View Full Version : how to bore

Alistair Hosie
08-11-2007, 09:53 AM
A hole in a wood saw blade I bought a ten inch saw blade from ebay didn't pay enough attention to the hole size which is 16mm I need 30 .The saw won't fit in my chuck too wide so I am stuck there also I have a stepped hole drill cone shaped which steps up in increments that might do or send to a specialist,or chuck away Alistair

08-11-2007, 10:03 AM
Very simple really.

You got a MILL aint you?

Just centre it and use your adjustable bore on it.

regards radish

John Stevenson
08-11-2007, 11:50 AM

Keep it up Sunshine you are doing a good job :D

No seriously Alistair don't use the step drill as they tend to wander even though they are stepped plus a saw blade is usually decent steel, not hard but tough and springy and will shag your step drill up in no time.

Best way is to bore on your faceplate or mill even.
Low speed, plenty of dollup and sharp tools.


08-11-2007, 02:30 PM
And a carbide tipped tool might be a judicious approach.

Ian B
08-11-2007, 04:13 PM

Your lathe can swing 10" but you can't chuck it? How about double sided sticky taping it to a faceplate and then (carefully) boring it out?


08-11-2007, 04:52 PM
he'll need a 20 inch swing lathe to chuck that ..
all the best.mark

08-12-2007, 12:29 AM
I had exactly the same problem. I used an adjustable boring tool in the mill. My boring tool takes a 3/8 shank boring bar, so I first replaced that with a 3/8 diameter stub. I adjusted so the stub traced out a hole slightly smaller than that in the blade. I went through a process where I alternately adjusted outwards and allowed the stub to rub the hole in the blade until the blade centered itself under the boring tool. I turned the spindle by hand during this operation.

Once the blade was centered, I clamped it down and replaced the stub with a cutter. The rest is adjusting, cutting, measuring, then deburring.

As with a lot of my projects, in hindsight I would have first turned a stub of the correct size to use as a gauge. Measuring with a dial indicator, then expecting the result to be exactly right doesn't always work out. Having a stub on hand makes the job easier, and can solve the problem of not having enough room around and under the cutter to properly use a suitable measuring tool.

When I do think to make the gauge first, I like to compare the size to the shaft or arbor that the part must fit on, then make the gauge that size, then turn down a short section that would be maybe exactly 1 thou smaller. Then when using the gauge you will know when it pops in the hole that you are so nearly there.

It would be good to know how much larger the hole is presently than the arbor it's meant to fit on. There will be some play, and you'll want to keep it that way with the new hole size. The first blade I enlarged the center hole in wouldn't easily fit the arbor, and I had to sand the hole out until it went on smoothly.

By the way, my application was to mount a 10 inch blade of good quality onto a 14 inch chop saw. I had to build up the fence area so I could cut right through material.

08-12-2007, 12:57 AM

08-12-2007, 01:19 AM
It appears that some are just a bit "thicker" than the saw blade.

Surely there must be a bit of round scrap /off cuts/ end of length after parting off, that you can use UNDERNEATH the saw blade as riser or packer. This only needs a hole in it a bit bigger than what the hole than what is about to be bored out, then you can use your regular clamps, with due respect to the blade, use shims under the clamps, to hold it ALL DOWN to the table.
Or if your really handy and have time to kill, make TWO wide rings, one on the table, saw blade sandwiched between the two rings and all clamped down tight, no more ringing whilst cutting, if it's going to upset your tender eardrums.
It's now high enough off the table so the boring bar does no damage at all.

HHHhhhhmmmmm, seems simple ideas allude some, who are just a bit thicker than others.

regards radish

08-12-2007, 01:19 AM
I used to work for a company that custom bored blades and also installed pin holes on larger blades (30+"). I would probably do one or two blades a day. We used to use a boring head with a carbide tipped boring bar to change the bore size. My boss was a little frugal, so as the insert lost its edge we would sharpen it on a diamond wheel. We would get 5-6 sharpenings on an insert!

The blade was clamped with strap clamps as close to the bore as possible. The opening was indicated to centre the boring bar, and we would start to bore the hole. We bored approx 0.0015" over the indicated size, which I was told was industry practice. The most difficult blades to bore were cheap 10" blades and some of the dado sets with multiple chippers (hard steel). All this was performed on an old Gorton mill with only 0.250" of backlash on the table!

Hope this helps.


08-12-2007, 02:17 AM

08-12-2007, 04:19 AM
I have a saw that requires a 5 1/2" blade with a 1/2" hole, a combination that isn't too common. But since cordless tools, there are 5 3/8" diameter blades with a 10mm hole. I use two plates of MDF with the blade "trapped" between (relieved for the carbide teeth/set). The whole "sandwich" is clamped to the mill table. Boring head with a boring bar finish the "enlargement". So far none of the blades have "spun" in the fixture, but I would add a steel pin in a gullet, if that happened.

08-12-2007, 04:49 AM

08-12-2007, 08:22 AM
he'll need a 20 inch swing lathe to chuck that ..
all the best.mark

now.... why the hell did i say that ...my mind was thinking power hacksaw blade thats why lol

just mount it in your lathe in the four jaw ...clock it ......and use carbide tipped tool to bore it .

you should just about manage it...as i think the swing of the 1024 is 11 1/4 inches .

all the best.mark

Alistair Hosie
08-12-2007, 05:18 PM
MarK I think mounting this in a chuck would not be so easy as you think.When you consider the design of the blade outermost area with tungsten teeth surely this would create difficulty when doing this.Also setting in a faceplate would this be easier as you only have about 3/4" on each side to tighten the whole thing before you hit bottom of the ways.I will lok at bothe ideas before cutting to see if they are practical " thanks so far" perhaps the milling machine would be best????Alistair

08-12-2007, 05:45 PM
milling machine ..only if you have more than five inches between the coluum and the spindle

all the best.mark

08-12-2007, 08:12 PM
Who cares about holes in the backing material, or top for that matter. Use a sacrificial aluminum plate and drill/bore right on through. "Perfect" fit and support with no (or at least minimal if you're half awake) risk to the table.

I picked up a bunch of old fixture "scrap" for just this purpose. Once in a while I can cut a virgin/acceptable chunk out to make something, and I would probably cry if I had to use a nice piece of heavy plate for such purposes, but it seems pretty easy to acquire pallet/fixture scrap that works fine. Anyway I've used it several times for stuff like this and it works great. It also reduce deformation and burs when drilling/hole-sawing/boring/whatever in any thin materials. Good to keep on hand...

08-13-2007, 07:22 AM
MarK I think mounting this in a chuck would not be so easy as you think.When you consider the design of the blade outermost area with tungsten teeth surely this would create difficulty when doing this.

No, it makes it easier. Use small bits of hardwood between the teeth and the 4 chuck jaws. The teeth will bite nicely on the wood and you won't need much pressure from the jaws to hold it when you consider the leverage. I use a similar approach when I bore out $600 diamond wheels for my wife.

08-15-2007, 02:08 PM

I am not sure that that would be effective with a table saw blade. I haven't attempted to do it that way, but it seem likely that the blade would flex and you would create an "out of round" hole.


When I use MDF, the hole in the top plate is to access the orginial hole for centering, the back plate only needs a "hole" to the extent that the boring bar doesn't "bottom out".


Thanks for the reminding all of the "forgotten factor". Alistair Hosie's saw blade is nearly twice the diameter of what I usually do this on. I am enlarging the hole from 10mm to 12.7mm, while he is nearly doubbling the arbor hole diameter. I am using a smaller diameter blade as the replacement blade, so any "eccentric error" has to be relatively large before it causes a problem. Finially, my blade is used to cut the full depth of the material; the fact that it may be slightly eccentric, doesn't result in the type of depth of cut measuring problems that a "less than full depth" cut would.