Parting Practice Chatter

I went thru all of the items brought up so far. I did tighten up the gibs more, but I think they we okay.

I think my tool post and compound need some attention. The fit must not be right because I can see it Rock forward a bit under a load. I'll work on that issue.

i was able to rotate the compound in line with the cross slide to give the tool post more surface under it instead of sitting skew across the end of the compound. That helped a lot, so I think I'm going to take a good look at the way it mounts and see what I can do to fix it.

Question abouts chips during parting. Seems like I see this with aluminum as well as steel. Toward the beginning of the cut the chip is long, continuous and shinny on the under side as it comes off. This, while the cut is smooth and no issues. But, as the cut progresses the chip starts to change to a flat broken flat color and sort of looks like fudge, not shinny. (is that how you spell something that shines?)

anyhow, the toolpost and compound seem to be the biggest part of my trouble.

thanks for helping me out! Let me know what the chips mean? I'm not sure it is the feed changing due to decreasing diameter but that makes the most sense, unless it is related to heat as it starts getting deeper and heats up?

jim
 
I think I'm getting it. Practice is helping me a lot as well as the suggestions. Thanks All!

i think I could benefit from a bit better cutter. I'm using a cheap T style from Grizzly and I can see it loose the nice edge on a single pass on a piece of 1018 CR 1".

i am still of the belief that I can learn how to use the machine with inexpensive tooling and as I get better I can get some tooling that fits my level of skill.

what else is popular for parting? So far all of my tooling is hand ground HSS except for one threading tool I bought just to see if I was grinding mine like the factory stuff.

thanks again everyone!
 
RVJimD said:
Randy,

i didn't see your post earlier.

i have tried that and it get so bad I'm afraid of snapping the tool.

Jim
Click to expand...

Hay its not parting if the tool dosnt explode :)

I can only hang about 0.75 - 1 inch out out of my tool holder before the blades seem to be to bendy (.75 tall about 1/8" thick).

Stuart
 
I found that as well Stuart , by the time I got deep into some three inch bar it was getting a bit twitchy no matter what speed i ran it at so I cut through the remaining the web with a hacksaw instead then faced things off.
 
All this parting has helped me discover a flaw in my setup. I never did use the four way tool post on my G0752 since I purchased a QCTP to go on it. I knew the rigidity of the toolpost was questionable and I even added a third bolt to the compound. Most people are doing a complete four or even six bolt mod and making a new clamping plate. When I looked at that I thought there was still a weakness in all the stuff sitting above the compound clamp plate, like the fact the mine seems to have a pretty large gap from the clamp block around the protractor portion. The other part I didn't like, but didn't understand until today was the T slot and T nut. Mine is pretty sloppy and when I tighten down the toolpost it pulls the T nut up into the slot and there is about .016" gap under it. This lets the toolpost rock toward the gap under the nut. I think the original four way post might be a tiny bit wafer which would help a bit. I think when the mill gets here I'm going to try making a T nut that fits a little better.

meanwhile I put a shim under the nut, which has really helped reduce my problems parting.

now I'm seeing my cutter fail. I'm going to have to order some different T shaped cutters, I can't hardly get thru a 1" piece of CR without taking the the cutter to the grinder. It chips off the cutting edge. I don't think I'm being too hard on it.

here are pics of the t nut and shim location.

image.jpg image.jpg image.jpg
 
Are you sure the hold down stud doesn't stick out of the bottom of the T nut and jack against the bottom of the slot? If it does it would bow the top slide surface upwards which would make the tool post rock on the hump, the gap underneath is irrelevant in my opinion.

Also it might be a good idea to get some leaded steel bar to practice on as it more forgiving as it self lubes a bit and can even be parted dry with care.

Bernard
 
Like you're learning rigidity is CRITICAL. Next is proper sharpening.

I really suggest you get some practice stock and learn to engage the power feed for cutoff. Find the best recipe and write it down. Like has been mentioned, most are chicken sh#t about it and don't feed enough. Once you have the proper rigid setup and know best speed feed, you can just do it every time automatically.

Karl

PS if you've not yet heard the sickening crunch, you don't have enough experience
 
Make SURE your T-nut is not sticking up out of the T-slot. Or you are tightening your toolpost down on the nut not the compound rest, give it roughly .025" clearance.

I had this happen on my 109, chatter, chatter and more chatter. I took a file to the top of my T-nut and all was smooth sailing from there.
 
Bernard,

I understand what you are saying. The nut is definitely below the slot. I don't see how it could be getting pulled up above flush, but I can see the post rock toward the cutter when it grabs the stock or starts to chatter. The shim helped a lot but I agree with you, the gap under the t nut should not matter.

How should I check the bottom of the post for flatness? That seems like the other potential problem.

jim
 
Here is where I think most of my trouble is coming from.

the AXA QCTP I put on is just over 2" square and the original four way post is almost 3". I think the AXA is the aftermarket post that guys are using on this lathe. I think the next larger size QCTP would be too tall to work out.

image.jpg
 
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