever needed to of course.)

Stuart

Originally Posted by Anorak Bob

The only trick now is the position of the grub screw. To engage the existing flat on the Taster's arbor would mean positioning the grub screw on the taper. A brass tipped screw, located in the drive key slot and bearing on the round section of the arbor would probably do the job. I need to think about this.

If it were me I would have no compunction about providing a suitable flat on the arbour for the grub to bear on (with surgical precision of course). It could be much smaller than the existing flat. My worry would be tapping the sleeve. It sounds hard.

Now the easiest thing would be to daub on the Super Bearing Mount but that would be a one way trip. Heating the Loctited assembly to separate the parts would probably root the Taster.

A shrink fit sounds good now, would have sounded better 3 hours ago before I bored the arbor for a slip together fit.

An additional milled flat to accommodate a brass nosed M6 screw might be the best solution.

Thanks Boys

BT

Originally Posted by Anorak Bob

Peter,

This one was one of my frequently used chucks before I chose to give it a change of life. I did check its fit in the spindle, bug snug unlike the previous arbor. I installed the old arbor to check the fit and it actually rattled. I had simply assumed it was ok previously and given that we all know assumption is the mother of all .... ups, I should have known better.

Bob

The nice thing is, it's all metal. Re-machine the taper on the poorly fitting one, weld another chunk of steel to the nose, make it into something else and who's to know or care....

I've got a buggered 40 taper arbor that I welded a big chunk onto and made it into a big 3 tooth dovetail cutter.

Never stuffing anything up just means you're staying too far inside your comfort zone. Damaging a machine by cutting into its table etc or damaging yourself are the only unforgivable stuff-ups IMO.

PDW

I have been following this thread with interest and I just have to ask the dumb question:

What is a Taster?

I have Googled and looked in most of my technical books, I cannot find a non-food answer

Originally Posted by Big Shed

I have been following this thread with interest and I just have to ask the dumb question:

What is a Taster?

I have Googled and looked in most of my technical books, I cannot find a non-food answer

Here you go Fred.

HAIMER Universal 3D Taster (M694) - YouTube

Thank you Bob, so it is a 3D edge finder, where does the Taster come from?

Never mind, found it

Taster - English translation - bab.la German-English dictionary

I'm still stumbling around in the bloody woods!

I installed a brass nosed M6 grub screw in the drive key cutout location and without milling a corresponding flat on the Taster arbor, it appeared to hold the arbor firmly. The one shortcoming of turning on the mill ( in the case of the 13 with 150mm of Y travel) is that there was insufficient room to test fit the Taster arbor in the bored hole while maintaining the position of the boring bar, unlike a lathe where the carriage can be moved away along the bed. I've ended up with a hole about 0.0005" oversize. I reckon that with the grub screw located in its present position, its allowing the Taster arbor to move slightly side to side, right angles to the screw axis. With an indicator reading off the Taster stylus there is about a thou movement if the body of the Taster is pushed with some force. I will insert some bar in the 30 arbor tomorrow just to confirm that it's not another taper fit issue.

I'm thinking now of a narrow continuous bead of Loctite Super Bearing Mount at the top and bottom of the straight arbor. Or maybe just the top (outboard end ). Or maybe some other compound not as permanent but hard setting. Devcon Steel Putty? There is a through hole in the tapered arbor that would facilitate press removal of the straight arbor should the need arise.

I also thought the additional 18mm I gained would have allowed me to reach the centreline of the dividing head spindle. Alas, I'm still 15 mm shy.

I could use the bitty Hercus head but its one bolt connection makes me a touch nervous. The Hercus mill with its half horsepower and a 3/4 inch slot drill once wrenched the head out of alignment. The 13 runs on 2.

Always something.

BT

Super glue? No I'd not kidding.

I made some live centres a few weeks back and used super glue (as suggested in the MEW article I was making them from) and it worked just fine. The bond isn't great, but it releases easier than Loc-tite, and I think would hold well enough for this application.

Pete

Hi BT,
Whats wrong with a second screw 120 degrees from the first?
I can see in thoery you'd need another two screws higher up(or maybe one onto the flat), but would they really be needed in practice given the loads involved?

Stuart

Just thinkin' out loud here Bob, but if you were to use the Hercus head, and assuming most of the work would be in the parallel plane, what if a couple of extra clamping/pressure screws were used to assist in the clamping process.

Phil
Bobs Hercus head.JPG

Originally Posted by Steamwhisperer

Just thinkin' out loud here Bob, but if you were to use the Hercus head, and assuming most of the work would be in the parallel plane, what if a couple of extra clamping/pressure screws were used to assist in the clamping process.

Phil
Bobs Hercus head.JPG

The little Hercus is pretty much a pretender. The only real factory bits are the body casting, the division plate and the threaded nose protector. More details here - https://www.woodworkforums.com/f65/he...5/#post1256903
Could still be that my method of construction of the clamped components is the Achilles heel. Back when I posted that show and tell I thought I had resolved the problem. I wasn't contemplating using the bitty head on the 13.

Other manufacturers of similarly configured heads used additional fixings. Here are a couple of examples of Ellis heads showing what I think is a more effective clamping setup.
Ellis 7" Dividing Head w 4" Buck Adjustru Chuck Z 727 20 | eBay
Ellis Dividing Head with 5 inch Chuck 0 875 thru Hole | eBay

For parallel to the table work I'm thinking maybe a single locating dowel at say 12 o'clock could be the simplest answer. Accuracy wise, the lookalike may as well be made of licorice. There is half a thou, probably more, run out in the spindle bore. The 12 position indexer has some play. But the thing tilts and could accommodate longer work pieces that the 13's original dividing head and tailstock. For rough work the little head does have some advantages.

BT

Stu , do you mean 180 not 120 degrees?

Originally Posted by Anorak Bob

Stu , do you mean 180 not 120 degrees?

Nope 120, I want 3 contact points in a triangle. Don't you already effectively have to points at 180 degrees?
Stuart