Lathe tool grabbing and related cutting issues.

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Zee--I find parting off to be one of the more "heart stopping" operations that I have to do on my lathe. I have been most successfull when parting off aluminum to use the lowest speed available (115 RPM on my lathe) and lots of cutting fluid (sprayed from an aerosol can). My lathe has a fixed speed motor but an internal gear transmission that lets me select the correct gears for various speeds, so torque is not a problem at these low speeds. I have scared myself so many times by having the "part" in the chuck suddenly try to "walk up" and ride on top of the parting off tool when I get close to that final "seperation" that now I just get moderately close to having the part cut off, then walk the part over to the band saw to finish the cut. I have even less success parting off mild steel. Although I have never stalled my lathe, I have broken a cut off tool, and that is a "life altering" experience. My parting off tool is HSS not carbide. I find it to be VERY critical that the cutting edge of the parting off tool be exactly on center of the lathes turning access. ---Brian
 
Brian Rupnow said:
.... I have scared myself so many times by having the "part" in the chuck suddenly try to "walk up" and ride on top of the parting off tool when I get close to that final "seperation"

I haven't tried parting off yet. Still to scared of it, but I have been doing lots of reading. Probably too much reading, because some of it seems contrary to other bits. Perhaps even the authors were not all of one mind on the subject. Anyway.

The situation you describe in the quote above. Isn't that usually caused(riding up on tool) by the tool being slightly higher/lower than center line? And my next question. When setting a tool for center line do you make a small .001 or.002 allowance for the torque twisting the tool point down when engaged in the work? Setting the tool higher than center line so that it reaches dead center when cutting?


Still so much to learn,
Kermit
 
Thanks Brian and Kermit. Your posts help a lot.

Breaking a cutoff tool...that sends shivers down my back. Very scary.

Yeah...I have had the problem where the tool gets under when I got close to center. (I'm a happy guy if there's a hole already drilled through.)

I'd be interested in what others think about setting the tool .001 or so high to account for pressure.

Thanks guys!
 
My opinion is that setting the tool above center can be done to an extent, that amount depending on tool overhang and other details. The problem with being above center is that you can add to your troubles, if overdone, by the tool not wanting to cut for lack of clearance, which you would compensate for by increasing the feed pressure until the tool is deflected enough to cut. At this point the resistance is lessened and the tool digs in too deep.

Parting tools are very strong in the direction that they need to be; but any sideways pressure or twisting can break them rather easily. Digging in and the work climbing over the tool would seem to cause both.

To get back to the question, I think having the setup as rigid as possible will be of more benefit than setting the tool above center.

Keep working on the setup, it will become easier, and when you are comfortable with parting you can always give trepanning a try!

Kevin
 
Poop.
Cracked the apron casting.
Not bad though. Still good.

This side of corner of nearest tapped hole...

IMG_0547.jpg


Was drilling...I think I was heavy handed...it went in very easy...then some resistance...a 'little' more pressure (you define 'little')...heard a snap. Thought it was the bit but it was whole. Didn't see anything then went on to tapping. That probably pushed it out enough to see.

Shouldn't cause any problems though.

Kevin...thanks...yeah...I think rigidity comes first.

All: Seems to be a bit of confusion...I was 'turning' with a carbide insert. I was 'parting' with an HSS cutting tool. Something happened with the turning and caused things to get loose (non-rigid!)...then parting tool had problems....and I can't say I remember if I checked tool height...it's a quick-change and I may have just slapped it on.
 
zeeprogrammer said:
Poop.
Cracked the apron casting.
Not bad though. Still good.

Careful there fella, just cause I snap a part don't mean you have to run in that race. :)

Gonna use studs in those holes? 'specially the one with the crack. Stud and loctite, tis the way now.

But that is a curious part supported underneath? I've cracked enough items in my day, but you sure did an odd one. Take a break for a while

Robert
 
Zee,
I wouldn't beat myself up too much over that. Easily worked around.

I can tell you from experience that the cast iron in these machines is unpredictable at best. I had a bit of a career change this year, went from a tool/die maker to a service tech of sorts. I've drilled numerous holes in machines doing retrofits, installing scales, lube lines, etc., and it's amazing what you can/will run into. Hard spots, voids, sand, you name it.

Kevin
 
Robert...you are the clear winner in that race and mighty big congratulations to you. ;D Be like me...forfeit.

No...just going to use SHCS...this is the lathe apron...you won't be able to see it until I take it off to adjust it again...next week maybe. ;D

Yeah supported underneath by parallels. But what you don't see is that there's another half inch of cast iron below. I think Kevin touches on it....maybe a hard spot...the resistance I felt...pushed too hard...and caused a bit of side force...crack.

Keven...see above.

Not to worry all. If you get a 'poop' out of me...I'm disappointed but not particularly upset. However, if you get poop's Dad...or worse still, poop's Grandpa...well then...best wait till tomorrow to have a chat. :big:

Thanks all.
 
Remember...it's just a cover for the gears in the lathe apron...

My first real modification of a machine!! (The mill's belt drive retrofit doesn't count...but the gear cover meant I had to drill holes in my little lathe!)

Well the rest of the holes went well. Then it was the plexiglass (maybe there was better material...but that's what I had). Two sheets...one as a spacer. First attempt resulted in shattering. Okay...not a problem...it's an excuse to get a dremel!

Second attempt went very well. I even managed to leave my trademark boo-boo. The boo-boo is at the bottom-right. I was sanding away to a line I'd made. I forgot the line was on the flimsy covering and the covering kept moving....I kept sanding to get to the line. (The trademark is nothing special...other than it's mine...even if anyone else makes similar mistakes...this one is mine. ;D)

IMG_0548.jpg


One more word on boo-boos. They are signatures. Unique. You should always be proud of the boo-boo. Someone might be able to make the same part...but it's very very difficult to make the exact same boo-boo. I'm proud of my boo-boos. (Mind you, I'm not advocating that boo-boos are good. Guess I'm just trying to find the good...pathetic eh?)

This 'girl' may not be pretty...but she's persistent.
 
Looks like a very sensible mod, Zee.

Yeah.. My shop is full of "signatures".


Dean
 
zeeprogrammer said:
Remember...it's just a cover for the gears in the lathe apron...

My first real modification of a machine!! (The mill's belt drive retrofit doesn't count...but the gear cover meant I had to drill holes in my little lathe!)

Well the rest of the holes went well. Then it was the plexiglass (maybe there was better material...but that's what I had). Two sheets...one as a spacer. First attempt resulted in shattering. Okay...not a problem...it's an excuse to get a dremel!

Second attempt went very well. I even managed to leave my trademark boo-boo. The boo-boo is at the bottom-right. I was sanding away to a line I'd made. I forgot the line was on the flimsy covering and the covering kept moving....I kept sanding to get to the line. (The trademark is nothing special...other than it's mine...even if anyone else makes similar mistakes...this one is mine. ;D)

IMG_0548.jpg


One more word on boo-boos. They are signatures. Unique. You should always be proud of the boo-boo. Someone might be able to make the same part...but it's very very difficult to make the exact same boo-boo. I'm proud of my boo-boos. (Mind you, I'm not advocating that boo-boos are good. Guess I'm just trying to find the good...pathetic eh?)

This 'girl' may not be pretty...but she's persistent.

You'll have that lathe modded to the point it's unrecognizable before ya' know it zee! That part's more fun than actually making stuff WITH the lathe. :big:
 
Congrats on your first mod.
I still haven't been able to bring myself to drill and tap any of my machines yet.
So far I've only had the courage to dismantle the top slide for cleaning and this was because I had no choice because due to swarf under it you couldn't fix it down ir would wobble by a couple of degrees.

I will get there eventually though.
 
Nice one Zee!

Didnt hurt a bit didn't it..... ;D

Dave
 
Good going Zee.

And IMHO - ANY reason to get a Dremel is a good one. Once you have one you'll wonder how you got along without it!

Regards, Arnold
 
Hey, congrats! I'm still amazed those gears are uncovered to begin with.


zeeprogrammer said:
This 'girl' may not be pretty...but she's persistent.
Ok, ok, I'm sorry I "called" you a girl... but that was all that fit in that sentence. ;D
 
Dean: Yeah, several examples of this mod around. I put the apron back on last night (after twice having to dismantle it...once because the shield was up against the half-nut and it wouldn't budge and once because the gear to the crank handle stuck out too much) Much smoother now. Can't wait to reassemble the rest.

websterz: Now I find myself thinking about those tapered gibs every time I move the carriage. But must get back to the mill engine.

tmuir: Yeah. It was the top slide that got me started down this road.

Dave: Well...the wallet wasn't too happy. ;D

Arnold: Yeah. The intent was to go to store, get in and get out. If I spend too much time there...I spend too much. :) Still, I found myself looking at all the Dremel goodies.

Vernon: Will the name calling on this forum never cease? :big:

Thanks all.

 
Zee,

Before you actually buy a Dremel, ask around the forum for opinions on which type to buy. I have four of them and each one has its advantages and shortcomings.
 
I don't know about elsewhere but where I am official Dremel accessories are outrageously expensive.

Its actually cheaper for me to go to the jewellers supply shop and buy professional buffing wheels, grinding disks, drills that will fit the Dremel over the official tooling.
This is about the only thing at the jewellers supply shop that is cheaper than elsewhere
 
mklotz said:
Before you actually buy a Dremel, ask around the forum for opinions on which type to buy. I have four of them and each one has its advantages and shortcomings.

Too late! Well...only so far as waiting to buy a Dremel. Opinions would be welcome.

I went for a low-end one as I didn't think I'd be using it much. I was, however, a bit mesmerized by a couple of accessories...in particular a plunge router. Thinking...hm...how might I use that. And then today...I'm at a hobby shop scrounging for any kind of 2-56 and 4-40 screws (I won't say why)...and I see a router table for a Dremel. Hm...how might I use that?

Any way...further down the road. If the Dremel I got proves insufficient...I have a son-in-law who's drooling over it.

Not knowing what I'll eventually do with it...I didn't want to expend too much for too much.

tmuir: I was more surprised at the cost of the individual bits and ends rather than the tool. It's definitely one of those tools where they get you with add-ons and accessories.
 
Dremels...

The battery powered ones are handier than a shirt pocket. I keep two on my workbench preloaded with the bits I use most (Cratex point and brass wire wheel). However, IMO, they don't have the power of the 120v plug-in model. I use the latter with the various accesories I've built (detailed elsewhere in this forum). The router attachment is handy by itself but, as I mentioned before, the clamp it uses to hold the tool can be (non-destructively) detached and used to hold the tool in various other self-made holders and jigs. You'll quickly find that, although the Dremel is sold as a hand-held tool, it's much more effective if bolted down and the work brought to the tool.

I have one with the attached flexible shaft. Since the shaft handle is cylindrical, it's much easier to mount this to the lathe toolpost to do various grinding and shaping chores.

Dremel accesories are expensive but you don't need that many. The rest you can pick up at various import suppliers or make yourself (all my precision sanding/grinding disks are homemade). The most important ones to buy, IMO, are:

The hand-tighten chuck - buy two and make a super pin vise out of the extra. As usual, nobody can bear to standardize the shaft sizes so, if you're going from tool to tool and don't want to waste time swapping collets, this accesory is golden. I wouldn't trust this chuck at the very highest speeds, however.

The right-angle attachment - depends on the type of work you do but this has served me well both while making models and also doing repairs around the house.
 

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