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Thread: Rough finish
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18th Jun 2013, 06:39 PM #1Banned
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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?
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18th Jun 2013, 06:58 PM #2Senior Member
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Bearings and oiling system may be designed to cope with 1600 only.
could risk seizing a bearing.
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18th Jun 2013, 07:23 PM #3Most Valued Member
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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
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18th Jun 2013, 07:25 PM #4Most Valued Member
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Hi,
You appear to have no back or side rake? That could help things
Stuart
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18th Jun 2013, 07:55 PM #5
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
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18th Jun 2013, 07:56 PM #6Banned
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Ummm yes!
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.
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18th Jun 2013, 08:27 PM #7
finish
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
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18th Jun 2013, 08:31 PM #8Most Valued Member
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18th Jun 2013, 08:52 PM #9Banned
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Another title escapes me
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.
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18th Jun 2013, 10:41 PM #10Most Valued Member
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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,
SimonGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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18th Jun 2013, 10:53 PM #11Dave J Guest
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
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18th Jun 2013, 11:08 PM #12.
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Cosmetic Adjustment ( or carborundum cheating )
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.
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18th Jun 2013, 11:21 PM #13
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
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19th Jun 2013, 06:23 PM #14Senior Member
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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).
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19th Jun 2013, 06:59 PM #15Banned
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Oh balls
Your balls are smoother than mine, you must rub them more.