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rws
08-11-2014, 01:24 PM
I have an idea of turning a piece of O1 or W1 down to within a couple tho of size, then use a die grinder to get the final size.

I have an air die grinder that I can fairly easily mount to my QCTP. If I use a fine stone, set the compound to about 10 degrees of paralell to the ways, then feed the grinder/stone as slow as the feed rate will go, I should be able to advance the grinder at a very slight amount, then get a better finish than achievable with a tool bit.

My question is what mounted stone would be best? Aluminum oxide comes to mind first, but there are also silicone carbide stones too. I thought the SC stones were for carbide use.

Ideas? Should I use a coolant flow? That may be messy with the grinder turning so fast.

gzig5
08-11-2014, 02:01 PM
Get it as close to size as you can because it is an excruciatingly slow process, at least when I've done it. Don't expect a commercial grade finish. The bearings in a typical grinder aren't up to it. That being said, I would use Alox first and the SC second choice. More important is getting one the size/shape you need. Make sure you dress the stone with the grinder setup. Mist coolant would be the way to go but if you are taking baby cuts, it probably isn't required. Not sure if it would help surface finish in this application. As always....cover every surface with tinfoil and damp towels to protect from the grit. Use a vacuum to collect debris at the cut as you go.

loose nut
08-11-2014, 02:22 PM
The really hard bit is getting/or balancing the stones.

Rosco-P
08-11-2014, 03:06 PM
Didn't Artfull Bodger go through this a few weeks back. Result was not great. Is your air die grinder of better quality than the typical $19 to $29 import that you'd expect better bearings, balanced spindle,etc. and a better finish? If available a surface grinder and spin index would probably get you the finish you want.

rws
08-12-2014, 07:09 AM
I only need to grind about 1 1/2" of the end of the rod. I would turn the piece to close, then grind in place. I don't think I need a "professional" ground finish, but I would like a finish better than what a tool bit gives. Using the slowest feed I have still didn't give the best finish, plus I'm sure I'm getting some deflection, the end is only .200" diameter.

dian
08-12-2014, 09:22 AM
poor lathe and a lot of trouble. get your mike and sand paper and be done with it. use oil.

Sun God
08-12-2014, 09:29 AM
Stuff that.

1. Vertical shear bit, 1 thou DOC, drowned in high-sulfur cutting oil, finest sliding feed you have, finish part oversize one-half to one thou.
2. Wet and dry paper, 1000+ grit, thin machine oil, polish to desired finish and size.

Using a die grinder like that is going to be an exercise in futility, and will almost guaranteed end up with a worse surface finish that the above regimen, and more than likely, no better in runout or size.

Old Hat
08-12-2014, 09:40 AM
Stuff that.

1. Vertical shear bit, 1 thou DOC, drowned in high-sulfur cutting oil, finest sliding feed you have, finish part oversize one-half to one thou.

Using a die grinder like that is going to be an exercise in futility, and will almost guaranteed end up
with a worse surface finish that the above regimen, and more than likely, no better in runout or size.

....+1....

If final I.D is critical begin step 1. early enuff to repeat it three times, and hitting size should be a picknic.
{providing you and your lathe are up to it.}

pass 1 to pass 2 tells and pass 3 takes you home.
Shouldn't need to sand it in.

Rosco-P
08-12-2014, 10:23 AM
Stuff that.

1. Vertical shear bit, 1 thou DOC, drowned in high-sulfur cutting oil, finest sliding feed you have, finish part oversize one-half to one thou.


The poor finish: rough like the metal is torn away; threadlike grooves; fuzzy appearance? Maybe your tool bit isn't really sharp? Machining texts all recomment final stoning of a edge before use. What is the profile on your tool bit? What kind of steel are you making this part from?

rws
08-12-2014, 10:24 AM
poor lathe and a lot of trouble. get your mike and sand paper and be done with it. use oil.

Since you don't know what lathe I have, perhaps you shouldn't say I have a poor lathe.

thaiguzzi
08-12-2014, 10:27 AM
There's something wrong if you cannot get a finish you want in a lathe with the correct piece of HSS. Slow speed, slow feed, correct sharp knife tool and you should get a truly marvelous finish. Worst scenario, finish off with fine Al/Ox paper and Scotchbright pad in between miking the diameter. I would not even contemplate a die grinder attached somehow to a lathe. Sorry.

rws
08-12-2014, 10:32 AM
The poor finish: rough like the metal is torn away; threadlike grooves; fuzzy appearance? Maybe your tool bit isn't really sharp? Machining texts all recomment final stoning of a edge before use. What is the profile on your tool bit? What kind of steel are you making this part from?

I use a rounded positive rake tool, turning W-1. Tool is stoned sharp, I can double check it, but I turned the piece down from a 1/2" diameter, and played with different tools. Regardless, I used the slowest feed rate I have which is quite slow. I still had some degree of surface tool marks. Granted, it certainly isn't a bad finish, but I was hoping for a better finish.

I fully realize I could use abrasive paper to smooth out the finish, but you are using hand pressure and that can vary some especially at the ends. I wanted to try a method that would use the machine feeds to keep the part the same end to end.

Danl
08-12-2014, 11:08 AM
Since you don't know what lathe I have, perhaps you shouldn't say I have a poor lathe.

I believe he was lamenting the eventual fate of your lathe, not the condition or age, due to concern over airborne grit and grime eventually harming it.....

Danl

GadgetBuilder
08-12-2014, 11:18 AM
You might try the vertical shear tool for the finish passes. I've found it takes 2-3 passes taking a couple thou per pass to get the best finish - the first pass generally removes most of the roughness, the next pass is really the finish pass.

To further improve the finish, lapping would be my choice. It is relatively slow, might take 5 minutes or so for the part you describe. You can feel OD changes of a tenth so you can concentrate on the high areas to speed the process. Reverse the lap periodically, avoid dwelling near the end of the part. It's a little more work than oil and abrasive paper but provides better control when you need constant OD along the length. Making an external lap and lap holder is not difficult or time consuming, see: http://www.gadgetbuilder.com/Lapping.html

John

Old Hat
08-12-2014, 11:45 AM
rws.....

You now have a handfull of posts indicating a deficiency most likely in your tool-bit grind.
Also explaining why you shouldn't need grinding.

My personal educated guess is your nose radious is far to big for this cut.
.020 rad max. rake should be high, even exagerated.
The higher your rake angle, the more attention neeeds to be paid to the actual
mean point of contact being at spindle center on small diameter work.

It sounds like you're not convinced.
That frankly puzzles me.

Rosco-P
08-12-2014, 01:03 PM
0.50" round stock, necked down to 0.20" for 1.50"
Is the end supported by a center in the tailstock? Otherwise you have 3x diameter unsupported, the grey area, approaching violation of the 3 to 5x diameter unsupported work rule. As OldHat pointed out your tool nose radius probably isn't helping your finish either.

Old Hat
08-12-2014, 01:17 PM
The finest Lathe Hand I ever had the privledge of learning from,
could be in another room while you attempt a cut.

Tell him what needed to be the result and give him "the Chip".
Like with a urine drug test, he wants a chip gleaned from the cut at midstream.
He might ask for the lead~in chip too.

Usually didn't even need to be told what allow you were working in.
With-in seconds he could nail you to the wall like a poster-child......
.... of how not to do it.

The chip tells the whole story!
He maintained that only two species existed.
One he could lead easily by helping them form mental images
of what is supposed to be happening at the cutting edge.

The other he asserted there is no hope for,
and they should look for a different occupation.

===================

I might add he wasn't well liked by the Planer Platoon.
There was no planer tool that he couldn't improve on,
no matter who ground it. And he didn't even like planer work.
Said he wants to lead a full life, and can't abide cutting only half the time!

rws
08-12-2014, 01:21 PM
The piece is not that long. In it's final shape, it will have two steps in it. Simple enough, but the end has to have a solid perfectly square end. I found it turned down to that diameter quite well. I turned the very end firt, leaving the non-critical larger step for the last cut, leaving as much full diamter intact.

So let's talk tool. First, what is this shear tool? Second, the nose radius; if I grind a .020" radius nose, that's a fairly small cutting surface. I used a rounded tool, a piece if 1/4" HSS ground so the nose end was about an 1/8" radius and as said before ground with a positive rake. Honed sharp. How would this leave a rougher finish than a sharper nose both fed at the same speed?

In speaking of grinding, I would protect the ways and everything else before letting all the debris fly around. I turn and finish rifle barrels all the time, turn them, using a large die grinder with flap wheels. The entire bed and carriage is covered with a canvas cover.

I have made one of these parts already, by the way. And while the business end didn't have the best surface finish, it worked perfectly. The next pieces have a bit different appplication, same configuration but this needs the smooth finished end.

Old Hat
08-12-2014, 01:32 PM
So let's talk tool. First, what is this shear tool? Second, the nose radius; if I grind a .020" radius nose, that's a fairly small cutting surface. I used a rounded tool, a piece if 1/4" HSS ground so the nose end was about an 1/8" radius and as said before ground with a positive rake. Honed sharp. How would this leave a rougher finish than a sharper nose both fed at the same speed?
.

That question and it's wording would have terminated any opportunity
you would have had to learn from the Man I typed about above.

It gives the appearance you aren't receptive enough to waste time on.
Sorry, that's how it hangs !

rws
08-12-2014, 01:41 PM
That question and it's wording would have terminated any opportunity
you would have had to learn from the Man I typed about above.

It gives the appearance you aren't receptive enough to waste time on.
Sorry, that's how it hangs !

Well Old Hat, I take exception to your comment and attitude. I was typing my post when you posted yours, and I never saw it. Niot that it has any meaningful comment to it, it shows you are jumping the gun and making accusations unwarranted. You Sir, are a waste of time.

This site deserves better.

Old Hat
08-12-2014, 01:43 PM
Take Care.

RichR
08-12-2014, 02:10 PM
Hi RWS

So let's talk tool. First, what is this shear tool?

I believe GadgetBuilder was referring to this:
http://www.gadgetbuilder.com/VerticalShearBit.html

Old Hat
08-12-2014, 04:12 PM
Hi RWS


I believe GadgetBuilder was referring to this:
http://www.gadgetbuilder.com/VerticalShearBit.html

Never heard it called "Rebate" before !
Cool. Nice work and diction in that link.

rws
08-12-2014, 04:14 PM
Thanks Rich. I'll give it a try.

thaiguzzi
08-14-2014, 10:28 AM
Hi RWS


I believe GadgetBuilder was referring to this:
http://www.gadgetbuilder.com/VerticalShearBit.html

Thank you Rich. Thank you Gadgetbuilder. Wow! I just knocked up this shear tool out of a piece of 5/8" square HSS on my little Stent T&CG (baby Clarkson). I've never had a problem using HSS for a fine finish or roughing out on my Southbend 9" equivelant Boxford VSL, but... that finish with the shear tool is something else. I made a shear tool for my 8" Boxford shaper a while ago and was impressed with the finish it gave on steel. Should have thought make one for the lathe. So i grabbed some nasty no-name steel out of the scrap box, roughed out, then turned an 0.003" finish pass with the shear tool. Seeing is believing ! My knife tools will now be turned into round nose roughing tools, and the shear tool will be used exclusively for finish turning. Cylindrical grinders - who needs 'em.
Now i know how steel wool is made, a bloke is sitting at a 48" centres lathe turning 0.001" off for grade 0 and half a thou off for grade 000 !!

Old Hat
08-14-2014, 11:19 AM
.
Now i know how steel wool is made, a bloke is sitting at a 48" centres lathe turning 0.001" off for grade 0
and half a thou off for grade 000 !!

That could be another whole fresh thread!
All the incredibal things that can be done with steel-wool, and I think I've seen it stocked
in one tool~room... in 25 years and a dozen shops.

Rosco-P
08-14-2014, 11:33 AM
That could be another whole fresh thread!
All the incredibal things that can be done with steel-wool, and I think I've seen it stocked
in one tool~room... in 25 years and a dozen shops.

Please share a few of your favorite uses in the machine shop.

I'm a fan or copper wool. Cleans up tooling, machine ways, doesn't scratch, removes rust without damaging parent metal. Used to get it cheap at the $1 stores, but now they are passing off steel wool with a copper plating.

Old Hat
08-14-2014, 12:25 PM
Need to back-burner that, my week is boiling over,
Start a thread if you like, I bet it'll fill in quick B4 I getto it!

Gotts run!

Paul Alciatore
08-14-2014, 04:11 PM
Yes, Yes, YES!

Turn it about 0.001" to 0.0015" oversize. Then use sandpaper strips, about 1" wide. Use them shoe shine fashion WITH OIL. Run the lathe at top speed.

Start with fine grade (100 or 150 grit) and proceed down with 220, 400, 600, 800, 2000 grit. You can get a near mirror finish with the 2000 grit and oil. Get it real close to final size with the 100 and 220 grit then use the finer grits to bring it to the finish you want.

The oil both improves the finish AND helps control the abrasive dust. Essentially, there is NO abrasive dust so your lathe can not be damaged by it. Almost no clean up time.

And almost zero set-up time, just change speeds.

The only down side is it is harder to achieve precise diameter control over any length.




poor lathe and a lot of trouble. get your mike and sand paper and be done with it. use oil.

mattthemuppet
08-14-2014, 04:46 PM
Hi RWS


I believe GadgetBuilder was referring to this:
http://www.gadgetbuilder.com/VerticalShearBit.html

I ground one of those the other day, it's simply amazing how little metal it can take off and the edge by definition won't leave any of the ridges that a "nosed" tool leaves, whatever the radius. Only downside that I've heard of is that it's hard to get it into a shoulder because of its design. Oh, and it'll make the longest fine metal strings around, which I had had problems with wrapping around the work piece and scratching it. I was thinking about how to grind some kind of chip breaker/ roller into it, but I haven't had time to experiment.

The Artful Bodger
08-15-2014, 12:01 AM
Ixnay on the die grinder which I found really wasn't much good at all but the Red Neck solution worked quite well although I never tested it to the limit.
http://bbs.homeshopmachinist.net/threads/63795-Red-Neck-shaft-finisher

rws
08-23-2014, 06:08 PM
Verticle shear bit! I ground one and had the chance to use it today. I turned a piece of W1 down to a couple tho, then put this bit to work. Swung the compound around to 10 degrees, and used that to take some small cuts. It worked very nicely! Had the feed set as slow as it would go, light cut, smallest sliver you ever saw!

Thanks to all that recommended this tool, sure did the trick!

J Tiers
08-23-2014, 08:23 PM
Shear bit, or no shear bit, there is much to be said for grinding with a grinder that has a chance to do the job.....(not a die grinder, which is just a larval stage angle grinder).

With a good tool post grinder, very good work can be done, better, I'd venture to say , that the shear bit. But a shear bit is good.