Trouble with parting off tools

[RonA]

Hi I own a Myford ML7 lathe but have always had trouble with parting off tools on steel stock.
I've tried carbide tip tools & recently purchased a quick change toolpost which came with one holder which takes a special HSS parting tool.
I always seem to get chatter on the tool despite changing workpiece speed & tool feed rates. Anybody have an tips or ideas to get a more even cut without the tool chatter. The tool tip is. aligned with the workpiece centre point
Any thoughts great fully accepted.
RonA

 

[mr_splatter]

I part off from the rear using the tool upside down. There is a lot of debate about whether this works better or not but it works OK for me. Whatever way you do it, ensure the tool is dead square to the job, put the lathe in back gear and take it slow but keep a feed on, don't let it rub. I won't say I have no problems now but generally OK. Sometimes I part so far and then cut off with a hacksaw (putting a board on the bed to protect it) and face off. A lot of people swear by the carbide parting tools but I use HSS on dead centre. Tool has some relief built in. Sometimes also good to part a small amount and withdraw and go in again a few thou to one side to open up the slot. Most problems seem to be from the tool jamming in the slot with a bit of swarf. Good luck!

 

[Stueeee]

Arranging the work so that you are parting off as near the chuck as possible reduces the likelyhood of chatter, using coolant (like diluted Cooledge B) helps too -if your machine doesn't have a coolant pump, just use a squeezy bottle.

If you do get chatter, try to take a gentle cut to clean the marks off the face of the work before feeding the tool back in normally.

 

[RonA]

Thanks for the replies it's given me something to think about, hadn't thought about reversing the tool. Will also take on board keeping the cut as near chuck as possible. I haven't got any coolant feed on the lathe but have occasionally used a drop of oil to ease the cut.

RonA

 

[500e]

Allways had better results with rear tool post as well Splatter

 

[MattF]

It's one of those things like knurling. One day you'll do it perfectly every time, others you might as well just give up even trying. Machine rigidity has more effect on the outcome than owt else, I'd say. Make sure cross and top slide are wound in as much as feasible, and lock the saddle and top slide if possible. You want to remove as much slop from the equation as you can. Get the blade cutting in without being too forceful else fearful, then just cross your fingers and hope. Personally, I gave up even attempting parting off when I had the Warwick. It just wasn't up to it, and I tried everything barring a rear toolpost, (never been a fan of those personally. I just don't like the thought of force pulling at the bed rather than pushing against it.), and I just never managed to achieve consistency. Got to the point where I just cut things off with the hacksaw and faced them instead. If you have slop or a somewhat flimsy bed, you'll likely be fighting a losing battle.

 

[Mr shiney]

Rear parting off tool, upside down every time! i have a glanze tool that I use. Goes through everything like butter without so much of hint of chatter. Doing it from the front especially on the chinese lathe I had is a terrifying experience!!!!

 

[BrokenBiker]

parting on my Chester is lovely, no chatter or anything, parting on the older r and a is horrifying and i don't do it.

main problem with the r and a is the tool post is a nightmare to line up dead square and altering the tool height is only do able with shim, which adds to the problem

 

[shenion]

How you grind the tool really helps. Adding a bit of back rake can help.

I find honing the bit makes a big difference.

The P or T type blades work a bit better. I also find a larger one is easier. I use a 3/32 more than the 1/16 one.

 

[Pete.]

Honing any lathe tool makes a tremendous difference. If you inspect a ground tool through a loupe and compare it to a honed one you'd understand why. Your average bench grinder wheel leaves the edge looking like it was cut with a chainsaw.

 

[RonA]

How you grind the tool really helps. Adding a bit of back rake can help.

I find honing the bit makes a big difference.

The P or T type blades work a bit better. I also find a larger one is easier. I use a 3/32 more than the 1/16 one.

I bought the new quick change tool post & it came with a brand new parting tool, still getting the chattering. As somebody said in another post, the chattering can get quite worrying

RonA

 

[julianthegypsy]

It also helps to have the tool as far back into the toolpost as you can to keep the overhang to a minimum, that will help reduce chatter too.

 

[brightspark]

and while your at it lock the saddle

 

[shenion]

I bought the new quick change tool post & it came with a brand new parting tool, still getting the chattering. As somebody said in another post, the chattering can get quite worrying

RonA

What angles did you grind into it?

 

[Shox Dr]

Honing any lathe tool makes a tremendous difference. If you inspect a ground tool through a loupe and compare it to a honed one you'd understand why. Your average bench grinder wheel leaves the edge looking like it was cut with a chainsaw.

The answer is to have a diamond stone on the other side, of the bench grinder.

Just don't grind tungstens on it

 

[graffian]

I use Eclipse HSS parting blades. I used to a normal 4 way toolpost and parting was pain,
carefully feeding to try and keep the chatter to a minimum.
Now I have coolant[makes loads of difference] and a rear toolpost. I just aim the tool and
pull the feed lever and it works beautifully; I have yet to have any problem parting with this
setup. I set the tool around centre, but not above centre[not below with a rear toolpost].

 

[Pete.]

The answer is to have a diamond stone on the other side, of the bench grinder.

Just don't grind tungstens on it

Why not grind tungstens?

 

[MrFluffy]

On the insert blades, Ive found at first I was getting chatter, but I was using them like hss tooling.
Once I went for it and set the feed rate what I felt was a insane rate from experience, big continous ribbons of swarf were produced. Might be worth putting it back in and going for it and seeing if your working it hard enough?

I parted off a 200mm block of 7175 yesterday, blade tool, right on the edge of whats possible on my harrison and hanging it right out the toolholder at the end to get the depth. But, no disasters.

 

[MattF]

On the insert blades, Ive found at first I was getting chatter, but I was using them like hss tooling.
Once I went for it and set the feed rate what I felt was a insane rate from experience, big continous ribbons of swarf were produced.

I've heard similar mentioned multiple times before. Seems to be one of those suck it and see things. Personally, I never had any problem using insert stuff at the same settings as HSS tooling. Seems to be a very random thing, how that tooling needs to be used.

 

[BrokenBiker]

Why not grind tungstens?

because the diamond wheel will pick up particles of tool steel when grinding tools and contaminate the tungsten when grinding that, or at least that is what I was taught. I have a separate wheel for tungstens with a sign on it that say do not use for anything except tungstens incase anyone else is using my tools