Making Unimat DB/SL Steadies

[Andy CarlsonParticipant @andycarlson18141]

A couple of jobs I have been contemplating for a while involve making new bases to allow tooling to be mounted to the bed bars on my Unimat SL. One is a fixed steady, the other a tool rest for using watchmaker’s hand gravers.

Most will likely be familiar with the bed arrangement – two 12mm round bars 40mm apart with the M8 feed screw equidistant between them. The tooling base needs to be split horizontally so that it can clamp around the bars.

I came up with a couple of options…

One is to start with two pieces of bar stock (say 1 inch by 1/2 inch Aluminium), machine them for the clamping bolts and then clamp together (with some packing between to ensure that they will actually clamp the bed bars when finished) and then drill for the bed bars and feed screw. I’m not sure that drilling along a join line between two pieces of stock is a good idea though.

Mounting on a faceplate and boring is a variation on the above theme… particularly given that I don’t currently own a 12mm drill, but can lay my hands on something slightly smaller and more imperial. Keeping the hole spacing accurate seems like a challenge if I do this though.

The other option is to start with a single piece of stock (say 1 inch square Aluminium), drill it and then cut it to separate the top and bottom halves. The challenge here is making that cut… This is way deeper then I have ever tried to cut with a slitting saw so the risk of clogging/jamming etc. is a worry. I’m 100% convinced that I would muck it up if using a hacksaw manually. One possible option is a bandsaw – there is a Sears Craftsman style one that I could perhaps use but so far we have only used this for woodworking. I’m not sure what band saw blades would be suitable and buying a new blade just for this job will add to the cost and general bother.

I am planning to do the jobs on a bigger machine – my Faircut 3.5 inch lathe.

Your thoughts on pros and cons (or better options!) are welcome.

Thanks in advance.

Regards, Andy

[Nigel Graham 2Participant @nigelgraham2]

I would go for the drilling then reaming or boring, on the joint line between two pieces, with the work so mounted that the parts stay togther for both operations on both bores and keeping the bores parallel.

The packing is best if quite thin. If the gap ends up too fine simply take a very light skim off one or both faces.

The resulting halves need be rigid of course so they don’t distort when clamped together. One approach is to make the section of Tee-form by cutting a rebate along both sides of both parts. Using two clamp-screws each close to one way bar without actually breaking though the bore wall, is another way.

Sawing the block apart after making the holes will work but even using a band-saw might not give very satisfactory, tidy results. Sawing aluminium-alloy needs quite a coarse blade to avoid it becoming choked by the chips.

 

Does your larger lathe have a Tee-slotted saddle? If so, the best method is boring between centres.

Whichever mehtod you use, mark the halves first so they go back together with the same faces coinciding.

 

 

[JasonBModerator @jasonb]

I’ve drilled and reamer or bored across a split line countless times, usually a bearing pedestal and cap all without problems so that would be the way I would do it.

[Andy CarlsonParticipant @andycarlson18141]

OK thanks both. Starting with two pieces seems like the way to go then. I shall amend my shopping list accordingly.

… and yes the cross slide has T slots. It’s a pre-war model engineering lathe so most people did not have mills at the time. I have a couple of vertical slides… two because the second one is Faircut branded so I could not pass up the opportunity when it cropped up 🙂 . My biggest ‘mill’ is the Unimat.

[Andy Carlson]

On Andy Carlson Said:

OK thanks both. Starting with two pieces seems like the way to go then. I shall amend my shopping list accordingly.

… and yes the cross slide has T slots. It’s a pre-war model engineering lathe so most people did not have mills at the time. I have a couple of vertical slides… two because the second one is Faircut branded so I could not pass up the opportunity when it cropped up 🙂 . My biggest ‘mill’ is the Unimat.

Andy, if you make a simple drawing of the supports you want to make I can give you some suggestions or help for a precise construction.

[Michael GilliganParticipant @michaelgilligan61133]

This may be sacrilege, but I would be tempted to make the ‘riders’ as vee-blocks.

MichaelG.

[renardiere7Participant @renardiere7]

V’s will give 4 points of contact per bar or three if the bottom clamp bar is left plain.  Round bores only two points of contact per bore.  Round bores will not constrain axially to the same extent as a V.

[Michael GilliganParticipant @michaelgilligan61133]

Exactly my reasoning … and it saves all that heavy drilling too

MichaelG.

[dk0Participant @dk0]

 

This is the original stady rest for the Unimat SL, if you need dimensions, just ask !

I made the self-centering stady rest for mini lathes and I’ll soon make the adapter square for the Unimat SL .

 

[DiogenesParticipant @diogenes]

Easier to accurately drill two holes in one piece of metal than it is to mill four matching angled rebates in two pieces, though?

Four (or even two?) vees would be very intolerant of inaccuracy?

[Diogenes]

On Diogenes Said:

Easier to accurately drill two holes in one piece of metal than it is to mill four matching angled rebates in two pieces, though?

Four (or even two?) vees would be very intolerant of inaccuracy?

It would rather depend upon the tools, materials, and techniques that the builder has to-hand.

There are some very good aluminium extrusions available … …

MichaelG.

[JasonBModerator @jasonb]

We don’t even know if the OP has a milling machine. ( EDIT He does not have a milling machine) Even with a vertical slide or on the unimat the milling option won’t be that easy.

If he only has the Faircut then I would be thinking of clamping the work to the cross slide, drill, bore and then ream. Wind cross slide to the next position and do the second hole.

[JasonB]

On JasonB Said:

We don’t even know if the OP has a milling machine. ( EDIT He does not have a milling machine) Even with a vertical slide or on the unimat the milling option won’t be that easy […]

Hence the propose intelligent-use of existing profiles !

Engineering ~Ingenuity

MichaelG.

[BazyleParticipant @bazyle]

Overthinking leads to complexity. All you need is one oblong with one vee on the front bar which provides location and ‘anti-twist’. Make a flat on the rear to rest on the rear bar and bring top to level if that is thought useful. Central bolt hole can clamp to flat bar underneath. I’m sure several lathes use this style of single reference.

[Michael Gilligan]

On Michael Gilligan Said:

On Diogenes Said:

Easier to accurately drill two holes in one piece of metal than it is to mill four matching angled rebates in two pieces, though?

Four (or even two?) vees would be very intolerant of inaccuracy?

It would rather depend upon the tools, materials, and techniques that the builder has to-hand.

There are some very good aluminium extrusions available … …

MichaelG.

I would machine it with a wire EDM, and with a single setup, the piece would be produced precisely and geometrically correct.
Another alternative is to make it with a 3D printer using thermoplastic material mixed with carbon fiber, which takes on very rigid and durable characteristics. I realize these are modern techniques and not within the reach of all hobbyists/makers, but they are simple, precise processes, and there are suppliers who offer this low-cost service!

 

[Michael GilliganParticipant @michaelgilligan61133]

Always good to have a few pictures of what we are dealing-with:

.

https://youtu.be/tqRUEY4UNgw?feature=shared

[ no idea why that didn’t embed ]

.

MichaelG.

[Michael Gilligan]

On Michael Gilligan Said:

Always good to have a few pictures of what we are dealing-with:

.

https://youtu.be/tqRUEY4UNgw?feature=shared

[ no idea why that didn’t embed ]

.

MichaelG.

Extremely clear and detailed video, Michael thanks for sharing!

[Michael GilliganParticipant @michaelgilligan61133]

There may be better options, but I reckon this could comfortably provide the material to fabricate two ‘riders’

https://www.1stchoicemetals.co.uk/product/4-x-4-x-3-8-101-6mm-x-101-6mm-x-9-53mm-aluminium-angle/

MichaelG.

[JasonBModerator @jasonb]

Presumably you are suggesting two short lengths (after cutting down the legs) that coul dbe tapped at the ends to take end plates Which would need clearance “v” in them?

As we have not heard from the OP for over a month, can we assume he has made the part by now as the thread has only just been brought back to life by dk0 it may not be worth spending more time on the subject.

[Michael GilliganParticipant @michaelgilligan61133]

As you wish, Jason

… it’s of no consequence to me.

MichaelG.

[dk0]

On dk0 Said:

On Michael Gilligan Said:

On Diogenes Said:

Easier to accurately drill two holes in one piece of metal than it is to mill four matching angled rebates in two pieces, though?

Four (or even two?) vees would be very intolerant of inaccuracy?

It would rather depend upon the tools, materials, and techniques that the builder has to-hand.

There are some very good aluminium extrusions available … …

MichaelG.

I would machine it with a wire EDM, and with a single setup, the piece would be produced precisely and geometrically correct.
Another alternative is to make it with a 3D printer using thermoplastic material mixed with carbon fiber, which takes on very rigid and durable characteristics. I realize these are modern techniques and not within the reach of all hobbyists/makers, but they are simple, precise processes, and there are suppliers who offer this low-cost service!

 

Stephano, Where is this low cost wire EDM service available?

I for one would like to use this process

Ian P

[JasonBModerator @jasonb]

You also need to provide a suitable file to use a 3D printing service. Many are not able to use CAD so it is not so accessible to them. If they can’t get someone to do the design work for free it becomes a lot more costly when you have to pay someone to produce the CAD file for you.

[dk0Participant @dk0]

Ian, regarding the EDM please send a private message

[old martParticipant @oldmart]

Since the steady will be fixed when in use, it could be made without the excessively over engineered pair of holes fixing it to the bed rails.

[duncan webster 1Participant @duncanwebster1]

All it needs is a bit of flat to locate between the 2 round bars, which could be done with file and saw, screwed to  a longer bit sat on top, and a 3rd long bit underneath to clamp it all together. No accurate holes of vees. Don’t introduce spurious accuracy.

[Author]

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