Imperial V Metric

I need to cut the steam ways in a steam chest on a cylinder. The sizes on the plans are Imperial but I am working in metric because all my tooling is metric.

steam way size converts to 2.4 mm. I only have 2 mm and 3 mm drills and milling cutters. Which is the preferred option, to drill undersize or the next size up please.

Edited By Garry Smith 7 on 01/05/2020 22:24:25

Hello Garry, going up a size would be preferable but you need to ensure that a bigger drill is not going to break out somewhere it shouldn't.

Having said that, a change from 2,7mm to 3.0mm should not make a lot of difference.

Brian

Thank you Brian. Just noticed my size was wrong and should read 2.4 mm

If you are worried that a 3 mm drill will ,break through aw all, buy a 2.4 mm or 2.5 mm drill (It will probably cut slightly over size anyway!

A couple of drills must be cheaper than having to buy another casting!

Howard

Edited By Howard Lewis on 01/05/2020 22:38:26

Buy a set of metric drills in .5mm increments should do you for the whole project and onwards.

You can get sets in .1mm increments too which is handy for exact tapping sizes etc but more expensive.

With your steam ports, if the 3mm is too big and going to break through, you could use 2mm in a pinch. It just means maximum performance might be reduced by the restricted steam flow. Which probably wont matter on a demonstration model not doing any actual work.

Invest in some drill bits, they're not expensive, unless you're giving up engineering after this project, you're going to need them again at some point.

3/32” on the plans possibly means that a 1/8” drill was considered too big or, more, likely too risky.

I just looked at the prices on the Arceurotrade site. Even with postage one is not talking a fortune! Even for several at a time for the standard length drills.

As Hopper says, these drills will come in handy sooner or later. I pick my drills for pilot holes for instance. I would rather wear out a size I have several of than use one which is the last on my inventory.

I buy one set and replace small drills, as they are almost considered as consumables - I don’t expect them to drill to size after a quick sharpening.

I just had a quick look on ebay, you can buy a box of 50 presto Sheffield made bits from RDG tools, 1 to 5.9mm in 0.1mm increments, ground steam tempered £33.71 posted.

I have quite a few of these presto drill bits, very good quality for little more than imports of dubious quality, and you get to support our industry in this country.

Depening on the metal available in the casting you could drill two 2.0mm holes side by side if there is a risk of a 3mm breaking through.

What do you do about metric threading when you want a tapping drill for M3?

Similar multi hole drillings

2 x 2mm drillings will increase the cross sectional drilling area by almost 40%, so for the same area one only needs 2 x 1.7mm drillings (but there will be more pumping losses, I suppose...)

But he has not got a 1.7mm drill, he wanted options for the drills that he has. better than a 60% increase from using a single 3mm hole too.

Plus as a beginner a 2mm drill will be a bit less likely to break in his GM casting when drilling at an angle than a 1.7mm

Edited By JasonB on 02/05/2020 07:38:36

regarding milling the ports then use the 2mm cutter and just move it over to get the required 2.4mm width otherwise you start having to look into redesigning the valve cavity etc.

Thank you Gentlemen I didn’t make myself clear. I have a full set of drills offering the minor point sizes between the 2-3-4 mm etc.

I was asking in relationship to Milling cutters. My preferred supplier is ARC Euro and they only sell milling cutters in the full mm sizes and not in sizes between the 2-3-4 mm etc.

The steam way I want to cut are not holes in the steam chest but are ports ie the size I require is 2.4 mm wide x 9.25 mm long hence my question do I go up a size or down if I only have milling cutters to the whole mm sizes.

If I was cutting a 2.4 mm wide slot I would not use a 2.4 mm cutter even if I had one. I would use a 2mm cutter to cut a slot that would probably be a little over 2mm wide. I would then clean up the sides taking light cuts until the slot was 2.4 mm wide.

Les.

Garry - down in size and then move the work sideways to open up to the required finished size, ie take 2 or 3 cuts to get where you want to be. You can't cut a 2.4 wide slot with a 3mm dia cutter.

Are Presto Drills still made in the UK?

These days it's not obvious who owns what or where anything is made, though China is often a good bet.

Easterbrook and Allcard were sold to the James Wilkes Group in 1989, Suter plc in 1993, Ascot Holdings in 1995, Kennametal Hertel Ltd in 1997 and most recently Suncraft International in 2006.

Suncraft 'is 'one of largest power-tool accessories manufacturers and exporters in China'...

Beware of trusting brand-names without checking. They don't guarantee anything. As far as I know Presto products have always been well-made, but I don't think Presto equates to 'Made in England'.

Dave

Good question, Dave ^^^

I was looking last night:

Presto has a ‘presence’ in Penistone ... but the Heritage statement does seem a little woolly:

**LINK**

https://www.presto-tools.co.uk/History

MichaelG.

.

Edit: https://www.28dayslater.co.uk/threads/presto-tools-penistone-road-offices-sheffield-oct-09.43910/

Edited By Michael Gilligan on 02/05/2020 13:25:52

They advertise as being made in Sheffield, and they have Sheffield on each individual drill, so why wouldn't they be? Surely there are laws that determine you can't make blatant lies about this?

But if you know otherwise, feel free to share

If slots required "On Size" cutters we would all end up with an infinite number of cutters, you use the next size cutter down but you cut the slot or pocket to the correct size!

I can't see anything on the Presto website claiming any of the current range of tools are made in Sheffield or the UK. 'Sheffield' can be put on packaging and tools because this arm of Suncraft is registered there, but I don't think it confirms anything is made in Sheffield. Certainly Presto tools were made in Sheffield for decades and the Heritage section of their website shows a modernish Guehring CNC machine, but when was the photo taken? It could be 20 years ago. Anyone been inside recently?

The original Presto works is discussed here, depressing. At Companies House Presto's purpose of business is '46620 - Wholesale of machine tools'. Likewise, on Yell, Presto International UK are listed under 'Tool Suppliers and Services'. I'm afraid neither 'Wholesale of machine tools' or 'Tool Suppliers and Services' imply manufacturing.

Does it matter? It's a shame the world has moved on. But if it became impossible for old Presto to operate profitably in Sheffield as a tool-maker, well done them for moving on to something that does provide jobs. As far as I know Presto tools are as good as they've ever been, wherever they're made.

Dave