Where to send a compound slide for scraping?

tobnpr · Oct 25, 2019

Just got a Sheldon making chips and noticed an issue with the compound.
Tapered gibs, when cutting on the right side of the toolpost (long part between centers), tool pressure would cause visible lift on the left front corner of the compound.

I eliminated it, but only by making screwing in the gib uncomfortably tight.
I don't notice it when cutting on the more commonly used left side of the toolpost(right side doesn't lift with the gib set correctly)

I suppose I can live with it if cost is prohibitive to send it out to get it scraped in, but wondering if there are any companies that would do something that small and rough ballpark price.

Thanks in advance for any suggestions.

thermite · Oct 25, 2019

tobnpr said:
Just got a Sheldon making chips and noticed an issue with the compound.
Tapered gibs, when cutting on the right side of the toolpost (long part between centers), tool pressure would cause visible lift on the left front corner of the compound.

I eliminated it, but only by making screwing in the gib uncomfortably tight.
I don't notice it when cutting on the more commonly used left side of the toolpost(right side doesn't lift with the gib set correctly)

I suppose I can live with it if cost is prohibitive to send it out to get it scraped in, but wondering if there are any companies that would do something that small and rough ballpark price.

Thanks in advance for any suggestions.

Most ANY "service", be it lawn maintenance, auto repair, plumbing, HVAC, roof patching, has to charge "burdened" rates and a minimum up-front cost. Smaller the job, harder that hits as a percentage. Any service.

Buy a Cee clamp that fits.. or buy a scraping book and VIDEO, chase-up the better You Tube's, and teach yerself how to help yerself. Avoiding mistakes is the hard part. The rest is just sustaining patience over the tedium of it.

Anything else is likely to cost more than the whole LATHE is worth, let alone the compound.

tobnpr · Oct 26, 2019

Understood, suspected that would be the case.
A dovetail slide probably isn't a good "starter" project, but I should start learning and practicing the basics and maybe someday.... in the meantime, I'll live with a tighter-than-I-like gib.

I thought that perhaps given the small size of a top slide (as compared to the saddle, for example) that it might be able to be cleaned up on a machining center without all the hand work.

L Vanice · Oct 26, 2019

tobnpr said:
Understood, suspected that would be the case.
A dovetail slide probably isn't a good "starter" project, but I should start learning and practicing the basics and maybe someday.... in the meantime, I'll live with a tighter-than-I-like gib.

I thought that perhaps given the small size of a top slide (as compared to the saddle, for example) that it might be able to be cleaned up on a machining center without all the hand work.

Short dovetails can easily be remachined in a good vertical mill using straight shank dovetail cutters of the correct angle, usually 45 or 60 degrees. It is important that the mill and the cutter are in good condition and the work set up true to the original axis. Then take off just enough to clean up the worn area. Scraping not required. You do not mill the seat for the tapered gib.

Tapered gibs, on the other hand, are very difficult to set up in a mill. It could be a job for a sine chuck and surface grinder or hand scraping. If you take much off the dovetails, the tapered gib might run out of adjustment, requiring you to fit a new (thicker) gib, if you can find one. Scraping the new gib might be beneficial in that case.

Also, much material milled off the dovetail can put the feed screw and nut out of alignment. Hardinge sold blank nuts and expected you to drill and tap them in place after renewing the dovetails on their slides. Or you move the feed screw bracket, possibly by slotting the screw holes and modifying the dowel pin holes.

Larry

jim rozen · Oct 26, 2019

Removing metal from a dovetail slide does several things. It typically moves the axis of the feed screw nut over (towards the
gib side) and downwards. The other significant issue is that the gib becomes too thin. This is especially bad when it's a
tapered gib.

hawkfan9 · Oct 26, 2019

If it's "that" worn, enough to allow movement as you describe, it is highly likely that after machining the dovetails straight, you will need to make a new gib to get the compound properly aligned and sliding correctly....as already stated.

A compound that is just machined/milled without scraping has no way to allow for lubrication. Dead flat and aligned is half the job. Scraping allows shallow pockets, a few tenths, for the lubrication to sit in. Without the scraping, you've got metal rubbing on metal, and in short order, another worn out project as the metal wears prematurely.

As Thermite already stated, unless you've got a buddy who is a scraper hand (obviously you don't, otherwise this thread wouldn't exist), you are unlikely to pay the premium to have the compound on this particularly inexpensive lathe scraped in. Besides, the compound needs to be scraped into the top of the saddle first, and then moving up towards the toolpost mounting area. Doing it half assed serves no point. A good guess would be several thousand dollars, unless someone is feeling generous.

I've taken Richard King's scraping class as a means to learning how to rebuild my own machines. I've rebuilt several of my own machines, and have scraped in several projects. I'm getting great results, but wouldn't dare call myself a scraping hand. It's an acquired skill obtained through lots of practice, and a good indicator as to why you see the very high price tags on full rebuilding of machine tools. Lathes, $5K to $10K, and up, and the price tag goes up from there. These are the numbers I have been quoted in the past, which is why I learned/am learning to do it myself.

thermite · Oct 26, 2019

tobnpr said:
I thought that perhaps given the small size of a top slide (as compared to the saddle, for example) that it might be able to be cleaned up on a machining center without all the hand work.

They can be. They are. If you had even a mill in the size of Burke #4, Nichols, the small Hardinge, you could DIY it. Tool marks could even be your "oil pockets"!

Better, however, you at least "flake" for that.

Machine it? Now you WILL want to make a new gib. Bronze is easiest. It can be scraped more easily than steel, it can be straightened without breaking more easily than Cast Iron.

What do you have to lose if you try scraping it, simply shim the existing gib?

You didn't learn to walk "all at once", did you? Most folks have to take the first step, learn to run only later. "Hire it done" and you never do learn.

Joe Gwinn · Oct 26, 2019

I'd figure out what is worn and by how much first. It may turn out to be something that one can replace without doing anything as fussy as re-scraping or machining precision surfaces.

jim rozen · Oct 26, 2019

thermite said:
....shim the existing gib?

Ah, the cheater way. A thin stainless strip, with the ends bent over to retain it in place, it goes on the
side opposite the gib. You'd be suprised at how effective that is.

thermite · Oct 26, 2019

jim rozen said:
thermite said:

....shim the existing gib?

Ah, the cheater way. A thin stainless strip, with the ends bent over to retain it in place, it goes on the
side opposite the gib. You'd be suprised at how effective that is.

Click to expand...

Stainless? That stuff galls more easily than you do!

At least man-up and buy an assortment of Bronze sheet stock. SKU 9300K6, here:

McMaster-Carr

You know you WANT to. If only 'coz I've had mine for ages..

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