Extracting a dowel pin from a blind hole

Fair enough, Jason ... You win

MichaelG.

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Edit: Thanks for posting the photo 

... Funny way to design a lathe, methinks.

Edited By Michael Gilligan on 28/01/2019 19:59:22

I have a Hobbymat. The bar is non-essential and non-structural.

It is a strange design really being an overgrown watchmakers bar bed lathe. In practice although the bed forms the guide some of the cutting force is taken by the hefty leadscrew which is far thicker than on normal minilathes. I often think it would be nice to rebuild it with only the tailstock on the original bed and a new saddle on say two ground bars.

Hi, Bazyle is correct and it does not make any contact with the saddle or the tail stock. It's only purpose is to stop swarf dropping straight onto the lead screw.

If I had the same problem, I would lay a washer that has a hole the same size as the dowel, on the end of the bar and then carefully build up the end of the dowel with TIG weld enough to get a pair of grips to pull it out. The washer will help to stop you welding it to the end of the bar.

Regards Nick.

Maybe the bar is there to help take the longitudinal reaction force of the leadscrew ?

It might be simpler to make a new bar.

Just mig/tig a piece of studding on to the pin and screw it out using washers and a nut.

Regards

Hi John, the bar is only held in place by three dowel pins, which will not restrain any longitudinal forces of any sort and it is described as a spindle guard in the parts list.

Regards Nick.

Wow, this thread went on a bit! Have to confess I stepped back last night to let you get your suggestions in

In no particular order...

Welding - the pin was about 3mm behind the panel so no chance of that. It's a 4mm diameter pin. Also, I don't have a welder (though this is tempting me to buy one!)

Drill - this worked, once I ditched the HSS bit and went for a 4mm carbide bit. I ended up wrecking one of these when the drill skipped. A 4mm endmill split the side of the pin and finished the job, fell right out.

The bar, incidentally, is mild steel, and so are the pins. 4mm dia, 15mm long. I've got some replacements on order.

The pin was in there ludicrously tight, which explains why it wouldn't push out. From the bits of metal which came out, it looks like it had rusted in... which explains why the previous owner left it alone. I'm quite surprised how short it was, only 10mm when it's supposed to be 15. Yet another bodge done to this machine by its previous owner, one of several sadly.

Thanks for all your help!

Edited By Phil Pemberton on 29/01/2019 23:49:25

Use tapped pins if possible to make life easy in the future.

Mike

I wonder if the previous owner had not been able to get it out, so cut 5 mm off, leaving you to work out how to get it out.

Ian S C

I just went to have a look at mine. I hadn't realised the pins go into blind holes in the main support at the RHS end of the bed. I had assumed they were through holes. I think I would either drill through so I could use say M5 screws or make a little bracket on top. Anything other than what it is.

edit: went and had another look. I'd ditch the bar and use a larger piece of Al angle as it could come further forward and down completely hiding the leadscrew.

Edited By Bazyle on 30/01/2019 13:16:03

[This posting has been removed]

Alas, Barrie, it's cost me a couple of good carbide drill bits! Still, she's fixed now.

I did find out why the pin wasn't embedded in the support when I tried to fit the replacement earlier. Looks like the previous owner cracked the support (which is made of plastic, seems to be Bakelite or similar) then "repaired" it with glue, filling the back with it in the process. I drilled out the hole to clean it and the repair gave way...

Regardless, a bit of drilling and some JB Weld later, and the pin is back where it should be!

Hi Phil, yes the support is similar to bakelite, the one on my Hobbymat was broken into a few bits **LINK** when I bought it, so I made a new one from a scrap piece of bearing housing **LINK**

Regards Nick.