Home Grinding Part

[rws]

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]

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]

The really hard bit is getting/or balancing the stones.

[Rosco-P]

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]

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]

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

[Sun God]

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]

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]

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]

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]

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]

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]

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]

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]

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.