Member postings for Andrew Johnston

If you're only making one use standard cutters to remove the bulk of the material on the curves and finish the curves with files. One could always mark out and file a template in sheet steel if really worried about the profiles.

Andrew

Use silver steel, then you can harden and temper to whatever value of Rc you want, up to a maximum of high 60s.

Andrew

Thanks for that, I asked because the Chester spec only mentions a spindle motor and a table feed motor. On the Chester machine it looks like the gearbox is on the head. I find it difficult to imagine that the Chester machine has two motors and two gearboxes. On the other hand although it is possible to feed from the vertical head to the horizontal spindle it would involve several gear pairs and a spline. Which equals money!

Andrew

Just out of idle curiosity do these types of mill have a seperate motor for the horizontal spindle, or is power transferred from the motor on the vertical head?

Andrew

I don't buy ready ground HSS tooling, just blanks, so can't post a link. What I have done over the years is beg, buy or liberate boxes of used HSS tooling. So when looking for a specific tool there is often something fairly close that I can adapt on the bench grinder. A quick look in the pile of HSS by the lathe found this, which will do the job:

I'm not sure what material you are machining, is it brass? If so then the tool can be even simpler, just grind a radius that is equal to 1/4" on the bottom corner of a 1/4" square HSS blank, square off the end and that will do the job. No top rake is needed for brass.

Andrew

I would centre drill and then drill, say 6mm diameter, to just short of final depth. Then one could use a ~10mm centre cutting endmill and finally the 9/16" slot drill. Personally after drilling I would use a short HSS boring bar. That way one gets a hole exactly to the size wanted and with a truly flat bottom. Slotdrills and endmills are ground slightly concave on the end.

When using a slotdrill as a "drill" in brass one needs to be careful in case the tool grabs. They are better than normal twist drills (due to a slower helix) but not as good as the slow helix drills specifically for brass and bronze.

Andrew

Same as for internal corners, several ways:

1. For general radii, on the ends of connecting rods for instance, a rotary table is a pain as it is only too easy to rotate a tad too far and leave an indent. I prefer to use filing buttons. Although controversial I regard filing buttons as sacrificial and leave them soft. It is often quicker to use buttons than mess about setting up the job on a rotary table

2. A rotary table for complex radial slots that need to be accurate in size and placement

3. CNC mill, especially good for parts with multiple radii and splines

4. Mark out and file by hand

5. Machine on a lathe if the geometry of the part allows, that can include turning a circle and then cutting away waste material

Andrew

There are a number of options:

1. Change the design so that a sharp internal cormer is not needed

2. Drill a hole centred on the intersection; then a milling cutter less than half the diameter of the drill will leave two edges that theoretically intersect at the desired point

3. Run the cutter beyond the edge in one direction to leave a semi-circular cutout

4. Use files, start with a square file and finish with a three square needle file to get a nice crisp internal corner

5. Use a slotting head, I happen to have one on the back of the Bridgeport

A slotting head is particularly useful for blind holes:

Andrew

My CNC mill came with concertina way covers. None of my manual machines have way covers and I see no point in fitting them. Just something else to get in the way.

Andrew

I decided what I wanted to build and then chose a lathe and vertical mill to suit. Ex-industrial machines, still in production, were choosen for two main reasons, apart from capacity. First, spares are available, albeit at a price. Second, there are useful accessories that simply don't exist for smaller machines. If I'd known how much other equipment I was going to acquire I would have laid the workshop out differently. Larger engines were an antidote to the day job (electronics engineer) where the components are now so small that I can't see them without a magnifier.

My dining room table has a number of marks where I have disassembled and cleaned items. But I have never soldered at the table. As a electronics guy i have a professional electronics workbench in the study. But, since I don't have a better half, I can do what I like in the house.

Andrew

Yes, I wouldn't start from there.

Use a piece of stock long enough to be held in a chuck so that the face, OD and hole can be machined at one setting. Then turn round and face to thickness.

When making mandrels i normally drill the spigot and partially tap whatever metric thread is convenient. Probably M4 in the above case. The spigot is then hacksawed axially so that when a screw is inserted, and reaches the partially tapped section, the spigot opens up. This will hold the work quite tightly, although in the above case very light cuts will be the order of the day.

Andrew

All three; emergency stop switch on the headstock, a full length stamp bar below the shelf in the cabinet and a spindle brake on the stamp bar. The normal forward/off/reverse lever is on the right side of the saddle.

Andrew

It's just as well I don't regard myself as a model engineer then. Although I am building two 4" scale traction engines:

The motion work and internals of the cylinder are largely to my own design, based on the full size engines:

Likewise the gears, regulator, simpling valve and water pump:

i have made almost everything on the engines, including most of the nuts, bolts and studs, and the chains and all gears, the main exceptions being the steel boilers and rubber tyres. The 6ft long parts were the rear wheel rims before rolling and welding.

As for scrap I used to keep metals seperate. The local council tip used to have a big skip for metal, plus smaller ones for aluminium and copper alloys, but no longer. Some years ago when i had a lot of swarf (70kg of cast iron and 5kg of copper alloy) i took it to a scrap yard. I got about £40 but when you consider it was a 60 mile round trip and took several hours it made no economic sense. Now that I am not machining for work (which was mostly aluminium) everything goes in one box and gets taken to the council tip two or three times a year. Apart from anything else the seperate boxes/bags took up a lot ot floor space.

Andrew

I would disagree, I have run out of X, Y, and Z, on the Bridgeport; grooving plates that are over 6 feet long, in stages:

Drilling a large plate:

When looking at the space needed for a mill you need to account for being able to actually turn the hand wheel on the table.

Andrew

It was normal to hand chase threads before thread systems started to be standardised in the mid 19th century. Once that happened it became practical to add a screwcutting capability to lathes. Also taps and dies started to become available in greater quanties, and better quality.

Andrew

Both my bench grinders, made by KEF and Wolf, are single phase and there is no provision for balancing the wheels. I normally buy grinding wheels from Abtec4abrasives.

Andrew

I balance wheels for the surface and cylindrical grinders; both have hubs with adjustable weights. But I've never bothered with bench grinder wheels. I don't have a problem with vibration. Rather than spend money on a sticking plaster it would be better to invest in a quality wheel and/or bench grinder. Dressing a wheel won't do much to address balance unless the wheel is running wildly out of true.

Andrew

I saw the appropriate thread on another forum. It was tempting to say scrap the whole thing, as it looked to be freelance and poorly designed and constructed. But I thought it better keep quiet; but having seen the boiler above it reinforces my view. There are very few things worse than taking over someone elses uncompleted project.

Andrew

Yes they are; the name endmill is a misnomer. They are intended for cutting using the side flutes.

Andrew

The plot thickens; it is not an issue with 316 but milling in general.

For a start there is too much stick out on the tool. The holder should be down to the top of the flutes. Given that there is significant cutting on the return pass something is moving that shouldn't be. I suspect the cutter is flexing for starters.

Andrew

Edited By Andrew Johnston on 05/07/2023 10:28:47