Thread: Rough finish

This is a ball turning attachment I've just finished, I've yet to make up a top tool clamp, as you can see this one is bit rough. Well it's pretty rough all over I suppose, I don't have a mill so had to do it all by hand with the aid of a small engineers square, that's the best excuse I can come up with anyway. The second picture is the ball I made but the finish is quite rough. There is absolutely no play in the tool itself and I noticed that the faster the machine spins (max of 1600 rpm) the better the finish. I get a similar finish on normal turning as well. I'm thinking of putting a larger pulley on the motor to speed up the lathe to around a max of 2000 rpm, question is, will this have any detrimental effects on the headstock gearbox?

Bearings and oiling system may be designed to cope with 1600 only.
could risk seizing a bearing.

Originally Posted by th62

This is a ball turning attachment I've just finished, I've yet to make up a top tool clamp, as you can see this one is bit rough. Well it's pretty rough all over I suppose, I don't have a mill so had to do it all by hand with the aid of a small engineers square, that's the best excuse I can come up with anyway. The second picture is the ball I made but the finish is quite rough. There is absolutely no play in the tool itself and I noticed that the faster the machine spins (max of 1600 rpm) the better the finish. I get a similar finish on normal turning as well. I'm thinking of putting a larger pulley on the motor to speed up the lathe to around a max of 2000 rpm, question is, will this have any detrimental effects on the headstock gearbox?

Looks like the cutter is not clearing the swarf to get a result like that.

I would be trying a different finishing cutter profile rather than spinning at a higher speed - and 2000 RPM is way higher than you should be using.

So it suggests your cutter setup is wrong. Look in that direction.

Rob

Hi,
You appear to have no back or side rake? That could help things

Stuart

Getting a good finish on mild steel with low speeds can be problematic, I've been using high rake inserts and they seem to do a fair job. I got some new ones off BT the other day that look promising.

The high angle clearance and super sharp edges seem to be the secret, that might help when grinding a custom cutter for the ball turner.


Regards
Ray

Absolutely correct gents, of course I new that all along? I’ll try making an angled too post tomorrow. I’m so used to using tool holders with rake built in, it never even crossed my mind.

Hi

The finish on the ball looks to be OK to me. If anything is wrong , the knurling seems to be out of sync, eg the teeth are not aligning and the knurl is rough.

BTW well done on making the ball turning tool

Mike

Originally Posted by th62

Absolutely correct gents, of course I new that all along? I’ll try making an angled too post tomorrow..

NO. You just need to grind the cutter profile correctly for the job.

It's not a big deal. Just have a read up on types of profiles on the web.

We are talking high speed steel here with coolant.

Rob

Thanks gents. The knurled part was held in the chuck while I drilled and tapped the ball, and of course it slipped, so I re-knurled it and that stuffed it. I was going to make a tool post similar to the diamond pattern tool holder. The tool holders I use now are similar to H&Fs dropheads, I want to replace them but not sure whether to get drop heads or diamond tool holders. Anyone use the diamond tool holders? I was thinking if I make the tool post along the same lines as the diamond style holder I can use the jig that comes with them for sharpening.

Hi,

I like your ball turning attachment. It's on my many things to do list. Can you please describe how you made the bearing seat for it? Is it just a single row bearing, double row or have you used 2 bearings some distance apart to give better rigity?


Cheers,


Simon

Hi,
Have a look at this thread below, the link under it is some pictures of a HSS tool/grind I get great finishes from.

http://www.woodworkforums.com/f65/po...g-tool-145389/

http://www.woodworkforums.com/f65/po...ml#post1419282

Dave

Originally Posted by th62

This is a ball turning attachment I've just finished, I've yet to make up a top tool clamp, as you can see this one is bit rough. Well it's pretty rough all over I suppose, I don't have a mill so had to do it all by hand with the aid of a small engineers square, that's the best excuse I can come up with anyway.......

TH,

I reckon you've done a commendable job for a bloke without a mill. I have a mill and I've never been enamored with the appearance of the overlapping cutter marks resulting from a correctly trammed head. Essential for flatness where required but as an exposed finish, well, to me it looks unfinished. I often resort to lapping on wet and dry paper against a clamped on wooden fence. The latter ensures parallel scratches. I then evenly chamfer or round off the edges with a needle file. This process combined with Vaseline smeared on the Coolpix lens has tricked a fair number of viewers on this forum. Might be worth a go.

BT

ps Just looked at Dave's post. Here is another option. Being lazy, it's one I like. Finish achieved at 1800 rpm with Kennametal's KC5025 grade insert on a 44 year old Hercus. The steel is 4140.

And Ray, the KC5010 inserts cut as well as the 5025s. The Chinese inserts, who knows.

Originally Posted by Anorak Bob

TH,

I reckon you've done a commendable job for a bloke without a mill. I have a mill and I've never been enamored with the appearance of the overlapping cutter marks resulting from a correctly trammed head. Essential for flatness where required but as an exposed finish, well, to me it looks unfinished. I often resort to lapping on wet and dry paper against a clamped on wooden fence. The latter ensures parallel scratches. I then evenly chamfer or round off the edges with a needle file. This process combined with Vaseline smeared on the Coolpix lens has tricked a fair number of viewers on this forum. Might be worth a go.

BT

Just another option BT. Silicon oil, not spray. Get it from lab/chem supply places. Can be used to hide scratches in glass for turbidity readings. Usually just for calibrations. It fills the scractches but is invisible. I think it would fool the best of us. Also used back in the dark (room) ages to do the same job on negatives for printing.

Dean

G'Day,
This is probably a case of the blind leading the blind (or should that be unsighted) as I have indulged in the black art of ball turning exactly twice now, I used a carbide insert for roughing out, switched to a radiused HSS tool for finishing then used emery and metal polish for the final finish. Due to the nature of ball turning, i.e. dragging a cutting tool through an arc by hand, no matter how slowly or carefully you do it, I think you are bound to get some variation in finish.
Regards,
Martin
(knob polisher to the crowned heads of Europe).
b1.JPGb2.JPGb3.JPG

Your balls are smoother than mine, you must rub them more.