Press fit 'piano wire' into steel bar

Hello

id like to make the jig in attached pic. What's the best way of creating a press fit of the pins you can see into the steel bar?

cheers

mike

Mike have a look here to see how to add your image

Presuming its the pic in your album, looks like the pin diameter is about 1/4" or so? Best off to use a piece of round silver steel or cold rolled mild steel for the pins. You can drill and ream the holes. Exact fit will depend on the exact diameter of the round bar you get and the hole the reamer makes. Test it out in a piece of scrap first. If pin is a loose fit in the hole, use some Loctite to anchor it. If pin is tight fit in the hole, spin it in the lathe and remove half a thou or so with some emery paper on the end you want to slide in and out of the hole.

Or use an adjustable reamer and ream the holes to suit your needs, tight fit in one half and sliding fit in the other.

Or you could drill and tap the hole in the half you want the pins attached to and thread the end of the pin to screw in. Make the hole in the other half a neat sliding fit. If you don't want to buy a reamer, you could drill the hole and turn the pin down to fit the hole.

As described by Hopper if the jig in question is this:

I'm too embarrassed to post a photo of my crude version of the same tool made from old angle-iron where I dodged the need for well fitting pins by leaving the bolt-holes slightly slack so the bars can be aligned by eye and tightened firmly up on the sheet. The sheet and irons don't slip even when the fold is neatened up by beating it flat with a mallet.

I'd rather have your nicely made tight-pin version though if I did a lot of bending. Getting the sheet properly gripped & aligned in my tool takes a deal of fiddling about, irritating if more than a few bends are made.

But is this what you mean? I wouldn't describe the pins as Piano Wire (though they might be!)

Dave

If you clamp the bars in alignment and drill through for a hand reamer, then ream through only so the tip of the reamer gets to the bottom of the hole, you'll find that the silver steel rod will be a tight fit in the bottom hole - you may need to take small amounts off with the reamer until the pegs can be forced in so the end is flush with the bottom. If you go too far then loctite is your friend.

Hello

thankyou very much for the feedback. I feel a bit embarrassed myself asking such a simple question when I see some of the questions here in the 'beginner' section.

cheers

mike

As John says about making use if the taper on a hand reamer but for something like that you could simply drill through with as close a fitting drill and Loctite the pins into one half

Hey no worries. We all have to start somewhere. Let us know how your project goes.

Get some Dowels from some where like here.

Dowels from ACCU

Ream through both pices, press into fixed piece or loctite if required open moving jaw out by .1mm with drill if needed. Should be good enogh, try on a bit of scrap first.

Steve

Hello

Googled your suggestion re the reamer approach ... so if I used a 2.88mm HSS drill, I would then use a 3mm hand reamer to fit the 3mm pins? Would that be the right approach?

2.88 mm HSS drill

3mm Hand Reamer

3mm pins

Cheers

Mike

Edited By Mike Quinn 1 on 20/03/2020 15:44:57

Sounds about right. Dowel pins sound like a real luxury but maybe cheaper than buying a length of silver steel. I think I'd use a smaller drill, say 2.7 mm (10% down on finished size) to allow for the drill making a slightly oversized hole.

Seems expensive for the drill, if it is a one-off job. Just sayin’. Doesn’t need to so precise.

Buying dowel pins or ground bar and suitable reamers to suit a press fit are good suggestions but not practical for a home workshop unless you have plenty of money to spend on tools. Standard bright round bar should be adequate for a simple jig as shown. (The shank from a twist drill or broken end mills are a cheap option for steel which can be hardened).

Drill and tap the holes for the clamp bolts first and clamp the 2 pieces togethert, then drill and ream the holes for the location dowels to ensure that they have the same centre/centre distance and Loctite the dowlels in place on the base part.

If the removable part of the jig has a tight fit on the dowel pins and their center/centre distance is slightly different it will jam and not slide on easily. (this appears to be not a precision application and the holes could be enlarged slightly). But if you want an exact location of the moving part, flats can be machined on the side of one pin as shown in the sketch. The round pin locates in both the horizontal and vertical direction but the one with the flats only locates vertically.

Paul

No different to the vice stop I describe here that many have made.

And to add that the location holes do not need to be excessively deep because the pins only need to protrude sufficiently to locate the part - longer protrusion means more precision in direction. Pins can be chamfered at the ends to avoid ‘binding’.

This means only making it for the maximum thickness that you intend to bend.

Edited By not done it yet on 21/03/2020 09:55:25