broaching

i want to make several capstans for my ml6 lathe so i can just swap complete units over and leave them set up for certain jobs.

need to make the bit in pic someone at club suggested broaching it.

never seen it done so wondered if one of the wsp series of books cover it?

and where i could get one made as can only see normal keyway ones.

or is there a better way?

i don't have a milling machine.

thanks

Looking at the size of it - and I'm just guessing - to broach it in the conventional way, with a long pull broach in a broaching machine - would need a very very very very expensive broach and a bigger and more powerful broaching machine than you could afford.

Push broaching it would be horrendous.

So unless you've got a very friendly contact at (say) a large marine power-plant and gearbox outfit, and you're prepared to spend a fortune on the broach, no.

I would resort to milling it on a rotary table if I had to do it "in house" for minimum cost..

I can't see the thickness of it, but either water-jet cutting or laser-cutting would be an excellent method. Laser-cutting a number of thinner pieces and screwing/riveting them all together would be a Good Plan, I think.

Forget getting a broach made for the job, they are very expensive tools to make and industrially only make sense if you are making tens of thousands of the component.

In any case a broach only functions if it can be passed through the component to cut the desired shape. Think of a hub to fit a splined shaft. This job would be completely unsuitable for broaching.
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​So, you are left with other means of manufacture. It is not at all clear from the picture which bit you want to make. More detail please..

​Brian

its 60mm across and 15mm thick if that helps? 

overall thickness is 22mm.

its just the base piece.

give me 5 mins and will try to strip it and get better pic.

Edited By naughtyboy on 10/10/2016 14:12:58

Edited By naughtyboy on 10/10/2016 14:15:06

Edited By naughtyboy on 10/10/2016 14:20:45

hope these make it bit clearer

For 15mm thick, you'd not have much success laser-cutting it; water jet would be the only sensible way, and you'd need to specify one of the more modern machines which can compensate for taper.

Lase-cutting say 5 off at 3mm thick would be my choice. I'd include some additional holes in it that you could use for location dowels to ensure it all lines up. You'll need somebody who has access to CAD to produce a dxf file for either process, and it needs to be drawn spot on what you want.

I would suggest having the parts made on a wire eroder, obviously not cheap though. I used to do this type of work in a previous life.

Tony

if broaching out of q what is a good way to get it made?

as looks like i will have to go down route of getting them made.

It looks, to me, to be a turning and milling job. Perhaps not simple for many of us, but more of a setting up problem for the angled cuts, but apart from that no real basic difference than cutting a gear?

The no milling machine is the problem to get over.  Local college course?  Friendly local group?.

Looks heavy for most vertical slides on a lathe, but doable if really wanted.

Edited By not done it yet on 10/10/2016 14:48:34

Edited By not done it yet on 10/10/2016 14:49:43

Ask Malcolm High of Model Engineer's Laser; he has a lot of experience in what can be achieved.

**LINK**

Usual disclaimer.

thank you Nigel sent email.

Laser cutting is a sort of precision gas cutting, and so leaves a very hard abrasive surface. For this application where I assume the tapered lugs give some sort of location I'd go for water jet, or even better as Tony Pratt says, wire eroding, but it isn't cheap. The cost is based I think on area of cut plus setting up charge, so if it can be thinner it will cost less. Of course a real hero would set to with hacksaw and file, not me but I've known really skilled men who could have done it.

A bit of lateral; thinking - what shape is the ratchet that fits into the cut-outs? Is it possible to drill or mill a simpler shape that will index just as well?

With a hefty vertical bandsaw you could remove most of the waste with four cuts leaving a relatively simple milling job.

Or get an apprentice to do it with a hacksaw and a blunt file

Neil

Make a simple cutter much as you would if making a gear cutter. Run that on a mandrel and use the vertical slide to move the work up into the cutter.

Just think of it as cutting a Vee form gear tooth, plenty of info on gear cutting setups for the lathe

If only a bare lathe, the bottom of the V could be broached by use of a home made square broach (see clickspring u-toob) after carefully drilling the bottoming hole on a circle marked on the lathe, the rest being roughed out with any method appropriate (manual or mechanical) leaving only the sides to be finished very laboriously or by some mechanical assistance.

Are the indiviual turrets adjustable or does the accuracy of alignment rely on this part?

Plus 1 for the wire eroding, I to used to run a wire machine alongside a couple of spark eroding machines.

Where in the world are you ? I know of a reasonable place (if they are still going I retired a few years ago)

If you have never seen wire eroding think posh band saw but using 0.20 or 0.25 mm diameter brass wire this feeds off a spool and electrically erodes the metal with water as a flushing jet. Depending on machine and operator skill very accurate to microns. Machinery and consumables expensive hence the high charge out cost.

Another simple way to do them on the lathe.

Put an angle plate on teh cross slide with a stud on it and sort a simple way to index 6 times. Mount blank on stud and then use a milling cutter in the lathe spindle to cut a slot the width of the Vees base, do all six in each plate.

Move the stud up so that you can then use the same cutter on ctr line to cut one of the sloping faces on all Vees

Either move stud down so you can do all the opposite faces or leave the stud where it is but put the other face of the blank against the angle plate.

Quite a simple method that does not need the work outsourcing or require making a spark eroder.

EDIT

Quick sketch of how it could be setup, angle plate on cross slide, bit of bar fixed to that with a stud surrounded by 6 peg holes. Put teh blank on the stud and use a peg through the dowel hole that is shown in your photos. Just raise/lower lower the flat bar and angle it as required to get the cut to side cuts to teh vee

Edited By JasonB on 10/10/2016 20:00:57

I'd look at Jason's suggested method. It will work fine.

One other possibility would be if someone you know has a shaper or a slotting attachment on a mill. Both those methods will deal with the angled slots on your shown part quickly. In fact, I'd be surprised if the original part was not made on a shaper or slotter if made 1900-1960 or so. JD

What a palava,

I'm amused by the answers, I wonder if the people wanting to spend Naughtyboys money would be so keen on wire eroding and water jet cutting if it was their cash ?

Originally these would have been done on a horizontal mill with a shaped Vee cutter and indexed round in a dividing head. The the most cost effective way to approach a production job like this as they wouldn't just make 1 or 2

Jason has got the best idea so far, simple, cheap and doable on the equipment that the OP has. Most, as usual failed to read the no milling machine bit.

If it was me ?

I'd do roughly the same as Jason has proposed but lay it down and use the tool post bolt as a pivit with nessesary bush and use a slitting saw between centres on a mandrel.

These slots believe it or not are not that critical on every feature. The critical bit is the angle and width of the slot as they are located by a tapered wedge. They don't need to be flat bottomed as noting touches the bottom so you could drill 6 holes for clearance and allow the saw to run into the hole.

Print the shape up in CAD on a bit of paper and stick it on the blank then offset to one side so the cut is radial to the centre and cut 6 slots, then move the blank to one side to line up the other side and cut those 6 slots.

Indexing believe it or not isn't critical either as you bore the turret for the detent positions.

My capstan turret as fits the TOS lathe came off a large Harrison and fits well up to a point but it's 4mm off centre and it's a lot of work to get it on centre due to the vee bed so I just made a new turret out of a big lump of cast iron that was lying around and drilled and reamed it from the headstock. The headstock doesn't know the turret is 4mm out of line .