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Hole cutter

Tool to cut a 4in hole in aluminium

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Stephen Rowley12/01/2019 07:16:02
57 forum posts
14 photos

I hope I have this request in the right place.

Due to a mistake I need a tool to cut a 4in ID hole in a 5in OD aluminium bar 6in long.

I could use a boring bar but after cutting a 70mm ID hole I have a workshop full of aluminium swarf and wasted a day of my life as only I have a Ragland Little John lathe so taking a cut greater than 4 thou stalls the motor (3/4HP).

Any advice would be most welcome.

David George 112/01/2019 07:28:35
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809 forum posts
282 photos

Where are you based as it looks like you could do with a larger lathe to rough out the core if someone with a larger lathe is near you they could help.

David

Speedy Builder512/01/2019 07:29:16
1766 forum posts
125 photos

a 3/4 Hp motor at that diameter in Al should take off more than 0.004" depth of cut. My Boxford would take about 0.1" . This not bragging, and doesn't answer your question, but I would seriously wonder if your motor was up to producing 3/4Hp. Daft question, is it wired up correctly and not just running on the start windings ? As for a hole cutter, if you can't take more than 0.004", then the width of the teeth will be about 0.03" - 0.05" so that would take far more power than you have available ?
Good luck anyway
BobH

Stephen Rowley12/01/2019 07:58:09
57 forum posts
14 photos

Thank you both for replying.

I have a good friend who has 2 very large lathes I could rough out the hole on but I would waste a hole lot of metal. I was hopping that someone may know of a core drill that would do the job so I could save something.

As to the motor, it came from my 20 year old Chesters 920 lathe that died of old age! I do have a very nice new 1965 BT-H 3/4HP motor I intend to fit when I find it again!!

Ian P12/01/2019 08:50:02
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2093 forum posts
89 photos
Posted by Stephen Rowley on 12/01/2019 07:16:02:

I hope I have this request in the right place.

Due to a mistake I need a tool to cut a 4in ID hole in a 5in OD aluminium bar 6in long.

I could use a boring bar but after cutting a 70mm ID hole I have a workshop full of aluminium swarf and wasted a day of my life as only I have a Ragland Little John lathe so taking a cut greater than 4 thou stalls the motor (3/4HP).

Any advice would be most welcome.

However the hole is cut you will end up with a pile of swarf. One way to avoid that would be to use a holesaw but even if one deep enough was available the job would still be a slow one.

By cutting a hole do you mean boring into a circular bar? Its not very clear from your description what the finished part will look like. Are you trying to end up with a 6" length of tube with 1/2" wall thickness?

The Raglan should cope with that more easily than you mention, is the belt slipping?

Ian P

pgk pgk12/01/2019 09:02:35
1349 forum posts
278 photos

Depending on the accuracy and project you might consider starting with 5" tube. M-machine list 5" tube with 3/4" walls.

pgk

George Jervis12/01/2019 09:10:03
54 forum posts
59 photos
Hi there

From one raglan LJ mk2 owner to another I know I'd have to take a seriously deep cut before my 1/2hp single phase motor would start to labour and I've never stall it, I'd check your motor first sounds like you might have an issue? these lathes are very powerful for their size
George
Stephen Rowley12/01/2019 09:32:49
57 forum posts
14 photos

What I am making are 12 lens sleeves for two 60 year old cinema projectors I am restoring.

What I want are 6in tubes 5in OD and 4in ID with a 1/2in wall. Originaly they were to be tubes 6in long, 5in OD and 70mm ID but this will not work so I have to open them out to 4in ID and to add a bit of fun the ID has to be eccentric to the OD by 1.5mm.

I started with 6ft of round aluminium bar 5.1/4in OD.

It is not the belt slipping, it is the motor stalling!

There have been times I wish I had kept to my 5in gauge super Duchess!

Ian P12/01/2019 09:37:05
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2093 forum posts
89 photos

I would cut your losses and buy the thick wall tube (M-Machine will cut it into your short lengths).

If you are gripping the parts in a 3 jaw then just put some 1.5mm packing under one jaw for the eccentric ones.

Ian P

Stephen Rowley12/01/2019 09:58:07
57 forum posts
14 photos

Unfortunately I have over £500 woth of aluminium sitting on the workshop floor and I can not aford an other £500+ for more. If I can not find a hole cutter I will just have to bore them all out one at a time.

One idea I have had sent to me is to buy a 3.1/2in hole cutter and weld it to a 3.1/2in by 6in steel tube

Ian S C12/01/2019 10:11:50
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7382 forum posts
230 photos

Any metal dealer that I know would take back the unwanted metal that you have, and either pay you, or swap it for the metal that you need.

Have you tried slowing the speed, don't be afraid to use back gear, it might be slow, but might be faster than taking .004" cuts.

Ian S C

Martin Connelly12/01/2019 10:31:52
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845 forum posts
95 photos

If you want to save the plug of material from the centre consider chain drilling from both sides then hacksaw to join the holes. If you can get a holesaw of the diameter you want you still want a "drain hole" or two through the block to let swarf fall out. Broaching cutters have flutes that feed the waste out but holesaws don't and clog up easily.

Martin C

Michael Gilligan12/01/2019 10:52:17
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13230 forum posts
578 photos
Posted by Stephen Rowley on 12/01/2019 09:58:07:

Unfortunately I have over £500 woth of aluminium sitting on the workshop floor and I can not aford an other £500+ for more. If I can not find a hole cutter I will just have to bore them all out one at a time.

.

I have no idea of the cost involved, but wire erosion would seem the obvious 'technical' answer

Companies like this might be worth approaching: **LINK**

https://www.cheshirewireerosion.co.uk

MichaelG.

Tony Pratt 112/01/2019 10:56:09
860 forum posts
2 photos

I don't want to rain on your parade but how is the lathe going to manage a hole saw if it can only take a .004" cut when turning/boring?

Tony

Andrew Johnston12/01/2019 10:56:18
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4689 forum posts
527 photos

If you're stalling a 3/4hp motor with a 4 thou DOC then you need to sort that out first. And changing the lathe is not the answer, it should be capable of much more. All talk of cutter types and methods is a complete waste of time if you don't sort out the stalling issue, as you'll neve be able to use them.

Andrew

Journeyman12/01/2019 11:01:02
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597 forum posts
92 photos

You can get a 100mm core drill from *** Amazon *** or perhaps an 80mm would be better. These are Silverline and cheap at £14 don't know what the quality is like. You might be ably to sharpen the teeth a bit with a suitable grinding wheel. IF your lathe is having difficulty at .004" I doubt whether it would have enough oomph to get one of these to work. Oh yes you need a suitable arbour for it as well.

As an alternative you may be able to find a local firm that will water-jet cut the middle out for you.

John

Edited By Journeyman on 12/01/2019 11:06:04

Stephen Rowley12/01/2019 12:03:18
57 forum posts
14 photos

I have replaced the old motor with the BT-H motor 3/4HP and can now make a 1/16in cut without any problems.

I had not thought about a water jet cut so I called a local guy who has one but thinks 6in is to thick.

The deepest metel cutting hole cutter I have found on the web is 45mm.

Steve

Speedy Builder512/01/2019 12:42:53
1766 forum posts
125 photos

Stephen, before you buy a hole cutter, how will the swarf get past the teeth. With stone and concrete etc, it is a fine dust and slips past the teeth, but in your application, the swarf will be too bulky to get past the gullet of the teeth. You will have to keep backing off the cutter to clear the scarf. Aluminium has a nasty habit of cold welding to the cutting edges, you will need plenty of coolant whilst cutting.
Faced with your problem, I would grind up some special boring bars. I will do a another post with some ideas, perhaps Andrew or Jason would comment as to wether they would work.
BobH

Tony Pratt 112/01/2019 12:49:58
860 forum posts
2 photos

The best suggestion by far is to swap the solid bar for tubing.

Tony

Speedy Builder512/01/2019 13:14:41
1766 forum posts
125 photos

Further to my last post, I would use a series of boring bars, cutting a depth of 1/2" at each stage and then only cutting 3" into the bar from each end - a bit like the channel tunnel !! Thats 36 tool changes for a 6" length and still quite a lot of swarf, but not as much as boring out the whole lot. Again, you will need to use coolant. See attached photo. The cutting edge of the tool needs to be ground back along its long axis by 1/2" and you would trepan a cut 1/2" deep with tool number 1, followed by tool 2 and 3. Then repeat for another 1/2" with tools 1,2 and 3. When you reach the half way mark, turn the bar around and bore from the other end. Note that tool number 1 is the narrowest tool being only 0.1" wide which can be made stronger by having a radius on the inside face of it and should well within the capabilities of your lathe.

img_3462.jpg

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