Official Luthiers Forum!

Just bought a used Ridgid 4512 saw. Checked lots of things before pulling the trigger on a marketplace sale…but didn’t bring a straightedge. The cast iron part is 20 wide by 26 long. It’s flat longwise, but when I put a straightedge across the width, there’s a .014 dip on each side of the throat.

There’s plenty of other saws around to replace it with, but, without checking, who’s to say whether they’ll be any better?

So I’m just asking what a reasonable tolerance for flatness should be in cast iron?

TIA

A couple thou, maybe..?

A .014” dip would make fret slotting interesting. Depending on how much down force you used on each pass, you could end up with a fret slot that was too deep and too narrow. Cross cutting sheet goods could also be interesting, meaning dangerous.

M

In terms of tablesaws 14 thou. is a non issue imo. They aint cnc:) Lotsa ways to make the
most/best use of them tho.

I'd expect better than what you are describing from a ground iron tool top.

I measured a couple stationary tool table tops. A fairly new Grizly horizontal belt sander and could fit a 0.002" feeler gauge under a precision straight edge in a few places but not a 0.004 feeler.

On a 60 year old powermatic table saw I was unable to fit the 0.002 under the straight edge though in a spot or two it felt like it wanted to start under a bit.

I've looked at this before cause I used to glue up necks and FBs on the edge of the table saw and wanted a flat surface for the clamping.

The real question is, will it effect sawing operations if there is a slight dip around the edges of the blade throat.

Personally I don't think it will bother you in ripping operations at all. Even when doing cross cuts you usually are not pressing down on the wood that close to the blade. edit -- One place you will have to be careful of is using a square to set blade angle, because the place you want to register from will be either side of the blade, right where your top defect is.

Also, the throat filler can be bumped up with adjusters if you have them or with tape as spacers to bring it up to level with the iron beyond the area around the throat.

Sure you would like better and expect better but I don't think it will be an issue in use.

Always good to see if the straight edge is straight, not all are.

_________________
Brian R, Wood Mechanic
N8ZED

As long as you already have it, why not try some scrap wood and see if you can really notice a problem?

I was trying to cut purflings/bindings and it was very much a problem, but I haven’t set it up properly. I haven’t given up on it quite yet, just wanted a sense of what level of fussiness I should expect…