Stuart Twin Victoria: Advice & General Questions

Ramon, Nigel,

Yes, stock size is finished size (only at one end). I did ask why not simply use round stock and mill the ends, but deleted the question before posting. I concluded that the size of stock round bar required to get the largest rectangular end, would be pretty big and cause more wastage of material. I think this is the sole reason rectangular stock was specified.

Id be happier using round, purely from the distortion pint of view.

Thanks both. Another amendment to the stock order list!

The other easy way to save a lot of time grinding is to start with small section HSS in the first place if you only want a small tool. Had a try to see what my sketched profile would look like just using a 3/16" sq tool I had been using for turning hence a bit too much sticking out the back.

I'm not averse to using flat stock particularly if the rod doe snot have a forked end which can tend to close up, This pile of bright and black bar.........

................Stayed true enough on my Easton & Anderson

Proof is in the pudding Jason and they certainly have come out well

It's all a matter of choice - I've certainly stuggled at times with stresses in material - mainly at work and it can be frustrating if it goes wrong but it's not impossible as you show - I just look for the point of least resistance.

Another alternative to flycutting is to simply shape the corners of an end mill or slot drill to the approximate radius required and use as normal. This is something I do a lot to put fillets in corners when milling (and chamfering) I do flycut on occasion but it's usually as a last resort or blocking out aluminium for I/C engines but much prefer to overlap mill to achieve a flat surface. Incidentally learning to tweak the corners of a cutter can extend the use of a cutter considerably and it's particulrly beneficial on machining 'brasses'

Edited By Ramon Wilson on 25/10/2020 11:04:13

I agree with Ramon, there's nothing difficult about grinding HSS tools. It's simply a case of understanding the angles. None of which need to be precise, just done by eye. I use a 5" Slibette (bought by my father 50 odd years ago in Cooks of Bedford) for grinding. It's got a coarse (46 grit) aluminium oxide wheel on one end and green grit wheel on the other end for grinding TIG welding electrodes. I also have a 8" Wolf grinder with an 8" wheel, but that's very fine and doesn't get used much. If I need to remove a lot of material I'll mill the toolbit first.

I use a lot of rectangular steel section, but mostly hot rolled rather than cold drawn. My conrods were hogged out of hot rolled bar on the horizontal mill before turning the taper and transition curves on the lathe:

I've never built any of the Stuart models so it's time for me to drop out of this thread as I can't add anything pertinent.

Andrew

Re. tool grinding, this is the wheel I've got, I think it needs to be much finer (and un-worn!):



Any recommendations - it's 6" diameter, 1/2" spindle and about 5/8" wide. Thanks.

I'd missed this post.

I'd forgotten: I've got a Rexon belt sander - I used to use it for profiling model glider wing ribs. I've got some new #240 abrasives for it. Also a linisher. They're just B&Q specials, but have performed very well over the years of general garage use:



I also found these spare wheels:



Unfortunately most of the markings are no longer legible. Do you think any of these would be suitable for HSS tool grinding?

Looks in better nick than mine

Looks like 1/2" dia. mild steel bar would accomodate the rectangular ends with minimal waste. Also, it would only be under 4 mm to remove on radius, to turn down to the minimum diameter of the circular section part. For what it's worth in material costs (only a few £'s), I'll get both, make a start and see what happens. Likewise with tool grinding. I need to sort it so might as well make some mistakes and start learning.

I've never really had any issues at all with fly-cutting on the mill - always got good surface finish, no chatter. Milling on the other hand has been problematic for me from day 1 on the SX2P, especially side milling. Chatter and 'ringing' never seem far away on anything from steel to aluminium, slot drills, end mills, cheap/premium tooling. Anyway, that was a different thread altogether. I suppose building the 10V, and it actually working, means that it wasn't that much of an issue for parts of that size.

Thanks all.

At 6" you have a suitable grinder but is that a wire wheel on the other end of your linisher? That could be your second finer grit wheel if so. The wheel on your other grinder certainly needs dressing - and would be ideal for roughing. Star wheel dressers do work but do so ferociously - have every thing covered up with something disposable and a vacuum held close by by a helper will be a big bonus to keep dust to a minimum - Better to do this outside if you can. Fine truing can be done by diamond if you have one. 46 grit for roughing and 60 for finishing is about ball park for HSS. Finer grit is okay for finishing but will glaze over quicker. Horses for etc

If you are happy with flycutting then go for it. Sound though like you may possibly have some bearing issues with your mill spindle if you experience excessive chatter/ poor finish when cutting on the side. What size cutters are you basically using. I would say that 85% of my machining even often on large parts are done with 6mm or 8mm throw away cutters - small cuts at higher speed and fast feed rates certainly takes the strain off the machine and removes metal just as quickly overall as a larger slower cutter will. Does mean a lot of handle swinging though. I do have a good range of cutters to choose from but definitely the most used (worn) cutters lying redundant in a box are mostly 6mm and 1/4 FC3.

Regards - Ramon

Edited By Ramon Wilson on 25/10/2020 13:37:53

Cheers Ramon,

The spindle bearings are fine. The mill is new - or at least first got used this May after buying it last year. I can only think that the tramming process - using shim steel under the column bolts, doesn't give enough bearing area and is causing some kind of resonance. I'm using 6/8/10mm end mills or slot drills. It's mainly side milling that gives the issues. The end of the sample aluminium base section I posted yesterday for example is about a 20mm deep x 10mm wide section, and when facing the ends to neaten it up, the cutter squealed like a pig no matter the speed, depth of cut, climb, not climd or whatever. I was trying to face it using the full depth of a 10mm end mill. Maybe it's just me I dunno. Fed up with it TBH, I just try to avoid it now.

When you say "throw away cutters", what do you mean by that? If you mean cheap, then I had some of those, and folks on here told me to buy premium stuff because the cheap ones were probably contributing to the issue.

I added an x-asis power drive (just a dc motor and speed control through a dog clutch) that reduces handle spinning on longer parts (and often gives me improved surface finish on wide surfaces).

Anyway, I'm currently finalising the materials list, and converting the drawings to metric, then I need to convert the ML7 to wide bed format to get rid of some wear, and add some slide bearings. Then I'm good to get on with machining again.

I'll just crash on with grinding some of the HSS tooling I've got, but never use, and see what happens on some test material.

It may simply need the bearing preload adjusting, when my X3 arrived the adjusting nuts were actually loose.

Throwaway cutters is the term used for the small usually under 6mm cutters though they can be had upto 10mm dia with a Weldon (sidelock) shank. They are not worth industry sharpening so have become known as throw away I also use them a lot as they are quite economical and the 3-flute design is a good all rounder. I usually get Hertel brand from MSC when they have them on offer, though not listed this month.

They work well on aluminium but the aluminium specific cutters are better still.

I'll have a look at getting some of those cutters next time - and I'll check the bearings, although they don't feel loose at all.

I replied to this earlier but for some reason it has not posted. I'm having a lot of problems today with the computer dropping in and out of internet connection.

No, I definitely didn't mean 'cheap' cutters (never a good idea) but Jason has explained what I mean perfectly. Any good brand of FC3 cutters will be ideal. There are cheaper versions on Ebay but despite their attractiveness the quality of life rarely holds up.

Any mill that is exhibiting the kind of issue that you describe is definitely suffering from a lack of rigidity - somewhere - it's finding it that can be a problem. As Jason suggests I would certainly begin at the spindle and check for any slackness in the bearings first, both vertically and radially,  then work out from there. Assuming the table axis's are firm and well supported squealing, chatter, juddering when cutting is usually a lack of firmness somewhere in the spindle set up or in it's guide in the head. Certainly worth spending some time on to improve it if possible - the machine should be able to be relied upon at the age it is.

A power drive is a very nice accessory to have - my Amadeal mill is still waiting for one, nearly six years after being told it would be a few months! The finer pitch leadscrew on that compared to my old Linley certainly makes for tired arms on lenghty parts!

Edited By Ramon Wilson on 25/10/2020 20:24:29

I've started a WIP thread for this here in case anyone's interested:

https://www.model-engineer.co.uk/forums/postings.asp?th=168849

Thanks for all the advice here folks; any further P.R. questions, I'll ask on the new thread.