Stuart 10V Build Log - Complete Beginner...

Thanks guys - that should see me through a good few steps.

If you go to Stationary Engines and find my Rons Jowitt thread go to page 2 and you will see Jason's pictures of his Sprung Indicator Rod both the parts and how to set it up and use it. There is also a drawing which he kindly sent. We'll worth making, I have used mine quite a bit.

I must learn how to make and add links.

Ron

Thanks Ron, Jason kindly pm’d me a as link to that. I’ll put it here next time I update it. I might try making something similar today.

I should also probably make adjustable saddle and cross-slide stops for the ML7 too at this point.

So thinking about the process of machining the bearings - I’ve got to turn bosses of different lengths on each end. It’ll be an intermittent cut from the outer ‘wings’ to the solid inner, so I’ll be moving the cross-slide in, cutting towards the Chuck, backing off, then incrementing the cross-slide in again before making another cut towards the Chuck.

Trouble is, I need to make the cuts to the same length towards the Chuck, and I have no limit stop. I spent most of yesterday’s hobby time making one that screws to the headstock on the lathe. It’s mode of scrap aluminium and some 304 stainless rod. I found a spare quick-release toggle, so decided to use that as a clamp, rather than threading the bar. I did add a cap head screw and lock nut to the end for fine adjustment though. It took a long time to make, mainly because I made it up as I went. I should have drawn it all out, but sometimes that’s the way it happens:







One lesson learned was that accurate alignment in every axis is critical for for consistent chamfering...next time I’ll get it better.

Now for the sprung centering rod...

I just set my topslide in line with the lathe axis and use the handwheel dial to set depth, touch the end of the work, zero the dial and away you go. I only use a stop on odd occasions such as a long blind bore.

I think the myford has the option to engage the half nuts and use the handle on the end of the lead screw as another option.

Correct however disengage the banjo and change gears first. Sounds obvious but I've done it three times now setting up to machine and broke the sheer pin on the leadscrew on my ML4, simple fix but directing I'm obviously a slow learner haha.

Jason, Jon,

My ML7 doesn't have dials I can zero, so I always have to remember the setting and how many turns I've backed off. If I go over the setting (or forget it), I get a step in the work. It's not great tbh. As a beginner, it's easy to turn a wheel the wrong way and really mess something up (ask me how I know!). I was going to upgrade to re-settable dials and thrust bearings, but I think I might just fit the bearings and a pair of cheap DROs (as with my mill) - everything seems so much easier with them, with no backlash to compensate for.

Yes, I can engage the leadscrew half-nuts and turn the handle at the tailstock end, but then I'm trying to keep to a figure on the dial at one end, where I really want to be looking at the workpiece at the other.

Anyway if my saddle stop doesn't work, I'll use the 'remember the setting' method I suppose. Building this engine really highlights what modifications would be useful to my lathe.

Cheers.

Anyway, cracked on with making a centering rod. I made it out of the remains of the 10mm silver steel I got for the spot-face tool, some brass off-cut and a random spring.











I 3D modelled this time so it only took a couple of hours to make. When it was assembled, I was a bit alarmed at how sinister it looked.

I noticed Jason's version had the point sprung loaded, but I wasn't confident I could make a perfect sliding fit (no reamers); my thinking was that any play in the pointed end might interfere with the DTI reading more than if the play was at the back, because the back isn't side-loaded by the DTI. Anyway, in the end there isn't any discernable play in the plunger.

Not sure about the cone angles, but I suppose I’ll see if it works soon enough on the main bearings...

Cheers!

Marked out the centre of the bearing with caliper lines scribed on some blue marker. I had to use an eye loupe to get the punch central - my eyesight certainly isn't what it once was:



Next thing is to mount them in the 4 jaw chuck and align them with the centering rod.

Trouble is, the drawing seems to be wrong: It calls for the bearing width to be 7/16" (11.11 mm), but it's not that to start with - it's only about 10.95mm (hence me buying the wrong sized ball-nose mill). It then calls for the bosses that protrude from this to be 27/64" (10.72 mm) in diameter. So that only gives about a 0.12 mm wide step around the boss - totally out of proportion to the drawing; it should be approximately double that. I guess I could use the calculated step width from the drawing, but then that eats into the bearing face area of the bosses.

I wonder if the drawing is wrong, or they've changed the dimensions of their brass castings?

The drawing has been that way for years, new castings may be a little smaller. It's not a critical dimension so could be altered. Something like 0.2mm deep cut or to round things up nicely 10.50mm dia

This is where experience over time comes in to know when you need to hit a size dead on, where it can have a bit of tolerence and where it is not critical. The easy availablity of measuring equipment these days does seem to have people looking for sizes to several decimal places where as in the past all the builder would have had was a steel rule and made just as good an engine.

Thanks Jason - understood about the drawings - they are obviously un-toleranced, so some intuition is needed. It was just that the inner faces of the bosses form the crankshaft thrust bearings, and the brass as supplied gives you half the bearing width; 0.2mm is the drawing face width, but that leaves you with virtually no land around the boss.

I might turn a spacer to clamp the boss to the mandrel, making it just small enough to get a defined land around the it, and use that as a guide for cutting.

If my memory serves me correctly (its a long time ago I built mine 40 years) I used a 11mm ballnose cutter and the bearings were a brass extrusion. Andrew Smith in his book suggested using a piece of 16 SWG? sheet wrapped round the curved area and the three jaw chuck. Hope this helps.

Paul

My memory is not what it was, the packing used should be 0.7mm or 1/32. Hope fully I have attached the revalent page from the book.

Paul

Also interesting that the metric drawing gives the diameter either side as 10mm which would be more than enough to compensate for any differences in the now cast part.

Thanks Paul and Jason,

I have that book - I wonder why it's missing the 11mm dimension for the 7/16" block width?

I've seen a couple of online builds where they've assumed the 1/4" dimension is the depth of the bearing axis below the upper surface of the block, and marked it out as such, ie with the as-cast upper surface as a datum. I don't think this is right: If the bosses are to be concentric with the semi-circular lower block, then that 1/4" below the surface will be slightly wrong. I assume it's actually the flat top face of the bearing that should be struck 1/4" up from the axis of the hole (or the lower O/D of the block).

All pretty irrelevant in practical terms, but it's interesting how people interpret the drawings w.r.t. the parts they're supplied.

Got distracted with some modifications to the mill - I got some thrust bearings and ball races for the x & y hand wheels. As standard they have plain bushes, and metal to metal face contact on the leadscrew ends. The stiction and feel isn’t nice.

So I removed the hand wheel blocks, mounted them in a 4 jaw chuck and milled/bored the bearing pockets. I used my home made centering bar to align the block - I could get it to about 0.00075” but no better for some reason.













Once re-assembled backlash was reduced by about 30%, just by being able to fully tighten the hand wheel nut. The biggest difference is in feel - night and day improvement with no noticeable stiction.

Very happy with that little exercise, especially as it’s the first time I’ve used a 4 jaw chuck. Next the y-axis, then back to motorise the x-axis so I can get more consistent surface finishes.

ETA: It took a lot of trial and error to get to my calculated bearing step depths, cutting a bit, then using the depth gauge on my digital calipers. Even then they were a bit out. I did use my new depth stop, and the fine adjustment screw on the end. I suppose I could calibrate that if I knew the screw pitch, but it's not a great way of doing it. What's the best way of ascertaining depth when blind drilling with the tailstock feed? Mine's got a very rough scale etched onto the tailstock shaft, no good for mm work.

Thanks!

Edited By Dr_GMJN on 27/05/2020 21:20:28

BTW can anyone recommend a decent DCMT straight tool holder?

With a hard stop use your compound slide to set depth. With the compound in line with the ways wind it to the right. Set the stop so that the tool is close to the workpiece face when the carriage is on the stop. Wind the compound until the tool touches the workpiece and set the compound dial to zero. Move the carriage away from the stop and advance the compound by the required depth. All set to cut to the correct depth.

Martin C

The ideal dimension would be from the underside of the two mounting lugs to the ctr of the hole as that is what ultimately sets the height relative to the A frame standard, cylinder etc.

When you say straight do you mean a holder that presents the tool straight on so the insert can be used for Whit threading?

Some people mount a cheap micrometer body to their depth stop or you can put a known size packer or even gauge block between stop and carriage then touch the tool to the work and when the packer is removed the tool will move in by that amount.

Just curious but how did you manage to use your centering bar to centre for a hole when the hole already exists, did you fit a plug or something into the hole..?