A few more things. First off use the thinnest parting tool you can get away with. Small lathes chatter with a wide blade. Definetly no wider than 1/8 inch. Secondly ABSOLUTELY DO NOT PART OFF A PIECE WITH THE TAIL STOCK CENTER HOLDING THE WORK. I think that has been suggested but it was not completely clear. Third, with the lathe off run the edge of the blade up against the flat side of the chuck. That way you can easily Compare and set it to 90 degrees. Fourth, If you can grind a tiny grove in the top of the cut off blade. Not across the tip but along the length of the blade. The grove allows the cut to proceed at slightly different places and balance out vibrations. It also collapses the chips sideways so they do not wedge and allows oil into the cut area. Fifth, If you are parting off a hollow piece, put a bar a little smaller than the hole in a chuck in the tail stock. insert the bar in the bored hole. It will support the piece and catch the part as you part it off, rather than sending it somewhere in the room. (the bar must spin totally free in the hole) And if something should go terribly wrong, it will keep pieces from flying, maybe at you. Sixth, i make my own cut off tools by cutting them out of circular saw blades. I like the ones with carbide tips that are ground with a groove down the center of the bit long ways. Then i reduce the front clearance to 8 degrees. IT has been great for me anyway. Seventh, you must grind relief into the blade on the front, both sides, and also from the tip back, looking from the top like a tiny dove tail. With blade type cut off tools some people try to use them as is and make deep cut offs. That can be trouble. Check out a reference on how to grind cut off blades. (If that is what you are using) Parting is one of the difficult things to do on a small lathe, often i part close to through and then saw the rest of the way with a band saw. (do not saw in the lathe unless you protect the bed from cutting through and marring the bed.) Don,t ask me how i know.
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Parting off question
- Thread starter Almega
- Start date
Everything that I have read suggest's that is a recipe for disaster! If you don't have a extremely rigid setup (like most hobby machine dont have), the tool can get sucked under the work, things WILL break!
A few thoughts...
Only do parting when you really need to. If you can manage cutting it with a saw, do so. It's a relatively "high-risk" operation that can go sour just because of a hard spot in the metal. When things go bad, stuff usually gets bent or damaged -and you could end-up with something flying at you.
1) Very low RPMs. 60-90 at most.
2) Always within 1 inch of the chuck jaws. Tighten the chuck jaws and avoid 3 jaw chucks because they don't grip in as many places and the piece flexes more.
3) Bit must be perfectly perpendicular to the work.
4) Bit must be on-center -Dead on. It will sag a little under pressure so don't start-out low.
5) Lock the carriage in place.
6) Snug-up all the gibs on the compound etc.
7) A lot of cutting oil.
8) Even steady pressure.
9) Double check you're wearing your safety goggles.
A long time ago, I was parting on an Atlas -not a good machine for this. Everything was going just fine and cut was half done. Out of nowhere, BANG! Piece is now jumped-up on the tool post and I'm wondering... What the hell just happened? OK, use a crowbar and wood blocks to get the piece off the tool post... straighten-out the mess. No big damage but parting blade was in pieces. Go inside to hit the head, look in the mirror and a piece of the parting blade is sticking out of the skin just above the goggles.
From now on, I part only when I need to.
Ray
Only do parting when you really need to. If you can manage cutting it with a saw, do so. It's a relatively "high-risk" operation that can go sour just because of a hard spot in the metal. When things go bad, stuff usually gets bent or damaged -and you could end-up with something flying at you.
1) Very low RPMs. 60-90 at most.
2) Always within 1 inch of the chuck jaws. Tighten the chuck jaws and avoid 3 jaw chucks because they don't grip in as many places and the piece flexes more.
3) Bit must be perfectly perpendicular to the work.
4) Bit must be on-center -Dead on. It will sag a little under pressure so don't start-out low.
5) Lock the carriage in place.
6) Snug-up all the gibs on the compound etc.
7) A lot of cutting oil.
8) Even steady pressure.
9) Double check you're wearing your safety goggles.
A long time ago, I was parting on an Atlas -not a good machine for this. Everything was going just fine and cut was half done. Out of nowhere, BANG! Piece is now jumped-up on the tool post and I'm wondering... What the hell just happened? OK, use a crowbar and wood blocks to get the piece off the tool post... straighten-out the mess. No big damage but parting blade was in pieces. Go inside to hit the head, look in the mirror and a piece of the parting blade is sticking out of the skin just above the goggles.
From now on, I part only when I need to.
Ray
Hello Daryl
I never made plans because it is not difficult to make.The blade holder is an Iscar that someone had mistreated,but can be any make as dimensions are normed.
The round thing is just a piece of scrap steel from shipyard.
The important dimension is from top of crosslide to center of lathe.Turn something so nice as possible,remove compound slide and put a stack of gauge blocks under until contact.A nicely endfaced block and feeler gauges will also do.Half the diameter of the chuckmounted piece and heigth of stack is what You are after.
Let us have a picture of Your lathe working space without compound slide.
If my crosslide had been machined all over I would have put tool bottom up on the far end so that swarf fell free.
I shall make a picture of the assembly seen from bellow as soon as possible
The value of Quick change Tool holders is overrated among amateurs with hobby lathes.
Kind regards
Niels
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I have a lathe that came with a spring "gooseneck" style of parting tool holder. I haven't used it on this lathe because I put a different toolpost on it, that the holder doesn't fit into. But I'm thinking it might not be such a bad idea. Instead of breaking the parting bit because of lack of rigidity, it's meant to bend out of the way momentarily.
What I can report is that I used the self-same gooseneck holder in a shaper machine. I was having trouble with severe chattering while making a slot. I tried it, and the result was impressive - it then continued to cut with no trouble, nice and smooth!
Jordan
What I can report is that I used the self-same gooseneck holder in a shaper machine. I was having trouble with severe chattering while making a slot. I tried it, and the result was impressive - it then continued to cut with no trouble, nice and smooth!
Jordan
With much struggling in parting off on our minilathe I finally came up with a blade that works really good for the aluminum we use.
I hope this makes sense. I made a quick drawing of what it looks like.
The end I tapered from left to right.
It parts clean and straight.
Oil is important when we do larger pieces but on 1 inch or smaller I can part with no problems.
I found it was very important to keep it free of any aluminum that tried to build up/weld to the sides.
I usually go over to polisher knock it off and keep the blade nice and smooth.
This is what works for us.
Ed
View attachment 48860
I hope this makes sense. I made a quick drawing of what it looks like.
The end I tapered from left to right.
It parts clean and straight.
Oil is important when we do larger pieces but on 1 inch or smaller I can part with no problems.
I found it was very important to keep it free of any aluminum that tried to build up/weld to the sides.
I usually go over to polisher knock it off and keep the blade nice and smooth.
This is what works for us.
Ed
View attachment 48860
Thanks for the tip. Do you have any photos or a reference that I could look at to see how such a tool would be set up? I think I have plenty of room off the backside of my lathe.
Have a look at http://www.hemingwaykits.com/CatalogueW180.pdf
and search HK1070 Rear Tool Post. This is the George Thomas design.
Additional info is in his Model Engineers Workshop Manual -this one
isn't easy to find nowadays.
Another reference is Useful Workshop Tools by Stan Bray (#31 in the
Workshop Practice Series) which has a chapter on rear-mounted tool
posts.
Here's another with some photos of one in use on a Myford
http://swarfer.co.za/lathe/reartool.php
Another of the Myford
http://www.flickr.com/photos/nottinghack/6404500313/in/set-72157628119084531
Here's a construction project (uncertain how detailed)
http://easyweb.easynet.co.uk/~chrish/cancelled account/projects.htm
and search HK1070 Rear Tool Post. This is the George Thomas design.
Additional info is in his Model Engineers Workshop Manual -this one
isn't easy to find nowadays.
Another reference is Useful Workshop Tools by Stan Bray (#31 in the
Workshop Practice Series) which has a chapter on rear-mounted tool
posts.
Here's another with some photos of one in use on a Myford
http://swarfer.co.za/lathe/reartool.php
Another of the Myford
http://www.flickr.com/photos/nottinghack/6404500313/in/set-72157628119084531
Here's a construction project (uncertain how detailed)
http://easyweb.easynet.co.uk/~chrish/cancelled account/projects.htm
I also like the idea of a rear parting tool holder.
I have been using one for years on my Myford Super 7 and don't think twice about parting things off.
The angled ones are best. These set the tool at an angle so that if anything flexes the tool will move away from the work a bit rather then dig in.
It also makes getting the hight correct easier and you just need to slide the tool in or out a bit rather than mess about with packing.
I also like the fact that with the tool upside down the swarf can fall out easier.
As for speed I tend to start with the next one down from what I would use for normal turning and from that point I let the tool tell me if it wants to go faster or slower.
A lubricant often helps if things are not co operating.
I have been using one for years on my Myford Super 7 and don't think twice about parting things off.
The angled ones are best. These set the tool at an angle so that if anything flexes the tool will move away from the work a bit rather then dig in.
It also makes getting the hight correct easier and you just need to slide the tool in or out a bit rather than mess about with packing.
I also like the fact that with the tool upside down the swarf can fall out easier.
As for speed I tend to start with the next one down from what I would use for normal turning and from that point I let the tool tell me if it wants to go faster or slower.
A lubricant often helps if things are not co operating.