Bolts for Unisaw

[George Symula]

First,as a NB to this forum (mostly an old Neanderthal), I'd like to compliment the participants for a wonderfully civil forum that has, as a lurker, provided me with great information. Thank you all...

Now my question....I have recently purchased a used 1988 Unisaw in great condition. It came with a 52" Unifence and an outfeed table but missing the old screws from the jet lock rails for the back of the left wing extension. I've tried to find bolts to attach the table from several sources, including Delta but no luck. From the parts list, I believe the screw (bolt) is 3/8-24 fine thread but I've tried that and a 3/8-16 coarse. Neither works. Is this a custom thread? Did you who have gone through this drill and retap and if so to what size?

Geo

[Jim Chilenski]

George,

I can't help you with the correct bolts for your Unisaw since I have a Jet, but is it possible that the bolts you need might be metric instead of standard in size? I know that several of the bolts in my Jet cabinet saw are metric depending on where the particular part was assembled.

Jim

[George Symula]

Jim,

Thanks for the reply. I believe that this year saw was manufactured in the US. Doesn't rule out metric but (I believe) the parts list identifies the screw as 3/8-24 which is a fine thread 3/8. I don't know if the fact that it is identified as a "screw" as opposed to a "bolt" has any significance. My machining experience was limited to 9th grade shop class in 1949 so I'm way out of my league on this subject.....Geo

[John Thompson]

Jim,

Thanks for the reply. I believe that this year saw was manufactured in the US. Doesn't rule out metric but (I believe) the parts list identifies the screw as 3/8-24 which is a fine thread 3/8. I don't know if the fact that it is identified as a "screw" as opposed to a "bolt" has any significance. My machining experience was limited to 9th grade shop class in 1949 so I'm way out of my league on this subject.....Geo

I have never seen the use of a metric on a Uni-saw.... but that doesn't mean someone might have re-tapped it at some time. You say the 3/8 x 24 won't fit. What does that mean exactly... too large... too small... whatever?

Have you checked to see if the threads have been stripped at the opening not allowing the 3/8" to seat and start their spiral? BTW... Delta tech should be able to tell you the exact thread size used for that model which might lead to the fact that is has been re-tapped.

Sarge..

[Mike Vermeil]

Most likely the threads are just messed up. If you can't ID the pitch by sight, trying running a 3/8's coarse tap into the hole. That's most likely what it is since fine threads don't work out too well in cast iron (based entirely on my experience only). If that's not it, it's probably fine thread.

[Rod Sheridan]

Hi, the correct root diameter for a 3/8-24 thread is .3320" which is a size Q drill.

A 3/8-16 root diameter is 5/16", .3125".

If the existing thread is a 3/8-24, running a 3/8-16 tap will ruin the existing threads, and cut very poor 16 pitch threads since the root diameter is already too large.

I would suggest trying to run a 3/8-24 taper tap into the hole by hand to see if it feels OK. If the thread pitch is 24, the tap will thread in part way by hand with no problem.

Then you can chase the threads with the tap mounted in a tap handle.

Regards, Rod.

[George Symula]

Wish I knew how to paste quotes....anyway....

John, the bolt won't start because it's too big. No evidence of stripping and I did talk to a Delta tech and he had no idea what the thread was or what a substitute bolt might be. I also talked to a couple of Unisaw repair facilities and they couldn't help either.

I think that Rod Sheridan has the answer. Since the part is identified as a screw, I'm beginning to think that the thread is tapered. I think I'll look for a tapered tap for a 3/8-24 and retap. Any comments??

Geo

[Josiah Bartlett]

I have an earlier Unisaw (34-450) with a 50" Jetlock, and my extension tables do not connect to my fence rails. It just bolts to the main table. I can go out there tonight and check out any holes if you want, I have a wide selection of taps and screws. Most of the bolts I've used on it have been UNF (fine) threads, and I have not found any tapered holes on either bolts or screws. I can pull the bolts out of the rear rail and see what they are.

I'm relatively sure 3/8-24 is not a valid NPT tap size, so you probably won't find a tapered tap.

[George Symula]

Josiah,

I'd appreciate the look. I am looking for the size that bolts the Jet Lock rail to the main table. There are two bolt holes...Thanks.....Geo

[John Thompson]

Evening George..

I was going to suggest to go to it with the tap... but Josiah may have come to the rescue with a missing link. Hopefully that will pan out as I don't personally think they used tapered bolts. I am curious as to what the problem is when it does get solved and it should one way or the other!

BTW.. if necessary, I can call Greg at Redmond and Son Machinery here in Atlanta as he has installed and worked on a ton of Uni's over the years. Or I know some ex reps from Delta that started their own tool company but I would bank that they know or could direct to who does. I can't believe that Delta does not keep spec books in their technical department on the older models. That' not impressive IMO.

Good luck as I will be keeping an eye out for the solutioin to this one..

Sarge..

[Josiah Bartlett]

They are definitely fine threads, 3/8x24, no taper. I noticed that it was difficult to get the bolt back in that I took out without cross-threading it, so you probably want to chase the threads with a tap. The jet lock bolt is and interesting piece, it has a long smooth shoulder and no actual head, just a slot for the screw driver.

Let me know if you need any more measurements.

[Steve Leverich]

George, just to help define things -

http://en.wikipedia.org/wiki/Screw#Differentiation_between_bolt_and_screw

The only tapered fasteners I'm aware of are wood or sheet metal or lag screws, not counting pipe (NPT) which is tapered but is not a fastener.

In general practice, I've seen the terms machine screw and bolt and cap screw used interchangeably.

If your bolts aren't the next SAE (fine thread) or USS (coarse thread) size downward (like 5/16") then they may be metric. 8mm bolts are almost the same size as 5/16 (just slightly smaller) and 9mm bolts are just under 3/8" in diameter - check out the top section of this chart

http://mdmetric.com/tech/tic1d.htm

and you'll see there are 3 or 4 different possible thread pitches for each size.

It'd be a lot easier if you had the bolt instead of the threaded hole - then you could measure pitch, etc, much easier :=)

Good luck in your quest... Steve

[Rod Sheridan]

Hi, there seems to be some confusion as to my previous post, sorry about that.

I hadn't indicated that the threads were tapered, I asked the originator of the post to use a taper tap, as taps come in sets of three, taper, plug, and bottom.

The taper is the first tap used, followed by the plug, and bottom tap for blind holes.

In a through hole of shallow enough depth, only the taper is needed.

Sorry about the confusion, I forgot that this was a woodworking forum, and should have been more specific.

Regards, Rod.

[George Symula]

Well...Success!! To those of you who resonded and are interested in the resolution, the 3/8-24 fine thead bolts, actually cap screws did work. I had to diassemle the table to get a good straight (level and plumb) start into the hole(?). Thanks to you who took the time to help.
Regards,
Geo