Morticing bit?

[Andy Kev.]

This is a bit of a rum one, so bear with me.

This morning I was having a chat with a colleague. who in a previous life had worked as a carpenter. I showed him a 1 foot, four fold ruler and he couldn't get over how small it was when folded down, and, being German, he'd never seen such a thing before in any event. The conversation turned to old tools and more specifically braces and auger bits etc. He said how when he was an apprentice, one of the old boys claimed to have a bit which cut square-edged i.e. complete, mortices. The lad said the German equivalent of, "You're taking the p**s!" but, he claims, the old boy brought in such a bit the next day and demonstrated it, using a brace.

The lad showed me a picture on his phone of the type of bit i.e. the pic was of a modern bit for a morticing machine. He said the old boy's bit was essentially the same. He swears that this isn't some kind of wind up and he's going to dig around during the weekend for evidence.

Nonetheless, I can't see this at all. Surely a morticing machine has a percussive function as well as a drilling function. How would you achieve that with a brace?

Additionally, I'm fairly sure that I'd have heard of such a bit on this forum.

So what do you think? P**s take or the holy grail of auger bits?

 

[Trevanion]

I don’t see why it couldn’t work in softer timbers if it’s got a worm screw on the front.

 

[Andy Kev.]

Do you mean with the square bit simply slicing its way through the wood, being pulled downwards by the boring part?

 

[Trevanion]

Do you mean with the square bit simply slicing its way through the wood, being pulled downwards by the boring part?

Yes, that’s pretty much the only feasible way I could see it working. Back end of the chisel butting up against the brace being forced through during cutting.

 

[Andy Kev.]

That sounds feasible. I'll do a bit of digging myself about this but I'll be surprised if I come up with anything.

 

[Doug B]

It would be interesting to see what holds the chisel part square & stops it rotating while both the brace & bit are turning

 

[AndyT]

My thoughts too. For thin, soft wood I expect you could just lean on it.

However, there is another, distant possibility. If you have ever looked at the decorative rivets on an old try square, or an inset shield on a penknife, you may have wondered how those fancy shapes were cut. The Sheffield toolmakers used a "passer drill" which could do those and could also make a square hole if one was needed.

Rather than describe it, I'll just link to Roy Underhill demonstrating one.

 

[Cheshirechappie]

Drilling square holes is something that crops up from time to time in the world of metalworking. The most usual method is to press a broach through a round hole, the cross-section of the broach starting round and changing gradually to whatever shape is required, and cutting teeth formed along it like a file or rasp. However, there's another method, used more as an occasional party piece than a serious production method, involving a three-sided cutter held in a floating holder and run through a guide, rather along similar lines to the passer drill Andy illustrated above. This video should elucidate;



It might be that the square hole bit your mate alluded to is something similar - be interesting to see what he comes up with!

 

[Boringgeoff]

G'day Andy,
A.Y.Pearl patented a square bit in the USA in 1893 (US Pat No 505844). Now, although the one I've got here is designed to be used in a pedestal drill, Pearls original drawings show it with the square tapered drive tang for use in a brace. The inner shaft rotates the lead auger at the same time as four lateral projections rotate the two side cutters, as can be seen in photo #1.
And as Doug suggested, in use I found it necessary to hold the square section above the cutters with a spanner to stop the whole thing trying to rotate. This means, if using it in a brace, you'd probably need an offsider to assist.
Cheers,
Geoff.

https://patentimages.storage.googleapis.com/2c/44/7c/bcf78be45e5394/US505844.pdf

 

[Trevanion]

I would never have imagined that!

 

[Droogs]

dont sparkys have some weird contraption that fits on a power drill for making square holes to fit socket back boxes?

 

[Boringgeoff]

I should add the tool is branded: MADE BY PEARL SQUARE AUGER MFG CO. NEW YORK. USA. Also includes three patent dates: OCT 3 '93, AUG 11 '96 and JUNE 18 '98. The dates are for US 505844, US 565500 and US 606575. Additionally I found a patent dated May 2 1905, US 788941
There are a couple of errors, the final date shown on the tool (June 18 '98) should be June 28 and in the text of the 1905 patent he mentions No 909575 ( confused his 9's with his 6's).
I won't waste valuable space by linking to those additional patents, anyone interested can find them at Google patents.
Cheers,
Geoff.

 

[Andy Kev.]

@Boringgeoff

Thanks Geoff. What an amazing looking device! I see what you mean about needing somebody to assist in using it but it seems to me that if some sort of G-clamp arrangement could be made (by a manufacturer, I mean), it might be possible to just get on with turning the brace. It shouldn't need the brains of an archbishop from somebody with an engineering background to come up with something. Just imagining morticing without loads of noise and without racking up electricity bills.

I'd love to get my hands on one of those bits.

 

[toolsntat]

@Boringgeoff

Thanks Geoff. What an amazing looking device! I see what you mean about needing somebody to assist in using it but it seems to me that if some sort of G-clamp arrangement could be made (by a manufacturer, I mean), it might be possible to just get on with turning the brace. It shouldn't need the brains of an archbishop from somebody with an engineering background to come up with something. Just imagining morticing without loads of noise and without racking up electricity bills.

I'd love to get my hands on one of those bits.

If a mortice is created by hand just deep for the square part to reference upon perhaps it would work well?
I'd certainly love to see and have a good with one of these.
Cheers Andy

 

[Benchwayze]

It would probably need to work in the same way as a chain mortice cutter. It would have to transfer the motion of the brace in the right plane to cut the Mortie as in the Square cutter featured above. Can't see any other way of doing it with a brace held vertically.

John

 

[Andy Kev.]

If a mortice is created by hand just deep for the square part to reference upon perhaps it would work well?
I'd certainly love to see and have a good with one of these.
Cheers Andy

I've been thinking a bit about this and have come up with the following:*

Take a 3/8" mortice as an example because it is a fairly common size. The square profiled cutter piece which surrounds the borer has on one side, running most of its length its a bar 1/4" wide and with a dovetail profile. The dovetail bar stops 3/8" short of the bottom of the cutter. Another bar 3/8" x 3/8" of solid metal but with a stopped dovetail groove fits to the cutter's dovetail. The solid bar has two screw holes through it so as to reinforce the attachment to the cutter dovetail which obviously has threaded holes to receive the screws.

It is around the bar that the clamping mechanism is attached. Let's imagine, for the sake of the principle, something which works like a typical Record G-clamp. It has a recess of some sort on its upper clamping point to accept the top of the solid bar and below it is simpler as it just has to clamp under the piece of wood being morticed or, perhaps better, under the workbench or maybe more likely, under a table which is part of the mortiser.

The next bit is the drilling mechanism. So far we have the idea of a brace being used in the normal manner and it should work. However, if our device were to be fitted with a crank handle, perhaps in the manner of a hand-driven bench grinder, it might make for a more stable construction. The handle would just need a gear system to get it turning a conventional brace chuck.

As for the actual process of morticing: the mortice is marked out in the conventional way. The cutter or a more robust marking bar, is placed on one end of the mortice and given a sharp tap. It could mark the centre point too of what would be a 3/8" x 3/8" square. A normal brace (say 1/4" diameter) is taken to this and mortice is bored to the desired depth or a minimum of say 3/8". The sides are tapped out with the cutter or the marking piece. We now have a hole into which the bar with the dovetail groove can fit. This goes in, it gets screwed to the cutter with borer, clamped and now we have complete stability and alignment for sorting out the rest of the mortice.

The first fully bored out hole could actually be used as a reference for completing the initial marker hole if it was only taken out to part of the depth.

*Disclaimer: I know bog-all about tool-making and engineering so feel free to rip this to bits.

 

[Doug B]

dont sparkys have some weird contraption that fits on a power drill for making square holes to fit socket back boxes?

Yep but it would be a hell of a big mortise

 

[croft36]

Do you mean with the square bit simply slicing its way through the wood, being pulled downwards by the boring part?

That is how my morticians machine works.

 

[croft36]

That is how my morticians machine works.

Mortise not mortician!

 

[Boringgeoff]

Taking onboard the ideas from you chaps, yesterday I made a guide hole in a block of fairly hard wood. I made this by running a 1" bit through then chiselling it out in the usual way. Clamping a piece of pine to the back of it I was then able to use the Pearl bit to cut a square hole. This was very slow going, little turning resistance so was able to use a 5" brace to speed the rotation, but had to push very hard.
On the two sides of the bit that don't have the cutter wheels there are a pair of what look like washers, these are actually chisels which are supposed to slice the ridge of waste as the hole progresses. They seemed to be the sticking point, so to simplify the job I would, every 1/8" or so, withdraw the bit, give it a quarter turn and reinsert it, this way the side cutters were able to dress all four sides of the hole.
When the bit has reached the desired depth there is still about 1/2" of waste to be cleaned from the bottom of the hole with a chisel. I bored a second hole adjacent the first without any tendency to deviate, but it was very slow going.
When I made the third hole you will notice that I got a bit off line and created a "dog-leg mortise" if there is no such thing as a DLM I wish to claim the rights to this design. For the third hole I bored a pilot hole with a slim gimlet which sped the boring up to the extent that I had to upgrade to an 8" brace due to the increased resistance. Still very slow going though.
This example of bit is 1" perhaps I should see if I can overlap the holes to successfully create a 1 1/2" mortise.

I found an interesting advert' for Pearl square bits at Worthpoint but I don't want to link it here because I don't know how risky that is. It shows a belt driven mortising machine as well as a hand cranked model. The write-up says the tool was available from Messers Thos Thompson & Co of 35 New Broad St, London.
Cheers,
Geoff.