Thinning a parting blade?

Hi all!

For my first lathe project, I'm making a new ali cylinder head for a .75cc DC Merlin diesel engine.

I've succeeded in cutting a workable thread so it screws into the crankcase quite happily. The next step is boring out the interior to accept the cylinder liner.

My question regards the subsequent cutting of the external cooling fins, and luckily I have a spare cylinder head to copy. I'm guessing that a thin (1mm) blade is used to remove material, and I'm wondering whether it's safe to take a 'standard' parting blade (3mm wide), and simply grind it down to size?

I understand that some relief on the sides of the blades is necessary.

Just wondered what the accepted method is?

Thanks,

Tim

Tim,

I have done what you suggest without problems. Don't make the thinned bit longer than it needs to be.

An alternative is to use a HSS hacksaw blade in a holder:

Rod

Tim,

Always good to hear from someone doing something on 'diesel' engines

I've done quite a few heads now using home ground parting blades ground from old cutter shanks - mainly FC3 throw away cutters. The big thing to be aware of is rubbing of the blade in the slot and the consequent build up of the ali on the tool so plenty of paraffin for lubricant - you can use WD 40 but the fumes given off can prove quite nasty to the respiratory system.

I hold the cutters in short lengths of rectangular mild steel as tool holders. The good thing with using this method is unlike grinding away a costly decent parting tool the tool can be rotated in the holder to give good clearance.

Hope that's of help.

Tug

Further to Rod's post about using a hacksaw blade I remembered I have these images doing a special head for an ETA 15d

I also did a scaled up to 5cc version of the above and used another cutter ground from a 1/4" dia FC3 cutter shank to do these very deep fins.

Best - Tug

Edited By Ramon Wilson on 09/12/2022 22:44:14

Thank you, gents!

Since my initial post, I've ordered a 1.5mm blade to grind down a tad, but I do like the idea of recycling an old hacksaw blade.....

Tim

You can also buy the blades in 1mm width from the likes of Eccentric Eng or if not too deep I use a 1mm insert that will do up to 6mm deep.

Cutting the 0.6mm gaps in EN16 to leave fins on a Whittle cylinder, tool is ground HSS and did 9 cylinders without regrinding. Youtube video link below.

**LINK**

Emgee

Emgee,

I enjoyed that video, nice camera work too.

Bear............

Hi Bear

Thanks for your positive comment about the video.

Emgee

Roderick Jenkins' post included an extract from L C Mason's "Using the Small Lathe".

I don't know whether this is still in print but those who do not know the book would do well to get hold of it.

It's a good tip, well worth a try, but don't be surprised if it doesn't work. Hacksaw blades, especially modern ones, are unlikely to be solid HSS. Very cheap blades are usually Carbon Steel - hard, but easily overheated, chipped and blunted. Top-end blades usually have HSS teeth bonded to a tough soft-steel backing; they're less brittle and have extra hard teeth compared with solid HSS blades, where the metallurgy is backed off somewhat to reduce breakages. And there are mid-range blades made like the top-end type, but for cheapness with ordinary HSS teeth on a mild-steel backing strip. Very cheap blades handled gently will work, and so will solid HSS if they can be found, but many posh brands and mid-range blades may not hold an edge because the backing strip is made of soft metal.

Dave

.

Good point, Dave

To the best of my knowledge Starrett Red Stripe blades are still solid HSS

MichaelG.

Mason's splendid little book has been reprinted by TEE https://www.teepublishing.co.uk/books/lathes-other-machine-tools-and-how-to-use-them/using-the-small-lathe/

Plenty of "all hard" HSS hacksaw blades available from Eclipse **LINK**. I have a good stock of broken hacksaw blades! And if they have broken they are probably solid HSS.

Rod

Edited By Roderick Jenkins on 11/12/2022 11:26:39

I see that TEE also have his Building a Small Lathe but, seemingly, not A Man and His Lathe - possibly on the grounds of political correctness!

Being revised as "A Person and Their Latte" for the modern generation of froth sippers.

Fixed that for you

Sorry to spoil the anti-woke taunt

**LINK**

Thanks for the correction. Sparey sits next to Mason on my bookshelf, hence my confusion of the two.

Encourage or disparage.

Again, thank you for the positive feedback, gents!

It just so happens that I have a couple of Starrett red blades in stock, so it looks like the one currently in use will be making the ultimate sacrifice quite shortly.

Tim