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A few newbie questions, sorry

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Mark Gould 116/07/2019 09:49:57
141 forum posts
92 photos

Gents,

1. What is the difference between an end mill and a slotting drill? I was looking on an ME site for some taper pin reamers and happened upon "slotting drills". I remember Keith Appleton mentioning them in one of his youtube videos but he never actually explained the difference.

2. Why are the backing plates for 3 jaw chucks and 4 jaw chucks referenced to a different part of the chuck? I don't have the description before me but I seem to remember reading that when machining a backing plate the chuck face that is machined to fit is different. I hope this makes sense.

3. Our Myford S7 has 2 oil cups under the headstock belt guard. they supply oil to the shaft that houses the countershaft, clutch etc. One of these oil cups ALWAYS requires oil and the other is always still full. Is this logical? Should I be worried and if so what should I be checking?

Thanks in advance for any help,

Mark

Edited to get the technical terms correct

Edited By Mark Gould 1 on 16/07/2019 09:50:57

Edited By Mark Gould 1 on 16/07/2019 09:51:29

Andrew Johnston16/07/2019 10:00:13
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4936 forum posts
560 photos

1. Traditionally an endmill would not be able to plunge vertically, but is designed to cut on the side. A slot dril normally has two flutes, and on the end one edge goes to the centre, so the cutter can be plunged straight down. For reasons of cutting geometry a 2 flute slot drill should cut a more accurate width on a slot than a multi-flute end mill. The distinctions are somewhat muddied now as 3 and 4 flute centre cutting endmills are very common.

2. I suspect it's simply what individual manufacturers specify rather than some fundamental difference between 3 and 4 jaw chucks.

3. Don't know; as someone has "helpfully" pointed out recently I don't have a Myford lathe. smile

Andrew

Paul Lousick16/07/2019 10:42:36
1212 forum posts
502 photos

Hi Mark,

I am not a Myford expert but if one of your oilers is always full could mean that you have very good oil seals or the port to the bearings is blocked. If it is blocked there would be no oil getting to the bearings.

Paul

Brian H16/07/2019 10:45:57
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1288 forum posts
99 photos

No need to apologise for asking questions Mark, there will usually be someone only too happy to help as Andrew has.

I would check that there are no blockages either in the oiler or the part that it feeds. It could be that on bearing is loose, and takes more oil and the other is tighter so oil is not lost, but it would be as well to check.

Brian

steamdave16/07/2019 11:27:49
418 forum posts
32 photos
Posted by Mark Gould 1 on 16/07/2019 09:49:57:

Gents,

3. Our Myford S7 has 2 oil cups under the headstock belt guard. they supply oil to the shaft that houses the countershaft, clutch etc. One of these oil cups ALWAYS requires oil and the other is always still full. Is this logical? Should I be worried and if so what should I be checking?

Thanks in advance for any help,

Mark

Seems to be relatively common with those oil cups.
I get the same situation - the right hand one always needing a top up, but I cannot find out where the oil has gone. It hasn't dripped anywhere that I can see and the inside of the cover is relatively clean.

Dave
The Emerald Isle

Dave Halford16/07/2019 11:38:23
489 forum posts
4 photos

Sometimes the sellers don't know which is which either.

I've got some four flute end mills modified by someone into slot drills smiley

Philip Rowe16/07/2019 11:56:35
173 forum posts
14 photos

Don't worry about the oilers, it would appear to be an odd quirk of the S7, mine does this as well and has done so from when the lathe was purchased new in 1973.

Phil

Roderick Jenkins16/07/2019 12:18:14
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1784 forum posts
459 photos

Question 2,

I think best practise is to have the faces with the bolt holes mating. On 4 jaw (independent) chucks the bolt holes are towards the middle which means that a smaller backplate than the chuck diameter can be used. With the 3 jaw chuck the bolt holes have to be around the periphery to avoid the scroll. The caveat is that this applies to screw on chucks.

HTH,

Rod

Bazyle16/07/2019 13:31:29
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4791 forum posts
187 photos

If the shaft is not a perfect fit but is pulled to one side/angle by the belts it may open up the gap on one oiler and close it on the other.

Mark Gould 116/07/2019 16:44:42
141 forum posts
92 photos

Thanks for the replies, my mind is at ease at least on the oiler cups! Roderick, I will try and get the straight in my head but it'll take time to sink in. Thanks for taking the time to answer. I see now that plunging a mill straight down would come in handy. My end mills can't do that.

old mart16/07/2019 17:48:09
785 forum posts
77 photos

The two flute slot drill can cut downward (plunge) and is recommended for cutting a slot like a keyway because only one of the flutes is cutting at any time. This puts a strain on the side of the cutter in one direction. Four flute cutters are commonly also available in a downward (plunge) configuration, but are not recommended for cutting slots for the following reason. Having four cutting edges means that two of the flutes at 90 degrees spacing get to cut at the same time, bending the cutter and producing a slot wider than the same size two flute slot drill. A three flute cutter just misses the multiple cutting problem, but is harder to find. Standard end mills do not cut in their centres and can only plunge a small amount, say 0.5mm for a 12mm cutter.

Being stiffer than steel, four flute end cutting solid carbide mills are better for keeping the slot width to size. For precision, it is best to use a size of cutter smaller than the slot and creep up on the width using extra passes.

Three jaw self centring chucks are quite different mechanically from four jaw independent ones, so the way they are attached to the backplates varies. There are chucks made to fit directly onto Myford spindles by doing away with the backplates and screwing the chuck body straight on. The advantage of this is the extra couple of inches gained, and increased stiffness. 

Edited By old mart on 16/07/2019 17:58:37

Martin of Wick16/07/2019 19:32:27
93 forum posts
4 photos

Should I be worried and if so what should I be checking?

Yes,

When running the lathe for a period, check for temperature over the bushes, particularly the unit not using oil. Any warmer than blood heat needs investigating.

Check the bush that is losing oil and determine where the oil is going. If you see oil escaping from the oilite bush and dribbling down the countershaft leg, the oilite bush will need to be replaced before damage is done to the countershaft spindle. The bushes are cheap (shop around the online bearing resellers of buy at a premium from Myford), the spindle is a v expensive component.

Check the bearing that is apparently using no oil as detailed in above posts. A bush in good condition will not be using use much oil - perhaps a slight top up after an hour or two of running. If this is not the case then check the oilway has no waxed or solidified oil. If oilway clear, it is possible that oil has solidified in the pores of the sintered bush. In which case I would replace the bush for the reasons given in the above paragraph.

The bushes are replaceable without taking the whole countershaft off the machine, but you will need to make some pullers using threaded rods and tube and some dies (piece of ally turned to od of .75in with wider section aprox 15/16 to extract and insert the bushes. It is important to completely fit the replacement bush with an accurately turned .75 in pin when pulling the new bush in, if you don't, you may distort the bush and not be able to get the countershaft spindle back in again.

I have a similar problem - one bush is actually OK but since I have to take the spindle out, it is expedient to replace both.

Nigel McBurney 116/07/2019 20:34:16
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623 forum posts
3 photos

On my circa 1974 Super 7 which I had from new ,i Found last year that one of the flip top oilers for the countershaft was not a tight fit in the casting,perhaps it was always a bit loose and the paint held it in, I secured the oiler with locktite,now reading of this failure of one oiler to feed ,it may be worth checking to see if the oiler is totally or partially blocked as the oilers are a light push fit were they assembled after painting and some paint was left in the hole.

Mark Gould 117/07/2019 18:06:23
141 forum posts
92 photos

Thanks again for the replies, old mart, Martin and Nigel. I will investigate further as this is something I want to have sorted. Thanks again!

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