Floats

[steve355]

Ok here’s a little project that may be of interest to someone. I want to make a new clutch of planemaker’s floats. I want some for skewed mortises, such as rabbet planes and frankly most moulding planes. I am not aware that any modern moulding plane makers use skewed wedges in their planes, whereas almost all vintage planes have this feature - it’s a key part of their design.

Anyway, starting with a piece of 1”x1/4”x36” O1 ground flat stock, blue up with machinists blue….

This then gets marked up and cut on the horizontal milling machine. In 3 passes actually, 2 @ 0.1” then a final pass at 0.075“. Done in 3 passes so the mill doesn’t complain too much, also I don’t need to worry about getting stuck, so I can use the table auto-feed and get on with something else.

Result is 6 float blade shaped pieces of O1. Very accurately cut and ready for skewing and teeth. Arguably I could have cut the skew angle in, but I’m going to mill it at the next stage.

 

[steve355]

Next step, blue them all up on both sides….

Now to scribe some lines. My little vertical mill doesn’t have a proper vertical scale, so I will need to work by eye to some extent. 2 lines needed… one for the 12 degree skew, and a second for the tooth gullets.

It just so happens that 50 thou (0.050”) gives a 12 degree skew angle across 1/4”.
It also just so happens that 50 thou is the correct gullet depth for 8 TPI

Give or take a thou or two, anyway. So 2 lines needed, one at 50 and one at 100 thou. This is done on a surface plate with a height gauge. Unfortunately my arm is in the way of the camera.

After this, all the floats have 2 lines scribed on both sides at 50 and 100 thou

Next to set up the dovetail cutter on the mill. It’s a 60 degree cutter, but I want a 10 degree rake on the teeth. Luckily I have a 10 degree template I use for setting the overall angle of the float, so I can use that. Probably not perfect, but close enough.

Tomorrow, mill the skew on the edge of the float, and cut the teeth.

Hopefully all this is of interest to somebody!

 

[Orraloon]

Watching with interest. Keep posting.
Regards
John

 

[steve355]

Some more on my little float project today….

Obviously this is more about metalwork and machining than woodwork. I realised a couple of years back that to make the woodwork tools I wanted to make, I’d have to learn machining and get some machines, so i ended up down a very deep rabbit hole, buying crappy old machines and refurbishing them.

But it’s interesting from a woodworking perspective to see how machining is done. Hopefully someone reading will get something from it, if they don’t know it already.

to recap, these are the kinds of mortises I am hoping to make.

On the left, a typical side-escapement torus bead plane, with a mortise that is skewed to the left at the front and square at the bed. On the right, a typical skewed rabbet plane with a mortise skewed to the right, going right down to the sole of the plane. It’s only possible to make skewed mortises with skewed floats, obviously.

So, I am making 6 floats: left skew push and pull, right skew push and pull, and square push and pull, all 1/4 inch wide. i actually already have lots of square floats, but they are quite skinny and I reckon 1/4” wider floats will help flatten wider mortises.

So the first step today was to mill the teeth on the square floats.

result….

Next step.… mill the skews on the skew floats

 

[--Tom--]

Great project, watching with interest.
Imagine you have it covered already but if I can help with Heat treatment let me know.
Will be worth a stress relief anneal before going to hardening and with each tooth acting like a stress riser the quench won’t be without risk!

 

[steve355]

I settled on a 12 degree angle for the skew. I recently acquired a new vice - a “sine vice”, which is a super-accurate tilting vice. The way it works is that a little tower of precision metal blocks (gauge blocks) is used to set the angle. This can be seen under the vice in the next pic..

It just so happens that to get a 12 degree angle, i need 0.8185 inches of gauge blocks....

So the 12 degrees is accurate to 0.0001“ which is frankly ridiculous (The gauge blocks are accurate to a millionth of an inch). Anyway, it’s good enough for a float.

once set up, I can mill the skew onto the float

They now look like….

They are a bit rough, but there’s no need to go for a nice finish because they’ll have teeth milled on them.

 

[steve355]

Next step, mill the teeth on the skews…. Same procedure as before.

result, my first ever skew float I realised I didn’t take account of the fact that the skew would effectively shorten the float, due to the reduction in thickness. Never mind, in practice it will be fine.

By the end of the day I’d done 4 of 6 floats, then my mill fell to pieces. Sort it out and finish in the morning.

 

[steve355]

Tom, that’s a really interesting topic. Usually I do my amateur “heat it tills it loses its magnetism, dump it in chip fat and put it in the oven for a bit” process. But it needs the right hardness because it needs to be hard but sharpenable by file - and straight of course. But all that is tricky with quite a large item (compared to a plane blade)

any advice very welcome.

 

[J-G]

It just so happens that to get a 12 degree angle, i need 0.8185 inches of gauge blocks...

You are obviously in a predicament. Having only Imperial slip gauges and a Metric Sine Vice !

You really need 0.8185499" or 20.791169mm, though of course I am being pedantic. Then again, you are talking about an angle being acurate to 'a tenth of a thou' ? again mixing units.

Using Gauge blocks at 0.8185" on a 100mm Sine vice will give you an angle of 11.9992566262° - within 0.0007433737945°.

You could (if you were so inclined) refer to the chart which should be in the lid of the box of slip gauges which will tell you how far away from the 'nominal' gauge size - in millionths of an inch - each slip is. Judicious selection of particular slips to make up the height needed MAY get you closer to the precise figure but for what you are doing the excercise is naturally futile.

I'm only commenting because you mixed the units which grates upon my psyche - particularly since one of my jobs as an apprentice was to create the table of differences which I mentioned should be in the lid of the slip gauge box

 

[steve355]

You are obviously in a predicament. Having only Imperial slip gauges and a Metric Sine Vice !

You really need 0.8185499" or 20.791169mm, though of course I am being pedantic. Then again, you are talking about an angle being acurate to 'a tenth of a thou' ? again mixing units.

Using Gauge blocks at 0.8185" on a 100mm Sine vice will give you an angle of 11.9992566262° - within 0.0007433737945°.

You could (if you were so inclined) refer to the chart which should be in the lid of the box of slip gauges which will tell you how far away from the 'nominal' gauge size - in millionths of an inch - each slip is. Judicious selection of particular slips to make up the height needed MAY get you closer to the precise figure but for what you are doing the excercise is naturally futile.

I'm only commenting because you mixed the units which grates upon my psyche - particularly since one of my jobs as an apprentice was to create the table of differences which I mentioned should be in the lid of the slip gauge box

Table of differences in the slip gauge box…. Well,,the last inspection was done in 1987 (at 68 deg Fahrenheit) and it the results are shown in millionths of an inch.

I am indeed in a predicament because in my workshop, only imperial is allowed. Whenever i have to introduce anything that’s horrible, ugly metric i have to put £1 in a swear box. However, the sine vice was such a good deal that I couldn’t turn it down. It’s a chinese affair but seems good. I haven’t put it on the surface plate yet (I know it should have been the first thing I did with it) but the machining seems fantastic. The vice came with lots of tables, but not one for mixed metric and imperial!

By the way, I have a 4” sine bar somewhere, but it’s not so convenient for this particular operation.

The sine calculator on little machine shop web site luckily knows that people have bought a metric Chinese sine vice. And allows for mixed units - see 2nd pic.in fact, I don’t have the standard gauge block set so I had to make it up differently.

Thankyou for calculating my margin of error. I am shamed by this. But I think probably at 2.5 tenths of 1000th of an inch, the float will probably work within acceptable tolerances

 

[J-G]

I think we both appreciate that we are chasing 'fairies' Of course, being in a 'workshop' rather than a controlled 'Inspection' environ means that working to better than 4dp is chasing fairies so you certainly shouldn't be 'shamed' - it was only your use of inch measure to describe an angular distance that pricked my conscience.

I'm sorry that you think so ill of the sensible Metric System - being based in 'Herts' I hadn't considered that you might have a Left-pondian approach

When I did my apprenticeship (1956-62) 'Matrix' were already using both Imperial & Metric so naturally I became fluent in both.

I've just calculated that your error is 2.676" - - - that is 'Seconds of a degree' of course not inches!

 

[Orraloon]

The metric system is so much easier to do calculations in. I started training for the merchant navy in the late 60tes and things llke ship stability was a real pain in imperial. If I remember right a cubic foot of water was 65.5 lbs. How much easier it became in metric when a M3 of water was 1 ton. That said in woodwork I can visualise feet and inches better than metric measurement. I guess its the system you learned first that sticks. We are still stuck with nautical miles in navigation however as one of those is 1/60 of a drgree or a minute of arc on the earth's surface.
Regards
John

 

[steve355]

I've just calculated that your error is 2.676" - - - that is 'Seconds of a degree' of course not inches!

There - that’s what I said all along!

 

[steve355]

State of play…. All teeth milled, I think I only got 2 teeth slightly wrong, which isn’t bad. I’ll fix them later with a file. Next to drill some holes for the cutlers rivets, then on to heat treating…. somehow

 

[steve355]

Holes for rivets….

 

[steve355]

Right, hardening time. Wife is out. See below my new hardening forge. As advertised, the coal briquettes seem to be burning at c 900 degrees. This will be fun. Thanks to Tom for all the advice!

 

[Orraloon]

Living dangerously!

 

[steve355]

Living dangerously!

Well, it’s not working. I need to get into 770+ and it is hovering at 720 and still magnetic. I think I may have to resort to the map torch.

BTW the coal fire was my idea, not Tom’s! It is supposed to burn at 900 C, but when it’s smouldering it’s more like 700. Not quite there.

But It’s thick steel at 1:4” and the cutting surface is long, so I thought it’d be difficult with a map torch.

Back to the drawing board.

Perhaps it’s time to invest in a little propane knife making forge.

 

[niall Y]

Get some lightweight refractory bricks and assemble a small corner feature/cubby hole, with lid. This should allow you to reach temperature with a Mapp Gas torch.

Edit. You could use a bellows/blower/hair dryer. with the coal fire. But then you are in danger of melting the grate, for which you no doubt would have to 'fess up

 

[steve355]

I made this a long time ago, and it didn’t seem to get hot enough, so it has sat on the shelf since. Perhaps time for another try