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Member postings for Martin Connelly

Here is a list of all the postings Martin Connelly has made in our forums. Click on a thread name to jump to the thread.

Thread: What Did You Do Today (2017)
18/03/2017 14:45:36

I was asked to square up the ends of some 2 1/2" sch40 316L stainless for a trailer axle and modify some stub axles to fit in the ends with a "hammer" fit. Holes were added to allow for some welding away from the thin lip and a fillet will be added all round the end of the pipe. Someone else will be welding it.

Martin

img_20170318_142909.jpg

Thread: The effect of lubrication on reaming tolerance
18/03/2017 07:40:55

Tony, I was commenting on the linked document only, nothing else. His graphic is labeled plus and minus 10 micro inches. For the size of hole he is using this is less than the variation caused by a 1 degree C change in temperature. The cooling effect of lubricants is important, using hand tools can raise the working temperature of the tool significantly. I do not doubt the differences that people are reporting but do think the working temperature of tool and workpiece are very important to precise hole sizing.

Martin

17/03/2017 20:13:27

The other thing that caught my attention in the report was the rpm used. At the high speed used heating of the tool can occur. In this case the cutting fluid with the best cooling properties will produce smaller holes than ones that let the tool heat up.

Martin

17/03/2017 13:19:41

I would suggest that for the typical person the different hole sizes stated are to all intents and purposes the same. The variation is measured in millionths of an inch. This is far below what the average machinist would consider acceptable variations in hole size.

Martin

Thread: Grinding wheel supplier recommendation
13/03/2017 23:38:34

There was a thread recently about CBN wheels from The Toolpost in Didcot. I have one from 5 or 6 years ago that shows no sign of wear. I would advise getting at least one of these for your grinder.

**LINK**

Martin

Thread: The Car as an extension to the Work Place !!
12/03/2017 13:56:22

Where I work we have a site wide ban on moving around when using mobile phones. This is because vehicles such as battery powered lift trucks move around relatively quietly and often the driver has poor visibility due to the mast in front of them and sometimes the load as well. Instructions are to move to a safe location and then use the phone without moving around. When I see someone moving when using a mobile anywhere now I think they should be standing still. My colleagues have reported similar feelings. When we have tried to tell people who are walking when using their phone on the site that they need to stand still we have had problems getting their attention. I have even had one person telling me that they were standing still while they kept on walking.

Martin

Thread: LATHE
10/03/2017 18:39:49

If your material is poking into the spindle it is hard to ensure that it is not drooping as the chuck is tightened. If it is poking out the end of the spindle then it can be held in that position by a cat head. For a long item that is not long enough for a cat head I think the steady and 4 jaw chuck option will give you a better chance of the bore being aligned to the rest of the workpiece. This makes some assumptions about what has already been done to the workpiece before the boring operation. I have not done any work of this sort to be sure, it just seems likely so any one with experience feel free to correct me if it is wrong.

Martin

Thread: >Ouch< well, almost...
09/03/2017 15:01:07

The diamond disks still produce dust, grit and larger pieces that can rebound off surfaces. You need a dust mask, goggles and hearing protection when using them.

Martin

Thread: Are we the last generation.?
09/03/2017 14:53:37

Since the sun is shining today and the temperature is into double figures I decided to clean the pond filter. As I put everything back in place the filter outlet hose tail snapped off. I decided the best option was to make one from some stainless steel. More fun than buying a new one and quicker as well. I found some 30 mm diameter bar an chucked it up. I used my CNC lathe with manual data input to make the part. I did not check when I started but I think it took about 30 minutes to make from picking up the bar to the point where it was finished. I can't imagine being able to buy one that fast.

Apart from the computer controlling the movement of the machine under manual instruction no other computer input was involved. So the question is does this count as manual machining or CNC?

Martin

img_20170309_104954.jpg

Thread: Crosslide backlash
05/03/2017 19:34:20

It can be argued that cross slide backlash can be ignored because you only work in one direction when manually turning a part. Typical manual turning is done by approaching the desired diameter and measuring as you go to hit the desired size. Backlash will make no difference to this.

Martin

Thread: Milling - What am I doing wrong
04/03/2017 08:10:22

Harold Hall's website has a list of the contents of this book.

**LINK**

You can see if it suits your needs.

Martin

Thread: Warco WM18 has arrived
04/03/2017 07:55:21

Do you mean ER25 not EM25? If so you can buy one with a parallel shank that can be fitted into one of your R8 collets. This will allow you to hold a drill or cutter a little lower without extending the quill. You will also have the option of how far out you extend the ER25 collet holder within the limits of the shank length. The risk with doing this is that there may be slightly more runout at the cutting point. It has not caused me any problems. You may find that it help with access for some jobs where a smaller diameter tool holder is useful.

Martin

Thread: Milling - What am I doing wrong
03/03/2017 18:56:00

The chips look very small to me. You may need to increase the feed rate to do more cutting and less rubbing.

Do you have a spindle lock? If not then trying to tighten the R8 collets tight enough to hold the cutter with enough force may be a problem.

Martin

Thread: Brass cylinder block correction question
27/02/2017 17:25:43

Could you mill out the web between the inlet and exhaust ports beyond the ports and put a plate in, tight fit and solder? It can't go anywhere if the solder softens.

Martin

Thread: Scaling drawings
19/02/2017 08:22:01

If you have balanced weights then scaling them up will result in balanced weights. 1kg of steel balanced by 1kg of lead will become 8kg of steel balanced by 8kg of lead. If you have an imbalance to start with then the imbalance will change with scaling.

Problems occur because volume increases by the cube of the scale but area increases by the square of the scale. If you double the scale the displaced volume of a cylinder increases by a factor of 8 but the inlet orifice only goes up by a factor of four. This can result in reduced output where increased output was expected.

Martin

Thread: Printed "Template"
18/02/2017 20:16:27

Roy, that's why I said if.

Martin

18/02/2017 19:47:21

Roy, if you want to check scaling in both x an y directions when printing off a plan it is easier if you can draw an accurate sized box to be printed off with the plan. The OP was about printing off, not about drawing on a piece of paper. The bigger the box the easier it is to check the scaling.

I have printed large layouts using an A0 plotter. The axis along the bed is usually correctly to scale but the direction the paper is fed is variable. Older printers using paper on rolls suffered from higher tension from a new roll with lots of weight. As the roll was used up the tension changed and the scaling changed. More modern plotters feed the paper through the machine and cut it off then reverse back to the start of the paper then print with minimal tension on the paper. Despite this the scaling along the length of the paper is rarely correct.

Martin

Thread: Scaling drawings
18/02/2017 19:33:11

MalcB, weight is mass times gravity so if the mass is scaling up by a factor of eight when linear scale is doubled then weight will also go up by a factor of eight unless gravity changes.

Martin

Thread: Printed "Template"
18/02/2017 14:49:37

Draw a box 100x100 or 4"x4" around the plan if is in CAD then when it is printed off you can easily check if the scaling is correct.

Martin

Thread: An introduction to my Grinding Rests
17/02/2017 18:47:13

Could you leave one of the arms at 8mm thickness and just have one at 3mm? I know that this asymmetry may not be as pleasing to look at but it would reduce the amount of work needed to do the modifications.

Martin

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