Heat Treatment FAQs

Remove all burrs from edges and from around holes. No sharp edges please and plan to finish grind after the heat treating process.

A hole in the tang is required, allowing us to hang the blades vertically. The hole should be at least 3mm in diameter. This includes hidden tang blades that may not normally require a hole.

To protect your blades we use an anti-scaling paint that must be applied to a clean surface. It is very important that you clean the blades before sending. Remove all paper templates, labels, dirt, oils etc and in particular ensure that all marking compound or layout fluid (Dykem, Rocol etc) is removed otherwise there may be an additional cleaning charge. Also ensure all edges AND holes are de-burred.

Most importantly. ensure all adhesive that may remain on the blade after removing templates, labels etc is removed or additional cleaning charges may be incurred.

Ideally, you should grind the blade after heat treatment. We use a modified oil/press quench system and having a parallel blank when heat treating helps us to keep the blade straight. We appreciate that you may not be able to effectively grind after heat treatment and must remove much of the stock beforehand. Howrver, please understand that in this case a little distortion may be unavoidable.

If you do decide to pre-grind before heat treatment the thickness of the cutting edge is important; it should not be less than 1mm. If it’s too thin there is a very real likelihood of the edge distorting into a wave pattern. This distortion cannot be corrected after it occurs. Non-aggressive and symmetrical grinding will help to reduce induced internal stresses which contribute to distortion. The main blade should be finished to #80 grit or finer and all edges should be taken to at least #150 grit or finer and definitely with the scratches running longitudinally rather than transverse.

Please we have had to discontinue our grinding service.

NOTE – Edges that are thinner than 1mm (40 thou) will markedly increase the likelihood of warping and/or cracking.

With the Royal M becoming so “nanny state” about knives please use the address details below.

Clarke Heat Treatment
Unit 22, Lower Bassett Down Workshops

Package your knives securely in the box/package so that they cannot move. They will escape from the box if they can slide or shift. Wrapping in newspaper or similar material works well. Putting a protective covering (such as cardboard) over the blade will help to prevent damage during transport. If using a padded envelope cut a sturdy piece of card to just fit the envelope and securely tape your blade(s) to the card.

PLEASE DO NOT use clear or brown packaging tape to secure your blades. The adhesive detaches from the tape and attaches to the blade. It is difficult to remove and may incur an additional cleaning charge.

If asked, say the contents of your package contains “steel” or “metal parts” and you’re not likely to have it rejected. Remember, you are not sending knives. The Oxford English Dictionary defines a knife as “having a sharp edge and a handle”

Remember you MUST include your Heat Treatment Request Information Sheet with the blades.

If you are unable to collect your tools they will be returned via the Royal Mail or Parcelforce.

Packages under 2kg will be sent by Royal Mail 1st class “signed for” service. Packages over 2kg will be sent by Parcelforce Express 48 tracked or Royal Mail Tracked – whichever is cheaper..

Please make a note on the Info Sheet if you would prefer a different service.

If you would prefer to arrange collection by courier you’re welcome to do so but you must use a courier who will give notification of when they will collect and the option for me to change that collection time online. I’m not always at the Forge (and never on a Monday – that’s part of my weekend!!)

I usually heat treat blades once per week on a Wednesday but sometimes Thursday. This gives me the best chance of getting the blades back to you by the following weekend.

I need the blades in my possession by the close of business on Tuesday each week (Monday if a Hamon  Service is required). Our post normally only arrives around 11h00 – 12h30 which is too late for me to prep and heat treat on the same day as delivery.

This is not cast in stone and may be delayed for personal reasons. I will always try to let you know if heat treatment is delayed by more than 24-48 hrs.

An invoice will be mailed to you once your order is nearly ready for dispatch. This will include return shipping costs if applicable. Once payment has been received your blades will be delivered to the Post Office within 24-48hrs (usually). No blades will be shipped (or may be collected) before payment has been received

Methods of payment are:-

  1. BACS transfer to Metro Bank, A/C No. – 29598746, Sort Code – 23-05-80
  2. PayPal to david@clarkeknives.co.uk
  • Maximum capacity is 900 mm (36”) in length
  • Axes heads etc must be able to fit inside a 125 mm dia tube

We will harden to your requested hardness (+- 1HRc) unless we feel that the request is unrealistic, in which case we will heat treat as closely as possible to your requested hardness.

If you are unsure what hardness is best for your material please ask for a recommendation on your Heat Treatment Request Information Sheet and we will heat treat to the appropriate hardness based on your material type and intended use.

We will hardness test where we think it is least likely to show, normally on the tang. If you would like the testing to happen in a particular place, please let us know on your Heat Treatment Request Information Sheet when you send your order. If you would like us not to test your blades please send an extra piece of the same material with your order that we can use as a test piece (and note the request accordingly on your Heat Treatment Request Information Sheet). We are reluctant to return your work without hardness testing as it is our mission to supply quality heat treatment services

However, please note we cannot test the core of San Mai or similar laminated materials due to the cladding. Nor can we test San Mai or similar materials on a scrap offcut as the core is usually too thin to be able to test. In the case of these materials we will heat treat to a procedure we know will give ( or get very close to) your requirements.

The short answer is yes, most likely they will distort. Almost all blades warp a little during the hardening cycle because the volume of the metal increases very slightly as the steel hardens.

At Clarke Heat Treatment we use our own hybrid system, developed over several years and many thousands of blades, utilising a combined system of oil and press quenching. Most blades stay straight within 0.1 – 0.3 mm curvature. However, we cannot guarantee this degree of straightness and our T’c & C’c detail the limits we can work to.

The customer will be informed of any blades that we feel are warped beyond our expectation, prior to their return (and we haven’t had to make that call to anyone yet!!!)

A batch is same material, same thickness.

The minimum charge is to ensure costs are covered for very small order quantities – eg an order for only 1 or 2 blades.

The minimum charge as specified in the Price List applies to each shipment order as received from a client and is only applied if the aggregate charge for all batches in that order is less than said minimum charge. It is not applied to each batch.

First please go to the Price List which should answer your queries. If you still have a question then please (preferably) email Graham at graham@clarkeknives.co.uk otherwise phone 07708 956 036

Please email Graham at  graham@clarkeknives.co.uk or call (07708 956 036). If you call please note that my normal working week is Tuesday to Saturday 😊😊😊