morrisman 21st August 2011, 08:40 PM On my Sheraton 9" lathe . My thread cutting problem is nothing in comparison to my cutting off. I have a Armstrong style cut off tool . No matter what you do, it's always given trouble . The work piece eventually comes out of the chuck.... it's that bad . Seems to be a design thing , as the tool digs in and chatters . Probably too much overhang with that design . The lantern tool post seems to flex whe the cut off tool is fed into the work piece.
Is there a better way ? I do have a few cut off blades , maybe I should make a dedicated holder for them. MIKE
pipeclay 21st August 2011, 09:13 PM Supply more information for an educated guess as to what might need to be looked at to correct the problem.
morrisman 21st August 2011, 09:44 PM This is a pic of the horrible thing ...................
Oldneweng 21st August 2011, 10:20 PM For my 2 cents worth. Is the carriage locked to the bed? Is there any movement in the cross slide, coumpound angle adjustment or compound slide? Parting off requires more rigidity than almost any other process on the lathe. I am used to a rotating tool holder as shown below.
179690
This is much more rigid. I have never used a lantern style toolpost, and I would have to say I think yours looks quite flimsy compared to mine. When you add the overhang this would limit this setup. Can you get the tool holder further back into the post, back to where the lump under the front is touching. The next thing to consider is whether you have to part off. Can you cut it some other way and then face off?
I have yet to do a proper part off myself. I have a part off tool holder from a cheap set of 9 carbide tipped toolholders but have not had much success with it. The tip just breaks. I have bought a HSS part off blade and need to make a holder for it.
Dean
morrisman 21st August 2011, 10:40 PM Thanks for the reply Dean
Yes, I do resort to holding the work piece in a vice and cut it with a hacksaw , then face it off in the lathe ..but it's tedious as you can imagine .
I have a 1/16" X 4" long cut of blade, I intend to make a solid holder for it with a high degree of rigidity ... with as little overhang as I can get
That pic is just a mock up .
At the TAFE they use a larger version of my crap holder ... but they have larger tool posts , more rigid .
Mike
Stustoys 21st August 2011, 10:53 PM What Dia are you trying to part?
What speed?
Is the tool dead square the the spindle?
Is it at or below center height?
Is the tip square?
The grinding on the tip looks a little strange.
Stuart
nadroj 21st August 2011, 11:30 PM You have a gooseneck type holder, which I think is a good thing. But is it just an illusion, or is the gap closed up? For it to work, it needs to be able to flex at the top of the groove. If it's clogged up or anything, it becomes like a solid holder, and doesn't have the ability to ride out a seizure.
By the way, I found this type of holder great for slotting in my Douglas shaper, which was giving trouble before I tried the gooseneck type.
Jordan
Bryan 21st August 2011, 11:30 PM Also consider your chuck. Most of my parting problems went away when I stopped using my bellmouthed 3 jaw chuck. You say the work comes out of the chuck which sounds like it's not holding well.
Dave J 21st August 2011, 11:36 PM I have seen guys put a machinist jack under the front of the parting tool which takes makes it more rigid.
You could make up one easy enough to suit, they are only a bold threaded into a piece of solid.
Keeping it cool while parting will help a lot to, because as you parting the material will heat up close in in the tool.
Dave
pipeclay 22nd August 2011, 05:41 AM As asked previously you need to be more comprehensive in the details of your procedure for people to be able to have realistic guessess.
azzrock 22nd August 2011, 12:25 PM hi mike lots of people don't like parting of. its often the last part of a job and you can get nervous
. i think slow speeds,. good coolant. having the job as close to the chuck as possible and supporting the work with a tail stock help as well. a well ground tool slightly pointed .... helps as well. safety glasses are a must..lately my favourite parting tool is a.rs braised tip carbide toll. i have the 40 and 30 grades. spinning between 300 and 500 rpm.
franco 22nd August 2011, 01:24 PM I have seen guys put a machinist jack under the front of the parting tool which takes makes it more rigid.
You could make up one easy enough to suit, they are only a bold threaded into a piece of solid.
Keeping it cool while parting will help a lot to, because as you parting the material will heat up close in in the tool.
Dave
Dave,
This works OK with a rigid type toolholder.
If it is a gooseneck type holder putting a jack under the front of the holder stops the gooseneck from flexing and being effective. I have a similar holder (i.e.gooseneck). Prior to getting this I used to have trouble parting off on the old, well used 9" Brackenbury and Austin lathe. After getting the gooseneck holder all the parting problems disappeared. My toolholder clamping system (Myford type clamp) is much more rigid than a lantern tool post as shown in morrisman's photo though.
Frank.
Stustoys 22nd August 2011, 02:31 PM supporting the work with a tail stock help as well.
Do you use tail stock for support all the way through?
I've been told this is a bad idea as the part can't fall off, but I haven't tried it.
Stuart
pipeclay 22nd August 2011, 02:55 PM Can be a bad thing depending on the size of the job and the type of material being parted,if caution is not used.
End result could be damaged tooling,damaged job or damaged opperator.
azzrock 22nd August 2011, 05:49 PM [
QUOTE=Stustoys;1364560]Do you use tail stock for support all the way through?
I've been told this is a bad idea as the part can't fall off, but I haven't tried it.
Stuart[/QUOTE]
im not shore if you should keep the pressure on with the tail stock all the way. I manly cut steel. and I haven't had any problems. i find aluminium a bit more tricky. worse comes to worse you can increase the width of the slot and part of in stages. i.e. take a cut of 5 mm and then next to that one another cut. the slot is thicker it takes longer but seems to work
azzrock 22nd August 2011, 05:54 PM .lately my favourite parting tool is a.rs braised tip carbide toll. i have the 40 and 30 grades. spinning between 300 and 500 rpm.[/QUOTE]
its 20 and 30 grade not 30 and 40.
blue and red
azzrock 22nd August 2011, 06:11 PM On my Sheraton 9" lathe . My thread cutting problem is nothing in comparison to my cutting off. I have a Armstrong style cut off tool . No matter what you do, it's always given trouble . The work piece eventually comes out of the chuck.... it's that bad . Seems to be a design thing , as the tool digs in and chatters . Probably too much overhang with that design . The lantern tool post seems to flex whe the cut off tool is fed into the work piece.
Is there a better way ? I do have a few cut off blades , maybe I should make a dedicated holder for them. MIKE
hi i have a more ridged tool post than the lantern style that you can have if you
like. that is if you ever get over this way. it wont fit that parting off tool you have in it
thou. you will have to grind one up.
179741
RayG 22nd August 2011, 06:43 PM Hi Morrisman,
If your part is coming out of the chuck, you have a pretty serious problem....
Either there is a problem with the chuck or your parting off tool is digging in,
Here are some quick suggestions..
1. Is the chuck in good condition?
2. Are you sure you have the parting tool set up parallel to the cross slide?
3. The width of the cut should be a little wider than the shaft of the tool. Maybe the tool is stuffed?
4. Is the tool set up on center, a little below won't hurt, but above center it will dig in.
5. Go to the slowest speed you can select, at least until you figure out what is happening.
6. Are you parting off as close to the chuck as you can.
7. Is the tool cutting evenly, if it's uneven, you can sometimes get twisting with the cheaper tools, and when it twists it grabs.
That's all I can think of, off the top of my head... I'm sure there are other tips.
I used to have trouble with those cheap parting tools, some of them would cut unevenly and twist.
Regards
Ray
franco 23rd August 2011, 01:15 AM morrisman,
I just had another look at your photo of the parting tool holder. I agree with nadroj - the spring action on your toolholder cannot be working, because the slit which should allow the end of the toolholder to move downwards to take the pressure off the blade when it is about to dig in is already completely closed at the bottom, and full of paint at the top end. If you open the slit so the sides are parallel right up to the hole near the top of the tool and clear out the paint so there is no obstruction to the movement of the end of the toolholder, you should see a definite improvement.
In the photo you have the lower end of the slit sitting on the rocker piece in the toolpost. Even if the slit was open and usable, this would prevent the end of the parting tool blade from moving downwards and away from the workpiece if it started to dig in. The bottom end of the slit needs to be clear of the toolpost, and the tool no higher than centre height, and preferably slightly below, for the tool holder to work correctly. This requires a fair bit of tool overhang, so a reasonably rigid mounting for the tool holder is an advantage. The lantern toolpost is not the best choice, though they were used successfully for many years on many different lathe types.
The blade I have on mine is 3/32" wide at the top, tapering down to about 1/16" wide at the bottom. Since I got my gooseneck tool holder I have had absolutely no problems parting steel up to about 40mm. Parting with my previous 1/8" wide tapered parting blade mounted in a rigid toolholder on the well used smaller lathe was seldom trouble free, with dig ins and broken parting blades occurring all too often. I think if you sort your tool holder out and use a tapered blade if yours has no taper, you will be surprised at the difference. A more rigid means of holding the parting tool holder would be an added bonus.
As well as fixing the toolholder, I second everything Ray says above - all these points can affect the parting cut.
Regards,
Frank.
jack620 23rd August 2011, 01:21 AM morrisman,
I have the same tool holder as yours, but with the same 3/32'' wide tapered blade that Frank has.
This bloke sells them:
http://lprtoolmakers.auctivacommerce.com/PARTING-TOOL-BLADE-M2-HSS-332x-58x-5-P1414860.aspx
Rgds,
Chris
morrisman 23rd August 2011, 11:05 AM Many ideas in there ..I've read it all OK . First . At TAFE they told me never to part off with the tailstock in position in the workpiece, it's disastrous and dangerous. OK I will remove the offending piece stuck in the gooseneck holder that prevents it from 'springing' .... and doing its job ! Good advice that. I do need a more rigid holder for the gooseneck . I will design a new one and hopefully that will alleviate some of the problem. I have it all set up as per the book . The chuck is OK . The cut off tool is dead on centre. I've tried various speeds , but that doesn't help . The blade in it is tapered , 1/8 wide at the top . You have all given me much food for thought . I think I will overcome this MIKE
franco 23rd August 2011, 12:43 PM I do need a more rigid holder for the gooseneck . I will design a new one and hopefully that will alleviate some of the problem. MIKE
Mike,
FWIW the first photo shows what I use for holding odd sized toolholders which don't fit the 4 way toolpost.
A long tee bolt, in this case the original one for the 4 way tool post, is used in the compound tee slot. A square piece of flat plate of suitable thickness (8 mm suits this lathe), goes over this bolt and sits on the compound to provide a flat surface for mounting the tool holder. A second similar sized piece of plate, in this case 10mm with a large clearance hole for the tee bolt is used to clamp the toolholder. This plate has a 10mm jacking screw on one side and a recess about 25 long by 15 deep cut in the middle of the opposite side, which leaves two short arms to clamp the shank of the toolholder, and allows the clamping plate to level itself on the tool holder. I have a couple of different length spacers for use between the clamp plate and the clamp nut to accommodate toolholders with various non-standard shank sizes.
This type of clamp is used on the Myford and a number of other small English and Australian lathes, is easy to make, and is much more rigid than a lantern toolpost. For comparison with the previous photo I have also shown the toolholder clamp on the Brackenbury and Austin lathe Maybe something similar to these would work on the Sheraton?
Frank.
morrisman 23rd August 2011, 04:22 PM Mike,
FWIW the first photo shows what I use for holding odd sized toolholders which don't fit the 4 way toolpost.
A long tee bolt, in this case the original one for the 4 way tool post, is used in the compound tee slot. A square piece of flat plate of suitable thickness (8 mm suits this lathe), goes over this bolt and sits on the compound to provide a flat surface for mounting the tool holder. A second similar sized piece of plate, in this case 10mm with a large clearance hole for the tee bolt is used to clamp the toolholder. This plate has a 10mm jacking screw on one side and a recess about 25 long by 15 deep cut in the middle of the opposite side, which leaves two short arms to clamp the shank of the toolholder, and allows the clamping plate to level itself on the tool holder. I have a couple of different length spacers for use between the clamp plate and the clamp nut to accommodate toolholders with various non-standard shank sizes.
This type of clamp is used on the Myford and a number of other small English and Australian lathes, is easy to make, and is much more rigid than a lantern toolpost. For comparison with the previous photo I have also shown the toolholder clamp on the Brackenbury and Austin lathe Maybe something similar to these would work on the Sheraton?
Frank.
Roger that Frank I see it's relatively simple to make up a more rigid holder like you did . I won't ditch the gooseneck just yet . Mike
azzrock 23rd August 2011, 08:35 PM ". At TAFE they told me never to part off with the tail stock in position in the work piece, it's disastrous and dangerous"
I wonder why it dangerous and where Ii got the idea to do it like this. Probably i just thought the extra support would help. Im going to have a little go at parting off now..
Anorak Bob 24th August 2011, 10:24 AM Sometimes you have to use the tailstock.
http://www.woodworkforums.com/attachments/f189/179112d1313313072-new-9-model-owner-restoration-hercus-aug-sept-2009-054-large-.jpg
morrisman 24th August 2011, 11:18 AM Anorak So the workpiece in the above pic is rotating in the normal direction ? I see the tool is on the opposite side from normal ... Mike
Anorak Bob 24th August 2011, 11:29 AM Anorak So the workpiece in the above pic is rotating in the normal direction ? I see the tool is on the opposite side from normal ... Mike
Mike,
The parting off tool is upside down. The work rotates as normal.
Bob.
morrisman 24th August 2011, 03:52 PM Mike,
The parting off tool is upside down. The work rotates as normal.
Bob.
Roger that . Is there any physical/mechanical advantage in having the force transmitted upwards rather than downwards ? Mike
Oldneweng 24th August 2011, 08:46 PM Mike,
The parting off tool is upside down. The work rotates as normal.
Bob.
Details of blade holding method would be appreciated by me as well Bob.
Dean
Anorak Bob 25th August 2011, 12:21 PM The rear tool post excludes the compound slide as a source of movement and because the slide and cutter are in tension when parting off, the slide dovetails are pulled up tight reducing the opportunity for vibration to occur. So the story goes.
The thing works well. Having the knurling tool sharing the post is real handy. One improvement would be to have the post set up as a rotating turret thereby removing the need to rotate the entire post when changing operations. Another improvement would be to locate the lower edge of the blade in a rebate.
The pair of 1/8" socket set screws ensure the verticality of the blade.
BT
http://www.woodworkforums.com/attachment.php?attachmentid=180017&d=1314235061
Oldneweng 25th August 2011, 07:48 PM Thanks Bob. I am looking for ideas to make a holder for a parting blade I bought recently. It has an angled top and bottom edge. No good for grooving. I think I will make a small fly cutter to cut angled slots at top and bottom of a two piece holder similar to yours but to mount in my 4 way tool post. Just have to fiddle to get angles and positions right.
Dean
Metalman 25th August 2011, 10:46 PM Some slightly O/T info for franco,
I was doing some work in the inner Sydney suburb Surry Hills recently and at lunch time I was walking around the area and came across the pictured building which was undergoing renovation. It is not that clear but on the front of the building are the words 'BRACKENBURY and AUSTIN. The street name on the pole is Wilshire. I do not know anything else about the company.
Mm.
morrisman 26th August 2011, 11:55 AM I have noticed that the long 1/2" cut off blades don't have any positive rake , they sit flat . But the shorter gooseneck style blades have a small section at the tip that gives some back rake at the tip .
Is it worthwhile grinding in a groove to provide back rake on the flat ones ?
Mike
Dave J 26th August 2011, 01:51 PM I grind mine to have rake.
Dave
franco 26th August 2011, 02:26 PM Some slightly O/T info for franco,
I was doing some work in the inner Sydney suburb Surry Hills recently and at lunch time I was walking around the area and came across the pictured building which was undergoing renovation. It is not that clear but on the front of the building are the words 'BRACKENBURY and AUSTIN. The street name on the pole is Wilshire. I do not know anything else about the company.
Mm.
Metalman,
Many thanks for that. Since they stopped manufacturing lathes before the internet age information about the company and its products is surprisingly hard to find. My somewhat hazy recollection (I was 14 at the time) is that my father was doing some work for Brackenbury and Austin or vice versa in 1948, and he bought the lathe straight from the factory. Many of them were sold as Gregco 918 or New Gregco.They were not as common as the Hercus or Myford at the time, but still turn up occasionally.
Frank.
Grahame Collins 28th August 2011, 09:02 PM We use HSS part off tools all the time and following the tafe guide book and loads of info on the net and advice from industry.
The students dont seem to have trouble when they observe the following:
Tool post with minimum over hang of the tool holder.
Tool holder and hold down clamps properly tight
Use centre height or the tiniest poofteenth above
HSS tool over set up projecting a tiny bit past center
Part off tool checked that it is dead square to the cut
Use 1/2to 2/3rds of normal spindle speed for diameter parted
Use just enough coolant to see whats going on
Feed in at a constant rate.
Sharpen the pointy bit to the side that's needed with out a feather or tit on it.
The rep from Wallers Precision Tooling ( shameless plug as they helped us) was in and gave them a few pointers.
The cherubs have not busted a HSS part of for ages ( not counting the Richard HEAD who wound the carriage into the non operating job and busted the tool )
Hopefully some of the above may be useful to you.
Grahame
nadroj 28th August 2011, 11:14 PM Use 1/2to 2/3rds of normal spindle speed for diameter parted
Thanks for the checklist, Grahame.
I hadn't realised you could actually spin that fast when parting off.
Jordan
morrisman 29th August 2011, 12:47 AM HSS tool over set up projecting a tiny bit past center
Grahame
Mike
pipeclay 29th August 2011, 05:29 AM I think he is saying have the cutting blade length a touch over the cetre distance of the job.
Pete F 29th August 2011, 09:52 AM I rarely have a problem parting off since modifying my parting tool holder so the blade sits properly vertical. In addition to the points made by Grahame I think the key is to have a SHARP tool. I will periodically touch up my blade with a hand held diamond stone to keep it sharp. Other than that plenty of lube as it's cutting.
Pete
franco 29th August 2011, 12:28 PM Grahame,
I agree with all the points you mention in post #36, except, in this special case, #3: "Use centre height or the tiniest poofteenth above". The O/P is using a sprung parting tool holder. These are designed to flex in the event of an imminent dig-in, allowing the tool to move down and away from the work to relieve the load on the cutting edge. If the tool is above the centre line of the workpiece and starts to dig in, moving the cutting edge down to a greater diameter when the toolholder flexes will make the situation worse. This type of holder needs the tool to be no higher than centre height, and still works OK if slightly below.
When using a conventional rigid parting tool holder, I completely agree with all the items on your list.
Frank.
Swarfmaker1 29th August 2011, 04:59 PM Quite often parting off problems are an indication of worn headstock bearings. Rear parting tool posts are better as the spindle is forced down into the bearings. Parting off in the lathe is a science unto itself. Often to achieve success you need to control a combination of variables. If your headstock is above suspicion and your chuck is in good order then the compound slide should be checked to ensure there is no slop or play. The compound tends to tilt towards the rear of the lathe when parting off. A Sharp tool , on or slightly below centre height and slow speeds with plenty of cutting oil help. Also parting closer to the chuck jaws is an advantage. Some materials require widening the slot as you cut. eg Aluminium due to it's tendency weld itself to the cutting tool.
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