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Model Forum / General / Models / March 2008How should I make this?
I need to make several 'Top Hats' out of stainless steel, below is a sort of cross section in my first attempt at ascii art. The part is about 45 diameter and 45 long and will have a wall thickness of 1.5mm thick. The flange (brim) is 3mm thick and 48 diameter. As 50mm barstock will not pass through the headstock of a 5" Boxford I have though about buying cut blanks, gripping the OD in the 3 jaw and fully machining the bore. Then machining the OD by holding the part on some sort of mandrel. (The inner and outer concentricity need to be within 0.2mm or so) My dilemma is trying to decide how to hold the part on the mandrel (which I don't want to take out of the chuck until I've made all of the parts. I have thought of making an expanding mandrel which is somehow activated through the headstock spindle but it seems overcomplicated Thanks in advance for any suggestions Ian Phillips llllllll llllllll lllllllllllllllllllllllllllllllllllllllllllllllll llll llll llll llll llll lllllllllllllllllllllllllllllllllllllllllllllllll llllllll llllllll >I need to make several 'Top Hats' out of stainless steel, below is a sort of >cross section in my first attempt at ascii art. [quoted text clipped - 29 lines] >llllllll >llllllll What lathe and what type of spindle nose ? -- Regards, John Stevenson Nottingham, England. Visit the new Model Engineering adverts page at:- http://www.homeworkshop.org.uk/ >>I need to make several 'Top Hats' out of stainless steel, below is a sort >>of [quoted text clipped - 40 lines] > John Stevenson > Nottingham, England. 1970's AUD 5" Boxford, standard screwed nose. Ian >>>I need to make several 'Top Hats' out of stainless steel, below is a sort >>>of [quoted text clipped - 44 lines] > >Ian In that case as you can't use expanding 5C mandrels then your best bet is a set of soft jaws and turn down so you can hole on the inner diameter which you turn first. If in stainless get sawn blanks, let them cut them and wear their saw out <g>. -- Regards, John Stevenson Nottingham, England. Visit the new Model Engineering adverts page at:- http://www.homeworkshop.org.uk/ > Thanks in advance for any suggestions Have you got a pipe center? I' thinking about boring the centre portions from bar stock then turning the outer with a 3-jaw and a pipe centre. I'm very much a starter at this sort of thing but it looks quite do-able to me. Chris  SignatureChris Eilbeck MARS Flight Crew http://www.mars.org.uk/ UKRA #1108 Level 2 UYB Tripoli UK Member #9527 LSMR > I need to make several 'Top Hats' out of stainless steel, below is a sort of > cross section in my first attempt at ascii art. [quoted text clipped - 29 lines] > llllllll > llllllll As you`re limited by the spindle bore it would be better to get cut blanks about 47mm long. Grip in the chuck and rough bore the hole. Do them all to that stage. Grip in the bore with your three jaw and turn and finish the OD all over. Bore a set of soft jaws and grip on the OD and finish bore and face off flange. Mark. > I need to make several 'Top Hats' out of stainless steel, below is a sort of > cross section in my first attempt at ascii art. [quoted text clipped - 29 lines] > llllllll > llllllll Can you make soft jaws? Do the hole and that side of the flange. Flip it over and grip from the inside with the soft jaws; do the outside. >> llllllll >> llllllll [quoted text clipped - 13 lines] > > Flip it over and grip from the inside with the soft jaws; do the outside. Several folks have suggested something like that. As the actual item is not as robust as the sketch would suggest, is there a danger that it will distort when held by the bore? Henry >>> llllllll >>> llllllll [quoted text clipped - 19 lines] > > Henry I suppose that is why I wanted to grip it with something that expands equally all round. I have considered Loctite'ing it to a mandrel then heating it after machining to loosen the bond. Ian >> I need to make several 'Top Hats' out of stainless steel, below is a sort >> of [quoted text clipped - 40 lines] > > Flip it over and grip from the inside with the soft jaws; do the outside. Soft jaws sounds a good idea but I don't have any. Ian >>> I have thought of making an expanding mandrel which is somehow activated >>> through the headstock spindle but it seems overcomplicated [quoted text clipped - 24 lines] > >Ian Do you have any old jaws for your chuck ? If so you can weld some lumps of mild steel on and machine those down. Sounds horrible and it is <g> but it works. -- Regards, John Stevenson Nottingham, England. Visit the new Model Engineering adverts page at:- http://www.homeworkshop.org.uk/ >>>> I have thought of making an expanding mandrel which is somehow activated >>>> through the headstock spindle but it seems overcomplicated [quoted text clipped - 29 lines] > >Sounds horrible and it is <g> but it works. Why not do _all_ the turning and boring with the over-length stock held in the chuck. Then part off 20 thou over length. clamp the parted off part to a faceplate using the top-hat rim and face the parted off end to length. You waste 1/2" of stock per part. Use it to make washers with :-) This does not seem to be a complicated part. I would cheat and do the last operation on the surface grinder or shaper, but turning will work just as well. "Mark Rand" <randm@internettie.co.uk> wrote in message > > Why not do _all_ the turning and boring with the over-length stock held in > the [quoted text clipped - 7 lines] > but > turning will work just as well. Not too bothered about starting with a longer piece of bar (more like an inch for chucking and parting) but the actual parting off would not be too easy on an AUD with 50 diameter stainless. Ian >"Mark Rand" <randm@internettie.co.uk> wrote in message > > [quoted text clipped - 15 lines] > >Ian If I can manage 95mm EN24T on an ML7, then you can manage 50mm 316 or 303 on an AUD! Carbide insert parting tools make a big difference with awkward metals. Of course, one could always relegate the parting to a bandsaw or power hacksaw. In desperation, if the parting off was too great a step, would be to turn the entire waste part into swarf with a facing tool! Mark Rand RTFM >>Not too bothered about starting with a longer piece of bar (more like an >>inch for chucking and parting) but the actual parting off would not be too [quoted text clipped - 15 lines] > Mark Rand > RTFM Mark I can part 50mm SS but none of my assortment of parting tools are quite right for it. A recent eBay item I won is a parting blade holder for my Dickson QTP but it needs a new blade and I have not been able to find the correct size. The short piece of blade that came with it is 5/8" high and about 1/8" wide. None of the suppliers I have tried list one that size. I suspect that the holder would work with a slightly narrower blade (2 to 2.5mm) but the toolholder has no makers name on it looks genuine Dicksons) so cannot be sure. I also have an Iscar double ended replaceable tip holder (blade only ) but it is 32mm high with nothing to clamp it to the toolpost. If only I had a miller, or room for one! Ian I have recently not op > Soft jaws sounds a good idea but I don't have any. They're only about £20 for common chucks and well worth having. If you can weld you can make them by grinding down an old set of jaws and tacking lumps of mild steel on. You can hold on as little as 1mm of depth with a freshly turned set of soft jaws. I use mine occasionally for making thin washers. A pro would do your job in two ops by holding the blanks with a few mm sticking out of the chuck, boring the i/d and turning the o/d of the flange part then holding on the flange with soft jaws and turning the rest. Total machining time on a cnc lathe would be about 5 minutes in a nasty material like stainless. You'd use a big F/O carbide insert drill with through coolant to rough the hole out in a single pass, finish with a boring bar, fit the soft jaws, turn the part round and turn the o/d. On a manual lathe with conventional tooling figure on several hours per part and lots of burnt out tooling. Stainless is a pig. You'll probably start trying to drill the bore with successively bigger HSS drills just to get something you can get a boring bar into, shag them all and wish you'd never started the job. SignatureDave Baker Puma Race Engines > On a manual lathe with conventional tooling figure on several hours per part > and lots of burnt out tooling. Stainless is a pig. You'll probably start > trying to drill the bore with successively bigger HSS drills just to get > something you can get a boring bar into, shag them all and wish you'd never > started the job. That's the most sense I have yet seen on this topic. SignatureCharles Lamont > Stainless is a pig. You'll probably start >trying to drill the bore with successively bigger HSS drills just to get >something you can get a boring bar into, shag them all and wish you'd never >started the job. 316 Se/ EN58JM/ 326S36 free(er) cutting 316 stainless ;-) Mark Rand RTFM >> Stainless is a pig. You'll probably start >>trying to drill the bore with successively bigger HSS drills just to get [quoted text clipped - 8 lines] > Mark Rand > RTFM 303, even easier !!! >I need to make several 'Top Hats' out of stainless steel, below is a sort >of cross section in my first attempt at ascii art. [quoted text clipped - 13 lines] > llllllll > llllllll Starting from sawn blanks 48mm diameter and 45mm long with some machining allowance on both dimensions. 1) Hold in 3 jaw with a few mm sticking out and drill/bore the hole to 42mm dia and 43.5mm depth. Check depth of bore and face off the bottom flange. 2) Turn round in chuck and face off the top flange. Part is now at finished length and i/d. 3) Now make a "pushing button" for use with a running centre - 44mm diameter bit of aluminium or mild steel about 30mm long. Stick the biggest centre drill you have into one end to fit over the nose of the running centre. 4) Chuck some scrap with 45 to 50 mm sticking out and turn that to a 41.95mm diameter plain mandrel. Chamfer the end. You can counterbore the end lightly to a diameter of 35/36mm if you're concerned that the bottom of the bores in your top hat bushes aren't perfectly flat or have a pip in them. Then it will just register around the outside of the end of the mandrel on a rim about 3mm thick. 5) Fit the bored blanks over the mandrel and press back hard with the pushing button and running centre in the tailstock. From now on you'll just be using friction to hold the piece while you turn the o/d and flange. I use friction to hold more jobs in my lathe than I do chucks. I'm always surprised that no one else ever thinks of using it or realises just how hard you can machine into something held this way before it slips. The same people presumably also won't give a thought to the fact that the only thing connecting the engine in their car to the gearbox and wheels is the same principle transmitting 100 plus bhp. SignatureDave Baker Puma Race Engines >I need to make several 'Top Hats' out of stainless steel, below is a sort of >cross section in my first attempt at ascii art. [quoted text clipped - 17 lines] > >Ian Phillips A llllllll llllllll B lllllllllllllllllllllllllllllllllllllllllllllllll llll llll D llll C llll llll lllllllllllllllllllllllllllllllllllllllllllllllll llllllll llllllll Whilst I like Dave Bakers option it seems to ignore bore "C" I would Buy cut blanks at 47 long Chuck in the "A" area as little as you are comfortable with Rough allparts at "B" and "C" within .5mm of finished OD and ID Turn around, chuck on "B" and complete roughing of "B". Rough out Bore "D". Rough diameter "A". Mark jaw 0 on part to allow putting back up with minimum error. Do all parts Finish bore "D" end face and diameter "A". Main problem now is holding to finish "B" and "C" Make a mandrel as follows R S T U 111111111111111111111111 111 1111111111111 1 1 1 11 1 1 1 1 1 Drill 10 1 1 1 Tap 10 1 1 1 11 1 1 111111111111 1 1 1 1111111111111111111111111 111 The "R" diameter and length is to allow chucking. "S" will be a slip fit in bore "D". A thick "O" ring will sit on diameter "T" and be compressed with washer "U" clamped up with a piece of 10mm studding through the spindle. The parts previously roughed and part finished can now be loaded to the mandrel with the "A" face on the chuck jaws and finished on "B" and "C". Some may say too much picking up and putting down, but the above tends to differentiate between roughing and finishing and the associated tool changes. Thats what I would do, but I have "all the time in the world". <G> -- Richard Email address is valid but remove burrs before sending! Oops. Just looked at my post, mandrel should really look like this - (View in fixed font) R S T U 111111111111111111111111111111111111 111 1 1 1 11 1 1 1 1 1 Drill 10 1 1 1 Tap 10 1 1 1 11 1 1 1 1 1 111111111111111111111111111111111111 111 -- Richard Email address is valid but remove burrs before sending! >>I need to make several 'Top Hats' out of stainless steel, below is a sort >>of [quoted text clipped - 13 lines] > > Whilst I like Dave Bakers option it seems to ignore bore "C" The part is described as a "top hat" so one would assume it doesn't have a bore C and isn't meant to be viewed in fixed font. SignatureDave Baker Puma Race Engines >>>I need to make several 'Top Hats' out of stainless steel, below is a sort >>>of [quoted text clipped - 16 lines] >The part is described as a "top hat" so one would assume it doesn't have a >bore C and isn't meant to be viewed in fixed font. There you go, my error. I must admit I always assume ASCI art is based upon fixed pitch font, and my reader is setup this way because of problems in the past, however incorrect in this case. I therefore like your option even more! <G> The "O" ring option that I described is useful though. ;-) -- Richard Email address is valid but remove burrs before sending! Use a Fixed Steady to hold the 50mm diameter stock -- Nouris > ... snip > [quoted text clipped - 6 lines] > > ... snip Here's a really simple design for an expanding mandrel. You will need a suitably sized socket head cap screw and a nice long socket key - one that will reach the mandrel from the outside end of the headstock spindle. A piece of hex-rod and a spanner would do the job. A 1st-taper tap and tapping drill to match the screw. Make the mandrel out of any suitable material you have, slightly oversize, and drill a hole right through with the tapping drill. Tap a thread from the headstock end of the mandrel until the end of the tap protrudes a little from the mandrel - this ensures that the thread is not cut to full depth at the end. Make two axial saw cuts in the end of the mandrel, at right angles to each other Insert the screw finger tight, put the mandrel in the lathe chuck and skim it to final size, and the job is essentially finished. The following link should make it all clear. http://tinyurl.com/2lf2tq Put the workpiece on the mandrel and tighten the screw from within the lathe spindle, which will expand the mandrel because of the tapered thread and grip the workpiece securely. You could, of course, use a long threaded bar instead of a socket screw and long key. SignatureRegards, Gary Wooding (To reply by email, change feet to foot in my address) -- Posted via a free Usenet account from http://www.teranews.com >> ... snip >> [quoted text clipped - 28 lines] > You could, of course, use a long threaded bar instead of a socket screw > and long key. Thats exactly along the lines I was thinking but your implementation is far simpler and easier to make than I was contemplating, its probably what I will do. Thanks Ian |
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