Thread: When 8 degrees is not 8 degrees

Hi Mike,

Why not set it to 0 and then see how parrallel it turns?(though this will only check the 0 points) I doubt its that close. Even if it is close I doubt its close enough for what you want. You'll need to set up off a sine bar or clocking off a test bar or some such.

Stuart

Originally Posted by Stustoys

Hi Mike,

Why not set it to 0 and then see how parrallel it turns?(though this will only check the 0 points) I doubt its that close. Even if it is close I dont its close enough for what you want. You'll need to set up off a sine bar or clocking off a test bar or some such.

Stuart

Hi Stuart

Yes I am now convinced that the 16 degrees required needs to be damn close to 16 degrees and anything else will not be good enough

I ground the taper on both my lathe ER32 collet chucks. Took a few goes to get it right, but I was checking it with a 16mm dowel in a 16 collet and blueing......... no really idea how close it is but I assume its pretty damn good......and in this case I'm the only one that matters lol

Stuart

Originally Posted by morrisman

Hi

I have been finishing a project, a ER32 chuck . I ran into this problem previously . I set the top slide to 8 degrees , and bore the chuck for the collets . Problem is, the collets will not fit correctly in the 16 degree bore . So apparently I don't have 8 degrees when the mark on the cross slide says it is 8 degrees. Are the top slide degree stamp markings inaccurate ?

How can I check this ? I am thinking of turning a piece of bar to a 8 degrees taper on its end , then use a sine bar on the surface plate to check if it is 8 degrees

Mike

Mike, the top slide graduations are never accurate enough for this. Think about it. Look at an engineer's bevel protractor. Then look at your top slide, how many arc minutes would you expect it to resolve? You want your collet chuck to be at least 10 times more accurate.

Turn a shaft between centers, choose a diameter at the upper range of your collet system, say between 16 and 20mm for ER32. Make the shaft diameter a little larger than the nominal collet diameter of your choice. Say you have a nice new good brand name 18mm collet, make your shaft 18.1mm. Now slide tailstock to the right, slide the collet onto the shaft, slide tailsock back to the left to support the shaft. Now you may use a DTI or a DI in a toolholder to set your top slide exactly parallel to your collet outer. Now you can remove the shaft and collet, and put your new collet chuck onto the spindle, and cut this 8 degree taper. This time chances are it will be an acceptable fit. Chris

Ok

I just made a gauge using the 8 degree top slide setting .

You can see from the result that the gauge is not 8 degrees as it is locating on the inner end of the R8 collet chuck .. so I will adjust the top slide and take a few light cuts until the blue is a closer fit

Chris ..yes OK good advice

Hi Mike,
The way Chris explains to do it is basically what i have done, the only thing i will add is the DTI or DI tip needs to be dead on center height otherwise you get a false reading. Either do that or set up your compound with a sine bar.

Merry Xmas,
Ew

Have a go at 8 degrees 17 minutes 50 seconds. I've spent a day so far making an ISO 30 arbor for my Haimer Taster and it's just dawned on me while I'm typing this that I have forgotten about the screw running though the centre of thing holding it all together. FM!

Merry Christmas Boys.

Bob.

Originally Posted by Anorak Bob

Have a go at 8 degrees 17 minutes 50 seconds. I've spent a day so far making an ISO 30 arbor for my Haimer Taster and it's just dawned on me while I'm typing this that I have forgotten about the screw running though the centre of thing holding it all together. FM!

Merry Christmas Boys.

Bob.

Bob, When things like that happen it is time to down tools, have a couple of glasses of a good red wine with some xmas turkey lunch and a little nap after lunch.Tomorrow it will all work out.
Merry Xmas to all.
Bob