How are hinges made?

I am building a grinder and I want to put the tool rest on a hinged plate, but I don't know how to make a hinge! So I looked at my stock of hinges and quickly ignored the tin folded up construction but the cast/extruded variety caught my eye.

The cast/extruded ones seem to rely on the hinge pin hole being "drilled" with a diam/length ratio of 1.5mm to 75mm i.e. 50 :1. This seems an awful lot of pecking to make sure the hole stays on axis. So how is this done in real life?

For larger scale hinges, sort of like angled work mounts, the components are 1/2" plate with short tubes welded to them, suitably jigged up before welding. Seems to be the wrong sort of scale for my application.

Another way would be to have pivots i.e. blocks mounted on the various surfaces with a spindle, but then you need end float control, so its quite a lot of work.

Or can some one recommend a robust hinge say 75mm long, with out too much play in it (Undrilled )

Frank

Frank the tube welded to a plate works in any size, just substitute silver solder for weld. I have done them down to 1/8" nuckle with 1/16" pin.

A good way to make a stiff shake free hinge hinge is to start by welding a piece of steel strip onto the side of a short length of tube producing a P shape body. Then force a piece of slightly longer thick wall "rubber" tube / hose into the tube making a pivot bearing and slide a suitble size pin though. Two or three units per hinge according to duty and taste. Put suitable sized washers between the rubber overlaps at the ends of the tube so you dont get rubber to rubber contact which will bind things up rather. Sqidge the bits slightly together before mounting. Maybe put threads on the ends of the pin and use nuts to make a controlled assembly before fitting. This style of construction provides a bit of vibration isolation, always handy on a motor mount, and is shake free if the pin is made a push fit in the hose. It will never be quite as free moving as a common metal hinge but the stiffness in rotation can be adjusted by varying the size of the pin from quite free to pretty stiff. In many applications, like your motor mount, a stiff hinge is better as the darn thing stays put whilst you bolt up the fixing strap or whatever. Use a bit of red rubber grease on the pin and washers.

For a tool rest you'd need to make it very stiff and arrange some way of clamping independant of the hinge.  Possibly using a thick wall on the tube bit and cutting the rubber a bit short with a through bolt as the hinge pin which could be tightend up to lock things would work.  That said I'd prefer two fixings so amke the hinge very stiff and provide as second bold working in a slot on the tool rest proper to set the position.

I've made a fair few over the years steadily eating into the stash of I' (nominal) iron water pipe pulled out when we re-plumbed in copper around 1970. Car heater hose for the tube, 1/8" to 1/4" thick strip for the ears depending whats in the shorts box. Inch to inch half wide with 1/8" and a bit (real precision job this) overlap each end seems to work OK. Anything longer makes pushing the hose in a right pain. I just use separate P units on the two parts rather than make proper hinge units. Works OK.

The force tube in a hole with some overlap and washers on top does quite well for shop made vibration isolators too. Better at high frequency buzz than lower frequencies. Ideally done with the hole in a dead material such as plywood.

Clive.

Edited By Clive Foster on 16/08/2015 10:55:34

Edited By Clive Foster on 16/08/2015 10:56:10

Hi Frank, many years ago There was a particular component the factory I worked in made for the Lightening aircraft and there was a 1/4" hole drilled through it about ( as near as I can remember) 3.5" long, the deviation tolerance was small, can't remember precisely but it was only a few thou, and I do mean a few!

The drill used was an Osbourne T32 HSS which had a very short spiral thus making its stiff, these are no longer available but look at the link for a similar drill from Ruko, this was followed up with a carbide long series reamer.

**LINK**

Yes there was a lot of pecking but not other way to do the job some 50 years back and "we" made batches of around 50 each time. It was a boring job I have to say but for a one of not really a problem. If you decide to go ahead I would use two drills, one to rough out and another to finish or bring the hole close to size then ream to size.

Regards John

Frank,

If you can live with [cover-up] the holes ... These are very hard to beat.

MichaelG.

I agree with Frank about the hinges he mentions but also look at solid brass with the same bearings etc, I find these top notch hinges with no clearances to worry about.

Hi Frank, you can get industrial grade hinges of various sizes that are plain, downside is they are normally in 3m lengths, If you have any fabrication workshops in your area, it maybe worth while asking if they have any in stock, I'm sure they would sell you a piece long enough for your needs.

Regards Nick.