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Myford Apron Dovetail Damage

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Mike Donnerstag15/07/2020 10:29:17
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201 forum posts
45 photos

I recently purchased a Myford Super 7 power cross-feed apron, but unfortunately the dovetail was damaged in transit, with a small chip around 5mm long and 2mm wide removed from the top edge, as in the photo below.

img_0613.jpg

My questions are:

1) Is the saddle still usable? Am I right to assume that it isn't usable as-is, as it would result in wear to the gib?

2) Can it be repaired? If so, should it be brazed, silver-soldered or welded? I seem to remember having read somewhere that weld on cast iron can create brittle areas and therefore braze is better. Am I right?

Many thanks,

Mike

John C15/07/2020 10:37:46
267 forum posts
93 photos

1. The saddle is still useable. The loss of bearing surface is negligible. The gib will only be damaged if it snags on a sharp edge of the hole. See below.

2, Yes. I would use an oilstone to smooth any rough edges, clean thoroughly and reassemble.

Good news I hope!

John

Journeyman15/07/2020 10:49:08
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1073 forum posts
210 photos

Perhaps fill the chip with one of the metal bearing epoxy fillers - JBweld or Devcon Steel for example. Then shape back to match original profile. May prevent the odd piece of swarf getting in there and causing damge.

John

Edited By Journeyman on 15/07/2020 10:49:28

Dave Halford15/07/2020 11:17:10
1818 forum posts
19 photos

If you decide to fill, find a piece of flat metal like a Stanley type blade to fit under the dovetail. Coat the plate/blade with 3 or 4 layers of wax (car polish will do) don't use oil, don't use any fewer coats.

Apply your choice of filler to the surfaces of the hole.

Clamp the plate/blade wax side to the dovetail.

Add any more filler required to fill any voids and scrape the excess off the top with another blade.

This will cut down any shaping required to next to nothing.

Hopper15/07/2020 12:12:24
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5505 forum posts
137 photos

Any kind of welding or brazing or even silver soldering is likely to cause distortion and a bigger problem than you already have. Smoothe off the edges and carry on. I would not even bother with any kind of filler. Too likely to get swarf embedded in it.

blowlamp15/07/2020 12:53:45
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1527 forum posts
98 photos

You might be as well to check the saddle for twist if it's had a knock.

Place it on the lathe bed with a finger resting lightly in the middle to keep it from rocking, whilst tapping in each corner with your best knuckle. Any area that gives other than a dull thud when this is done is probably not in full contact with the bed and will need sorting out.

Martin.

Pete Rimmer15/07/2020 19:38:16
1096 forum posts
69 photos

Make a burr file and get rid of any high spots then just use it. Take an ordinary thin flat file and rub it on a stone a bit to take the edge off the teeth. Now run the file flat across the dovetail surface. It will only cut high spots and leave the way surface unharmed.

Mike Donnerstag16/07/2020 19:10:18
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201 forum posts
45 photos

Great advice - thanks to all who posted. I did order some JBWeld, though I will probably just leave it smoothed.

The whole saddle was quite black, perhaps leftover from some kind of rust remover? I tried to shine up the non-bearing surfaces in several ways, in the following order, moving from mild to more agressive, all of which lubricated with WD40 or white spirit:

1) a slipstone to remove any high spots, though this was very of course very slow in removing the 'black' surface

2) green scotchbrite, which didn't do much either

3) fine emery cloth, backed with a small square of wood, which did slowly remove the black surface, leaving the silver cast iron

I assume it doesn't really matter how I make the non-bearing surfaces more cosmetically appealing, though does anyone have a quicker way that they use for all flat cast iron surfaces? Citric acid perhaps?

Mike

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