Holdfasts

[DigitalM]

I bought a couple of Simon James holdfasts in the for sale forum, they're 18mm diameter. Will they work in 20mm dog holes? I've got a 20mm forstner bit and a 19mm spade bit, which would fit in the pillar drill, otherwise I'm at the mercy of a 3/4" auger bit and brace, and trying to work out how to be perfectly vertical with that.

 

[Phil Pascoe]

If they are 18mm I'd get an 18mm bit - they're not expensive (Wood Beavers are lethal things). There are many ways of getting then vertical, a mirror or an old CD to sight the reflection is a common way, but if you have a drill press just put a hole through a piece of scrap at a perfect right angle and clamp it down to start the hole (you can centre the bit before clamping it down tightly) - you don't need a guide once the hole is started properly. When you're done run a router with a small rounding over cutter around the holes - it'll stop any splitting around the surface.

 

[bugbear]

...but if you have a drill press just put a hole through a piece of scrap at a perfect right angle and clamp it down to start the hole

If you don't have a drill press, you can use your brace and auger to make a hole as square as you're able in a piece of scrap, then plane the face of the scrap until the scrap is perpendicular to the hole (and vice versa, of course).

BugBear

 

[AndyT]

The holes don't need to be perfectly vertical to work. Just use the right diameter bit, sight carefully and get them as straight as you can.

If you really want a guide, screw two square cut blocks together to make an internal corner and rest the bit inside the angle.

 

[nabs]

I have got the same hold fasts and used a 3/4'' bit with no problems.

I agree that the holes don't have to be perfect to work - I kept the brace perpendicular by eye when making the holes and needless to say they are not perfectly straight. I also have a bench top that some would say is too thin (40mm) for holdfasts, but they still grip with a single tap from a mallet.

 

[matthewwh]

I wouldn't feel very confident about using a spade bit to drill a hole that I'm going to spend years looking at. The holdfasts will function in a 20mm hole, but the majority of bench fittings are designed to work with a 19mm hole, so if you ever want to use them for anything else...?

If you've got one, a freshly touched up 3/4 auger in a brace should do a nice job, ideally you want a small chamfer / countersink on them too to transfer the load point just below the surface and stop the edges of the holes chipping as you use them.

These are the bits that we recommend with them https://www.workshopheaven.com/star-m-japanese-f-type-bit-singles.html, not the cheapest in the world, but they do a superb job.

 

[memzey]

I second that. When I bought my holdfasts from Matt I got one of those auger bits with them and it worked a treat.

 

[bugbear]

The Jennings bit here would work a treat.

post118866.html?hilit=cleaned,%20polished#p118866

And did!

http://cornishworkshop.blogspot.co.uk/2 ... ebate.html

BugBear

 

[DigitalM]

The Jennings bit here would work a treat.

post118866.html?hilit=cleaned,%20polished#p118866

BugBear

Thx. I'm going to practice with some of the methods mentioned and see if I can get good results with the 3/4 auger + brace.

 

[DigitalM]

If they are 18mm I'd get an 18mm bit - they're not expensive (Wood Beavers are lethal things).

What's the story with the Wood Beaver brand Phil mentioned? Can't work out what he means. Are they bad?

 

[NickN]

I think 'lethal' as in, will get aggressively through just about anything! Very decent bits they are, tried but don't own any.

 

[DigitalM]

Ah, I see. They seem to be aimed at tradesmen for quickly getting through joists etc. That makes sense.

 

[ED65]

Just wanted to add a bit (sorry for the pun) about spade bits and hole quality. I think to be fair only the edges of dog holes need to look presentable and most people will relieve those or actually put a proper roundover or chamfer on them using a router so plenty of scope for cleaning up a slightly ragged edge if it does occur. But as I posted recently in another thread spade bits are perfectly capable of boring cleanly and leaving a clean entry hole:

Some spade/flat bits do need a tweak or two, and most need sharpening, but they can work well if sharp, the shoulders are even and the spur is central.

 

[MikeG.]

I'm with you ED65. I think spade bits are fantastic, and they can cut clean as a whistle. The ability to start them precisely where you want is their huge advantage over Forstner bits, and a few seconds with a file is enough to restore their edge, or adjust their diameter to precisely what you want.

 

[DigitalM]

I'm with you ED65. I think spade bits are fantastic, and they can cut clean as a whistle. The ability to start them precisely where you want is their huge advantage over Forstner bits, and a few seconds with a file is enough to restore their edge, or adjust their diameter to precisely what you want.

Hmm, I've got a 19mm spade and some offcuts of what I was cutting into. I think last time I used a spade but my RPM was way too high and I started cooking... I bet they perform better at sensible speeds.

 

[Ttrees]

Spade bits work really cleanly cutting backwards, if you ever decide you need a particular sized square bottomed hole.
Its very easy to file square the bottom end, and duplicate the two cutting bevels.
Some bits may require filing off the hex edges till round...better to look for round shanked spade bits.

 

[MikeG.]

I'm with you ED65. I think spade bits are fantastic, and they can cut clean as a whistle. The ability to start them precisely where you want is their huge advantage over Forstner bits, and a few seconds with a file is enough to restore their edge, or adjust their diameter to precisely what you want.

Hmm, I've got a 19mm spade and some offcuts of what I was cutting into. I think last time I used a spade but my RPM was way too high and I started cooking... I bet they perform better at sensible speeds.

Take a file to it, and you'll surprise yourself at how good they can be. You just file a flat but tilted cutting edge, tiffle up the sides of the point occasionally, and as the sides can act as a cutting edge too, a couple of passes with a flat file will cheer them up a bit.

 

[custard]

last time I used a spade but my RPM was way too high and I started cooking... I bet they perform better at sensible speeds.

Take a file to it, and you'll surprise yourself at how good they can be. You just file a flat but tilted cutting edge, tiffle up the sides of the point occasionally, and as the sides can act as a cutting edge too, a couple of passes with a flat file will cheer them up a bit.

You can tickle away all you like but spade bits are still crepe for deep holes. They're the worst bit for clearing waste, which is why they overheat in all but the shallowest hole.

 

[MikeG.]

So I'm outside with a 240V drill and a lump of 6x6 green oak, wanting to drill 50 or 60 twenty mm by 80mm deep holes in preparation for chiseling out half a dozen mortises. You've taken my spade bit off me.........what am I supposed to use?

 

[DigitalM]

So I'm outside with a 240V drill and a lump of 6x6 green oak, wanting to drill 50 or 60 twenty mm by 80mm deep holes in preparation for chiseling out half a dozen mortises. You've taken my spade bit off me.........what am I supposed to use?

Come on in and have a nice cup of tea.