How to mill hornblock etc slots into O gauge frames?

[JeffP]

Sorry in advance if this is obvious, or been asked before,(I did search, honest), but I'm unsure. and Google comes up with "proper" model engineering, 5" gauge etc.

I have an Emco mill, have had it for 25 years, but it's only ever been used as a pillar drill.

I also don't possess any milling cutters yet, and would welcome advice as to what to buy, or what to avoid.

So....how would I mill a slot into a frame without damaging the vice, and am I right in thinking I would screw the frames to sacrificial timber?

[Guest WM183]

What scale, and what material are the frames? I find it very unlikely that a mill is the right tool for the job. A piercing saw is how I do it, and I do have a mill as well. 

[JeffP]

7mm scale, O gauge, brass or nickel silver.

Any advice re tooling?

[Madreddog]

If you are going to use the mill I wouldn't use wood. The frames need to be clamped down very firmly especially if they're thin. If the cutter decides to snag you will bend them and cut material out you didn't mean to. Bolting to either a block of aluminium or steel with lots of clamping point is best.

 

Tooling needed; Quality milling chuck such as a Clarkson Autolock with it's collets (small version. Beware! they were made in three sizes!). Collets are in two sets of four (metric and imperial). Metric have a groove in the outside of the flange to distinguish them from imperial. You need to know what the spindle fitting is on your mill. I'm guessing MT2 but check first. Many small mills don't use a drawbar to retain the chuck and instead use a flange. It may be the case that you have to buy the original Emco chuck however.

 

Cutter; slot drill is probably the best option especially if it is a four or six flute. Don't get a two, this is more likely to bite and cause damage. Make sure it is HSS and is a good brand. Don't buy a cheap unbranded one!

 

To machine the item use lots of *very* thin cuts. Maybe 0.1~0.2mm at a time and go very, very slowly winding that handle. One wrong move and you might be buying a new set of frames!

 

 

[Izzy]

You really need a pantograph milling machine to profile frames. Be aware that using ‘ordinary’ size cutters will not produce a square slot, you need very small diameter, 1mm etc. for that, (still with rounded inside corners). And just running a cutter up into material will not produce a correctly sized slot anyway, even with light cuts, tends to be oversized (the deeper the cut the more the cutter gets ‘pulled’ into the material). Don’t believe cutter deflection doesn’t happen, it does. This is from experience. Using the co-ordinate table to accurately drill hole centres is a great benefit though. Turing them into slots via filing is long winded, but still easier in the long run, and simpler.

[JeffP]

Many many moons ago whilst at college in Clifton, Nottingham, we discovered the college workshops, open to students and staffed by a very able and very clever guy called Clive, "Mac" to his friends.

There I made cabinets for speakers for my hi-fi, locking nuts for the Cibies on my Escort, and used the Taylor - Hobson pantograph milling machine to engrave all sorts of stuff including a complicated switch panel for my car.

I'd love one now, but they are massive and very heavy, and cost £££ if you can find a good one.

[Izzy]

7 minutes ago, JeffP said:

the Taylor - Hobson pantograph milling machine to engrave all sorts of stuff including a complicated switch panel for my car.

I'd love one now, but they are massive and very heavy, and cost £££ if you can find a good one.

I’ve known a couple of people who had them. Alan Gibson, who used to mill all his profile frames he sold on it as well as sinking all his wheel dies, perhaps the new owner has it now. The late John Watson also managed to find one in recent times. I’m sure I’ve seen that Proxxon do a little engraving version these days but how capable it would be is another matter. You do need a bit of ‘heft’ even for small work with a lot of machinery.

[JeffP]

Never mind Christmas, it's beginning to look a lot like I need to practise more with the saw🙄