Member postings for Avon

Hi, I checked with the foundry today and the material is LM25 and as you suggest it was a piece of scrap riser.

I found today that a higher feedrate and lubrication with WD40 helped improve the finish immeasurably, I suspect I shall see another improvement when I get the new cutter.

I also tried climb milling, but the machine doesn't seem to feed the work evenly and I didn't detect any improvement in finish.

After all that, I think I've still got some work to do to try different combinations and I'm learning a lot!

Thanks for all the comments - they've really helped.

Thanks Jason, I think I've seen the sort of thing on the Zoro website. I'm going to check with them tomorrow and hopefully get some new cutters before next weekend! (when I have time to enjoy my workshop).

thats more like the finish I want to achieve! I don't think it can achieve 2000rpm, but it can do considerably more than I've been using - I looked for advice on figures in book I have. I'll give it a go.

I'll also investigate getting new cutters - do you think they need to be threaded on could plain shank be held effectively just by the collett?

HI Dave,

Its a scrap bit of casting which is why it looks manky. Foundry & Fabrication at Totnes have cast the baseplate (aluminium) for my hot air engine and its Flyweheel (ali-bronze). Its the same material as they use for casting gearboxes for cranes and having seen the quality of their finished product this is a very machinable alloy. (I collected them yesterday and their Production Manager was kind enough to show me the foundry and workshop - its such a pleasure to talk with a knowledgeable and enthusiastic professional).

I confess I didn't detect any vibration, but I'll try holding it differently - I've nothing to loose and lots and lots to learn.

You make a good point about buying a new and comparing - I thought they would be expensive, but just seen one for about £6.00 which is not extravagant.

Thanks for your help.

The phot below shows the poor finish I'm achieving when milling a piece of aluminium. Its not just cosmetic either, it feels rough to the touch. The setup I've tried is as follows:

Milling Machine: Centec 2A fitted with a Clarkson Autolock. No discernible movement in the cutter or the work.

Cutters: various 5/8" 2 and 3 flute cutters, which may not be as sharp as they could be as they're my fathers old ones and I don't have the means (knowledge) to sharpen them.

Cutter RPM: I've tried 400rpm and 600rpm with a slow feed rate, cutting depth of about 15-20 thou,

I suspect the problem is blunt cutters, but want to be sure before buying new ones.

If I have to buy new ones what would be recommended - I'd like to keep the clarkson autolock, but don't know whether the thread would be the same on new cutters.

Any advice gratefully received.

Peter

Dear All,

Many thanks for all the replies, it is certainly a more varied debate than I had imagined. I haven't yet investigated the clover plate and grinding, but will do. What I have done is another thorough clean (it was only stripped and derusted etc last year, then carefully checked for differences between chuck key positions and now have a chuck that has a little under 0.1mm (4 thou) runout which given the comments seems usable. Certainly much better than some of the figures I'd measured.

Having carefully inspected the scroll wheel I can see numerous dents etc where it looks to have had swarf trapped. I could try stoning any raise areas, but think I'd cause more problems. For now, I'll stick with understanding the problem and using collets, 4 jaw or turn between centres as necessary.

Thanks for all the comments - really appreciated.

Hi Old Mart,

Just to avoid misunderstanding your statement 'reduce the fit between the backplate and the chuck register by 0.3mm' means to allow more of a gap between the locating circle of the chuck and the raised portion of the back plate: I would then nip up the bolts once I've checked the chuck runout.

Apologies for what is probably a dosy question!

Regards

Peter

I've discovered that my 3 jaw chuck doesn't hold work 'on-axis', I've put a DTI on various diameters with the following total runout measured:

1. With a ground 1/2" steel bar held in the internal 3 Jaw Chuck: 0.25mm

2. Same bar held in 1/2" collet: 0.04mm

3. Mandrel, just next to headstock bearing: 0.0mm (no discernable movement)

4. Mandrel, inside the collet taper: 0.0mm (no discerable movement)

The run-out using the chuck is too much to allow me to turn something and then reverse it to complete machining.

What do I do to fix it? Is it possible to fix it?

This is on a Smart & Brown, Model M, Mk 1.

Grateful for your advice.

Now actually started building my Hot Ai Engine. Have finished the patterns which are now in Totnes for casting. And the transfer cylinder has been turned out of a piece of 1 1/4” tube - the most daunting bit of boring I’ve ever done as the finished wall thickness is only 1/32”. On one cut the the swarf came out in just about one single piece - right across the workshop and then some!! (Sorry about the picture orientation, but can’t find the rotate button!!)

Noel, Andrew, many thanks for the very quick replies.

Sadly Andrew you were pipped to the post and Noel and I are arranging the transfer. Sorry to disappoint.

I should have said - I'm in West Devon and I think it'd be expensive to post as its pretty heavy.

For what its worth I use Onshape - its a cloud based CAD package from the original developers of Solidworks. I create parts from sketchs - how many parts I create in on sketch tab depends on my mood. These are then combined into an assembly with various constraints applied. Drawings can then be produced from individual parts, sub-assemblies or assemblies.

There is no limit to the size or number of models you can have other than a 'free' user's models are available to any other user to copy. Unless you wish to retain some IP in your drawings that isn't a problem.

I think its a brilliant piece of software.

Hi this motor was bolted on the back of my Father's S&B Model M Mk1, I have replaced it with a new motor mounted internally as intended and this is now cluttering up my too small workshop. As far as I know it ran perfectly well when last used - whenever that was.

If you want it please let me know - I don't intend to charge for it, but if you could see you way to making a useful contribution to our local Scout group I'd be grateful.

Well thats given me something to think about. Other materials are possible, but it is the heavier material choice that came up in discussion. The original instructions merely suggest a zinc based alloy, but the foundry have little call for such and so proposed the bronze.

I'll let you know how I get on.

Many thanks.

HI,

I'm getting a hot air engine base plate and flywheel cast by a (relatively) local firm. They've offered me what I believe to be a good price to do the base in Aluminium and the flywheel in ali-bronze. The latter is in order to get a decent weight into the flywheel.

I'd be grateful for advice on whether there are any particular diffficulties with machining and drilling the flywheel that you can envisage.

Grateful for all and any advice.

All the best.

Peter

I remember wrapping wet papertowel around the cold end - it went like the clappers! I've been thinking about how to improve it, but first I'm just going to get it made and running.

Where did you source your transfer cylinder material - I haven't found any tube with the thin wall required - I've considered rolling my own from suitable plate, but thats another complete project in itself.

Regards

PS. Get your grandchildren to take the photos!

Just come across this thread. It's exactly what I'm doing and made my version at much the same time as Bos'un. I never did find the plans on the internet, but sourced then from a school in Woolangong South of Sydney when working in Perth. I never did find where my original went.

Does anyone have a link to the other two booked in the series: stream engine and electric motor oil believe?

Bos'un - where did you get your flywheel cast?

HI Nick,

Spot on - there's a slight raised area on the clip which is moved away from the trip bar when pulled out.

Interestingly, the option of dividing the 'live' across the contacts would effectively reduce the current in each. In order to simply ensure consistency between phases they would need to be wired in series.

Regards Peter

HI All,

Well some success with the existing setup. It appears that the adjustment on this contactor is simply to pull the clips tabs out on each contactor (2A pushed in, 2.75A pulled out according to the notice which I found hiding in the bottom). See photo below. The clips are looped bits of brass at the end of each arm - they appear to be holding the bale arm in the photo.

Definitely no NVR, but it seems to be working ok now and I'm the only one who uses the workshop.

Will probably investigate a starter, but for now I just need to find some sharp tools!

Many thanks.

Peter

I think Mike P is probably spot on - a good description of the device.

Nick, there's no other switchgear and certainly no coils - I've had it all out to replace degraded cabling. The two pairs of wires at the top: one pair to the main winding and the second (via a changeover switch for forward/reverse) go to the switched starter winding (physically out of phase with the main winding to create a starting effect as I understand it, it is switched by a centrifugal switch in the motor). There's no NVR mechanism.