How to machine out a metal channel by hand?

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How to machine out a metal channel by hand?

This topic has 27 replies, 20 voices, and was last updated 26 June 2022 at 12:24 by John Doe 2.

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24 June 2022 at 16:43 #602946
John Doe 2
Participant
@johndoe2
Hi folks,

I need your advice. I am making stands for our rocking horse, but the channel I glued in, made from some metal pipe, is a slightly too small ID for the support hoops' OD. (I know, schoolboy error!).

How can I relieve the channel neatly to allow the hoop to seat properly?

I have no workshop or milling machine etc, so need another way to do it – filing by hand would probably be too hit or miss?

I was wondering about something I can put in my 1/4" router and move along, grinding out the channel from above, or maybe a parallel reamer?

The channel measured 10.00mm ID and the hoop OD measures 10.20mm, (I originally thought they were the same).

Any thoughts?

Edited By John Doe 2 on 24/06/2022 16:48:18
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24 June 2022 at 16:43 #11242
John Doe 2
Participant
@johndoe2
24 June 2022 at 16:47 #602947
Dave S
Participant
@daves59043
Might be easier to make new hoops for the horse end.

Dave
24 June 2022 at 16:49 #602949
JasonB
Moderator
@jasonb
Probably easier to reduce the round hoop by filing
24 June 2022 at 16:54 #602950
Tim Stevens
Participant
@timstevens64731
Or perhaps find some straight tube with slightly thinner walls to lay in the wood slots? Perhaps brass – which as another option would be easier than steel (and a better bearing surface) to make from flat strip, as long as you get the thickness right first?

Cheers, Tim
24 June 2022 at 16:56 #602951
Martin Connelly
Participant
@martinconnelly55370
Clamp the two parts together and run a Ø10.5 drill down the resulting hole, from both ends unless it is a very long drill.

Martin C
24 June 2022 at 17:13 #602955
John Doe 2
Participant
@johndoe2
Thank you so far, liking that last suggestion.

Just to reinforce, I have no workshop, so cannot make new hoops, and the channel is already glued in. (Yes, I know……it's a cock-up on my part).

Edited By John Doe 2 on 24/06/2022 17:15:21
24 June 2022 at 17:34 #602958
SillyOldDuffer
Moderator
@sillyoldduffer
Assuming the channel is impossible to remove I'd file the hoop because it's easier to get at than the inside. Shouldn't take too long with a sharp coarse file. I'd roughly file a series of flats to get rather under wanted diameter, and then smooth the untouched parts a little more carefully to a pop fit.

The only good news is it isn't a precision job. The filed hoop doesn't have to be a circle or have an exact diameter. It only needs to fit where it touches and look as good as the woodwork!

If the channel can be removed, it could be spread more open by forcing a larger diameter rod into the slot with a big hammer or a vice. The wedging rod would need to be about 12mm diameter. The main difficulty is holding the job during spreading. The wooden frame it's already glued into would probably do, but it might get damaged.

You have my approval to use Strong Industrial Language. I often make 'nearly right' errors and the resulting extra bother drives me mad!

Dave
24 June 2022 at 17:44 #602960
AdrianR
Participant
@adrianr18614
I assume you used epoxy to glue the channel in so I would heat the channel up to remove it from the wood.

Then heat the channel to red heat to anneal it.

To open the channel up I would cut a strip of metal from a drink can to wrap the hoop, then force the channel over the hoop and strip. After this, the channel should be slightly wider than the hoop.
24 June 2022 at 18:22 #602963
DC31k
Participant
@dc31k
Broomstick, sandpaper, sellotape, cordless drill.
24 June 2022 at 19:00 #602965
Bill Phinn
Participant
@billphinn90025
Maybe it's just perspective, but the channel and hoop diameters look substantially wider than circa 10mm to me.

As others have suggested, a long piece of dowel wrapped in sandpaper and a drill, or maybe an extended-shank drum sander if you can contrive one, would be my attempt at a solution.
24 June 2022 at 20:04 #602971
old mart
Participant
@oldmart
I would cut up some empty aluminium drinks cans for shims and try fitting it between the channel and the hoop. Use clamps or mole grips to squeeze the parts together. You may have to carefully separate them with a hammer and drift. The object is to stretch the channel slightly. Extra shim thickness mught be needed. If you have a vise, the job would be much easier.
24 June 2022 at 20:15 #602972
Calum
Participant
@calumgalleitch87969
What glue did you glue it in with?
24 June 2022 at 21:04 #602980
Simon Williams 3
Participant
@simonwilliams3
It's not without its perils, but hammer the tube side to side to flatten it slightly. So long as it can move through the limited arc of the rocking horse movement, it won't matter if the tube is oval. The height isn't an issue as the receiving channel is open one side.

Nice exercise in planishing…

Good luck

Simon
24 June 2022 at 22:37 #602988
Ian P
Participant
@ianp
Not really solving the problem but your woodwork looks to be to a very high standard but how did you make it without a workshop?

My thoughts on a solution to the diameter problem are that if the U channel really cannot be removed then reducing the diameter of the bent steel hoop by filing would be the best option. Even if its already painted then just file the 'sides' of the hoop so its ends up slightly oval leaving the upper paint intact.

You could use an angle grinder with a metal grinding (rather than cutting) disk to carefully widen the gap in the steel channel but it would need to be done slowly to avoid heating the metal (and therefore destroying the bond of your adhesive)

Ian P
24 June 2022 at 22:39 #602989
Hopper
Participant
@hopper
You need to remove 0.2mm off the diameter, or 0,01mm off the wall thickness. Largest round file you can fit in there will do it in no time. Anything with emery paper will take longer.
24 June 2022 at 22:55 #602993
Paul Lousick
Participant
@paullousick59116
I have used grinding stones and rotary burrs in a router to remove metal which did an excellent job UNTIL the bearings gave out. (warning: wear safety gear, routers spin at 20,000 + rpm and stones can shatter)

So I would recommend that you do as advised and use a file, emery paper and elbow grease. Removing 0.2mm from either the channel or pipe should not be too hard.

Edited By Paul Lousick on 24/06/2022 22:58:53
25 June 2022 at 00:18 #602998
Hopper
Participant
@hopper
Correction: 0.1mm off the wall thickness,not 0.01! Still easily file-able.

But it would be just as easy, or easier, to file down the round bar with a flat file, as Jason suggested. You can finish it off with long strips of emery tape wrapped once around the job and pulled back and forth to make a nice smooth and round finish.

Edited By Hopper on 25/06/2022 00:21:40
25 June 2022 at 07:43 #603003
David George 1
Participant
@davidgeorge1
I would look at heating the metal channel to soften the glue and remove it. It would be a bodge to do any other and so simple with a hot air gun not a flame.

David
25 June 2022 at 08:37 #603007
Brian Wood
Participant
@brianwood45127
It might be possible to spread the channels progressively by hammering in a short section of larger diameter bar, levering it out and moving it along as you go.

Brian.

Edited By Brian Wood on 25/06/2022 08:37:58
25 June 2022 at 09:00 #603013
Pete White
Participant
@petewhite15172
The answer is in the name, "ROCKING horse", we are talking a toy here, not fine limits IMO, It is easy to overthink things….0.2 mm? Remove a little bit of metal from somewhere and make it "fit"

Edited By Pete White on 25/06/2022 09:01:19

Edited By Pete White on 25/06/2022 09:04:36
25 June 2022 at 09:08 #603015
Sam Longley 1
Participant
@samlongley1
Wooden dowel..Cut a thin strip of emery & spiral wind it on the dowel & super glue it in place The emery will be a bit longer than the channel. Place in electric drill & place it in the channel.Make the dowel longer than the channel & support the end away from the drill with a bit of wood with a hole in it. Then you can run the emery the entire length of the channel. Drill one end, wood support, held in ones hand, the other. It will gradually wear away the metal as it spins.

Edited By Sam Longley 1 on 25/06/2022 09:09:33
25 June 2022 at 11:51 #603037
John Doe 2
Participant
@johndoe2
Thank you all very much for your time and suggestions.

The first great idea was clamping the two stands together to form an approximate tube to machine out. I had not thought of that.

I do not want to file the hoop pieces as that might weaken them or leave stress risers on the metal – it's quite a heavy horse. Also, I won't be able to hand file them perfectly round.

I would rather not remove the channels as that will probably mark or damage the wood. They are epoxied in and I should of course, have double checked the fit before glueing the channels in. A classic case of "measure twice, cut (or glue) once" !! (but see below)*

I am going to try clamping the two stands together and then running a 10mm drill through, then emery paper taped and wrapped around a smaller diameter drill, or a piece of dowel to open out the channels. At least that will result in reasonably concentric channels, my hand filing won't be quite as good. Hopefully there is only a small amount to remove before the hoops will drop in.

Once they do, I will put some valve grinding paste in the channels and rock the horse to smooth everything out, then clean and lightly grease.

*Part of the problem is that this was originally all a secret for my Mrs, whose horse it is – it had no stand when we bought it. So I could not keep going back to the horse to check measurements or the fit, because that would have given the game away. I hope she appreciates all my work ! By the way, I do not like the traditional rocking horse stands with the long horizontal pieces running under the horse, hence my dual tripod design.

PS, I have a garage, with hand tools and hand held router and drills etc, but not a workshop, or even a vice, (yet). I made the wooden stands by using pre-turned baluster sections for making staircases and very carefully hand cutting them to fit together and glueing it all up.

The hoop rods really are 10.20 mm – 10.30 mm diameter – measured with callipers.

Edited By John Doe 2 on 25/06/2022 11:52:29
25 June 2022 at 16:01 #603053
John Doe 2
Participant
@johndoe2
Well, clamping both stands together did not work because the two channels did not meet perfectly round but slightly oval, so I had to resort to filing each one by hand.

I filed the channels and also the hoops too, because the bar the hoops are made from did not have a very round cross section, so they jammed on part of their swing. I used a half-round file and a round file wrapped in sandpaper for the channels. For the bars I used a flat file with that opposite action one uses for filing a smooth curve where you move the file opposite to the curve you are filing instead of following round the circumference – can't think how to describe it but I expect you know what I mean.

It wasn't a huge job in the end, luckily, and it all fits very nicely and freely now. I will add a hint of grease on final assembly, and possibly a cover over the top of each hoop. Got to finish the wooden stand next.

Thanks again for your suggestions.
25 June 2022 at 16:50 #603064
Bill Phinn
Participant
@billphinn90025
Well done, John. The wood still looks very clean in spite of all the filings etc. that must have got in to the grain.

It's nice to see that low-tech toys are still valued by some people at least.
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