Lathes & M/C tools

[ozzyo]

In the ideal world, you have a hollow peg of say 8mm that is taped m6, that the insert would fit over, then you would have a stepped face washer that would locate over the insert with the Allan screw used to hold the insert.

 

OzzyO.

[bertiedog]

Drawing of the profile cutter set-up, you can see there is no clearance problem, as both the object and tool are round. The support bar can be mild steel, the hole tapped, or a full bolt with nut can be used. Use mild steel washers on each side of the cutter to protect it, and to grip it very firmly indeed

 

Stephen.

[bertiedog]

One other general point with any profile tool in a smaller lathe is the cross slide must be well adjusted on the tight side, and the saddle must be locked solid, even if no special lock, use the adjustment strips

 

On the Sieg there is no lock on the saddle, it must be added, there are simple home brew additions on the net or kits are made. All parts can be made in the home workshop or on the lathe itself.

 

The reason is the degree of drag is much higher than a single point tool, and a snatch and jam could occur if the saddle moved. Tightening the cross slide minimises the chance of chatter.

 

If a row of blanks is cut one after another then the saddle must be moved each time and locked, do not use the topslide, it adds the chance of snatch, lock it solid with the adjustment screws or jam to one end of stroke.

 

A profile tool in a Myford will impose no strain, but in a Sieg sized lathe precautions must be taken.

[Horsetan]

....A profile tool in a Myford will impose no strain, but in a Sieg sized lathe precautions must be taken.

 

What guidance would you give for a Unimat 4?

[bertiedog]

What guidance would you give for a Unimat 4?

 

The Unimat 4 should be able to use the profile tool , but might struggle a bit making them. It could turn the master disk OK, but might have trouble making the plunge cut into the disk to make the actual cutter.

 

It is the low speed needed, not so much the power, there is however a way round it and that is to hand crank the lathe spindle. Rex Tingey, (he wrote books on the Unimats), used such a handle on his Unimats to cut steel, and cast iron, that was too hard for normal cutting.

 

It needs a mandrill fitted into the back end of the lathe spindle and a crank handle in wood etc., fitted., any home mechanic should be able to rig it.

 

You can turn it yourself, or get the wife to do it!! No chatter or strain as it cuts, slow, but sure.....the only chatter will be from the wife as she turns the crank!!

 

By all means try with the motor on the lowest speed, or rig extra pulleys and belts to lower the speed, it may be able to cut OK.

 

The Sieg can manage it, it has better low speed range, and more power. Hobbymat sized lathes should have no troubles at all, anything larger will be all right with the work making the tooling.

 

People do tend to think the limits of a lathe brings restrictions, often a small bit of lateral thinking will provide the answer, and you can use a 1/2th horsepower motor with a Unimat, a motor, belting and a layshaft behind the lathe, a new drive pulley to the first original pulley, and the Unimat would rival much larger lathes.

Same applies to capacity,...... want turn larger diameter objects?, then fit block lifters under the headstock and raise the tool post, few lathes are so flexible as the Unimat, especially the original Unimat 1 , which has few limits! On the Unimat 1, simply spin the headstock 90 degrees and use cranked tools, six inch diameter flywheels can be machined!

[Horsetan]

The Unimat 4 should be able to use the profile tool , but might struggle a bit making them. It could turn the master disk OK, but might have trouble making the plunge cut into the disk to make the actual cutter.

 

It is the low speed needed, not so much the power, there is however a way round it and that is to hand crank the lathe spindle. Rex Tingey, (he wrote books on the Unimats), used such a handle on his Unimats to cut steel, and cast iron, that was too hard for normal cutting.

 

It needs a mandrill fitted into the back end of the lathe spindle and a crank handle in wood etc., fitted., any home mechanic should be able to rig it......

 

Useful information - thanks for that.

[polybear]

You can purchase a very nice Wheel Holding Fixture here:

 

http://81.169.175.242/fohrmann/de/artikeldetail.php?type=4&kid=16&uid=8839&PHPSESSID=4ac3ccf1bf7ec1e141d00624e3dadf6d

 

They also sell wheel flange cutting tools for RP25 and NEM profiles.

 

No connections etc. etc.

 

Brian

[bertiedog]

With respect to the Fohrmann design , but it is possible to make such a holder on your lathe, and the design is limited to metal wheels as far as I know.

It is meant to grip cast metal wheels made of mazak or brass etc., for re-profiling, by pressing the wheel hard onto the mandrill with a screwed on cap., which fit the stub shaft that supports the wheel for concentric mounting.

If plastic spoked wheels are machined no strain must be taken by the plastic, it will distort,

The best solution for Sharman and Gibson wheels is to make a mandrill which has the centre to give concentric mounting, but the rim is gripped on a raised fence, that is duplicated on the cap of the device. The rim is touch by the fence only, no pressure on the plastic.

The tyre machining can be tackled, but the back and front may need to have light cuts taken to remove the area that the fence touches.

Stephen.

[Horsetan]

I picked up some tool blanks yesterday, so I think we could call that "a start"....

[ozzyo]

I picked up some tool blanks yesterday, so I think we could call that "a start"....

 

 

 

Photo please, and where from?

 

OzzyO.

[Horsetan]

Photo please, and where from?

 

From eBay. Seller turned out to be just up the road from me in Barnet, so went to collect on way home from stables. He and his wife showed me their fully-fitted workshop which they have crammed into their attic (don't ask how ) - lathes, grinders, pillar drills and tools and bits as far as the eye can see. And their son's model railway layout, a mix of 2-rail and HD 3-rail. He also builds live steam models in Gauge 1 and above.

 

He has spent his working life in engineering, and now looks after someone else's classic car collection. His wife works for a car bodyshop in Edgware. I did ask whether he might be able to make me some P87 wheel form / profile tools, but he said that he didn't have the eyesight any more for something so fine!

Still, worth a try.

 

Seller's photo below - nothing special, just four blanks:

[bertiedog]

Those are good HSS cobalt blank squares for normal lathe tools, we were referring to profile tools which are the negative of the final shape for one plunge machining of the tyre.

 

These tools are pre hardened and tempered tool steel a lot harder than silver steel.

 

In practical terms they are not much use for profile cutters, although some shapes can be ground into the cutting edge, by thinning the front edge to about 2mm or so on a bench grinder,and then grinding by hand the shape needed, complete with relief.

 

Now on the face of it this sounds ridiculous, but the availability of small diamond coated Dremel type burrs and cutters actually makes this practical.

 

I am not saying that a tyre profile could be done, I could do it, but have 40 years of grinding experience to fall back upon. and I have a TTH reduction engraver/mill to do it.

 

When a bar tool is used to form profiles it is known as a form tool, usually plunged in one go ito the work, or has dual function, one part does the form and a spur tip does parting off as a second operation.

 

I use this type of tool to make handrail knobs, it uses one plunge to make the ball and stem, and the the spur completes the stem to any depth needed and then machines the base and parts off.

 

 

The shape is shown in the drawing, and all can be ground into the lip by standard coned micro diamond burrs, or even diamond files.

The tool needs no top rake, just the relief, done by simply angling the Dremel grinding. After one plunge it produces the ball and stem plus short base with square base, but the tip at top right may be used to cut the stem in the left direction to any length and leave a rounded stem base. The tip is then used to machine the base and part off, ready for the next one straight away.

 

Taper stems can use the very same tool, the ball is made on the crosslide, and the stem on a taper set on the toolslide, and then back to crosslide for the base and parting off.

 

The principles can be used for various shapes for fittings where small quantities are needed. In theory a profile cutter could be made as before on a disc, it would be hardened, and then used cut the shape in to the HSS square bar end, but the HSS steel tool would have to be softened right out, and re-hardened after the process, really the two disk method is better. for wheel profiles.

 

Stephen.

[Horsetan]

Those are good HSS cobalt blank squares for normal lathe tools, we were referring to profile tools which are the negative of the final shape for one plunge machining of the tyre.

 

These tools are pre hardened and tempered tool steel a lot harder than silver steel.

 

I've bought the wrong thing, then.

 

I am not saying that a tyre profile could be done, I could do it, but have 40 years of grinding experience to fall back upon. and I have a TTH reduction engraver/mill to do it.

 

Shall I send them to you, along with drawings to show what I'm after? It would be a real help......

[ozzyo]

H/T,

just use them as normal lathe tools. Them tools are top dog. You can also use them as parallels.

 

OzzyO.

[bertiedog]

I've bought the wrong thing, then.

Shall I send them to you, along with drawings to show what I'm after? It would be a real help......

 

Even if you use the HSS tools as form tools it would not suit the Unimat really.

 

If what you want is tyre profiling then used the disk method, all the cutting is well within the Unimats capacity, especially if hand cranking is used.

 

The HSS tools are general purpose moly Cobalt High Speed steel, a pre-hardened grade for most fine quality work, you can make an infinite number of tool shapes on the tip. If you new to lathe work they can make left/right facing and cut, or parting off, all by grinding on a bench grinder.

 

However form tools( like wheel profiles), are complex shapes, and not normally ground freehand, I could do it, but it would be infinitely better to use the disk method.

 

For the Unimat you need some 1/4 square mild steel, to make the holder for the disks, some 1/2 to 3/4inch Silver Steel bar for the disks, a 6mm drill and a 6mm nut and bolt to attach the cutter to the bar, which in turn goes into the toolslide.

 

The previous drawing shows the principle, and it should be an afternoons work to do the lot. You will need a gas ring or torch to heat the steel.

 

Grinding the shape into the end of the tool bar is really confined to such shapes as the handrail knobs., the same style of multi faced tool can be used for buffers.

 

The Unimat would struggle a bit cutting buffers in one stage in steel, but could do it in brass, but why bother, when a multi tip tool will do the same.

 

I am assuming that you know a few lathe basics, the use of the knob scales to get the tool to the same place in each repeat operation, keeping a chart of multiple moves, rather like a computer program. This would not suit mass production, but low volume repeats.

These days a CNC lathe will do complex shapes repeatedly, in my day a Britain or Ward would be set up with a series of steps to stops which allowed multiple cuts without mistakes or measurement.

 

Should you wish, the Unimat or a Sieg can be converted to CNC , then any shape can be programmed, but this approach is costly at first.

 

The best way is to learn the basics and pick the method the lathe can handle, and the Unimat is very capable, in good hands it is as good as any small lathe or better. It can even handle ultra precision clock making with ease, including all the gear making and pivot making.

 

Wheel profiles are very straightforward once the tooling is made, and that should be done by you to gain the experience, it is not hard at all.

 

Although I have not seen them I assume the commercial German Fohrmann ones are a bar end ground tool, but these are probably made on a CNC grinder.

 

Stick to known methods and the one I would advise is the disk method, any queries as to each sage of making it just ask.

 

Stephen.

[Adrian]

the Unimat is very capable, in good hands it is as good as any small lathe or better. It can even handle ultra precision clock making with ease, including all the gear making and pivot making.

 

I know Gerald Wingrove turned out several fine models with the help of a Unimat.

 

 

 

[57xx]

I've made form tools from bits of tool steel before just using a bench grinder. It wasn't too hard but then they weren't for fine shapes such as wheel profiles (they were actually for making specialised combustion chamber inserts).

[shortliner]

I have no idea what this would cost to ship - but you don't often see them for sale in this condition - A Unimat lathe and accessories

http://www.flickr.com/photos/39176469@N08/sets/72157626336281036/

[bertiedog]

Nice condition, but they do turn up regularly on Ebay, at a premium price in good order, but unless they are a total rust bucket, fully restorable by any home mechanic.

The main bed rods are stock steel, but can have larger fitted, the main bearings are standard stock sizes, the belts easily replaced with heat jointed belting, the motor can be off board, any type including DC. Most spares are still made for consumable items, and cast items damaged are not difficult to duplicate on other machinery, Cracks in castings can be "soldered" with eutectic alloy repair rods.

 

The only down sides are the poor chuck closing method, by rods, and the lack of morse tapers. Most of the rest is near perfect for the capacity, which is small, but can be stretched. There are several books on them by Rex Tingey and others. and plenty on the net about using the Unimat One.

 

The Unimat 3 and four are not so flexible, but are very capable. The big hiccup was the change from Austrian production to being made by Sieg, the early lathes from China were poorly assembled and with a built to a price finish. This has been addressed by Sieg and cured, but meant a lot of lost customers.

 

Watchmakers widely used the Unimat One, the original machinist centre, designed by the Austrians to sell via Sears Roebuck in the US, in a wooden fitted box. This concept became too expensive to continue with, and Elliot , the UK importer handled the simpler Unimat 2, which had the accessories as extras, rather than part of he package.

 

They also cured the early motor problems , with a heavy duty motor with a continuous rating, but Unimat made the same mistake again on the 3 and 4, by supplying a motor rated for intermittent use only. Again the current Sieg made versions have a motor rated for continuous use now.

 

I have, and regularly use, a Unimat One, now with a DC motor, used mainly as a precision milling machine. The original motor was a special fro Elliot, in the right colour and finish, that Elliot supplied in the 1960's. It looks like the normal motor, but was fully rated.

Stephen.

[Ralph R]

Anyone who is interested in making their own wheels would do well to take a look at the work of Sid Stubbs. There is a lot of information giving a lot of detail on the Manchester Model Railway Society website at www.mmrs.co.uk or this link goes direct to the page with all the information you need to turn your own form tools - www.mmrs.co.uk/technical/wheels.htm

[buffalo]

The invisible ink strikes again See this post.

[ozzyo]

Hello All,

I've been thinking about getting a digital read out for my lathe cross slide. Has anyone any experience of them, are they easy to set up, are they accurate (I think they will be).

The one thing that I'm worried about is the metal swarth will this affect it?

I'm also thinking about mounting it at the tail stock end of the cross slide is that a good move?

 

OzzyO.

[bertiedog]

They are quite accurate and the rotary type that go under the knobs are swarth and liquid proof, however the whole concept is only as accurate as the lathes own lead screws, and backlash can plague operation, everything that is allowed for manually with backlash still applies with digital dials, measurements can be taken, but only in the backlash take up direction.

 

A true system which can measure relative position must have backlash free drive screws, and these are very costly indeed, several hundred pounds per screw.

 

CNC can operate without backlash free lead screws, by constantly parking the movement and making relative measurements from the parked position, after the movement the parking resets the back lash.

 

Where positional references are derived from scales backlash may not be important, but must be allowed for. The best CNC use backlash free screw or hydraulic drives.

 

For home us the simplest addition is to use a digital vernier ,taken apart or modified to be attached to the saddle and the movement is measured direct to the static portion of the slide. Cheap digital verniers are able to be modified quite easily, with extensions etc to mount in place. They are swarth resistant, but not liquid proof.

 

As usual the old rule is best, never rely on dial measurement, they are merely indicators , measure with separate instruments....but after saying this certain measurement can be done from dials with greater convenience.

Stephen.

[ozzyo]

Hello Bertydog,

 

thanks for the reply, but as I said it would be mounted at the back of the cross slide, and so will measure the movement of the cross slide its self. Not the rotation of the lead screw.

On the cross slide of the lathe backlash is not to much of a problem unless you are doing bores and undercuts. As most of the time you are only cutting from the front! ie. the outside diameter.

 

OzzyO.

[flubrush]

Hello Bertydog,

 

thanks for the reply, but as I said it would be mounted at the back of the cross slide, and so will measure the movement of the cross slide its self. Not the rotation of the lead screw.

On the cross slide of the lathe backlash is not to much of a problem unless you are doing bores and undercuts. As most of the time you are only cutting from the front! ie. the outside diameter.

 

There are a few suppliers of all the bits you need - such as Machine-DRO

 

http://www.machine-dro.co.uk/index.php?target=categories&category_id=3

 

Jim.