Saturday, 29 August 2009

Nice bit of knurling

I've told a few people that I'm making a knurling tool and some of them look at me with a puzzled expression and ask what knurling is. I've been trying to find a good example of this and have noticed that there are not too many around. Obviously in the workshop there are plenty of examples but not too many on the high street.

The other evening I was passing the Czech & Speake Shop on Jermyn Street and noticed the rather eye catching display in their window.

Czech & Speake Shop Jermyn Street, London

In the back of the window, there is a big photo of a knurled wheel.

Czech & Speake Knurling

After a bit of investigation I discovered it was an Edwardian style lavatory roll holder available in chrome, platinum matt, platinum or Durabrass™. Hopefully when I get the tool finished I'll be able to create results to this high standard.
Edwardian style lavatory roll holder

Monday, 24 August 2009

Pinball Machine Makers

The paper on Friday reported of a man making a Bill Paxton themed pinball machine.



I've always liked pinball machines and wondered at their electromechanical marvels but given the complexity I've never seriously planned to make one.

However, it turns out that there's a few people who are mad enough and talented enough to make their own pinball machines

Diary of a pinball machine repairer
Critical Mass Pinball Prototype
Software for designing pinball machines
Pinball News

Saturday, 22 August 2009

Knurling Tool Work in Progress

Some pics of the knurling tool in various stages of being built.

Knurling tool parts, work in progress

Arms drilled and deburred

One arm slots sawn

The next steps are to saw the other two slots and then machine or file the slots square. I think that I should be able to mill the slots on the lathe in a similar way done with the t-nuts. The main issue is clamping the arms at the right height as they are too large to be held in the tool post but I'm hoping to be able to clamp them on the cross slide with some packing.

Friday, 21 August 2009

Countersinking

For the knurling tool I'm making I decided to attach a couple of the parts together with some countersunk screws.



This raised the question of how do I ensure I've drilled it the right size?

Conveniently in the UK the Din 7991 standard for countersink bolts has a 90° angle hence the calculation turns out to be simply that the diameter produced is half the depth drilled. This is the depth with the drill bit resting on the surface, not with it resting in the hole.

So for my M5 bolts I need to drill down 5mm to get a 10mm diameter hole for the heads.

There do appear to be other standards for countersinks including an 82° angle. I believe that woodscrews also are different to metal screws but I've not had any to check against.

Wednesday, 19 August 2009

Drilling Tips

I had to drill some steel plate yesterday and even though I was using a vice and pillar drill (drillpress) the drill started to wander as it was a little bendy.

This happened twice, once on a through hole and once on a blind hole.

Pillar Drill / Drill Press

My first tip is for that through hole. Simply stop, take the work out the vice, turn it over, remark the hole, centre punch and start again. This worked just fine for me.

The second item was a little more challenging. I needed to have a blind hole which was going to be tapped and the drill moved again. This time I could not turn over the work so I switched to a centre drill, put more clamps on the vice and gently drilled a new hole with the centre drill. This was followed up with the origional 4.5mm drill.

There will be some pictures of this when I do the write up on the knurling tool.

Monday, 17 August 2009

The master becomes the student

Since I was a lad my Dad has been repairing and rebuilding wooden boats. Hence whenever I have any questions on wood (or rope), I give him a ring for his advice.

In the last few years he's moved from racing boats to cruising the clyde and islands around the west of Scotland and hence his boat is a little larger than before. Following a trip around Bute one of the plates that held the mast stays had broken and bent the bolts.

Given that the parts for classic boats can't just be bought down the shop, he needed to make a replacement plate. Shortly after, I got a call about how to drill 10mm holes in 6mm thick stainless steel. We had a long discussion about drilling slowly, using coolant, cobolt vs HSS drills and making sure that the metal was clamped firmly. You can see below that the results came out very well.

Stainless Bracket

This week I got a report that the bracket is working fine and my Dad is off sailing again. It's nice that the tables have turned and that I'm now the one being asked for advice.

Wednesday, 12 August 2009

CNC Rotary Indexer from Sherline

Thanks to Robot Magazine I've found out about the Sherline CNC Rotary Indexer Part No. 8700.

Numerically Controlled Rotary Table from Sherline

The advantages of attaching a stepper motor and control box to your rotary table is that you don't need to deal with the mathematics, plates and counting associated with a regular dividing head. It can be used to drill holes in a circle, for milling curved objects, gear cutting, large diameter turning and even be combined with other Sherline CNC tools for more complex operations.

The controls have 5 modes, division (e.g. 4 steps per revolution), degrees, job (manual), programmed and slave where it can be controlled by the output of a different CNC device with direction and step controls. The controller has backlash elimination and can ramp up and down the speed for movement which is great for accurate positioning.

The table is priced at $725 which although quite expensive by my standards is still within the range of an average hobbyist. The manual is comprehensive and gives instructions for someone unfamiliar with a rotary table, a mounting diagram and a nice exploded picture of the table with parts numbers for spares. There is a lot of supporting information on the sherline website and there is a strong following so there are plenty of other hobbiests and groups using the equipment.

The through motor handle seems like a good idea but a side effect of using it is mentioned in the manual which is that it can act like a generator and potentially damage the control box. Another issue mentioned in the manual is that turning on and off the power might affect positioning so you may have to re-align work if it is machined over several sessions.

It looks quite similar to the DivisionMaster product designed by Tony Jeffree which is available in kit form from the Model Engineers Digital Workshop. The key differences being the Sherline's through motor manual handle, programability and the latter's lower price due to being in kit form.

Saturday, 8 August 2009

Project Links

A collection of projects to make with the lathe or mill

Duncan Munro's Metal Pages has a variety of projects from furnaces to workshop furniture to advanced projects such as a gear hobber or a dividing head.



Astronomer and model engineer, Chris has a large number of drawings and cad files with his workshop projects. He also provides a series of notes on workshop techniques such as adjusting your lathe or hardenning steels.

Frank J. Hoose also provides a good range of advice on adjusting your mini-lathe.

Adjusting the mini-lathe

Finally some very professional results from Ishimura who has an excellent range of projects for the metal worker with text in both English and Japanese.

Friday, 7 August 2009

Gib-strip adjustment

When I started machining the square bars, I realised that there was movement in the cross slide and hence I was getting an uneven surface on the faces of the bars.

Gib Strip Adjustment Screws, and cap head screw to lock the slide in place for precision machining.

On the right hand side of my cross slide is a set of 4 screws which are locked in place with small nuts. These adjust the gib-strip which is a bar down the inside of the dovetails which hold the cross slide in place. By adjusting the screws you can ensure that the cross slide moves in a straight line without being too stiff. This arrangement is designed to compendate for any wear in the mechanism. You will find these adjustments on a wide range of equipment such as lathes, mills, grinding machinges, x-y tables and anything else that uses a dovetail slide.

In Model Engineer's workshop No. 154 David Lewis suggests an interesting idea which is to put small ball bearings on the end of the screws to spread the load of the screw onto the gib-strip. I've not tried this but his collegue, a former Adcock & Shipley apprentice said it was the best modification that could be made to a slide.

Reference

Mini-Lathe Tuning
Mini-lathe deep clean

Thursday, 6 August 2009

Machining square things in a lathe

This week I decided to start some work on a caliper knurling tool, based around the ideas in the Workshop Practice book, Making Small Workshop Tools.

After sketching some plans, the first thing I needed to do was saw up some metal to make the body, arms and mounting lug. The size of the tool is basically determined by the size of the knurling wheels and the size of the lathe. So in my case the arms are quite chunky being made from 70mm long by 16mm bar and I've used some 9mm plate to make the body. The basic components are all square so I decided to make them in the lathe.

"But a lathe is for round things, you mean milling machine?".

Although I've previously experimented with milling in the lathe in this case the components just required squaring off which is quite straight forward to complete in the lathe. The components are mounted in a 4 jaw chuck and faced off in the same way you would do with round or hexagonal bar.

Machining one of the knurling tool arms

Squaring up a the body

Now that I have some squared up components, the next step will be to drill them but that's for another day.

End results

Other References

Thor's Metal Projects
Grahame Howe
Ishimura (two designs)

Sunday, 2 August 2009

Finished Gates

Metal Gates

After many weekends of work, the gates are finally finished and fitted. I can now focus on some of my own projects, hopefully I'll be able to get started on a caliper style knurling tool. I did manage to sneak in some simple milling this weekend. The gates needed some spacers so I milled the end of some bar flat using the lathe.

Workshop Practice Series