
146 S.E.2d 793 (1966)
266 N.C. 542
Ray A. VEACH
v.
BACON AMERICAN CORPORATION and H. J. Davis.
No. 444.
Supreme Court of North Carolina.
March 2, 1966.
*795 Roberts, Frye & Booth and White, Crumpler, Powell, Pfefferkorn & Green, Winston Salem, for plaintiff.
Deal, Hutchins & Minor, Winston Salem, for defendants.
BOBBITT, Justice.

Defendants' Appeal.
The partners purchased the Lodi Buffer with knowledge it was used equipment and upon receipt and installation thereof had knowledge the manufacturer of the buffer wheels (as shown on Exhibits 3 and 4) was the B & J Manufacturing Company.
*796 As to the seller of a chattel known to have been manufactured by another, the rule has been stated as follows: "A vendor of a chattel made by a third person which is bought as safe for use in reliance upon the vendor's profession of competence and care is subject to liability for bodily harm caused by the vendor's failure to exercise reasonable competence and care to supply the chattel in a condition safe for use." Restatement, Torts § 401. Under this rule, liability depends upon whether such seller, by the exercise of reasonable care, could have discovered the dangerous character or condition of the chattel. Restatement, Torts § 402; Wyatt v. North Carolina Equipment Co., 253 N.C. 355, 360, 117 S.E.2d 21, and cases cited; Cf. Swaney v. Peden Steel Co., 259 N.C. 531, 538, 131 S.E.2d 601.
If, under the indicated circumstances, the seller knows or should have discovered a latent defect in the chattel of such nature that he, by the exercise of due care, could reasonably foresee it was likely to cause injury in the ordinary use thereof, and the seller fails to warn the buyer of such defect, the seller is liable to a buyer who, without any negligence of his own, makes ordinary use thereof and is injured on account of such defect. Douglas v. W. C. Mallison & Son, 265 N.C. 362, 370, 144 S.E.2d 138, and cases cited.
Admitted evidence, whether competent or incompetent, must be considered in passing on defendants' motion for nonsuit. Early v. Eley, 243 N.C. 695, 700-701, 91 S.E.2d 919, and cases cited; Kientz v. Carlton, 245 N.C. 236, 246, 96 S.E.2d 14.
The evidence, much of it circumstantial in nature, was sufficient, when considered in the light most favorable to plaintiff, to permit, but not to require, the jury to find as facts: (1) That the partners had no prior experience with buffers or other equipment used in connection with recapping tires; (2) that Davis was a man of knowledge and experience with reference to such equipment and the use thereof; (3) that plaintiff, while operating the buffer, was injured when struck by a blade that flew out from Exhibit 3 as the result of the breaking of the pins that had held it; (4) that on and prior to March 11, 1961, the pins of Exhibit 3, which held the blades and separators, had become worn to such extent as to constitute a hazard to the operator of the buffer, and that an inspection thereof by a person having knowledge and experience with such equipment would have disclosed the buffer wheel in this respect was unsafe for further use; and (5) that Davis failed to exercise due care to inspect Exhibit 3 in order to determine whether it was safe or unsafe or failed to exercise due care in his inspection thereof or after inspection thereof failed to warn the partners of the danger of using Exhibit 3 in the operation of the buffer.
The evidence, under the legal principles stated above, was sufficient, in our opinion, and we so hold, to require jury determination as to whether plaintiff was injured on account of the actionable negligence of defendants.
True, there is evidence of plaintiff's contributory negligence. "When a person has knowledge of a dangerous condition, a failure to warn him of what he already knows is without significance." Petty v. Cranston Print Works Co., 243 N.C. 292, 304, 90 S.E.2d 717, 725, and cases cited. Plaintiff testified he had disassembled Exhibit 3 a number of times in the process of inserting new blades. Each time the pins were completely exposed except the ends permanently imbedded in one of the plates. H had operated the buffer approximately four months. Even so, his lack of prior experience with such equipment and the assurances given by Davis as to the condition of the equipment are to be considered in determining whether plaintiff, in the exercise of due care, could and should have observed the pins were worn to such an extent that further use of the buffer wheel with these pins was dangerous. In our opinion, and we so hold, plaintiff's evidence does not establish his contributory negligence *797 so clearly that no other reasonable inference may be drawn therefrom. Swaney v. Peden Steel Co., supra.
The conclusion reached is that the issues of negligence and contributory negligence were for jury determination and that defendants' motion for nonsuit was properly overruled.
The court admitted, over objection, opinion testimony of Cecil Gladstone Mock. Mock testified he had been in the tire recapping business for eight years; and, while he was not familiar with a Lodi Buffer, he was familiar with buffer wheels similar to Exhibit 4. He was then questioned as indicated below concerning Exhibit 3. The challenged testimony must be considered in the light of testimony tending to show the facts narrated in the following paragraphs.
McKeown identified Exhibit 3 as the buffer wheel on the buffer when he arrived at the shop and cut off the motor. He testified, over objection, he "could see that the buffing wheel had flew apart and there was blades on the floor," and that glass from broken neon lights and other debris "was all over the floor." Referring to Exhibit 3, he testified the section "where the two pins are broken" was out except for the ends of the two pins imbedded permanently in the holes therefor in one of the plates. He testified that blades, some broken and others whole, were scattered around on the floor.
Plaintiff testified he stopped at the shop on his way back to the hospital some two hours after his injury; that Exhibit 3 was "on the buffer, with one section out of it"; and that he told McKeown "to take it off and keep it."
McKeown testified Exhibit 3 was not used "after the date of the accident"; that the condition of Exhibit 3 at trial was the same as when he found it after the accident except the separators and blades in three of the sections had been removed, thereby exposing the six (unbroken) pins that had held the separators and blades in these three sections; and that, on each of these pins, there were worn places or "ridges" and "those are open and visible to the naked eye." McKeown testified Exhibit 3 was in his possession from the time he found it until he delivered it to plaintiff's attorney, and this occurred "several years ago" and since then Exhibit 3 had been "in somebody's possession other than (his) own."
No missing blades, separators or pins, or fragments thereof, from the missing section, were offered in evidence. There is no evidence as to when and by whom the three complete sections, except for the pins, were removed from Exhibit 3. Nor is there evidence as to where or under what conditions Exhibit 3 has been kept since it passed from McKeown's possession several years ago.
While there is evidence the Lodi Buffer was "a trade-in," used equipment, there is no evidence as to the date of its manufacture or of its sale as new equipment. Nor does the evidence disclose by whom it had been used or the time and circumstances of its prior use.
Testimony as to worn places or ridges or notches refers either to markings on the six (unbroken) pins presently available for inspection or to the ends of the two missing pins remaining in the holes in which they were permanently imbedded and the portion of the plate in the area of these holes and portions of pins.
When plaintiff offered Mr. Mock "as an expert in the field of tire recapping equipment, and particularly buffing wheels," the court stated: "I think he can express an opinion, but I do not know I have to find he is an expert." Suffice to say, there was no finding that Mock was an expert of any kind.
Referring to Exhibit 3, plaintiff's counsel asked this question: "Assume these facts, Mr. Mock: that the wheel which you are holding had been reconditioned completely *798 in or around March 11, 1961, (sic) and had been used in buffing tires every work day afternoon from 5:00 till 9:00, or approximately that length of time, and had been used all day on Saturday from March 11th till August 15, 1961; now, do you have an opinion satisfactory to yourself as to whether or not this wheel had been completely reconditioned on or about March 11, 1961?" Defendants' objection was overruled and Mock answered: "No, sir, I don't believe it had." Defendants' motion to strike the answer was denied. Over defendants' objections, Mock was permitted to point out the bases for his opinion as to the condition of Exhibit 3 on March 11, 1961.
Referring to "where two pieces of spikes * * * or pegs are still remaining in this wheel (plate on Exhibit 3)," plaintiff's counsel asked this question: "Do you have an opinion satisfactory to yourself as to what portions of these remaining pegs that are exposed on the top side, or the inside portion of it, was holding these pins together at the time it flew apart?" Defendants' objection was overruled and Mock answered: "Yes, sir. It looks like a third it was wore two-thirds through."
In other particulars, Mock was permitted to testify, over defendants' objections, to his opinions as to the condition of Exhibit 3 on March 11, 1961, and as to what occurred on August 15, 1961, on the basis of his inspection of Exhibit 3 in June 1965 and the assumed facts set forth in the first quoted question.
On cross-examination, Mock testified: "I have not seen these exhibits (Exhibits 3 and 4) before today. I do not know what their condition was back on August 15, 1961."
In the absence of a finding or admission that the witness is an expert, the competency of opinion evidence must be considered in relation to the rules applicable to nonexpert witnesses. Kientz v. Carlton, supra, and cases cited. A nonexpert witness may testify only as to facts of which he has personal knowledge. Robbins v. C. W. Myers Trading Post, Inc., 251 N.C. 663, 666, 111 S.E.2d 884, and cases cited. In gist, Mock was permitted to testify over defendants' objections as to his opinion with reference to the condition of Exhibit 3 on March 11, 1961, and with reference to why the pins broke, solely on the basis of his inspection of Exhibit 3 in June 1965, and one assumed fact, namely, that Exhibit 3 was used by the partners during the hours indicated between March 11, 1961, and August 15, 1961. This testimony was incompetent and prejudicial. Indeed, a qualified expert could have testified to his opinion concerning the condition of Exhibit 3 on March 11, 1961, and as to what caused the pins to break, if they did break, only upon the hypothesis that the jury found as facts that Exhibit 3 was in the same condition in all relevant respects when exhibited to him in June 1965 as on August 15, 1961, immediately following plaintiff's injury. Stansbury, North Carolina Evidence, Second Edition, § 137.
The court charged the jury as follows: "* * * or if the plaintiff has satisfied you from the evidence and by its greater weight that a reasonably prudent person in the same circumstances as that of the defendants would have delivered to the plaintiff a machine of this type with a guard over it; * * * if the plaintiff has satisfied you in any one of these aspects, and * * * that such negligence on the part of the defendants was a proximate cause of the injury resulting to the plaintiff, and if you so find by the greater weight of the evidence, it would be your duty to answer the first issue YES." (Our italics) Defendants excepted to the italicized portion of said excerpt.
There is no reference to the absence of "a guard over it" in plaintiff's specifications of negligence. Plaintiff offered and the court admitted solely for the purpose of illustrating the testimony of witnesses Lodi Bulletin No. 288 on which is portrayed a Lodi Buffer referred to by plaintiff as "a fair representation of the type machinery that I am talking about * * * with the *799 exception that the guard and the dust collector shown here was not the type that we got." Plaintiff also testified the Lodi Buffer they got "did not have a guard."
Assuming, but not deciding, it was contemplated that the Lodi Buffer involved herein would be equipped with a guard of some type, the absence of such guard was a patent, not a latent, defect, and hazards proximately caused by the absence of such a guard were reasonably foreseeable. Nationwide Mut. Insurance Co. v. Don Allen Chevrolet Co., 253 N.C. 243, 116 S.E.2d 780, and cases cited; Douglas v. W. C. Mallison & Son, supra.
Neither plaintiff's pleading nor his evidence entitled plaintiff to recover on the ground his injury was caused by defendants' negligence in respect of failure to deliver a Lodi Buffer equipped with "a guard over it." Hence, the challenged portion of the quoted instruction was erroneous.
For the reasons indicated, defendants are entitled to a new trial on the issues arising on the pleadings in respect of whether plaintiff is entitled to recover on account of the alleged actionable negligence of defendants.

Plaintiff's Appeal.
The award of a new trial on defendants' appeal necessitates consideration of plaintiff's appeal from what was in effect a nonsuit as to his alleged cause of action for breach of warranty.
A seller's liability for breach of warranty does not depend upon proof of his negligence but arises out of his contract. Wyatt v. North Carolina Equipment Co., supra; Douglas v. W. C. Mallison & Son, supra.
The partners, in said contract of March 11, 1961, ordered the equipment listed therein "SUBJECT TO THE TERMS AND CONDITIONS OF SALE ON REVERSE SIDE OF THIS SHEET."
Under "TERMS AND CONDITIONS OF SALE" appear, inter alia, the following:
"9. Seller guarantees all equipment manufactured by it to be free from defects in workmanship and material when used in normal service for a period of 90 days from date of delivery to the original purchaser, the obligation being limited to making good any part or parts which are returned to the factory, transportation charges prepaid and which, upon seller's examination prove to be defective. Buyer specifically and generally waives any and all claims against seller for loss of use of equipment or any other damage of any kind or nature. This guarantee is in lieu of all other guarantees either expressed or implied and no salesman or other individuals are authorized to assume for seller any other liability in connection with the sale." (Our italics)
While Davis' statements, nothing else appearing, would seem sufficient to constitute an express warranty, Nationwide Mut. Insurance Co. v. Don Allen Chevrolet Co., supra, and cases cited, in view of the italicized portion of the "TERMS AND CONDITIONS OF SALE," Davis' statements, being in conflict with the terms of the written agreement, do not constitute a warranty by the vendor, to wit, the corporate defendant, and are not competent as evidence of breach of warranty. Notwithstanding, as indicated above, Davis' statements with reference to the condition of the Lodi Buffer are relevant and competent as bearing upon whether plaintiff was contributorily negligent.
Our attention is called to the following notation on said contract: "$50.00 Max for Repairing Equipment." Much of the equipment sold under said contract was used equipment. There is no evidence as to what equipment was to be repaired or as to the nature of contemplated repairs. Suffice to say, the evidence to the effect the Lodi Buffer "had been" reconditioned and completely rebuilt at the time of the negotiations *800 negates any suggestion that this notation refers in any way to it.
The conclusion reached is that the ruling involved in plaintiff's appeal, considered as a judgment of nonsuit in respect of plaintiff's alleged cause of action for breach of warranty, should be and is affirmed.
On defendants' appeal, new trial.
On plaintiff's appeal, affirmed.
MOORE, J., not sitting.
PLESS, J., and RODMAN, Emergency Judge, took no part in the consideration or decision of this case.
