PM Research Milling Machine by Rik Thistle - FINISHED - late 1800s - 1:12 (est)

[Rik Thistle]

Paul,

 

Yes, it is a bit strange how that Way is set-up. But it does add another part to be made, which helps keep me busy.

 

The crop below shows the Saddle, and over on the right the details of the 2x #1-72 tapped holes. The Way is definitely fixed to these 2x holes.

[The plan wasn't lying flat when I took the pic hence the 'bent' lines].

 

As an aside, the 2x counterbored holes described on the left (above) are interesting. The Saddle is counterbored from both sides with a 'Number 53' drilled hole separating the opposing counterbores. The upper of the 2x counterbores is used to hold the Bed feed nut (Pt 19) in place on the top side, and the lower counterbore is used to fasten the Saddle feed Nut (Pt 20) on the underside of the Saddle.  I suspect there will be a tricky assembly procedure when all parts are made 😉

 

Above.  Once the Way is settled in it's final position it is pinned in position (1/16" drilled hole)..

 

 

 

Richard

[Toolmaker]

Hi Richard,

I think I am up to speed now. 

You were noting that the separate dovetail piece had to be so to enable access to the partially hidden hole in the above picture, which takes the knee nut. Agreed.

Being simple, I thought you were concerned about reaching the steel dovetail screws and pointed out that you need to turn the saddle 180 deg in the above picture, duh 🙄 

 

Assembly is fasten the saddle nut in place, slide saddle onto knee whilst locating knee nut. Fasten knee nut with cap head. Add part four and hold in place against fixed dovetail. Offer up separate dovetail slide  slide and fit for play and then install a dowel. I don’t think 1 dowel is good engineering as the part could rotate on that to the extent of the play in the screw threads holding the dovetail piece.

 

What does part 4 look like? Do you still need to machine the dovetail in that?

 

You could dowel the piece on now and re machine the complete saddle dovetail knowing that in the doweled position it is all nice and parallel. Then machine part 4 to suit. You will have to be able to remove the dowels for assembly.

 

There! Clear as mud! 
 

Enjoy

 

Paul

 

[Rik Thistle]

Paul,

 

Good stuff.

 

 I don’t think 1 dowel is good engineering

Agreed. But I guess they have to draw the line somewhere. On a full sized machine, definitely, but for this model it's more symbolic than anything.

 
What does part 4 look like? Do you still need to machine the dovetail in that?

See below..
 

I've already machined square the sides of the Bed (shown above), but am waiting for a small T-Slot cutter to be delivered before doing any more on the Bed. I could make my own T-Slot cutter out of a 3mm end mill, say, but I am trying to keep a balance between enjoying the build, learning some new things but occasionally taking some short cuts.  Joe Pie shows in his Shaper build (IIRC) how to make a small T-Slot cutter, but I'm taking the easy way out on that one 🙂

 

You could dowel the piece on now and re machine the complete saddle dovetail knowing that in the doweled position it is all nice and parallel.

Agreed, to some degree. The Saddle Feed Nut (Pt 20) would need to be fitted underneath prior to the dowelling and machining procedure. I don't know if that would complicate vice clamping or the later fitting of other parts eg part 27, the Saddle Feed Screw needs to align with the threaded hole in the Saddle Feed Nut - see Note 3 below.

 

So there are a lot of inter-related parts that, with an expert machinist, could be made stand-alone and then align perfectly. I'm tending towards leaving some features on some parts unmachined (as Note 3 suggests) and then finish the machining on the sub-assemblies.

 

Paul, great questions and thoughts - thanks again. As with any 'first build' I'm partly making it up as I go along 😉

 

Richard

[Toolmaker]

9 hours ago, Rik Thistle said:

As with any 'first build' I'm partly making it up as I go along

You and me both Richard, unfortunately your the only one with the plans, hahaha

 

Due to my current strong pain killers I am yet to decide if we are at cross purpose on my latest convoluted plan. Why is it you feel the feed nut needs to be in place. Is it for alignment? I’m maybe thinking it could sit in a slot as opposed to a hole…….but then again it could be the drugs!

 

Best regards as always and if I become annoying just shoo me away.

 

Paul

[Egilman]

Actually it is poor design, but then it IS only a model mill... 

 

Proper procedure would be to cut the dovetail into the saddle on both sides from a one piece casting to ensure parallelism of the dovetails, then counterbore the access for the cross slide nut... the counterbore would not affect the dovetail slide's operation in anyway and the whole thing being one piece, would be twice as strong...

 

An over simplification if you ask me... and many more opportunities to make mistakes given the number of extra machining operations....

 

But then again it is only a model, not intended for actual operation making parts...

Edited April 30, 2023 by Egilman

[wefalck]

Ein think it just poor design - or they had certain design constraints we don't know that led to this poor design. If the saddle had been a tad longer - and the table in consequence perhaps wider, the counterbore for the saddle feed-nut could have been free at the bottom of the dovetail. 

 

I have taken apart a number of antique machines of that age and they are normally designed so that you can take out the feedscrews and -nuts for maintenance or replacement without having to take apart the whole machine. The (bronze) nut are subject to wear and need cleaning and replacement from time to time. In this case you don't want to upset the whole alignment of the table-dovetail.

 

Anyway, as was noted before, this is only a model and once completed, no one will worry about this anymore.

 

[Egilman]

10 minutes ago, wefalck said:

they are normally designed so that you can take out the feedscrews and -nuts for maintenance or replacement without having to take apart the whole machine.

Exactly...

[Rik Thistle]

Paul, Egilman, wefalck,

 

Thanks for the comments. It helps me better understand the project and keeps me on course.

 

your the only one with the plans

🙂 Yup. To be fair to PMR I'm trying to show only parts of the drawings for IP reasons.

 

Why is it you feel the feed nut needs to be in place.

Note 3 above asks that the unfinished Feed Nuts are assembled in position before drilling their tapped holes. It is for alignment, as you say. Otherwise the a pre-drilled Nut hole could be out in two axes, plus at a slight angle to the Feed Screw. A slot would give adjustment in one axis.

 

Proper procedure would be to cut the dovetail into the saddle on both sides from a one piece casting to ensure parallelism

Yes, and even add a gib. But...it's only a model and for what it is, it is plenty bangs for the buck .... and keeps me entertained. 

 

they had certain design constraints we don't know

I kinda have the feeling that, as they were designing the model, they knew they would have to compromise in certain areas otherwise precision machinery/skills would be required to build it. I also think, that with 20:20 hindsight, they later probably thought that certain features could have been better implemented eg the saddle dovetail. But once a design hits the model maker's foundry there is no cheap way of turning back the clock - so they went with it. Overall, it is a very good and challenging model.

 

Richard

 

PS: Paul, the pain meds aren't affecting your reasoning AFAICS - your Qs keep me on my toes!

 

 

 

 

Edited April 30, 2023 by Rik Thistle

[Toolmaker]

11 hours ago, Rik Thistle said:

To be fair to PMR I'm trying to show only parts of the drawings for IP reasons.

Good thinking, it never entered my head that someone might try and make this without buying the plans. More fool them I say.

 

Regarding the nut/dovetail thing; I was suggesting you screw and dowel the steel dovetail on to the cast aluminium part, then machine the complete dovetail to clean up true, parallel etc. Then the steel piece can be taken off/put back on at your leisure. The dowels would always maintain its positional accuracy. Two 1.5mm holes should suffice.

 

Every possibility you and I are going around in circles here, but that’s ok

 

Regards

 

Paul

[Egilman]

15 minutes ago, Toolmaker said:

The dowels would always maintain its positional accuracy. Two 1.5mm holes should suffice.

If the dovetail HAS to be in two pieces, this is the engineering way to fix it in place... although for modeling purposes, one pin is sufficient... There is also the dis-similar metals issue to consider... Aluminum and CRS do not work well together over the long term...

[Rik Thistle]

Phil, Egilman,

 

Yes, I think we are in agreement. Good point on the Galvanic corrosion issue. I've not checked where they are on the Periodic table but since it's a model that will be kept in a dry house it shouldn't be an issue.

 

I was making the other 3x smaller Pulleys today. I also cleaned up the cast Tool Trays. And there is a Pulley Spacer needed. All straight forward stuff.

 

But during the coming week I may start on the two Mild Steel, circular section items I included drawings of a few posts ago. I'll stare at those drawings for a good while though before cutting metal....there may be other parts I should consider first. I think this is one of these projects that the optimum build order will only really become apparent after I have actually built one 🙂

 

Richard

Edited May 1, 2023 by Rik Thistle

[Rik Thistle]

Hi all,

 

This week I have been working on Pulleys (Pt 9), a Spacer (Pt 39) and the Spindle Shaft (Pt 23). 

 

These form major parts of the drive system that operates the cutting tool (Pt 51), fitted to the Arbor (Pt 49).

 

Firstly, 3x Aluminium Feed Pulleys were turned on the lathe.

 

Below. A straight forward part, with two of the pulleys requiring a clamping grub screw hole to be tapped.

 

Below, a collection of the finished pulleys, five in all. The Spacer (Pt 39) is also shown, top left and next to the narrow end of the Step Pulley.

 

Now things start to get a bit interesting again. The mild steel Spindle Shaft (below) has a relatively long but small diameter section (0.124") that is also drilled through with a Number 51 drill (0.067"), leaving a wall thickness of 0.028". And the other end has a tapered hole, and a stepped end.

 

I spent quite a bit of time thinking about how to make this part on the lathe and the best sequence of machining operations.

 

I felt it best to get the drilled holes out of the way first. For the #51 hole I started with a 1.6mm Stub drill to try to keep the hole as straight as possible. And then drilled the full depth with the #51 drill.

 

Below. The part was then turned round in the lathe and the #24 hole drilled (0.153").  This hole's diameter and depth is to allow the tapered reamer to get in deep enough.

 

Next, the tapered reamer (3/16") was used. 

There are two No 1 x 1" tapered pins supplied with the kit, to allow two versions of the Cutter Arbor (Pt 49) to be made, if one wishes. These pins have a taper of 1:48 (ie a 1/4" change in diameter over 12"). Metric pins use 1:50.

 

With the holes complete, the 0.124" diameter section was turned to size in stages...ie only having about 1/4" length being turned down to size at any given time.

 

Below, cutting in 1/4" lengths worked fine - I got away without having to use a revolving centre. I also took the opportunity to turn about a 1/2" length of the Shaft down to the 0.249" diameter - this would allow me to use a 7mm collet to grip it plus a revolving centre at the tapered hole end. Edit - the revolving centre 's size stopped the cutting tool getting close to the workpiece, so a fixed centre was used instead.

 

Below. Removing the bulk of the remaining material down to the 0.249" diameter.

 

And a Left and Right hand tool was used to finish of the 0.249" diameter.

 

The parts sitting next to the Stand.

The tapered pin, shown above (bottom right) will have a hole drilled in either end. I'd like to drill it in the lathe to make sure the holes are on the centre line, but I suspect I'll have to mount it in an angled V Block in the Mill, and then do my best to find the centre line of the tapered pin.

 

The only way I can think of drilling it in the lathe is to make a tapered, split holder held in the 3 Jaw chuck and Super Glue it in to the holder (otherwise the drill pressure could push the pin backwards, for one of the two orientations). Any ideas welcomed 🙂

 

Below. All parts assembled into position. Everything fits fine, although the Spindle Shaft did require a light touch of fine Emery to get a decent rotating fit.

 

And for the coming week I have my focus on the part below.  This is the draw bar that pulls the tapered Cutter Arbor (Pt 49) into the tapered hole in the Spindle Shaft. This one will be a challenge....the long, spindly part is less than 1/16" diameter. I think I may try doing what I did with the Spindle Shaft ie only turn a short length down to diameter at a time...and use a revolving centre to stop the part whipping. And I'll be re-watching Joe Pie's Shaper videos to maybe copy what he did (....used an SRBF support?).  Again, suggestions welcome.

 

OK, well that's it for now. The garden calls. Back soon'ish.

 

Richard.

Edited May 16, 2023 by Rik Thistle

[Django]

These posts make me nostalgic for the machines that I learned on.  They weren’t powerful or fast, but they had style and a solid feel and you could depend on them once you knew their quirks.  Your models are excellent.  I hope that you keep them coming.  

 

After the reversing gear and governor for my fathers Stuart #7 and Unicorn, I am at a loss for my next build.  My lathe can’t swing a Major Beam’s flywheel and the Reeves ME Beam has questionable casting quality.  I was considering another Stuart Beam Engine, but going all out on scale details this time.  I don’t think that I have enough time left for a Steam Traction Engine.  As you know, it is a feeling of great satisfaction when they finally run.

Edited May 7, 2023 by Django

[Rik Thistle]

My lathe can’t swing a Major Beam’s flywheel

 

Yes, my Mini-lathe can only machine a maximum size of 7" flywheels. Otherwise I'd be looking at a wider range of suppliers.

 

Polly Models do a decent range of interesting models ... https://www.pollymodelengineering.co.uk/sections/stationary-engines/anthony-mount-models/index.asp  ....but the ones that really catch my eye have flywheels that are a bit larger than 7" diameter.

 

I like watching my Stuart Beam working since it has a slow enough RPM to be able to see all the moving parts doing their thing - it's quite absorbing and relaxing. I only use compressed air - I've never attempted to use steam.

 

Richard

[Rik Thistle]

Hi all,

 

Here's the latest update on progress.

 

The parts ringed in red are discussed in today's post. The blue ringed item (the Draw Bar) has been 'pushed back' (...more later)

 

Firstly, Part 4, the Bed casting (Aluminium). There is quite a bit of machining required on this part and, as usual, figuring out the order can be a bit challenging. With hindsight, it might have been better to cut the dovetails first, before cutting the T Slots. Otherwise there is a slight danger of the part collapsing in the vice.  Also the Bed casting has a slightly offset split line where the two halves of the cast mould did not align perfectly - that need some tweeking with files and Emery. The holes in either end were drilled first.

 

Below. Using a 1/16" cutter to prepare for the T Slot that runs down the side of the Bed. I did this in 2 or 3 passes. It's Aluminium and quite soft.

 

Now using the T Slot cutter. It took a bit of web searching to find a suitable tool.

The drawing calls for the T Slot to be 0.125" wide. 0.075" deep and 0.125" down from the surface. I managed to find a cutter that was 0.117" Dia and 0.057" deep - That meant taking a few cutting passes whilst adjusting the width and depth of cut for each pass....it was a bit tricky.

 

Now cutting the same sized T Slot but on the top face of the Bed where a milling vice would be clamped

 

Below. Finally, cutting the dovetails that would fit in the Saddle (Part 3). It soon became apparent why the Saddle had a separate Way made of Mild Steel - answer shown later 🙂

 

Next was Part 6, a Bracket and it's Spindle, Part 33.

 

All the Bracket needed doing was taking a light skim off the faces and drilling the holes.

 

The Bracket, Feed Pulley and Spindle attached to the rear of the mill.

 

Next was the arm (Part 7) that determines the position of the Worm used for driving the bed. I machined Pt 7 but didn't fit it to the bed yet since I need to make the Worm etc to see how it all aligns.

 

Below, Drilling out the holes aftet filing off any casting artefacts.  I wouldn't have used this clamping method if it was a Mild Steel part.

 

Below. The Bed now mounted into the Saddle dovetails.

 

Below. It can now be seen why the Saddle had a separate Way, made of Mild Steel. Otherwise the round bosses on the end of the Bed would stop it sliding on to the Saddle.  So the Bed is placed on the Saddle. Then the Way screwed in to place. The two screws are positioned such that they just miss the side of the Bed.

 

Finally, I had thought I might have tackled the Spindle Draw Bolt this week...but after a lot of thought I went with plan B - order in some 1.5mm (0.060") Dia rod and fit it in to the square end of the Draw Bolt. I didn't feel comfortable about trying to turn down (from 3/16") to under 1/16" over such a long length.

 

However, there is tooling on the market that allows one to do such turning. Below is a tool holder that has a Phosphor Bronze insert that the larger diameter (eg 3/16") runs in whilst the tool, right next to the insert, trims down to the smaller diameter.

 

There is a good video here showing how it is done....   'Slender Rod Turning Moving Steady' - https://www.youtube.com/watch?v=yDrXDVB1ABI

 

Well, that's it for this week. I'll still be working on more Bed fittings etc for the next week or so.

 

Bye for now ,

 

Richard

 

Edited May 13, 2023 by Rik Thistle

[Toolmaker]

Hi Richard,

It seems I have been asleep on watch and have missed a couple of updates. It’s all moving along and looking well.

 

That tapered pin is a sneaky little widget. It looks simple enough until you come to execute. I looked at the drawings that showed it and the picture of the assembled model, and in both it looks like the hole in the end is not central. Am I seeing that correctly?

 

This is my offering;

 

Al/Al round bar, drill and taper ream so your taper pin sits under flush by a couple of mm. So longer than the pin and the pin is fully inside.

Mill the al/al bar to give 2 parallel sides or 4 if you prefer. At the mid point drill and tap through to the taper hole. This s for a grub screw. 2mm or perhaps 3mm will be fine. 
Locate the taper pin in the al/al fixture with a bit of force, tighten the grub screw and Mill the ends of the al/al flush to the pin. 
Stand in vice with the bottom on a parallel which adds further security for the pin not pushing out and do your work. 
Turn over and repeat.

Remove pin and dress you grub screw indent. It won’t be seen on assembly.

 

This all seems long winded, but 1 offs can be that way.

 

Thank you

 

Paul

 

 

[Toolmaker]

On the subject of turning long thin diameters, did you ever use roller boxes for turning?

[wefalck]

Naive question: what are 'roller boxes' ? A fixed steady with rollers (a lot of people nowadays use roller bearings for this)?

[Rik Thistle]

Paul,

 

looks like the hole in the end is not central.

 

Ah, good spot. There are two options for the Cutter Arbor (PMR supply two tapered pins). Fig 3 does show the #53 hole offset.

Thanks for the ideas on the tapered pin. Yes, there are quite a few ways to solve the issue of centrally drilling the ends. I'll make my mind up when I get back to that part(s), probably selecting the quickest 'good enough' solution 😉

 

Toolmaker, Wefalk,

I do have a fixed steady ( https://www.arceurotrade.co.uk/Catalogue/Machines-Accessories/Lathes/SIEG-C3-SC2-SC3-Mini-Lathes/C3-SC2-SC3-Accessories/C3-Fixed-Steady/C3-Fixed-Steady-090-020-00200 )  but I feel it's a bit too chunky, wide at the jaws and doesn't have roller bearings. A travelling steady would be better also, but again it is the same size as the fixed. As I mentioned I do have a Plan B solution prepared so will go with that.

 

Thanks for the comments and advice.

 

Richard

[wefalck]

I made for my watchmaker's lathe a smalled fixed steady: https://www.maritima-et-mechanika.org/tools/attachments/attachments.html#Micro_steady, but the same concept could be used for a travelling steady somehow attached to the cross-slide. The principle is similar to the one you showed earlier, but instead of bushings of various size, a V-notch is used.

Travelling steadies are difficult to install on a watchmaker's lathe, as the longitudinal slides sits on the cross-slide, so that the steady would move out, when you feed in the tool. 

 

 

[Rik Thistle]

Wefalck,

 

Thanks for the link. Excellent pictures there.

 

The V-notch is a clever solution. And it will be able to accommodate different diameters, whereas the 'bushing tool' (as you note) would need a range of accurately sized bushes for each rod diameter. 

 

I can see how the V-notch will work well for small cutting forces. I wonder if it could be scaled up to somewhat larger diameters? What is the maximum diameter you have cut using it?

 

Richard

Edited May 15, 2023 by Rik Thistle

[wefalck]

I have used it mainly for mast-making from steel rods, up to 4 mm I think.

[Toolmaker]

4 hours ago, Rik Thistle said:

Yes, there are quite a few ways to solve the issue

Yes, you could bore soft jaws on the lathe.

 

5 hours ago, wefalck said:

what are 'roller boxes'

 

[wefalck]

Ah this kind of tools that are used in tailstocks or revolver-heads in 'Swiss lathes'.

 

I have a sort of miniature version for my watchmakers lathe that works with bushings and is used to cut watch stems or screws without putting lateral pressure on slender parts. Some of the woodworkers' dowel-cutters are designed in a similar way.

[Rik Thistle]

Toolmaker,

 

Thanks for the roller box video. Interesting.

 

Soft jaws - coincidentally I ordered a set of 3 soft jaws on Saturday, but not for this project. 

 

For the co-axial and offset drilling of the taper pin, I am not overly concerned about achieving this - the project is only for a 1 off - if it was a batch run I would make a fixture/jig of some sort. I'll probably find a way to clamp the tapered pin vertically in the mill, find the pin's central axis, drill and tap the #0-80 thread, invert the pin, again find the central axis and then offset in the X and Y plane (I have X, Y and Z DROs). I'll post pictures etc when I get to that challenge.

 

Richard

[Javlin]

Nice work on the build feel like I am watching Mark Novak on Ytube he rebuilds parts for rifles at times actually simpler than what you are exhibiting at times.

[Rik Thistle]

Jumping back a few posts, we had discussed the reasons for using only 1 locating pin on the Saddle Way....

[Image above from one of the PMR plan sheets]

 

As shown above, it turns out that the pin is not for locating the Way but rather as a means for the adjustable T-Nuts to restrict the bed movement in the X-axis. I imagine the full-sized machine would have had some kind of rudimentary microswitch back in the day?

 

It's only as I get close to building these parts does the light bulb switch on!

 

Richard

[wefalck]

I didn't see the drawing before, but all these machines had such carriage stops, as they were intended for production work. My mill has little screws in the stops left and right, that allow a fine adjustment of the carriage movement.

In other cases these stops acted on a dog-clutch that would disengange the carriage drive.

[Rik Thistle]

stops acted on a dog-clutch that would disengange the carriage drive.

 

Thanks. I imagine that, at the turn of the last century,  these machines would be entirely manually operated?

 

Was there any means to set up the mill to automatically skim 0.030" off the surface of a thick plate clamped to the Bed ie make 3 or 4 passes in the X direction, then indexing in the Y direction at the end of each pass?

 

Off to do some further reading up on how 'automatic' 1900s milling machines could be. Any thoughts/advice welcome.

 

Richard

 

PS: Yes, that's a new image.... I had shown some photographs of the finished mill previously, but the line drawing does makes things a bit more obvious. My one pair of eyes do sometimes miss things - that's why multiple pairs are a great assistance. I try to find a balance of putting enough info online for discussion, help advertise the PMR product, but also without giving away too much PMR IP. 

Edited May 17, 2023 by Rik Thistle

[wefalck]

In most cases the 'automation' only concerned disengaging carriage drives, but by the end of the century certain 'screw' lathes to turn small parts, such as screws obviously, were automated and controlled mechanically from templates cut from sheet metal. Mechanically they were quite sophisticated.

 

Shapers and planers typically had automatic table advances using ratchet-wheels and ratchets driven by excentres. I am not sure that such features where ever installed in milling machines.