Gallery, Projects and General => The Design Shop => Topic started by: ant... on May 11, 2010, 08:32:02 PM

Title: Internal Tube Sander
Post by: ant... on May 11, 2010, 08:32:02 PM

Im making aluminum moulds on the lathe, they are just alloy tube but i turn a slight taper on the inside.
To get rid of the tooling marks its easy to use any rotating sanding device and stick it in the tube but this isnt great for removing marks going round the inside of the tube and their is nothing on the market (so far as i know) that will do a lineal sanding action inside a tube.  This lenghtways sanding action is best for removing the rotating tooling marks left from the lathe, at the moment its taking me about 4 hours by hand.

Yesterday my mini compressor died but it left me a good motor which has a functioning piston action, although not long enough to stick in a tube.  So I intend to remove the piston and replace it with a long metal rod, the only problem I have is how to support the rod so it travels straight and friction free.

Is their some bearing system which can hold a rod? or what do you recommend?

Title: Re: Internal Tube Sander
Post by: Gadget on May 11, 2010, 10:05:30 PM
Could you use a brake or cylinder hone instead. It is rotary but would polish the inside pretty smooth  in short order.
Title: Re: Internal Tube Sander
Post by: ant... on May 11, 2010, 10:46:08 PM
Hi Gadget - thanks for your input

Truth is ive never tried a cylinder hone but i assume it would be the same as all the other rotating abrassives ive tried, not so good at removing grooves which follow in its direction of travel.  Plus im not sure it would like the slight tapper, one end is slightly larger to help release the part, unlike an engine cylinder.

The inside of my tubes need to be polished to a perfect mirror finish or any marks get transfered onto the carbon parts.  The normal method is to sand in one direction until you have removed all marks, then go to a finner grade and sand those marks out from the other dirrection, until finally you are at 1200 grit and ready to polish.  This is how i finish my tubes but to sand down the tube always has to be done by hand.
Title: Re: Internal Tube Sander
Post by: Divided he ad on May 12, 2010, 03:57:39 AM
Hi Ant,

Just looking at the drawing you have and thinking about holding the rod so that it travels true, well oiled bronze bushes in a larger tube that is well secured should do it I would think?

A bit like the peck drill that I made (on hear somewhere?)

Then all you need is a device to clamp your tubes at the correct angle and turn them slowly as the abrasive piston pumps away.... Easy eh?!  :scratch:

If I get any brain farts today I'll draught a Crap-O-Cad.... But that's only if I think it'll work  :scratch:

Sounds like you're having fun though :thumbup:

Title: Re: Internal Tube Sander
Post by: Gadget on May 12, 2010, 07:53:42 AM
The cylinder and brake hones are spring loaded and will follow the taper just fine. They will leave a smooth surface and if you move them up and down while honing will remove the groves left from turning the bore. Brake hones are fairly cheap, it might be worth a try. I'm betting it will be at least as smooth as the piston type sander you are considering.
Title: Re: Internal Tube Sander
Post by: 75Plus on May 12, 2010, 10:38:01 AM
Just a thought. Would not the proposed solution tend to change the taper? The pressure on the abrasive would increase as the diameter decreased causing the smaller part of the bore to be expanded.

A brake cylinder hone is spring loaded with the pressure applied at the center of each individual hone resulting in equal pressure on both ends.


Title: Re: Internal Tube Sander
Post by: DMIOM on May 13, 2010, 06:32:28 AM

The conventional cylinder hone route should be OK I would have thought, if your mold has a constant draft angle, and you can get (or adapt) one with suitable length arms.

The hones ( are pivotted and will take up the angle (within reason) of the taper, In operation, the drive shaft needs to be on the axis of the cylinder; the stones are then kept in contact by the centrifugal force as the hone is spun up.

It won't do well though if you try to operate a smallbore hone set off-centre in a large cylinder - the independently-pivotted arms will just flop about, giving effectively interrupted cuts - but, if necessary, making a longer set of matched arms shouldn't be hard.

The hone assembly does need to be spun-up to get the hones out to their operating radius - unfortunately it won't for example, work by having the hone mounted in a tool holder or in the tailstock, and then spinning the work still mounted in the lathe.  Best would probably be to mount the hone in a mill or drill press with the work centred underneath and raise/lower the quill to work the hones.

If the diameter of your mold is too great to use a set of hones, another alternative would be some form of toolpost grinder (search on here); in which case you'll need to leave the grinder set at the same angle you had on the compound when you turned the original taper. If you are going with your reciprocating sander, as Joe/Ralph have highlighted, you'll need a smaller drum so it is only in contact with one wall at a time, and the action shaft will have similarly have to be set at the same taper angle.

Title: Re: Internal Tube Sander
Post by: ant... on May 14, 2010, 12:51:55 PM
Hi Guys
Just because I love a laugh more as much as anyone, im going to show you my progress  :lol:
This device vibrates so much i had to screw it into a concrete slab, it worked and did a great job for about 60 seconds before it tore its mountings out.
The pole is made from steel which is too heavy and add vibration, its travel is too long (2cm) which make the vibration more violent.

After a mornings work and ruining one of the concrete slabs in my back garden patio, i finally made this:

The power internal sander could be modified to work, with lighter materials and better gearing, but ive decided to try your Cylinder Hone idea first.
This Cylinder Hone is onle 17 and it has 3 different grit levels.  If it does work it will hide away much easier than my mad contraption :smart:
Title: Re: Internal Tube Sander
Post by: Gadget on May 14, 2010, 07:23:53 PM
Use a real light oil with the hone, it will do a better job. Let us know how it turns out.
Title: Re: Internal Tube Sander
Post by: ant... on May 14, 2010, 07:26:48 PM
Thats the first time ive ever heard of using oil with an abrassive, dont get me wrong ive tried it but the fine ali dust turned the oil to a thick mud.

ill try oil though, thanks for the tip.
Title: Re: Internal Tube Sander
Post by: Divided he ad on May 16, 2010, 04:18:29 AM

Oil with an abrasive.... Never sharpened a chisel on an oil stone?

You should always use a huge amount of oil with a hone. It will "pick up" otherwise and score the bore heavily, and that's with engine cylinders not something as soft as aluminium.

We used to do this sort of thing   
    (I used to work for an engine re-manufacturer :thumbup: )

but the fine ali dust turned the oil to a thick mud

You have to keep oil flowing through the bore to wash off the "mud" as it flows down through the bore. 
you could do the whole operation in short stages cleaning the cylinder and stones with a solvent then re-applying oil etc.

If it works you could set up a filter system and an electric pump to recycle the oil and keep it squirting into the cylinder?

Proper honing oils.... Now there's a minefield!!  Thin mineral oil (probably with cleaning agents added?). You could search for it if you have a few hours spare! 

Hope this is of some help?

Title: Re: Internal Tube Sander
Post by: ant... on May 16, 2010, 06:27:11 PM
Thanks for that tip Ralph, you have probably saved my hone from going through the window  :bang:

And no ive never sharpened a chisel or used a sharpening stone.  But if you have ever got oil on your wet&dry it sure clogs up fast.

Title: Re: Internal Tube Sander
Post by: Rog02 on May 17, 2010, 02:29:14 PM
OK for what it's worth:

On our side of the pond we use kerosene for lubricant when glaze breaking cylinders and FLOOD it through.  I think you guys call it paraffin.  Diesel fuel will work too (I'm not big on the bio-diesel mixes for this kind of stuff). 

The trick is to keep enough flow to wash the grit and debris away which means either a large spray bottle or a pump of some sort.  Same goes for Wet-R-Dry sand paper which with a sheet of glass can make for a very nice bench lapping fixture for things like lathe bits, scrapers, and wood knives.

Title: Re: Internal Tube Sander
Post by: ieezitin on May 20, 2010, 08:41:00 AM

I just read all this thread and going back to one of your original questions about a bearing for linear movement, there are bearings called ball bushings, they have rows of balls housed in a tube that travel in the same direction as the shaft is reciprocating, extreme precision is achieved, but then the shafting has to be hardened and ground to match your bearing unit.

Not a cheap set up but is within reach.

Title: Re: Internal Tube Sander
Post by: ant... on May 20, 2010, 10:52:25 AM
Hi Anthony

Thanks for that info on the bearings, when ive got time im going to finish that sander off.  It needs a serious steel housing to rain in its 1.5hp, but when its finished I can see it being very usefull.

That Cylinder Hone came today, ive not tested it yet but i will publish my report as soon as.

Title: Re: Internal Tube Sander
Post by: RichardShute on May 20, 2010, 04:04:52 PM
As commented a couple of times above, but I'll repeat it for emphasis, use something like paraffin or diesel or even white spirit in copious quantities. If you use 'oil' you will end up with a black paste and a clogged hone. If you were to use the drill press rather than the lathe to drive the hone, you could stand the tube on end with the bottom in a pot/tin/bucket of whatever you choose. That way, each time the hone goes down to the bottom of the bore, it will splash new fluid all round. Not quite as good as a pumped flow, but a lot better than an occasional squirt from a bottle.

You can use the above with wet & dry as well, I regularly do so for minor lapping jos.

By the way, did anyone say use lots of fluid?.......

Title: Re: Internal Tube Sander
Post by: ant... on May 23, 2010, 12:08:14 PM
Hi Richard

Im glad you mentioned that 'Black Paste', thats what I was talking about in my previous post.

My lathe is a 3-1 so i can use the mill and put the cylinder in a bucket, just need to work out how to keep it still.