Thread: Saw blades bored out? troubles! advice please!

Originally Posted by tfscott

Hey all!
I bought a new CMT Dado set (CMT 6" and 8" Dado Blades : CARBA-TEC), with a 5/8" bore

I bought this with the intention of getting it bored out to 3/4" bore.

I was quoted a price of $11 a blade, and said that it would be easy, and ready on wednesday - this was from a blade saw sharpening shop.

I have only a basic knowledge of metalworking, today i went to pick of the blades after getting a call to say they are ready and the guy said that the black chippers were super hard to drill though and had ruined his $400 reamer? (long tapered cutting tool) and he had to start doing them on the mill which also stuffed up his drill bit (he showed me an ordinary steel twist drill bit). He said that they may need to be sharpened on his cnc sharpener to get them concentric but upon inspection it looks as though he has already done it - to all the chippers (but not the side blades) - meaning its not going to give a flat bottom.

He still needs to get a new reamer in to do the remaining two blades, (which he has started). When i tried the saw blades, only two fit, (measuring 19mm with the callipers), the rest measure 18.9mm meaning that they do not fit on the arbour. I asked for 3/4", which is 19.05mm.

I understand that the chippers are a hard steel/ alloy, but is the ordinary way of going about this? I was reading on the internet that you can put them on a metal lathe and use a carbide bit?

Cheers,
Tom

If the guy is using a reamer it sounds like he doesn't have a lathe.

A tool post grinder would make short work of that and so would a carbide boring bar.

The way this job would be done would depend upon what equipment the saw works had IMHO.

Rob

Hi Tom,

Normally TCT circular saw blades aren't all that hard, and could be reamed with a HSS reamer, but the dado blades sound like they are harder than normal saw blades.

Carbide tooling ( as Rob suggests ) would do the job nicely.

For saw arbors, you want a close fit, and a saw sharpening shop should have plug gauges for the standard sizes, and possibly a setup for testing concentricity and axial runout.... although with smallish dado blades I doubt either issues would be a problem.

Regards
Ray

thanks for the responses guys, it is good to have at least some idea of the normal processes - quite annoying as the are a large saw blade sharpener and i didn't think i would encounter any real problems with getting this done

cheers

Hi,
A few years ago I had a couple of 10" HSS 160T blades with 30mm bores opened out to 32mm. The shop that did them had a machine that ground the bores to the larger size. The same machine was also used to sharpen and balance the blades. Unfortunately those people are no longer in business.
Which is a pity since I could do with having them re-sharpened !

Regards:
BaronJ.

Rule number one. Never buy a new blade with the intention of having rebored, it simply is not cost effective. Rule number two. Always go direct to a professional machining company that does saw blades, they are in the yellow pages. It sounds like the company you took yours too has know idea. It is a simple process when you have the right equipment but will cost alot more than the $11.00 you were quoted.

I agree with this being a job for a pro saw company.

As a hardness indicator for TCT blades I offer the following.
A few years ago I needed a roller nose adapter ( The "E" shaped piece between the bar and the nose) for a 60" chainsaw bar and wanted to use the steel from a 100T 12" CTC blade that had lost a few teeth.
Before using the steel from the CTC blade I made a test adapter using mild steel (RH image). This adapter was cut out to rough shape using a thin kerf cutting wheel and HSS drills, and then shaped to final size using a linisher, files and a small sanding drums on a dremel .
When I tried this with the CTC blade steel (LH image) I ruined several HSS bits before reverting to masonry (carbide) bits. It was also too hard for files and I ended up using conical carbide die grinder bit in place of the files.

I bought a 400mm Tungsten blade for my Panel Saw to be able to rip down some 100mm radiata slabs. There was a traveling tool man at a car show in the village. I don't think the blade is Chinese but it could be eastern European. I knew I needed 30mm bore and this blade sure looked like it was. Anyway...didn't fit. measured as best I could with verier calipers and looked to be .5mm small. Taking it to town and having it done would have made the cheap blade too dear......I cut a piece of MDF and fitted it to a face plate and turned it round on the wood lathe. Then I set it up in the metal lathe and did a final truing. I then turned a recess in the centre and made a plug to fit the new blade. When the plug was fitted into the recess I pushed the saw blade over the plug then screwed the saw blade to the MDF. This meant that the blade was true concentric. I then pulled out the plug and used a tungsten boring bar to very cautiously open out the saw's bore the .5mm needed. I knew that if I took too much that would be game over or make the bore well over size then make a bush to bring it back to the 30mm needed. Well to end this long story......it worked. When I fitted it to the panel saw it ran very sweetly. And yes the base metal of the blade was pretty hard even for the tungsten boring bar.

Originally Posted by chambezio

And yes the base metal of the blade was pretty hard even for the tungsten boring bar.

This is really a job for a tool post grinder and even (dare I say it) for a lathe mounted pencil grinder with a diamond burr.

The problem with carbide is that it is really quite poor at doing very light cuts. A grinder on the other hand can do a gnats whisker without a problem.

Something to think about.

Rob

Thanks for your responses they were very helpful in understanding how it should have been done, it is a saw blade sharpening sharpening company is melbourne.

I assumed they would be on-top of it.

Cheers