Thread: Need suggestions for hole cutting in alloy

If you need 80 of them it might be worth making a pattern and getting them cast at a foundry then just machine the castings true (if necessary).

About 15 years ago, I bought some thick walled aluminum tube to make carburetor adapter stubs for my BMW motorcycle( I was fitting Dellorto's to a R100RS) so I know that some of thing was available then and I assume it still is. It had a wall thickness of approx 20 mm so that sort of thing may be useful to you. I got it from a Aluminum fabricating business, ie they made roo bars and trays for utes, etc.

If you have access to a lathe, I dont understand whay you arent doing the whole opperation in the lathe.
Cutting the interior hole with a hole saw is going to be slow and inaccurate and you will be plagued with clogging and waste clearance issues.

While I'm mo machining wizzard I do understand this would be the easiest way.

Get the tube that is both under size ID and oversize OD

mount it up in the lathe in a 3 jaw chuck

use a boring bar to machine the inside diameter

use a normal tool to machine the outer diameter

part the end true

part off the desired length

Job done.

cheers

A Canadian mob called Metal Supermarkets (http://www.metalsupermarkets.com) has extruded seamless Al 6061-6511 at 2.5" x 0.5" wall (63.5mm OD, 38.1mm ID). My catalog is silent on lengths available, but it looks like you'd need slightly less than 20 ft. The web site shows a store in UAE, but CA or USA would likely give better service. Really oughta be something similar in Oz.

My first thought, though, was castings. Lost wax from machinable wax could eliminate final machining except polishing and sprue removal. Probably not enough quantity to justify injection molded patterns. Regular sand casting could be simpler, as Bob suggests. In any of these cases, the pattern must be oversize to allow for cooling shrinkage; the foundry can likely advise on appropriate ratios. A couple test castings would probably be needed for final design.

Joe

And if you get a sandcasting shot peened youend up with a nice finish

Originally Posted by colinshannon

Hey all,

I need some suggestions for a project...

I need to end up with a 'tube' of alloy with an outer diameter of approx 57mm (minimum) and an inner diameter of approx 42mm (maximum).

There are 2 pieces required, on with a length of 35.5mm and the other with a length of 29.6mm.

Now, I am machining these on the lathe so I can essentially cut to whatever length required, no problem, it's the hole size of 42mm that's the problem.

Suggestions most welcome, this is what I've done so far.

Firstly: The easy way would be to find some tube with suitable O/D and I/D, however it appears never the 2 shall meet, either the O/D is perfect but the I/D too large, or vice versa. If I found tube with say a 60mm O/D and a 40mm I/D that would be perfect as I would just machine to required dimensions.

Secondly: I can always drill a large size hole in the solid bar while in the lathe then machine the material out, however this process takes forever (I need to do 80 of these things), and wastes a huge amount of material.

Thirdly: I've been doing it this way, but not entirely satisfied. Bought a hole saw kit (was assured it was fine for soft metals), cut a 'core' out of the alloy bar (when cut to length), with the hole saw mounted in the drill press, takes a while as well but does the job, then mout in the lathe to machine down to the final dimensions.

Now, I would really love to find suitable sized tube but have had no luck, I've asked my normal alloy supplier and nothing, and I've checked on the Onesteel website, again no joy. If anyone knows where I might get this from please let me know. Failing that, does anyone have any other suggestions on the easiest way to achieve the hole in the middle. Would a high quality hole saw (eg: P& N) do the job a lot easier than a universal 'assured for soft metals' type hole saw?

Sorry for the ramblings, but again, any help or suggestions greatly appreciated.

COlin

There is no easy way ,I wouldnt be using a hole saw .
Sound man has got the answer .
If you could but tubing in every imaginable size ,all the machinists would be out of work.
If you set your lathe up correctly you could easily knock out 80 of those rings in about 4-5 hours , depends on the type of lathe you have I guess.

Thanks for the input,

I do realise it would be much simpler to do the whole operation on the lathe, and would love to find some alloy with oversize OD and undersize ID but just can't! Essentially I am achieving the same thing by using a hole saw, this cuts the hole at 38mm (give or take) then I machine out to 42mm using the lathe, the end result is I've created my own tube - was just hoping there may have been a supplier of tube with a suitable wall thickness (near enough to be machined out). I know I'm never going to get the exact measurement, life couldn't be that easy, but if I could get it as close as possible would make it easier.

I will definately check into the other suggestions as well.

Thanks again.

COlin

this is of no help to your problem at all but when cutting ally, anyway, always use vasiline on the blades or what ever your using, stops clogging and in turn stops a fair bit of the heat retention, especally when using saw blades and cut off discs. Sorry for the thread hijack...

Colin,

What is the job?

Depending on the job/heat treatment required / surface finish/hardness etc, etc- simply casting up the tube in suitable lengths would be pretty simple.

There are a number of us that own furnaces / home foundries, and making a mould suitable for sand casting seamless tubing (and a matching core box) would be pretty starightforward.

All you would need do is make the pattern / corebox, and source some suitable alloy.

Would love to offer my services, but alas the bathroom requires my attention for the next few weeks.

Hope this helps......

Shane

Hi Shane & Yogi,

Thanks for the follow up posts. Will remember to use Vaseline when cutting alloy in future - thanks for the tip.

Shane,

I've attached a pic of what I start with (the subject of this thread is how to get the hole in the middle - this was done with the hole saw), and what it ends up like. Essentially they are large scale model car wheels (polished lip). Hardness, heat treatment not a concern as they are for static models, not RC cars etc, basically the only requirement is polished finish on the lip (smooth overall), and easily machinable.

Would love to accept the offer of any services if suitable, c'mon man, whatever happened to showering out the back with a hose and bucket?

No one seems keen on the hole saw idea, but the fact is it does work for my case (as is proven by the pics), yes it takes a while to do, but it may just be my 'lot' in life at the moment unless I can find an easier way. Would the higher quality hole saw do a much better job than the Bunnings cheapie?

Thanks again, and if any other suggestion come to light, please advise.

Colin

Oi,

Forgot to add the pics...sorry!

COlin

The Super Drill would do much the same as your hole saw but get closer to the final size. Could be useful for projects further down the track.
Not much different to using a boring bar in the lathe though.

Colin,

Well, I'm sort of in the process of building a golf cart, and after finding out the price of golf cart tyres & rims, I decided to cast & machine my own rims. Sadly, haven't worked out how to make tyres yet.

Anyway, casting what you're after would be a snap.

I would love to offer my services, but I (we) are actually showering downstairs, with with black plastic & a couple of towels for privacy - and the girls are not too impressed...... Hence the reason I can't help right now.

If you were prepared to wait a while, no worries. But if there is a rush, there are several others here in Brissy that have foundries.

Shane

Hey Dan, that drill looks pretty good, do you know of anyone who has used one?

Shane, no worries. I'll see how I'm going for time (ie: how soon my guy wants these done). Off the top of your head what would you charge to make these? Send me a private message if you would prefer the world not to know.

On the golf cart, how about casting your wheels from a suitable rubber. I've just started experimenting with casting resin, silicone etc, and the array or products and materials available is huge, I'm sure you could get something suitable for the tires. Try a company called FGI (Fibreglass Industries). THey are here on the Gold Coast - nice fellas that should be able to give you the right advice.

Thanks.