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Making holes in dovetail saw blade for handle, high carbon alloy

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pgrbff

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I recently sent my 20tpi c/c dovetail saw blade in for sharpening. It's a long process, my wife took it to England when she visited, posted it and it was returned to my sister-in-law before posting it back to me.
For some reason, and it only arrived yesterday, so I haven't had an opportunity to call them, they have replaced the blade entirely. Very kind of them seeing as the current price for the saw is over £150.
How do I make clean holes in the blade for the handle? I can't imagine it will be very easy to drill a clean hole through such thin steel even with a quality cobalt drill bit.
 

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Phill05

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You can use a carbide masonry drill to cut the holes make sure you have the blade clamped down well to stop any movement.
 

Phill05

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Mark it out and put a centre pop where you want the hole and drill it should be no problem
 

Ttrees

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I'd experiment on some scrap hardpoints as there's lessons to be learned,
I've had small cobalt bits which would not cut stainless without a sharpening,
whether or not you can punch the steel without hardening it,
some here suggested going heavy with the pressure to get under any work hardened surface for stainless.
Interested to see how you get on as I have some hardpoint sawplates which I'm guessing
will be a whole lot easier to file than some of the old saws I've picked up cheap, not done a dovetail saw yet, the few I have filed had hard spots and pretty much wiped the files out after one profile job.
On the lookout for some nice three corner files in the few local shops since, but found nothing compared to an expensive double extra slim one which still seems a tiny bit large for a wee dovetail saw.
 

Jameshow

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Also go slow you don't want the drill bit work hardening the steel....
 

Cabinetman

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On the lookout for some nice three corner files in the few local shops since, but found nothing compared to an expensive double extra slim one which still seems a tiny bit large for a wee dovetail saw.
I didn’t really look at them but I came across some the other day which were aimed at the chainsaw market, might be worth a look. Ian
 

pgrbff

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Mark it out and put a centre pop where you want the hole and drill it should be no problem
As the "cone" of the point on a drill bit is actually deeper than the thickness of the blade it is difficult to imagine it would leave a clean hole, no matter how slowly I went.
 

pgrbff

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I'd experiment on some scrap hardpoints as there's lessons to be learned,
I've had small cobalt bits which would not cut stainless without a sharpening,
whether or not you can punch the steel without hardening it,
some here suggested going heavy with the pressure to get under any work hardened surface for stainless.
Interested to see how you get on as I have some hardpoint sawplates which I'm guessing
will be a whole lot easier to file than some of the old saws I've picked up cheap, not done a dovetail saw yet, the few I have filed had hard spots and pretty much wiped the files out after one profile job.
On the lookout for some nice three corner files in the few local shops since, but found nothing compared to an expensive double extra slim one which still seems a tiny bit large for a wee dovetail saw.
I only have modern saws I could practise on and I don't imagine they are hardened to the same extent across the full width? I don't know much about saw construction.
 

Phill05

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As the "cone" of the point on a drill bit is actually deeper than the thickness of the blade it is difficult to imagine it would leave a clean hole, no matter how slowly I went.
As I said before make sure the blade is clamped down not able to lift and the "cone" cuts clean through into a base board or a hole in the base board "honestly no problem" I have done it many times through harder material "thin Stainless steel"than the saw blade.
 

Alasdair

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I think you need a solid carbide drill bit. From memory I think its a spade type bit or carbide tipped. You can use masonry bits but they may need sharpened first with a diamond stone first. You could always see if there is a local machinist company that could drill them for you. Does the saw company that did the work have the facility to drill them?
 

pgrbff

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I'd experiment on some scrap hardpoints as there's lessons to be learned,
I've had small cobalt bits which would not cut stainless without a sharpening,
whether or not you can punch the steel without hardening it,
some here suggested going heavy with the pressure to get under any work hardened surface for stainless.
Interested to see how you get on as I have some hardpoint sawplates which I'm guessing
will be a whole lot easier to file than some of the old saws I've picked up cheap, not done a dovetail saw yet, the few I have filed had hard spots and pretty much wiped the files out after one profile job.
On the lookout for some nice three corner files in the few local shops since, but found nothing compared to an expensive double extra slim one which still seems a tiny bit large for a wee dovetail saw.
Not cheap for a file, especially if you have to get it over to Ireland, but sold by a sawdoctors who make top quality saws.

 

pgrbff

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I think you need a solid carbide drill bit. From memory I think its a spade type bit or carbide tipped. You can use masonry bits but they may need sharpened first with a diamond stone first. You could always see if there is a local machinist company that could drill them for you. Does the saw company that did the work have the facility to drill them?
I'm sure they could but I'm in Italy and they are in the UK.
Not quite as easy to get work done like that here in Italy. Would probably cost more than the saw. Very different culture, not really into DIY.
 

Alasdair

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Had a quick look on Amazon and found this link. There not too expensive but not sure if they would do the job
Hope it helps I used similar for drilling tempered steel plate.
 

D_W

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I have two ideas for you as I've made a few saws (but only half a dozen or so):
1) buy a bit that's harder than the steel by a wide margin (bit with a carbide tip)
2) use a bit that's high quality HSS and will drill partly into the steel and heat it (And win the battle and perhaps need sharpening after a couple

By #2, I mean that a HSS bit will also heat and if you heat both the saw and the bit past the point where the bit loses temper, everything will go awry (this might be hard to do at lower speed). If you heat the steel a little bit, but the drill bit itself doesn't overheat, then the bit will win.

Secondly, don't drill bare plate (you can do it, but don't bother as to do that, you need to be able to drill through thin sheet sharply and very slowly).

put the plate between two pieces of wood instead. If you use something hard like a carbide tile bit or a masonry bit, then drill the hole through the wood to the saw plate with a different bit first.
 

IWW

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I've made something north of 100 saws so I've drilled a few holes through varying thicknesses of saw plate & chewed up various types of bits over the last dozen years or so & learnt a few lessons along the way. I think you are over-anticipating the difficulty, drilling the two holes in your saw will not be a major problem with a decent new or fairly new HSS bit; typical saw plate is about 10 Rockwell points less than a HSS drill bit, a newish bit will go through 20 thou plate easily, but you certainly won't get many holes before the bit dulls too much to want to cooperate further.

You have several choices. The easiest would be to get a new HSS bit & be prepared to sacrifice it (if it's good quality it should still cut softer materials after two holes in thin plate but it will be considerably less sharp than it was!).

Option two is to buy the type of jobber bit with carbide tips which are meant for cutting all materials from plastic to steel (according to the pictures on the package). These are more accurate than masonary bits & will drill dozens of holes in saw plate with no problems (these are what I mainly use). Solid carbide bits are available, but not cheap, so unless you plan on drilling a lot of holes, not worth it. I discovered that you don't need lubricant with these bits when drilling thin plate, cutting fluid seems to speed up deterioration of the edge rather than preserve it (this is purely from personal experience, and I don't know why it's so).

Option 3 is to use a masonry bit - these vary in quality a lot, are usually not sharp enough to cut steel accurately and on thicker plate, can heat up enough for the tips to let go if drilling "dry", so I'd least recommend that route.

To mark out the plate for drilling, set the new blade in place carefully, then use an ordinary HSS bit in your battery drill to make an indent in the right spots. A couple of seconds with moderate pressure should give you a decent mark & is usually enough to start the bit without skating. You can finish the hole with the battery drill, but a drill-press is my preferred weapon, it takes a fair amount of pressure to make the bit bite & drill cleanly without over-heating (use a smooth bit of firm hardwood as backing when drilling).
You will almost certainly get a bit of flare on the exit side of the hole, which you can ignore if it's minor, but if your handle slot is a very neat fit, you may need to wipe the plate carefully over a stone to remove that.

For a two-bolt saw, you want to get those holes neat & accurate to ensure a good fit and the blade doesn't rattle about in the handle (nothing more annoying, imo!). The easy way to ensure you get as good a fit as possible is to mark & drill one of the holes, then set the plate back in the handle, insert a bolt, & mark hole #2. If one hole does ends up a bit "off" it's not the end of the earth, it's easy to extend it a little with a small chainsaw file. There are many, many old saws out there with over-large holes that are perfectly usable as long as the bolts are kept firmy twitched up, but you want to avoid that if possible..

Lastly - Tom, I've re-purposed many old hardpoint blades. Once you slice off the hardened teeth and about 1mm of the plate (you can see from the blueing how far the hardening extends, it usually survives for the useful life of the saw), the rest is indistinguishable from the saw plate bought by the roll, by my crude assessment methods (file-ability, 'spring' & wear characteristics). I don't know what alloy is typically used for hard-point saws but I have seen one manufacturer & supplier to the saw-making industry say they used 1080. Whatever they use, it seems to be hardened & tempered to much the same specs as that used for re-sharpenable saws. All but one I've re-purposed have been fine. Of the saws I've kept, I can no longer remember which is which & I certainly can't pick them apart in use, except this one that I made about 3 yrs ago from an Irwin blade (I think that was the brand). It gets a lot of use & stays sharp as long as any other saw I own:
Sw oak recyc blade.jpg
(The shape of the toe end is to get rid of the "hang-hole" :)

I've only come across one example that I deemed a bit too soft - it was the cheapest of several hard-points that I bought purely to test how usable the plate would be. The 'soft' saw was utter junk, the teeth were so badly formed it would barely cut at all, & veered off to one side so much it was impossible to cut a straight line (all the teeth on one side were about 2/3rds the height of the alternate teeth!). Imagine some poor beginner trying to cut joints with a saw like that!

Old saws are not usually as file-destroying as the one you mentioned, but there are certain 'models' like the Disston 77 that are much harder than their regular line and certainly do a number on files, particularly the inferior files available nowadays...

Cheers,
Ian
 
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kwigly

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I use hand punches. For thinner dovetail saws I have used the small hand punch pictured, but for full size handsaws the bigger "Whitney" punch is easier. For accuracy, I locate the hole positions using the saw handle as a guide, and centre dimple the location using a transfer punch
DSC00796.JPG
. This dimple then locates on the pin of the hand punch
 

Fergie 307

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If you have a friendly local engineering shop the they could do this using a carbide milling cutter. You will get nice clean holes and will probably just cost you the price of a beer.
 
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