Thread: Dawn 250mm QR vise restoration.

I have a Record 52 1/2 with QR, but my problem is the other way around it will tighten and release enough to take the pressure off the piece then it starts to jump so I have to use the QR to back off further, if I hold the QR bar up in position while I turn then it will release.

So with your vice try holding the QR bar in position while you tighten it could be disengaging while you turn and may need further adjustment to keep it in place.

So it seems we have similar issues, but different vises, and I guess slightly different operating systems. I will go through it again in the morning, but from what I saw today, it seems the "half nut" it allowed to drop enough for it to jump a tooth, but I don't understand why yet. I think I will need to put it back on the bench and take some of it apart to further understand what is going on there, but I will do as you suggested first, it certainly cannot hurt. It seems to be a pretty simple operating system, I must be missing something simple.

I may have the answer to my question, I just re-watched the restoration video, and I am thinking that I have the flat bar around the wrong way, the hole at the front is offset, and I think it can bolt up fine both ways, but not operate properly....I will check. I seem to have all of the parts though, and that is helpful to know.

Can't assist but can attest that they are a wonderful vice to use. Mine is near 45yo now from new and buggar to get in under my work bench to look at.

Edit,
I don't experience any of the issues mentioned with the QR lever - I can exert more than enough force on the jaws for secure clamping. I think many of the issues arise from operator error or abuse. Before using the QR lever I always back off the clamping force and only use the QR lever to quickly re-position the vice jaw - not for releasing clamping force. Very occasionally I do some maintenance and use graphite powder on the quick nut and a drop of oil on the QR lever bush through the vice body.

Link failed - attached an image.

Mine does the same, I have found that if I hold the quick release lever down while I tighten the vice it will hold hold as tight as I want, it works OK for general light clamping.

Cheers. Rick

Well, thank you for that, I have looked at everything more closely now, and it seems there are several different designs of that vise. The one I bought was not fitted with the flat QR bar, but it was there in the box, and I am thinking now that it is a narrower one for a smaller vise. My bar measures 25mm wide, and looking at pictures I see, and the amount of play with mine, it needs to be at least 30mm wide with the mounting screw hole closer to the centre of the bar, not right on the edge of it. There is a guy with one on ebay, and I have asked him to confirm the width of his for me....it is a minefield out there buying used.

I have the same brand & size vice, I have found that it also slips when you try to OVER TIGHTEN when clamping.

I have found that it holds the item quite firmly for working purposes.

and have always felt that it is a design feature to prevent damage to the QR mechanism.

It is not like a machinist vice that you can tighten the f#ck out of it...

Graham

Looking at the flat bar here, it looks wider than mine and the mounting hole is further from the side than the one I have, meaning that the bar is able to move sideways, and with minimal clamping force it flexes enough for the nut to drop down a bit to jump a thread.Untitled1.jpg

Originally Posted by macg

I have the same brand & size vice, I have found that it also slips when you try to OVER TIGHTEN when clamping.

I have found that it holds the item quite firmly for working purposes.

and have always felt that it is a design feature to prevent damage to the QR mechanism.

It is not like a machinist vice that you can tighten the f#ck out of it...

Graham

Thank you for that Graham. I made a stronger/wider QR bar today, fitted it to the vice, and it is much better than it was, I can easily use is as it is. For interest, I talked to Dawn, and the reason these were discontinued was because of this issue, once they are over tightened....with a bar extending the handle, and that skip a tooth, they are never the same, and replacement half nuts are no longer available, and have not been for about 15 years. At today's prices,the 250mm QR would be $800-$900, so it does make you think. I will see how I go with it, but I am thinking that having a new half nut made would be a good option, if it can be done at a reasonable price.

Originally Posted by zseriesrob

Thank you for that Graham. I made a stronger/wider QR bar today, fitted it to the vice, and it is much better than it was, I can easily use is as it is. For interest, I talked to Dawn, and the reason these were discontinued was because of this issue, once they are over tightened....with a bar extending the handle, and that skip a tooth, they are never the same, and replacement half nuts are no longer available, and have not been for about 15 years. At today's prices,the 250mm QR would be $800-$900, so it does make you think. I will see how I go with it, but I am thinking that having a new half nut made would be a good option, if it can be done at a reasonable price.

All threads will eventually wear through constant use, but much, much faster through abuse.

Ok, overnight I had the idea of adding a strengthening rib to the flat QR bar, and came up with several designs, but finally settled on this, mainly because I thought if it was no better, I could simply remove it without too much effort, and as I have sometimes found welding, unless done very well, the material can twist with heat. Anyway, it is completed using the old mortise and tenon type of joint, and 6/4mm socket head bolts. This has improved it again, and I think I will retain the new mod, but if the nut can be re-cut, or a new one made, it will be done. I messaged a guy I used previously for a similar job, but I have no reply yet, I may need to look for someone else.
Above, Rick mentioned above about holding the QR lever while tightening, and that now works on this vise, so it is very usable the way it is now.
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